# Kentli LiIon AA batterys with 1.5V regulated output



## Julian Holtz (Sep 25, 2013)

Hi guys!

Anyone heard of these:

KENTLI AA 1.5Volt lithium polymer rechargeable battery

They must have squeezed in a little switching DC/DC converter to get the 1.5V.

Capacity of the LiIon cell must be around 700-800mAh, judging from the strange "mWh" rating they use.

I guess that the switching converter is activated if the positive contact is depressed. Otherwise, it would be on all the time, and drain the battery with rather high quiescent currents.

This means in return, that the battery must be inserted shortly before use, and is rather useless in long-term applications like TV remotes.


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## TEEJ (Sep 25, 2013)

I think it also means that in use, an Eneloop would have more run time?


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## uk_caver (Sep 26, 2013)

A freshly-charged standard Eneloop would seem to be a little over 2000mWh, so these cells would seem to have more energy capacity _if the figures are accurate_.

That said, with a mAh capacity of ~1870, that's a shade lower than a standard Eneloop.

A lot would depend on the application.
Put into a 3-cell LED light with a linear regulator, these cells would give pretty much the same runtime while causing more heat to be generated.

Used in a light with a buck and/or boost driver, the higher claimed capacity should give longer runtimes, though not massively greater than an Eneloop Pro, and for much higher cost and more inconvenience re: chargers.

Also, with a completely flat output, that would essentially render any kind of battery monitoring impossible, rather than just difficult.

Maybe someone will get hold of some and see how the claimed capacity works in reality, though at _that_ price...


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## Julian Holtz (Sep 27, 2013)

I also doubt their claim of 2800mWh.

At 1.5V output, this would translate to a capacity output of 1866mAh.

For the LiIon cell at 3.8V, this would mean 736mAh.

700-800mAh is the norm for normal LiIon cells of the 14500 (AA) size. Now take into account the space needed for the DC/DC converter and its efficacy, which will be 70% at best.

So let's take 600mAh x 3.8V x 0.7 = 1600mWh
1600mWh / 1.5V = 1070mAh


These are the limits of technology if they don't have Harry Potter in the design department.


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## stp (Sep 27, 2013)

Julian Holtz said:


> For the LiIon cell at 3.8V, this would mean 736mAh.
> 
> 700-800mAh is the norm for normal LiIon cells of the 14500 (AA) size. Now take into account the space needed for the DC/DC converter and its efficacy, which will be 70% at best.



On one of the pictures from link in your first post if you look closely you can read: 760mAh (3.7V)
It's on the wrapper of the battery on the side, white letters on black background.


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## moozooh (Sep 27, 2013)

These would actually be great for any voltage-demanding appliance that doesn't have a boost driver and can't handle PowerGenix's voltage range, i.e. a portable laser or something else like that. I really don't appreciate the fact that I absolutely have to use lithium primaries for my laser in order to make it burn as well as expected beyond the first ten minutes of battery life.


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## ginbot86 (Oct 4, 2013)

I bought a 4-pack of the Kentli AA batteries. When they arrive I'll get some 'internal' pictures and some battery capacity and internal resistance measurements. :3


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## stp (Oct 5, 2013)

ginbot86 said:


> I bought a 4-pack of the Kentli AA batteries. When they arrive I'll get some 'internal' pictures and some battery capacity and internal resistance measurements. :3



I'm interested mostly in capacity and patiently waiting for your report


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## arnstein (Oct 8, 2013)

This is interesting. I have an old Sony camera flash that only gives about 12 flashes on a set of 4 NiMH cells. Performance using lithium primary cells is much better.

Perhaps the higher voltage of the Kentli cells would work well in my flash.

Can you charge the Kentli cells in an ordinary Xtar charger, or is a specialized charger required?


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## StorminMatt (Oct 8, 2013)

Another thing to keep in mind is that the power output of these cells is going to be limited by the electronics. In other words, these cells may have problems delivering sufficient current to high drain applications. Also, reliability of the electronics could be a concern. I would imagine that, in the name of keeping costs low, quality might not be the best.


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## ginbot86 (Oct 8, 2013)

arnstein said:


> (...) Can you charge the Kentli cells in an ordinary Xtar charger, or is a specialized charger required?



You can't charge this with a standard charger. There is a secondary contact (a ring around the 1.5 volt battery 'nipple') but you can probably get an electrical contact using a small spring (the original charger for these batteries does this).



StorminMatt said:


> Another thing to keep in mind is that the power output of these cells is going to be limited by the electronics. (...)



That's why I decided to buy these batteries. I was also interested in the power output of the battery's built-in regulator.


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## chillinn (Dec 4, 2014)

Its been quite some time... did your Kentli cells arrive? What are your impressions? What is the actual capacity? The voltage consistency must be its selling point... no moon mode.

Even though they're $10 each, 2 month ship, I'm surprised to find there is not more technical information on them on CPF (educated speculation is nice, but it doesn't compare to the shared experiences of the accuracy-blessed members).


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## ginbot86 (Dec 4, 2014)

The first set I ordered never arrived and I eventually got a refund from the seller. I bought a new set (with the OEM charger) on eBay and it arrived a few months ago, but the testing and teardown's been on the "Pending" list for a while now. x3

One reason I haven't gotten to it is because I need to remake my battery fuel gauge setup to work with a 1.5-volt source; it should be done soon and I hope to get a teardown and capacity test in a few weeks' time.


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## chillinn (Dec 4, 2014)

Sorry for my impatience. I just learned of their existence yesterday, yet I swear since learning of the existence of 4.2v Li-ion earlier this year, instantly I wondered if these existed. In considering the fantasy, prior to yesterday, I thought they'd be fantastically popular because of the energy density which I fantasized was the same as a 4.2v cell. Though I'm pre-emptively disappointed with the capacity, I am surprised by the makers claim and interested in its output curve. I am not turned off too much by the price, but the more I think about it, the crazier it sounds. That being said, I still want them.

