A123 cells questions - RC-Monster Forums

joeling · **A123 cells questions -** 09.09.2009, 10:28 PM

I'm interested in these. I want something safe & fool proof for my 'fun' runabout the house type rcs like the tamiya TLT-1 or equivalent. My questions :

1) Is there a difference betwwen LiFe & LiFePo4 (A123) cells specifically with regard to the chraging regime. I.e. can use charger for LiFe to charge A123 type of cells ?

2) LVC - How inherently safe is the A123 type of cells? They are similar to Lipo in a sense that they have a minimum cutoff voltage ? What happens if this voltage is breached ?

I know that a lot of questions have been answered when these were intoduced a while back but never bothered to study carefully.

I don't want lipo in my 'fun' rcs as my kids also get to drive them & the esc does not have any LVC built in. Getting an external LVC is kind of a hassle & I want the vehicles to be safer. Nimh will do but I want something that can hold charge a little better & not having to charge it up before fun time can start.

Regards,
Joe Ling

fastbaja5b · 09.10.2009, 04:00 AM

Life and A123 charge the same.

I run Life packs in a stock Traxxas Slash, when the car stops, I recharge the pack at 10 amps, no LVC and never been an issue.

It;s pretty much idiot proof, and ideal for getting the younguns into RC.

09.10.2009, 04:15 AM

Hi,

1. No. LiFe or A123 is short name of LiFePo4. So if there is LiFe marking on charger it is good to go.

2. LVC - no need for LVC on LiFe. LiFe cells have low voltage limit (2.0V for cell) but... When you use for example 2S2P configuration pack you get 4600mAh 6,6V voltage battery (I am using 2x of such packs in my Savage Flux HP). So when pack is depleted it has ~4-4,5V... You can guess that your car will not run as with full voltage... 4-5V is really not much for normal 540 motor (for brushless also). It began to struggle, and stopping from time to time... So if you immediately stop using car and disconnect battery - you are on a safe side.
But you always can be even safer and buy LiFe Low Voltage Meter from ebay for about 5$ and connect it to balance wires - it will start beeping when you get to the limit...
When building or buying packs, get packs with balancing wires and do balance charge at least first ten times. After that if packs balance and behave normally (there is no big difference in cells V) it is safe to quick charge (manufacturer recommends do not exceed 10A).

Good luck.

PS: A123 are very safe - even if you will go below 2V for cell (way below), they do not explode, only leak.

PPS: only drawback of A123 is they are big and heavy - you can not fit them everywhere...

othello · 09.10.2009, 06:12 AM

@audriusv
Can you point me to the A123/LiFe low voltage alarm on ebay you mentioned? Only found 2-4s lipo low voltage alarms which are not suitable due to their 3-3.3V low voltage setting. A123 low voltage setting should be @2-2.3V.

07:13 AM

sorry, now can not find cheap alarm... it is seems that I get mine from some HK shop... what I find now

http://www.chargery.com/cellMonitor.asp

But I think that it is solution...