New A123 cells - thoughts on charging options

[matrixshaman]

I just got some B&D VPX7 packs and scavanged the A123 systems new 18650's out of them. I currently don't have a Hyperion charger or some of the new high end chargers made to charge these that seem common with the RC users. I don't really plan on spending that kind of money either since I have no need to fast charge them like they do. I do have a huge regulated Power supply with metering that has fully adjustable voltage and current that I know will work fine for charging these BUT it's in a place that is temporarily almost impossible for me to get to. So until I can find it or another unit I've got that is also a good contender for charging these I thought why not use the Ultrafire charger that is 3.6/3.0 volt switchable? It's made for either the regular 3.6 volt Li-Ions or it will do the LiFePO4 cells that are 3.0 volt and will charge them to 3.6 volts where it cuts off IIRC. And it just happens that 3.6 volt is where the A123 3.3 volts cells need to be cutoff at based on the A123 specs I've found. I know this charger would be slow but I'm in no hurry. I'm just wondering if I've missed anything about why this couldn't work as I have not seen any mention of it.

 

[VidPro]

from everything i read on the RC sites researching them , 3.6 would be fine, it can go over a little bit and it doesnt kill them
they are basically discharged at 2.5V and arent supposed to be discharged below 2V.
they claim you can also discharge to as low as 1V and not Kill it, but you know how that goes, follow the specs or it will start to decline.
EX: i can discharge a li-ion to 1 Volt too, once and recharge it quickly and it might not croak immediatly, but it sure aint good for it, cause every one that goes way down like that, a few times becomes junk.

 

[matrixshaman]

Thanks VidPro - I'm trying to wade through all the info right now on the RC groups. I did just finish a charge on one of the A123 18650's with the Ultrafire WF-138 charger on 3.0 volt setting and it finished with green light - voltage with no load at that point was 3.55 volts. I got these primarily for the WE Boxer but I think I'll be exploring other uses too. The seem ideal for some high power hotwires.

 

[SilverFox]

Hello Matrixshaman,

I have been running some tests on these cells charging them with a normal Li-Ion charger (Schulze... ). So far, so good, but I only have around 50 cycles on them...

I charged some in my WE M300 charger, and it charged them to 4.6 volts. That was too high. They went open circuit at that high a voltage.

Tom

 

[Sub_Umbra]

Hi SilverFox-

Which model Schulze do you use?

 

[cat]

http://www.rcgroups.com/forums/showthread.php?t=795122#post8844692

DIY circuit, parts list. Use between LiPo charger and A123 pack.

The device will turn on as soon as a battery pack is connected as long as the pack voltage is under the cut out voltage. When the pack voltage reaches the set cut out voltage, the pack is disconnected from the charger. If the pack voltage drops far enough.

Here's the main thread. (Really, it'll save you a lot of wading. Which can be ..quite tedious.)
http://www.rcgroups.com/forums/showthread.php?t=747911


There is also the A123 charging adapter (A123 Daptoer):
http://www.infinity-hobby.com/main//images/batteries/A123Dapoter.pdf
...cuts off at 3.7V

 

[SilverFox]

Hello Sub Umbra,

I have the isl 6-330d/RS.

Tom

 

[matrixshaman]

CAT - thanks for the links - I've been wading through a lot over there. I did find this inexpensive smart charger with a cutoff of 3.8 volt. This is what user 'everydayflyer' uses as a cutoff in charging his A123's. He seems to be a big proponent of them and has hundreds of charges on his cells. This smart charger can charge 1 cell but there are 3 other models that will do 2, 3 or 4 cells to the same level. This is the One cell for about $20
So far though I'm fine with using my Ultrafire at the 3.0 volt setting which seems to top out at 3.55 volts. I'm going to try doing some comparison tests with the Boxer using these and the regular rechargeable 18650's as time allows.

 

[jimjones3630]

Matrixshaman,

Thanks for the sale link. Folks have asked me and now will have a inexpensive resource for them.

CAT - thanks for the links - I've been wading through a lot over there. I did find this inexpensive smart charger with a cutoff of 3.8 volt. This is what user 'everydayflyer' uses as a cutoff in charging his A123's. He seems to be a big proponent of them and has hundreds of charges on his cells. This smart charger can charge 1 cell but there are 3 other models that will do 2, 3 or 4 cells to the same level. This is the One cell for about $20
So far though I'm fine with using my Ultrafire at the 3.0 volt setting which seems to top out at 3.55 volts. I'm going to try doing some comparison tests with the Boxer using these and the regular rechargeable 18650's as time allows.

 

[LuxLuthor]

On a related topic, I posted some useful information in this thread. My preference is now the Emoli cells for our amp applications. I'll post pix there later this week of Makita pack cells.

 

[Riscy]

Can anyone tell me how fast to recharge A123 18650 cell? or anyone measured the charger period.

I have 12 cell in series connection of 18650M1, for the fast charge rate, I calculated I would need 44V and 5A current, which mean I need 220W power from the charger, correct?

With 220W for such a limited space, will cause concern about self-heating effects.

How long I need to run this 220W before the cell is fully charged?

While this cell is much safer, do I need BMS for each small cell? I can put in temperature sensor if needed.

All comment welcomed.....

R.