Way off subject, but I also discovered NiOX yesterday as well... and now count... at least 13 different AA/AAA battery chemistry/voltage combinations commercially available including primaries and secondaries, and if LSD is really distinct from non-LSD NiMH, its really 14. _"At least_," only because I'm not a deep researcher, and as I said my adventure started months ago not years, but to be specific, prior to 2014, all I thought there was available was duty, alkaline, L-energizers, and NiCd. I believe we are in the midst of the golden age for batteries. There are quite a few massive, busting at the seams CPF belly-rubbing love-mine-and-whats-available flashlight these days threads, I think they come up periodically, but we need a dedicated AA and a different AAA battery thread like that (as well as for the other popular standards). I know there's many tester result threads, and query threads, but that's not what I mean. I'm starting to see that batteries, in a way, are not unlike coins or stamps on the one hand, and bottles and bottle caps on the other. If I can figure out what I'm trying to say, I'll start one myself.


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## ginbot86 (Dec 6, 2014)

No worries! I slacked off the past month by not having put out any blog posts and my blog's view count was down, consequently.

I've just peeled off the label of one of these and it's laser-welded at the top. I'll have to find a (fairly) non-destructive way of getting into this battery, maybe a carefully used pipe cutter...

EDIT: Got it open, the laser-welded seam came apart with only 2 turns of my pipe cutter. Inside is a cylindrical (!) Li-ion polymer cell, curiously labeled with 2.66 Wh of energy (compared to the outer label which stats 2.8 Wh...


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## ginbot86 (Dec 6, 2014)

Just finished my teardown and subsequent blog post!

http://ripitapart.wordpress.com/2014/12/06/teardown-of-kentli-ph5-1-5-v-li-ion-aa-battery/


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## StandardBattery (Dec 9, 2014)

Seems like one could make a little cap for these batteries which would allow them to be charged in some standard chargers, such as those that have adjustable connectors in their battery bays. This would make these cells more appealing.


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## chillinn (Dec 10, 2014)

ginbot86 said:


> Just finished my teardown and subsequent blog post!
> 
> http://ripitapart.wordpress.com/2014/12/06/teardown-of-kentli-ph5-1-5-v-li-ion-aa-battery/



I'm not sure how many are reading this thread, but something tells me I wasn't the only one breathing a sigh of relief after your last post. Then... wow, nice blog. Nicely done. Thanks... thank you!


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## ginbot86 (Dec 10, 2014)

StandardBattery said:


> Seems like one could make a little cap for these batteries which would allow them to be charged in some standard chargers, such as those that have adjustable connectors in their battery bays. This would make these cells more appealing.



So far, I was able to charge these batteries in my Intellicharger i4 using a small ring that I made out of some solar cell "bus wire" which is essentially just some thick copper ribbon. A spring can be used to do the same thing (heck, the official charger I have uses a spring to connect to the battery's 3.7-volt terminal).









I hope to have performance data within a week or so. I'm wrapping up a bunch of test data I collected on a fairly cheap Duracell-branded power bank, with a custom-made board for measurements. I'll adapt that board so I can simultaneously measure the battery and 1.5-volt outputs' voltage, current, and mAh delivered. Gotta love Texas Instruments' line of battery fuel gauges for this sort of work. :twothumbs


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## StandardBattery (Dec 10, 2014)

ginbot86 said:


> So far, I was able to charge these batteries in my Intellicharger i4 using a small ring that I made out of some solar cell "bus wire" which is essentially just some thick copper ribbon. A spring can be used to do the same thing (heck, the official charger I have uses a spring to connect to the battery's 3.7-volt terminal).
> 
> 
> 
> ...



:thumbsup: Good going. I'm waiting for your data before picking up a pack.


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## ginbot86 (Dec 10, 2014)

I've just hooked up the battery to my test rig. I'm letting the cell voltage settle down after charging, then the testing shall begin!

(Given how the internal cell's labeled energy content is less than what's on the outer label, I'm not going to be _too_ optimistic about its performance. But there's only one way to find out!)


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## StandardBattery (Dec 11, 2014)

Yeah the labeled energy on the inner cell vs spec is troubling. I was thinking that given the down conversion in the voltage maybe the specs are using 1/2 the cell current in their test and thus get a bit more energy from the cell. I admit though I'm probably dreaming.


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## ginbot86 (Dec 11, 2014)

It could be the case. So far I'm just running a test on the cell only to get a baseline on how the cell itself performs, and possibly do a second run to match the cell up to Texas Instruments' battery database and see what particular chemistry variant it uses.

One possible explanation for the energy discrepancy (other than them just fudging the numbers) is that they're using a high charge-termination voltage and a very low discharge-termination voltage (that is, they're pushing the voltage limits on the cell to squeeze a few more mAh of capacity, but at the expense of cycle life). Given the simplicity of the buck converter circuitry, I think the only thing that's preventing the cell from being drained to zero volts is the protection circuit and possibly the UVLO (Undervoltage Lockout) feature on the converter itself. Once I get a log of the cells' raw performance, I'll hook up the cell to the original circuitry (including the charger) and log what voltages the cell experiences.


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## StandardBattery (Dec 11, 2014)

That's a very good approach, very thorough way to perform the analysis of this type of battery.


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## ginbot86 (Dec 20, 2014)

StandardBattery said:


> That's a very good approach, very thorough way to perform the analysis of this type of battery.



Thanks! I'm sure my analyses may not be as rigorous as say, HKJ's methodologies, but I want to at least have a fairly thorough analysis as many people out there will likely base their purchase decisions on my data.

