# Best ROP battery.. EVER?



## KevinL (Jun 5, 2007)

Before we start...THIS IS UNVERIFIED INFORMATION. I'm starting this thread to solicit discussion about a revolutionary new approach. If you are a newbie and/or uncomfortable with sitting on the bleeding edge of development (including cuts, 2nd degree burns and risk of loss of fingers and bits and pieces of you  ) please do not attempt to use any of this info. Stick with the tried, tested and proven ROP design and use NiMH cells. The NiMH ROPs, to the best of my knowledge, are the safest ROP we have built to date. 

Now on to the fun part :devil:

http://www.a123racing.com/html/starterkits.html

Apparently, in a nutshell, this revolutionary new cell delivers MASSIVE amounts of current on the order of 30C continuous and charges in as little as 15 minutes using their supplied charger. Holy cow. Absolutely holy cow. I can't believe I missed this while I was away. Moooooooooo.

Plus it is supposed to be a much safer chemistry with reduced possibility of going kaboom when you least expect it, it's supposed to be tolerant of abuse under various conditions that we may encounter in the field (or not).. I'll leave you to read A123Systems' safety pitch yourself. 

And it fits in a C-cell Mag, although I think we'll have to bump it up to 3C Mag for this. Our current ROP/LE lithium solution based on 18650 cells has issues, and namely these are:

2C++ discharge - we are operating at close to, if not the limit of what the cells are capable of. This was never a great idea to begin with but we the flashaholics had to do it in the name of more lumens 

Lithium ion safety - I have repeatedly highlighted the issues with lithium ion safety and handling to ROP users. Thankfully we have had no incidents to date, but wouldn't it be nice if we can come up with a better and safer design? 

Fast charge - something we cannot achieve with conventional Li-ion cells. A 6AA NiMH based ROP can be fast-charged in 15 minutes but that requires two Energizer 15-minute chargers or equivalents. And the cells get really hot. 

Heat - you know it's bad. nuff said. 

Voltage maintenance - apparently the A123 cells maintain a FLAT 3.3V discharge curve even under very heavy load. We will not be imposing a heavy load on them (relative to their maximums), maybe 3-4C at most. Yes, their rated voltage is lower, but remember conventional lithium ions sag VERY heavily under load. I have recorded losses of up to 2V on freshly charged cells under a mere 2A load. 8.4V - 2V = 6.4V.. that's about where we are with the A123's, right? Hence, brighter ROPs.

Plus this is a solution to the folks who are using inferior grade NiMH cells and complaining the ROPs don't put out enough light. I'll reiterate: I have ONLY ever recommended CBP1650s or equivalent high-rate NiMH capable of a nominal 5-10 AMP continuous discharge for NiMH based ROPs. I personally use Sanyo 3600mAH sub-Cs good for at least 20A. 

And less likelihood of popping bulbs due to lower initial voltage on fresh packs. 


The only tradeoff I can see is that the A123 cells currently have lower capacity and a much higher cost, however it would provide a very nice ROP pack. 

What do you guys think?


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## frosty (Jun 5, 2007)

I seem to recall reading about this a while back, but I could be wrong. I can't remember who posted the info, but I'm sure it was on CPF.


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## DrifT3R (Jun 5, 2007)

yeah, I read about it in a rc magazine about half a year ago. Pricey though.


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## JimmyM (Jun 5, 2007)

There are also the eOne-Moli cells that are good for massive current but have the standard 3.7V lithium ion voltage and can use common Li-Ion chargers. So a pair of those would be better still than the A123s
An ROP-Hi bulb shouldn't pop at 8.4V.


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## bfg9000 (Jun 5, 2007)

Yes, the A123 cells used in Dewalt 36v packs were first mentioned here in 2005 and have been available direct for a year. The Molicel used in the Milwaukee V28 has been around for two years so the very first examples are just now going out of warranty.


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## TigerhawkT3 (Jun 5, 2007)

I emailed A123 Systems around last week, asking if they had other cell sizes available or were planning on coming out with more sizes.

They said no.


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## HiltiHome (Jun 5, 2007)

Those cells have already been tested by silverfox..

scroll down half the page


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## Outdoors Fanatic (Jun 5, 2007)

Why not *LiPo* batteries? ( Lithium-Polymer )

http://www.batterieswholesale.com/lithium_battery.htm

12C continuous and voltages available from 7.4V up to 11.1V. More info on LiPo here: 

http://www.ultimatecharger.com/LiPo.html

This one looks amazing, check the specs on this bad boy:

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLXR6

Now I just need a good host for that battery...


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## TigerhawkT3 (Jun 5, 2007)

Outdoors Fanatic said:


> Why not *LiPo* batteries? ( Lithium-Polymer )
> ...


Probably because, unfortunately, LiPos are rectangular, and most flashlights are cylindrical.


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## Outdoors Fanatic (Jun 5, 2007)

TigerhawkT3 said:


> Probably because, unfortunately, LiPos are rectangular, and most flashlights are cylindrical.


I know that... But this is CPF we are talking about! Hardcore flashaholics always have a solution for anything... Maybe it's time for a new rectangular body?


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## KevinL (Jun 6, 2007)

Where can one get the Molicell?


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## bfg9000 (Jun 6, 2007)

Molicel IMR26700. They make a 2.4Ah ICR18650 version too.


