AA NiMH charger versus charger for SLA battery question

[tpcollins]

I have a unit with (8) rechargeable AA Eneloops that I could charge by plugging into it a charger with a 4.0mm x 1.7 DC plug. What would be the "normal" DC output for a wall charger that would charge this setup?

I assume my little Zeus 12 volt charger for "SLA batteries only" that puts out 16 volts @ .3A wouldn't work? Thanks.

 

[Etsu]

16 volts output sounds like it would fry your Eneloops. So yes, don't use a lead-acid charger on NiMH cells.

My Sanyo Eneloop wall-charger says it outputs 1.2v @ up to 2A per cell. My main smart charger says 1.8v @ 0.7A per cell. I presume something in that range would work.

I'm assuming you're charging in parallel. If you're charging all 8 cells in series for some reason, then perhaps 16v might work, though I still wouldn't risk it. Charging 8 cells in series might be tricky to get all fully charged without damage.

 

[Rosoku Chikara]

I have a unit with (8) rechargeable AA Eneloops that I could charge by plugging into it a charger with a 4.0mm x 1.7 DC plug...<snip>

Can you describe this "unit" or provide a photo? Are you saying you have a charger ("unit"), but don't have an AC -> DC adapter to run it? Sorry, but I don't think I understand your question.

 

[inetdog]

IMO the OP has a flashlight or other battery powered equipment which can charge the batteries internally if supplied with external DC. The question which can only be answered by the specs of the unit is how tight the voltage and current tolerances for that source are.
In particular, can a DC source such as a battery or battery charger be used.
The batteries will certainly be charged in whatever series or parallel configuration in which they are used.

Sent from my XT1080 using Tapatalk

 

[tpcollins]

This is for a Foxpro ecaller, I realize it's not about flashlights but this forum is the only one I trust when it comes to batteries and chargers. Here is the Foxpro charger with batteries - I'd like to get just their charger but they don't sell it without having to buy the batteries.

http://www.gofoxpro.com/site/products/accessories/8-aa-nimh-battery-kit

Here is a pic of the front where the plug goes into the ecaller, and the backside of it showing the batteries. There is an (8) AA pack with a 9 volt type connector that pops out so I can remove the batteries and charge them (4) at a time in my Sanyo charger. I'd prefer to just plug a charger in and charge all (8) at once.

 

[Rosoku Chikara]

...I'd like to get just their charger but they don't sell it without having to buy the batteries...<snip>

Well, I think I understand the problem now. Let me see if I got it right. You own a $400.00 electronic Coyote caller, complete with really cool looking remote control, but you don't want to spend another $24.95 for the recommended AC adapter because it comes with 8 "unknown brand" AA cells (claiming to be LSD) that you do not need?

Frankly, I think I would buy the $24.95 "recommended AC adapter" and sell the batteries on eBay!

I think the "bigger" question may be whether or not, simply plugging an AC adapter into such a set-up will safely (correctly) charge your Eneloops. (In other words, I wonder whether the "recommended AC adapter" would do a proper job.)

Let's see here... some one may need to help me with the math:

- Your Eneloops appear to be 1900 mAh. So, my MH-C9000 would charge them at 200 mA for 16 hrs. during a "Break-In" procedure, and that is considered "good."

- Can't tell from the picture exactly how all 8 of your cells are wired, but it looks likely that they may be "2 x 4" in series = 1.2v x 4 for a total 4.8v (This needs to be verified, they could be 1.2v if all in parallel, and 9.6v if all in series. And, they could also be a total of 2.4v if they were wired as, what I am calling, "4 x 2" in series.)

So, if my understanding of this stuff is correct (and it may well not be), I suppose that if you attached a 5v DC power source with only 200 mA "power" to your Eneloops (assuming they total 4.8v), they would likely charge safely enough in 16 hrs. (I caution you again that I could be giving you misinformation, but surely others will soon chime in to correct me.)

But, I simply do not understand how this would work without some kind of charging circuitry somewhere. What would restrict the power to only 200 mA, and how would it know to shut off? (I guess that in theory, if you had some way to shut it off, then you could even increase the "power" and shorten the charging time to some extent. Perhaps that's why the "recommended AC adapter" takes 8 hrs. Maybe that is a happy compromise.)

Others are going to have to help you with your problem. Good luck!

(I am greatly looking forward to what others have to say about this "interesting" matter.)

 

[tpcollins]

Well, I think I understand the problem now. Let me see if I got it right. You own a $400.00 electronic Coyote caller, complete with really cool looking remote control, but you don't want to spend another $24.95 for the recommended AC adapter because it comes with 8 "unknown brand" AA cells (claiming to be LSD) that you do not need?

I think I would buy the $24.95 "recommended AC adapter" and sell the batteries on eBay!

That's about right, the reason I could afford the ecaller was I didn't waste money on junk batteries! Plus I have 100% positive feedback on eBay and don't want someone to get mad at the crappy batteries and ding my rating . . .