On that note, testing is still underway. I've just gotten back from a week-long trip so I was unable to get much data during that time; once all the data I want to collect has been processed, I'll make a blog post on my personal blog regarding the battery's teardown and performance data, and also make that information available here in its own thread. As a bit of a teaser, here is a graph of the battery's voltage output with respect to current:


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## chillinn (Dec 20, 2014)

ginbot86 said:


> As a bit of a teaser, here is a graph of the battery's voltage output with respect to current:



blind eyes could blaze, uh, nods as good as a bat... I mean to say that's _weird_. But that's what the claim is that it does... look at how it does that; that's weird.


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## StandardBattery (Dec 20, 2014)

*That's a good teaser!* I can see an advantage of having the regulator in the battery, allowing the circuit/device itself to be simplified with less components.


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## SemiMan (Dec 20, 2014)

Julian Holtz said:


> 700-800mAh is the norm for normal LiIon cells of the 14500 (AA) size. Now take into account the space needed for the DC/DC converter and its efficacy, which will be 70% at best.



While I am not saying it is over 70%, what is your logic for claiming that it can't be?


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## chillinn (Dec 20, 2014)

StandardBattery said:


> ...in the battery, allowing...



As digital electronics keeps minaturizing towards physical limits, I hope we'll see more things in the battery... well, not adopted industry wide, but types of specialty batteries that include built-in data collection and memory for it would be keen. An couple itty-bitty LEDs, a tiny digital voltimeter and fold-out charging prongs (to plug directly into a wall outlet) would be a little wiz-bang, but sellable, but not for those who need lots of batteries charging.


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## uk_caver (Dec 20, 2014)

StandardBattery said:


> *That's a good teaser!* I can see an advantage of having the regulator in the battery, allowing the circuit/device itself to be simplified with less components.


I'm not sure how many battery powered products (particularly lights) would benefit at all from having a perfectly regulated power source.

For a start, without implementing some complicated circuitry for power source->device communication, a fully-regulated power source means the device has no way of knowing when power may cut out (if the device is intelligent) and no way of simply reacting to falling voltage (like a circuit which is resistor-limited or which has regulator dropout leading to a 'long tail' in the output-vs-time curve.

By far the worst-behaving light I have used in terms of response to declining power source was a 3xAA one which had a buck-boost converter which was perfectly regulated and diligently sucked every last drop of power out of the cells before hitting its limit and falling over without warning.

I really can't see what the point would be in choosing an overcomplicated power source which tended to impose that behaviour on anything connected to it, denying equipment even the kind of information which something running off a protected lithium cell can extract from the supplied voltage.


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## ginbot86 (Dec 21, 2014)

It's a bit of a tradeoff. A battery that has a well-defined slope when discharging lends itself well to coarse voltage-correlation fuel gauging, but a battery with a flat discharge curve can only be gauged via coulomb counting (tracking mAh in a sort of calories-in-versus-calories-out sort of idea). That said, I have not yet had a chance to do a data log of the output voltage through a single discharge cycle

As for batteries with data collection, there are fuel gauges that can provide protection and gauging (and also have lifetime data tracking) and be able to report that information to a host processor. (I'm probably derailing this thread a tad, but the iPhone 6 and 6 Plus have highly advanced fuel gauges that keep very detailed information about the battery's performance.)


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## StandardBattery (Dec 21, 2014)

Your right in that general lights would not be a particularly good candidate, and any device designed for such a cell would then be limited in its power sources. Still I think it might be useful for some small electronic circuits, but maybe more so hobby stuff.


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## ginbot86 (Dec 28, 2014)

After several days of "I'll get to it" I've set up my test rig to perform dual-logging of the cell and DC-DC data on my computer. I was thinking of just doing one run per discharge rate, but at the moment I'm on the second run of a 2000 mA discharge.

From the last (technically first ) run of data, the 760 mAh rating comes from the OEM Kentli charger terminating at a rather high 4.228 volts. While not immediately damaging, it does concern me in terms of endurance (i.e. the cycle life of these batteries may be reduced when using the OEM charger). Also, at 2 amps discharge, the DC-DC converter gets *hot!* The efficiency graph over the discharge curve shall be interesting...

Teaser time #2!





EDIT: Looks like the cell goes into over-temperature protection when at sustained high current loads... I'll probably have to redo this 2000 mA run later.


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## chillinn (Dec 28, 2014)

StandardBattery said:


> Your right in that general lights would not be a particularly good candidate



I agree, can see the logic and argument that this may be so, but otoh, knowing the behavior of the battery and its capacity, it might be interesting in-use to have a flashlight that does not dim, and how bad could it really be if you're baby-sitting the light (and keeping track of its use)? The capacity is hated, but the curve is tempting... but ouch 4x the price of good NiMH. But I might "collect" them anyway, realizing I can't personally justify, even remotely, cost against utility. I expect that most of the batteries I'll eventually own I bought because I like the pretty label. Don't judge me!


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## turbocolts (Jan 16, 2015)

Great post! I received my kentli's AA's in November 2014 and have been using them at work every day since. I am a automotive technician and do a lot of diagnostic/engine work. Having good light is a must! I use a Coast HL27 LED Headlight (309 lumen, 3x AA). Using the regular Duracell/energizer NiCa batterys for the past years, and dealing with the constant low starting voltage (1.2v) and also having them drop down to .9 volt and produce very limited light..... I was left with wanting better. I tried the AA lithium non rechargables.... great batteries! but it gets exspensive very quick to be buying those batterys again and again. When im working I generally use the light for 3 or 4 hours max a day, and to keep the light output acceptable with the NiCa's I was constantly charging multiple sets and swapping the out about every 2 to 2.5 hours to keep the voltage from dropping too low (I use my multimeter at work to moniter charge levels) 

Its been about 2 months now using the kentli's AA's and overall I am happy with them. Being that I use 3 AA's to power my headlight,once I finish a charge cycle I am left with no more batterys. I ordered another 4 kentli's so I can pre-charge them, and have them ready at any time to swap back into the flashlight once the other set shuts off. I find im getting around 1.5 hours to 2 hours of use at full light output (dimmer control at max). Definalty a lot less then the NiCa's but it absolutely rules to have 1.5 volts at all times powering the LED. MUCH MUCH more lightoutput with these batterys. I find that if I turn the dimmer down to around 60-70 percent I get way way more life out of the kentli's.. (around 4-5 hours of use, and also it pretty much matches the max light output with the NiCa's are capable of). 


