Melting heat shrink and soften solder on A123 pack - RC-Monster Forums

snellemin · **Melting heat shrink and soften solder on A123 pack -** 09.20.2007, 09:15 AM

Hey guys,

The heat shrink is shrinking even more and the cells are showing. The solder on the balancing cables are softening. This is a 3s1p pack that goes in my FLM rustler. It has enough punch to pop wheelies all the way till the pack dumps. I started noticing this last sunday at the dragrace. I'm thinking I'm pulling more that the rated amp discharge rate of the batteries with the Mamba Max setup with the heavy rustler. The 3s2p setup should reduce my heating problems, correct? Or should go for a different motor?

crazyjr · 01:29 PM

If you got a 5700 or 7700, its possible. If i am right, they (the A123's) are only supposed to be rated for 60amps constant. I know i have gotten close to that on my truck but not sure if it was over or not. I am not running the A123 cells though

jhautz · 09:29 PM

In 1p config you will be stressing them. I found the packs got pretty hot in 1p on my LS10 also. I was running 4s1p but have since swithched to 3s2p and get almost identical performance, but much better run time. The voltage drop on the a123 cells in 1p was really huge. the 13.2v 4s pack was dropping down to 8.9v (2.23v/cell

)at the current peaks of 80amps and the packs got pretty hot. Hotter than I liked anyway. Thats only 35c and they are rated for 70C peaks so I think that the a123 specs are probably a little optomistic for real world use. 3s2p gives me almost exactly the same minimum voltage at the current peak, but that is on a 3 cell pack so the cells appear to be handleing the load much better.

2P should fix your issue.

snellemin · 09.20.2007, 04:59 PM

Ok cool. I'll get me another 3s pack. That is some major voltage drop with the 4s pack.

snellemin · 09.24.2007, 10:13 PM

I got my second 3s1p A123 pack today. Soldered up the plugs and ran it 3s2p. Man, my Rustler became a missile, even more so then with the 4s1p. Batteries are not as hot anymore.

What's_nitro? · 09.25.2007, 01:00 AM

Missiles are fun!!!

I'm glad you got that fixed. It would be a shame to be the first person to ignite an A123 pack.

snellemin · 09.25.2007, 01:54 PM

Here are some pics of how the 3s2p fits. Also the Jato driveshafts are holding up nicely. Just need to shrink some heatshrink and add the Park BEC.

What's_nitro? · 09.26.2007, 11:55 PM

Hey, nice servo-saver. Is it any better than the stock? Care to divulge where it was purchased?

snellemin · 09.27.2007, 09:28 AM

it's a shaved down dynamite servo saver. Works good for me and I'll purchase another one soon for my next build up. Was like 7 bucks at my LHS.

tashpop · 09.27.2007, 10:43 AM

i just picked up the same one for my emaxx last week. probably the same hobby shop. i asked for a kimbrough(sp), but they didn't have any and he said that one was better because of the metal insert in the center. i got it and so far its holding up. the spring is softer than my last kimbrough saver i had, so time will tell if this can hold up to my weight. i'm sure in you truck its a perfect match.