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## Raoul_Duke (Jun 6, 2007)

I bought a bunch from this guy

http://www.bigerc.com/

He was very helpfulll, and instantly responsive to all my questions. V-Good service and shipping tho the UK. ( He did think I was a bit weird buying these to put in a flashlight thought  )

I bought the Emoli cells, as I wanted greater capacity than the A123's, and still good current providing capabilities, and the 70mm length worked well for the mods I had planned. I also Didn't fancy running unprotected Li-ions, and the emolis, and a 123's seemed like a safer alternative.

They say 3000mAh capacity, but I hear in practice you realy only see a good 2600mah.

Still they looked to perform very well at a 9A current draw.
http://www.wattflyer.com/forums/attachment.php?attachmentid=11910&d=1148246211

I was speaking with another CPF member a few months ago, and he found that two of these cells in a 3C mag blew the philips 5761 lamp, but the rop high was doing very well on these.

BTW the Emoli cells come with a cardbaord wrapper. Somtimes this does not fit in the C cell mags. 

You have to remove this, and re-wrap with thin electrcal tape to make them fit.

They seem like a very sturdy cell, with a stainless steel case.

I was told they can be charged just like a regular Li-ion cell, but need to find a nice simple charger that will charge at a max of 9A. I dont know what that will do to the cell but it does say charge at up to 3C 

I haven't used them yet, as I am still collecting parts for my lights, but hope to build all sorts of hotwire mags with them, and the smallest, but easiest should be the ROP, when I get a 3C


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## SilverFox (Jun 8, 2007)

Hello Kevin,

You can find test results up to 20 amps draw in this thread, near the bottom of the first post.

Tom


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## jimjones3630 (Jun 9, 2007)

Here are a bit cheaper and can order individual cells.

http://www.maxamps.com/products.php?cat=62


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## KevinL (Oct 21, 2007)

Raoul_Duke said:


> I bought a bunch from this guy
> 
> http://www.bigerc.com/
> 
> ...




Fantastic, this is the information I need. Steel case.. sweet 

Normal Li-ion chargers cut off at 4.2V - are you sure you can use normal chargers for the A123s? I don't seem to see a whole lot of special A123 chargers available on the market though. 

ROP high on an 'inherently safe' chemistry would be a dream.. the only concern I've always had about the ROP (apart from hot bulbs and flying glass dangers inherent to all hotwires) is the demands on the battery packs. I am personally surprised that so many people have gotten away with less than perfect batteries. I wish they would pay more attention but I guess I can only guide them, not make them.

Either way, I'm very interested in this A123 stuff. I have a 3C that could use an upgrade!


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## Raoul_Duke (Oct 21, 2007)

KevinL said:


> Fantastic, this is the information I need. Steel case.. sweet
> 
> Normal Li-ion chargers cut off at 4.2V - are you sure you can use normal chargers for the A123s? I don't seem to see a whole lot of special A123 chargers available on the market though.
> 
> ...



Emoli And A123 are different types of cells.

Emoli can handle a 9C draw ~ 45A

A123 even more.

Emoli 2600 the 2800 real mAh 9 stated 3000, but slightly less, I think on 4A draw ita 2800mah 

A123 2300mah.

A123 have the benifit of running flat, but need a special charger to get the best out of them, aluminuim case ( I think). around 66.5mm, but only 3.6V hot of the charger, 3.3 nominal.

emoli charge on a li-ion charger to 4.2V, 3.7V nominal. Stainless case, 70mm long.

why so interested in a stainless case?

Jeese that took you a while for a responce. 


You need some moli cells for the easiest switch to rop, using the chargers yuou already have, just dont discharge below 3V, you'll know when you hit 3v as outpu plummets drasticly, and you'll love it.


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## jimjones3630 (Oct 21, 2007)

For the record A123 cells are recommended to be charged with A123 program. Most major brand charges have A123 charging program or can update software with A123 program.

Now, that's over with. A123 are easy to charge using almost any charger or any program. Just charge to 3.6v per cell. Have usedr bench power supply. posted in anyother section is the link below for all you ever wanted to know about A123 charging.

http://www.rcgroups.com/forums/showthread.php?t=525664

A123 x2=6.6vnominal power up a 5761 without soft start. and bet good output with ROP HO, or LO
below are some of bulbs batt. configurations I've tried.

Emoli x2= 7.4vnominal add favorite NTC = 6.9vbulb 5761 is stunning.
Emolix2 1111 is stunning
Emolix2 without NTC suspect too much for ROP.
Emoli x3=12.6v powering 100w 64625, 62138, 64623, and 50w 64610 12v bulbs.
A123 x3= 9.9vnominal power up 1164, 1166, 1185, 64430, Tungsram 57580. 

jim


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## KevinL (Oct 22, 2007)

Great, thanks for the crash course 

I've been out of action for a long time, unfortunately, so it's taking me a while to get caught back up. 

Most brands I find do not explicitly state support for A123, which doesn't leave me confident. I'm not keen on destroying cells, no matter how 'safe' they claim the chemistry to be. I am aware some of you have the expertise and I've read the rcgroups thread (talk about giving one a headache, I gave up because the information is SO scattered), but I don't. 

Probably agreed the Emoli cells offer a compromise between safety and ease of using existing chargers. I might take my chances with the BatterySpace LiFePO4 chargers though.


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## Zot (Oct 22, 2007)

Check out what you can do with A123s here:

https://www.candlepowerforums.com/threads/178130


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