I do agree that it seems that the overtemp protection inside the batteries is shutting them down before the actual LiPo cell reaches termination voltage. This is a little disappointing and keeping the batteries from reaching there full potential. As I wear the light on my head, I can really feel the heat on the rear mounted battery pack. With the NiCa's I could not feel much heat at all ever from the battery back. only from the LED. With the LiPo Kentli's they get fairly warm, (definalty noticeable through the plastic cover). The LED light also gets much hotter as well with the LiPo's installed.

I pretty much discharge the batteries every day (3 out of the 4 anyways) so I have put them through quite a few charge cycles so far, and have not noticed any really noticeable decrease in performance as of yet. I can say tho, I should be much happier with them once I have 8 of them so I can have 3 pre-charged AA's ready to rock once I get my 2 hours of use out of the ones I start the day with.

Ill keep this post updated aswell over the next year on how these batterys hold up. I also am pretty hard on these batterys as I drop my light, step on it, and have also dropped the batteries from about 4 feet high onto concreat floors (the NiCa's seem to want to deform around the bottom of the battery as time passes and makes it almost impossible to insert them into the NiCa charger over time and extended abuse of being also in my MagLight LED pro mostly causes this damage as the batterys sit inline, and when the light is dropped, they smash into each other. don't seem to have this problem with the Coast HL27's side by side mounted 3 x AA.

Thanks!


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## Phlogiston (Jan 18, 2015)

I'd be careful with the Kentli cells if I were you. For a given level of damage, lithium-based chemistries are a lot more prone to catastrophic failure than NiMH cells. 

I've heard that most Coast lights are direct drive, with just a resistor to control LED current instead of a full-on regulation circuit. If that's true, it makes sense that your light would draw more current and run hotter at higher voltages. There are also losses in the voltage reduction circuit inside the Kentli cells, which will cause them to dissipate more waste energy as heat.


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## chillinn (Jan 18, 2015)

I've cooled to the idea of acquiring these. I really really like the label! That is nice graphic design. More importantly, of course, I like that output curve, _except_ for the knee and sheer drop in voltage. I'm totally 180º on my gabbing above at how easy it would be to realize, at the right instant, it was time for a cell change. If I can't catch my LiMn at the knee, can't catch my other Li-ion at the knee, can't catch my NiZn's at the knee, nor even can I catch my NiMH at the knee... no way I could catch that cell before the voltage drops. If they were $2 a cell, I might gamble, because the constant voltage looks really sweet. But ouch, when you damage a cell its like ripping up a Hamilton. Hope they come down in price, because I am curious, but my curiosity rarely reimberses.


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## uk_caver (Jan 18, 2015)

I guess making an unregulated light regulated _is_ a practical use of these cells.


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## WalkIntoTheLight (Jan 18, 2015)

uk_caver said:


> I guess making an unregulated light regulated _is_ a practical use of these cells.



It's probably cheaper, safer, and more practical to just buy a regulated light. With a regulated light, you'll get a flat output for 90% of the discharge, then you at least get a warning before the battery dies completely. And you can use higher capacity, cheaper, and more reliable Eneloop cells.

I just don't see the point in using a battery like this in a flashlight.


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## tandem (Jan 18, 2015)

How long before some photographer clueless about lithium ion charging pops one of these into their bog-standard NiMH charger?


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## uk_caver (Jan 18, 2015)

WalkIntoTheLight said:


> It's probably cheaper, safer, and more practical to just buy a regulated light.


Oh, quite, it's just that I'm trying to be positive against my usual nature.

If someone really liked everything else about a Coast/LED Lenser light (variable power, focussability) then these cells could remove the unregulated nature of the power control if that was undesired.
Clearly, for a lot of people it would be better if such lights were variable constant-current ones which ran nicely on NiMH, which would be pretty trivial from an electronics point of view, but I guess then they probably couldn't make the '309lumens, 3h45 runtime' claim.

For myself, I don't like continuously variable power and don't need zoom since I use twin beams, but that's just my personal preferences.


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## turbocolts (Jan 18, 2015)

Well the biggest thing for me, is the increase in light output from using the kentli's over a standard NiMh (sorry for calling them NiCa lol).... 

at only a 1.2 volt cell the NiCa's just don't come close to the constant 1.5v available from the kentli's LiPo's. and now that I have 4 more kentli's coming in the mail, having a extra set charged ready to go, cures the shorter run time woes that comes with the LiPo's. Totally worth it in my books.


What are my other options for a Rechargable 1.5v cell?? You mention Eneloop cells. Sorry, im not totally current with those batteries, what are the specs?


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## chillinn (Jan 19, 2015)

turbocolts said:


> What are my other options for a Rechargable 1.5v cell??



NiZn cells have 1.6v nominal (but fully charged may be 1.9v). They're not as resiliant or resistent from abuse as NiMH 1.2v Eneloops, nor do they have comparable low self-discharge (LSD) quality, nor will they provide as many recharges, and they need a special dedicated NiZn charger. Their output curve has a sharp knee and fast drop-off, and using them below 1v damages the cell, but it is considered a much safer chem than Li-ion.



turbocolts said:


> You mention Eneloop cells. Sorry, im not totally current with those batteries, what are the specs?



see the Eneloop sticky

Originally sold by Sanyo (still available), the brand has been taken over by Panasonic. They are loved for their resiliance, consistency and lifetime recharge cycles. They come in clones, too, the Duracell Ion Core rechargeables, and Amazon branded rechargeables are the same cell relabled. There are others.