 

[samgab]

You can't (well, shouldn't or oughtn't anyway) just use constant current/voltage to charge NiMH cells (such as an SLA battery charger).
To properly charge them you need a sequence of carefully calibrated cutoff parameters, such as negative delta of V, delta of temp over delta of time, max temp, max voltage, and max timer cutoff, at least.
So if I were you, I'd keep using the Sanyo charger you already own - charging them 4 at a time - and eventually when you can afford it, get a quality 8-individual-bay AA charger like the Maha MH-C801D, for instance.

 

[Etsu]

The recommended charger says it will take 10 hours to charge depleted batteries. So, I'm betting that it's just a dumb trickle charger, not a smart charger that looks for -dV or voltage or temperature.

Get the output specs of the charger, and make sure you charge your batteries the same way (same voltage and current). Verify that the recommended batteries have roughly the same capacity of your Eneloops. You can drop the current a bit and charge a bit longer, to reduce the risk of damaging your Eneloops.

Bah... way easier to just buy the recommended charger!

 

[tpcollins]

The recommended charger says it will take 10 hours to charge depleted batteries. So, I'm betting that it's just a dumb trickle charger, not a smart charger that looks for -dV or voltage or temperature.

Is that a bad thing or not?

I'll probably wind up buying their darn battery/charger pack. However, I can get a DC plug and make my own if I knew there was a better "wall charger" that I could attach the plug to and make work better.

 

[Rosoku Chikara]

Is that a bad thing or not?

I'll probably wind up buying their darn battery/charger pack. However, I can get a DC plug and make my own if I knew there was a better "wall charger" that I could attach the plug to and make work better.

I think the key point here is that whatever you do in the way of charging your Eneloops 8x at a time while still in their battery pack is going to be "less than ideal" as far as taking the best care of your Eneloop investment. (I am not saying that you are going to destroy them. I think trickle charging is fairly safe, and "relatively" easy on batteries.) The problem is that the only real alternative to "dumb" trickle charging is going to get to be pretty elaborate. So, if all you are going to do is trickle charge them anyway, why not "bite-the-bullet" and use the "recommended" AC charger. (Although, I truly can sympathize with your frustration.)

In my understanding of the matter, your only real solution would be something like a "Hobby Charger." Have you ever noticed how they work? They charge battery packs made up of multiple cells, but they charge each cell individually, without taking the battery pack apart (the cells are all soldered together, so they cannot be easily removed). In other words, there is one "Power" connector that connects to the vehicle (car, plane, etc.) when the battery pack is being used to power the electric motor. But, when it comes time for charging, they use another complex flat connector (like computer flat ribbon cable) that connects each cell individually to the charger for charging. All rechargeable cells need to be on their own separate charging circuit and charged individually in order to keep them in peak performance. And, this gets to be difficult to do, if your cells are all soldered together into a battery pack, but those guys have figured out how to do it.

In your case, I suggest you either go with the simple trickle charger (if you want convenience) at some "minor"(?) risk to the life of your Eneloops. Or, take them out each time, and charge them in a "real" charger. I think samgab is giving you some good advice:

<snip>... So if I were you, I'd keep using the Sanyo charger you already own - charging them 4 at a time - and eventually when you can afford it, get a quality 8-individual-bay AA charger like the Maha MH-C801D, for instance.

 

[ChrisGarrett]

Is that a bad thing or not?

I'll probably wind up buying their darn battery/charger pack. However, I can get a DC plug and make my own if I knew there was a better "wall charger" that I could attach the plug to and make work better.

It looks like it's a 12v system, since they sell SLA/AGM batteries on their site and their NiMH carriers, that they sell for cheap, are mostly 10 and 8 unit AA cradles.

Do the smart thing and call up the company and ask for the tech department and ask what their wall wart outputs in DC. I'm going to guess it's 12v at 1A!

Call them and know for sure.

Trust me though, if you go to Rat Shack, their wall warts aren't cheap. You might as well buy the FoxPro package, for what you'll pay at poop Shack.

Chris

 

[tpcollins]

UPDATE - I carry a spare set of (8) Eneloops in the ecaller's case. I just bought another identical (8) AA cell holder with the same 9 volt type hookup that matches the one in my unit. So that I don't mess up my unit or the batteries, I'll continue to charge them (4) at a time in my Eneloop (Sanyo) MQR06W charger and just swap battery packs whenever necessary.

Since you guys swindled me into buying all of the flashlights I have, I can at least glean some good information from you! Thanks.

 

[Rosoku Chikara]

UPDATE - I carry a spare set of (8) Eneloops in the ecaller's case. I just bought another identical (8) AA cell holder with the same 9 volt type hookup that matches the one in my unit. So that I don't mess up my unit or the batteries, I'll continue to charge them (4) at a time in my Eneloop (Sanyo) MQR06W charger and just swap battery packs whenever necessary.

Since you guys swindled me into buying all of the flashlights I have, I can at least glean some good information from you! Thanks.

You know something? I almost suggested that very thing in my last post, but I decided that you were probably "too cheap" to spring for a spare set of Eneloops!

Good Luck!