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## WalkIntoTheLight (Jan 19, 2015)

turbocolts said:


> Well the biggest thing for me, is the increase in light output from using the kentli's over a standard NiMh (sorry for calling them NiCa lol)....



Sure, but if you bought a properly regulated light, instead of a cheap Coast light, you could use regular NiMH batteries and would get a constant bright output without any dimming.


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## chillinn (Jan 19, 2015)

tandem said:


> How long before some photographer clueless about lithium ion charging pops one of these into their bog-standard NiMH charger?



Nothing will happen. See post #19 above. I was just thinking the safety of these are annoying, forcing you to buy another charger that you shouldn't need, but, as shown, a ring makes them compatible with our favorite Li-ion chargers.

And gee whiz, tandem... how many cameras have you broken? Have you tried smiling with your eyes?  jk. Most serious photographers are pretty serious about their equipment. Did you mean "tourist?"


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## uk_caver (Jan 19, 2015)

Why 'photographer', I wonder?

What photographic uses would they be good for?
Cameras which take AAs seem largely designed to be happy with NiMH (and these cells would clearly screw up battery monitoring).
For something like a flashgun, NiMH are ideal since they can supply pretty much whatever current a flashgun might want.


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## tandem (Jan 19, 2015)

uk_caver said:


> Why 'photographer', I wonder?
> 
> What photographic uses would they be good for?
> Cameras which take AAs seem largely designed to be happy with NiMH (and these cells would clearly screw up battery monitoring).
> For something like a flashgun, NiMH are ideal since they can supply pretty much whatever current a flashgun might want.



Photographers aren't always well versed in electronics. If they believe this cell can give them faster full output cycle times (likely could) someone out there is bound to try it.


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## tandem (Jan 19, 2015)

turbocolts said:


> Well the biggest thing for me, is the increase in light output from using the kentli's over a standard NiMh (sorry for calling them NiCa lol)



If you haven't tried using Eneloops NiMH then you must try them. They are not your daddy's NiMH or NiCd cells. Eneloops (and a few other similar Low Self Discharge - LSD - designs) perform exceptionally well in high current devices while maintaining voltage well. They aren't terribly expensive and the chemistry is intrinsically safe. 

Best of all, they won't blow up on your forehead. 

A multi-cell lithium ion or lithium-polymer powered light is *not* intrinsically safe. Your light wasn't designed for them. Despite having been opened up and some discharge testing performed, there's little known about their long term performance and safety. The charger is an unknown quantity as yet. Does it charge them correctly and safely? Unknown. 

Here's a two cell lithium rechargeable light that blew up while being held at the tail end in someone's mouth recently. And here's some news video showing the fellow in the hospital. 

There's no circumstance other than zombie apocalypse where I would pop these into a multi-cell light. 

Every single incident of a lithium rechargeable flashlight *explosion* that we are aware of in this community has been a  multi-cell light configuration and of those incidents, _cells with a poor quality record or dubious history are implicated in most of those explosions_.

Why tempt fate?


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## chillinn (Jan 19, 2015)

tandem said:


> Why tempt fate?



You can (and some recommend you should) tempt fate and live dangerously. I don't, but most should consider it. I know what you meant, though, and it is wise advice... don' tempt fate obliviously with volatile high-energy cells.


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## tandem (Jan 19, 2015)

I probably should have put it differently: 
_
Why needlessly risk putting a bomb with a random timer on your forehead?

_


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## DK-Fire (Jan 25, 2015)

Hello from Denmark

i tried to read this thread about the KentLi rechargeable lithium batteries, but when english is not my best it's very hard to follow all the technical stuff you are writing 

I am trying to find AA lithium batteries, but i can't figure out if the KentLi's are any good...

This is what i need them for, and it is recommended that it runs on lithium batteries... But it's going to be very expensive as it only runs for about 2-6 hours on a set of 4 (depends on how many features u use in the scope)
http://www.atncorp.com/x-sight-night-vision-rifle-scope-5-18x

Would it be an option to try the KentLi batteries ??

Hope my english is good enough to understand


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## StandardBattery (Jan 25, 2015)

DK-Fire said:


> Hello from Denmark
> 
> i tried to read this thread about the KentLi rechargeable lithium batteries, but when english is not my best it's very hard to follow all the technical stuff you are writing
> 
> ...


It's too bad that scope has poor power design. I think these cells may be worth a try. Run time could be limited though, but at least you could use them during testing and short outings. Leave the lithium for longer trips, backup, and during update to be safe. There are not many options so I think it's worth trying.


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## DK-Fire (Jan 25, 2015)

StandardBattery said:


> It's too bad that scope has poor power design. I think these cells may be worth a try. Run time could be limited though, but at least you could use them during testing and short outings. Leave the lithium for longer trips, backup, and during update to be safe. There are not many options so I think it's worth trying.



I think so too.... It would be nice to hear from somebody who maybe has tried the KentLi in devices that can only run on Lithium. Just to see how big the difference would be


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## tandem (Jan 25, 2015)

DK-Fire said:


> Would it be an option to try the KentLi batteries ??



Before answering the question, I need to ask a different question: Do you want to operate that expensive scope mounted to your rifle loaded with explosives (ammo) *safely*?

Consequences of not being careful? If you fail to monitor cell health and one of them is dangerously out of whack compared to the others and goes into reverse charge while in operation in your scope, the stack of four cells may end up exploding. Not a good scenario if one's eye is nearby at the time. Of course explosive venting can happen with Lithium Energizer primary cells too if you happen to mix a mostly drained cell with 3 fresh cells. Being careful / prudent is always a good idea when handling any lithium based cell chemistry where more than one cell is connected in series. 

Of more immediate concern, the charger has been observed to charge them to too high a voltage; Charging lithium ion cells to too high a voltage is destructive to the cells at the very least; if taken too far, the cells can be put in a dangerous state. Will another copy of the charger terminate the charge properly? Or might another copy allow even higher and more dangerous voltages to be reached? Unknown. What is the quality of the charger implementation? Unknown, but the first data on it (over charging) is not encouraging.

Other unknowns include the genealogy of the internal lithium cell itself. Who made it, and what is the maker's track record? What performance data is available for it? 

To use these cells you, the user, have to not view them as just another version of a ubiquitous AA "consumer" cell. It may look the same but it isn't. You need to approach using them with the mindset that you are an experimenter. Some experiments go wrong. Very wrong.

If you are prepared to test the native cell voltage off the charger (not the 1.5V output but the unregulated output directly from the cell) using a Digital Multi Meter, to monitor the state of all cells over time using your DMM, to verify that they are not being dangerously over-charged, then sure, you probably could put them in any device that takes AA format cells that doesn't pull more current than the cell can safely handle.

If something goes wrong, you'll be on your own. The maker of that scope certainly will not honour its warranty. 

Just remember you are venturing into the world of experimentation here.


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## tandem (Jan 25, 2015)

Charger quality is important. Many rechargeable lithium cell incidents involving property damage or injury occur during the charging process or occur later when the cell(s) are in use as a result of bad charging conditions.

This link relates a story by an informed user who had three of four Kentli chargers fail. He also notes cycle life of the cells at roughly 100 charge-discharge cycles. This is very poor performance and may indicate:

- poor quality cells incorporated in the product
- over-charging by the charger
- a combination of both

Good quality lithium ion cells charged to their maximum designed voltage should give many hundreds of charge-discharge cycles. For now we should only assume the source cells are of poor quality. As poor quality cells are more frequently implicated in multi-cell explosions / vent with flame / rapid disassembly incidents, there's ample reason to distrust this product.

The user also notes real life performance as being equal to using a good quality, intrinsically safe, 2700 mAh NiMH rechargeable cells. The "Kentli" cells delivered 3.5 hours runtime as do his NiMH cells. The NiMH cells are safe to use, cheaper to buy, and good chargers for them abound. For that reason alone it doesn't make sense to acquire these cells for many uses.

Energizer Lithium primary (non-rechargeable) cells by contrast deliver 5 hours runtime.

The cells + charger are a possibly good idea implemented badly by a maker who can't be judged at this time as anything other than trustworthy.


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## DK-Fire (Jan 25, 2015)

Thanks for the information Tandem.... Maybe i should just order a stack of Energizer Lithium :-/

I just don't understand that there are so many other great rechargeable lithiums.... But not in AA..... WHY :shrug:

I also read a little about the Eneloop, but can't figure out if they maybe could replace the Energizers...


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## StandardBattery (Jan 25, 2015)

DK-Fire said:


> Thanks for the information Tandem.... Maybe i should just order a stack of Energizer Lithium :-/
> 
> I just don't understand that there are so many other great rechargeable lithiums.... But not in AA..... WHY :shrug:
> 
> I also read a little about the Eneloop, but can't figure out if they maybe could replace the Energizers...



Lithium-ion cells have a higher voltage so they can't replace AA directly. That's what makes these cells interesting.

reports I've seen on using NiMh cells in that scope report very limited run time. You might want to look for other reports. They appear to power up the device, but I would not use them during firmware updates. If you have some standard NiMh rechargeables then give them a try.


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## DK-Fire (Jan 25, 2015)

Anyone know if these are any good ?
http://www.batteribyen.dk/genoplade...tk-miljoevenlige-genopladelige-batterier-3203


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## tandem (Jan 25, 2015)

DK-Fire said:


> Anyone know if these are any good ?
> http://www.batteribyen.dk/genoplade...tk-miljoevenlige-genopladelige-batterier-3203



The GP Recyko LSD cells appear to be ok. They are NiMH cells though .


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## tandem (Jan 25, 2015)

DK-Fire said:


> Thanks for the information Tandem.... Maybe i should just order a stack of Energizer Lithium :-/
> 
> I also read a little about the Eneloop, but can't figure out if they maybe could replace the Energizers...



I say try the NiMH first.

If Eneloop (or similar low self discharge rechargeable NiMH cells) do power your scope acceptably and for an acceptable length of time, they'd be a good and perfectly safe solution for you. Also... they are not expensive at all and will last for many hundreds of charge/discharge cycles. Some versions will last for thousands.

If you have other devices in your home that could benefit from NiMH cells, they are a good investment and would present zero risk for you to try out. We have more than 100 Eneloops ourselves in this household and the vast majority are not used in flashlights.

We are using them in flashlights, XBox controllers / four-cell high output photo flashes / two-cell remote triggers (PocketWizards) / clocks / telephones / remote controls / various toys / RC controllers / portable emergency radios / cycling lights / decorative electronic candles / outdoor lights / and so on. Maybe we have too much electronic gear, but I think our household is not that unique.


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## dealgrabber2002 (Feb 6, 2015)

*Rechargeable Lithium AA*

Thread Merge

Has anyone heard of or tested these rechargeable lithium AA batteries?

click

I never heard of this. It's lighter than NiMh, holds 1.5v instead of 1.2v. Charge limit up to 4.2v and ultra low self discharge.


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## CuriousOne (Feb 7, 2015)

*Re: Rechargeable Lithium AA*

Hm, built-in converter?

step up and step down in same case?....


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## Timothybil (Feb 7, 2015)

*Re: Rechargeable Lithium AA*

Someone was doing some testing of these a few months ago. Search on the battery name and you should find it.


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## ginbot86 (Feb 7, 2015)

*Re: Rechargeable Lithium AA*

That'd be me. I still have a bunch of data to collect and haven't had much time to get my test setup going again, unfortunately. In particular, I have yet to collect capacity data at lower discharge rates, efficiency and also thermal effects at varying loads. Less important is the chemistry characterization through Texas Instruments' chemistry database, and possibly a battery endurance test (I'd have to come up with a custom rig to do this automatically though).

That said, the buck converter in these stops at about 3 volts, which is good; at least it doesn't drain until the protection circuit kicks in at 2.3 volts. The charging IC in the Kentli charger is a TP4057, the smaller sibling of the venerable TP4056 that's frequently mentioned here and is configured to output 300 mA in the constant-current charging stage; that's interesting as the TP4057's charge termination voltage is much higher than the TP4056's...


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## tandem (Feb 7, 2015)

*Re: Rechargeable Lithium AA*



dealgrabber2002 said:


> It's lighter than NiMh, holds 1.5v instead of 1.2v. Charge limit up to 4.2v and ultra low self discharge.



And on the downside as compared to NiMH chemistry:


Basically an unknown maker.
LiPo inside. From an unknown maker.
Cycle life unknown but according to an early report, poor. 100 charge-discharge cycles compared to 500 or thousands with NiMH. This doesn't speak well to the base LiPo cell quality.
Vent with flames potential. See LiPo.
718mAh actual capacity
3 dead chargers out of 4 received

As for weight, does anyone actually care if their AA format cells are X percent heavier?

Yes, the cells require the use of a customized charger with special contacts so, hooray, someone is unlikely to pop them on a NiMH charger and have unpleasant issues.

Nifty idea but without a reputable reliable maker standing behind it. It'd be better to design (or choose) equipment around 3.7V nominal and use a real li-ion cell not having so many limitations.

Thumbs up for exploring them though.


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## ginbot86 (Feb 7, 2015)

*Re: Rechargeable Lithium AA*

I can see why the chargers would end up DOA. It's... designed pretty poorly, or at least the mains-input side is. I just feed power through the USB port on it with an external 5V supply and haven't had problems yet. As for endurance, I've been keeping an Excel spreadsheet of my fuel gauge's reported capacity, both maximum "chemical capacity (Qmax)" and normal-load capacity (FCC), as well as internal resistances. I'm at cycle 18 and haven't noticed capacity degradation, but internal resistance is already beginning to rise! I'm also quite curious as to see how the degradation curve of this battery will turn out...







The more complex a system is, there's more to go wrong. In this Kentli battery there is protective circuitry as well as over-temperature protection in the buck converter itself, but the heat generated from the buck converter still has me a bit concerned...

As for the weight of the battery, it's just a side-effect of using a Li-based chemistry.


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## tandem (Feb 7, 2015)

*Re: Rechargeable Lithium AA*

^^^ very interesting. 

Sure appreciating the opportunity to live vicariously through your exploration here.


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## Raphion (Feb 8, 2015)

*Re: Rechargeable Lithium AA*

Looks like much more cost and many times more things to go wrong than NiHM, with no advantages at all, unless you're trying to make a cheap unregulated flashlight work kind of like one with a good built in regulator.


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## ginbot86 (Feb 16, 2015)

*Re: Rechargeable Lithium AA*

Yet another teaser! As one part of my upcoming blog post, I'll go over the equipment I used to test this Kentli battery and its charging performance.
Here's the block diagram I made in Microsoft Visio (click to enlarge - it's a big diagram!):





On a side note, I got my setup going again, this time with a temperatue probe I can attach to different components. So far, I have it attached to the metal frame of the DC-DC converter, so that I can log the converter's temperature as well as current, voltage, and passed mAh. I want to see how HOT the converter gets when I try to draw 2 amps from it!


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## CuriousOne (Feb 16, 2015)

*Re: Rechargeable Lithium AA*

Actually, weight is a thing you have to consider. For example, after converting my on-camera flash from 4xAA NiMH's to 4x14500, weight decrease was easy to feel.


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## XSVZ (Mar 12, 2015)

I've been using these batteries is my wirless stage equipment for a year now, recharged every week and see many advantages.

Possibly they are more designed for lower current draw than powerfull torches ... ? Will you try some tests at lower current draw 200mA/500mA.
- I experience no heat
- The lack memory loss is great as I recharge for every gig rather than relying on battery monitors
- The extra voltage give me better range and performance
- Lack of weight is great for mics and beltpacks

Love your work ginbot86, keeping an eye on further updates.
Tandem I understand you fears around danger ... but to claim photographers are dumb enough to not follow basic instructions about using the correct charger is irrelvant. Those of us who buy and professionally use expensive electronic equipment are tech savy enough to follow this simple rule.


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## ginbot86 (Mar 13, 2015)

Much of my current testing is focused on very low loads (currently focusing <200 mA or so), and naturally it takes a long time to produce (a 65 mA test run took about 25 hours to complete!). Lately, one of my fuel gauge boards has been having connectivity problems, forcing me to throw out several logging cycles because of incomplete data. As such I'll have to either repair that board or use another fuel gauge board to continue testing.

At high loads (over 1.5 amps) the DC-DC converter gets very hot, and at 2 amps the converter circuit gets very hot, easily reaching 70+ degrees C (160 degrees F), which also results in pretty poor efficiency at these high loads (65% at 2 amps).


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## ginbot86 (Mar 15, 2015)

... looks like I'll have to move to another fuel gauge board. The screw terminals I put on the board have snapped off (didn't put the terminals all the way into the PCB, so it failed simply by metal fatigue), and will have to repair the board later. In the meantime, I'll just transfer my fuel gauge settings to a newer chip and hopefully the measurements remain good still...


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## ginbot86 (Jun 17, 2015)

If anyone's been following this thread, I've just posted a review of this battery's performance: http://www.candlepowerforums.com/vb/showthread.php?402929-Review-of-Kentli-PH5-1-5V-Li-ion-AA


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## turbocolts (Aug 6, 2015)

Just updating my progress with these batteries. Again im a automotive technician using these kentli batteries on a 5 day a week basis. I purchased a extra set of 4 of these batteries in January to have a better supply of fully charged batteries (my head mounted light uses 3AA's, and my mag light LED pro uses 2 AA's). Anyways its now august 2015 and I am still very happy with the batteries. The time they last hasn't seemed to change hardly at all and I have not have had any failures of any of the batteries everntho I am pretty hard on them, (they get dropped every now and again). The charger has been consistant and besides the odd time it wont turn on the charge light (spinning it inside the charger restores the connection on the half ring contact every time instantly) it has worked flawlessly. I still take note that they do heat up, and have put them in the charger hot (right after a discharge), also using the battery before full charge is reached, or directly after the charge is finished. and never had a issue so far. I used some alkalines (duracells) for a bit, and noticed right away they didn't put out as much light as the kentli's. Went back to using the kentli's in that new maglight asap and it works much better on the LiPo AA's.

Ill continue to update this post in 2016 on how they are still holding up.

ALso I must note that externally the batteries seem to hold up quite well. no deformation of the bottom or top contacts/plates has been noted, where as the Duracell/energizer rechargables I use seem to not take very well. heavy deformation is present on those Nickel based rechargeable batteries.

Granted the life of the batteries is no where near a fresh set of alkaline or NiMh's.... but having the extra set of 4 batteries, I just pop in fresh ones after about 2 hours when they turn off (instantly, or sometimes they pulse/flash/strobe the light before conking out.)


Im happy with them anyways. And yeah, I guess my coast light may not be the "best" around, and is unregulated,. But my snap on tools rep put a 5 year no question's asked warrantee on it, even if I run it over with a truck ahaha. (went through around 5 of the lights in the last 2 years so far ahah)


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## EugenM (May 27, 2016)

First of all i apologize for replying to an old thread, but i feel like most people here didnt understand the application for these rechareable batteries.

I registered once i saw ginbot86 excelent review of the batteries in question (thank you very much for your hard work) as i was looking for an unbiased report of kentli products since i am considering buying some of them myself, from what i understood from the tests done i realized that the application options for such batteries that can constantly output 1.5V and even lowering the weight is actually pretty important in:

1) *RC Cars*, It helps keep top performance of the toys much longer and also has a bonus of less weight=more torque which not even duracell or energizer non rechargeable batteries can match, this is a pretty big deal in RC cars since the cars can still run sub 1.5V but at a big performance drop.

2) *Wireless Controlers*, yes unfortunatelly low voltage problems happens even with expensive logitech controlers which constantly looses signal because of the battery voltage decreasing without even reaching 50% of battery capacity.

3) *Wireless Microphones and Receivers*, same as 2).

4) *Flashlights*, a dimmed flashlight is an useless flashlight.

5) *TV Remotes,* this is a bit controversial but i would rather have a TV remote work properly at all times and then simply stop working than hitting that stupid button over and over again with the remote clearly indicating that a button is pressed but the TV/DVD/PowerBox not receiving anything unless pointed at its IR with a sniper scope (im exagerating but you get the point).


If you would ask though why was i interested in said batteries for me the most important part is the RC Car, i absolutely hate paying 10€ for a pack of AA batteries that already outputs crap performance without even reaching 50% of its charge...


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## HKJ (May 27, 2016)

They are interesting, but fairly expensive and you only get a gain in a few cases.

With RC cars you might hit the current limit of the cells.


In my comparator try comparing them to: Energizer lithium and Eneloop
http://lygte-info.dk/review/batteries2012/CommonAAcomparator.php


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## EugenM (May 30, 2016)

HKJ said:


> They are interesting, but fairly expensive and you only get a gain in a few cases.
> 
> With RC cars you might hit the current limit of the cells.
> 
> ...




Hello thank you for that link, it confirms what i suspected a very long time, duracell sucks in comparison to energizer lithium aa, now you prooved my point that im not a crazy person


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## Gauss163 (May 30, 2016)

After reading ginbot86's extensive reviews on his blog, I concur with HKJ - these Li-ion 1.5V AA cells have value only in very limited applications. One especially large problem is the fact that the discharge curve is so flat that normal fuel gauges will not give any usable reading of remaining capacity, i.e they will indicate close to 100% almost right up to the point where the cells shutsdown, like having an auto fuel gauge that always reads full until you reach one-tenth of a gallon, when it abruptly drops to an empty reading. That's not acceptable in most devices.

The same problem will occur in any analogous battery that uses a buck/boost regulator since, keeping the output voltage constant masks the true cell voltage from the device's gauging logic. This could be alleviated by logic that regulates the voltage to mimic a typical NiMh/Alkaline discharge curve, but I've never heard of any such implementation.


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## Behemot (Oct 18, 2016)

There's been another analysis here http://www.txsound.com/blog/saga-kentli-lithium-ion-1-5-volt-aa-evers/

I'd say it's just overpriced PoS. That self discharge is terrible, real capacity is scam as usually, chargers are crap and the number of cycles…plus if you drop it on the floor you can burn or explode, great! If you don't need 1.5 V than use Fujitsu Reachrgeable High Capacity (or the rebrand from Panasonic). Some ppl also combine single rechargeable with single alkaline to get higher voltage…

If you need 1.5 V and lots of power than it's better than using alkalines. But even better would be to kick a designer of that device to his ***, especially if the device is younger than 5 years and it STILL asks for 1.5V cells.


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