Redrocket6.0

Hello, i have a fairly new 3903 emaxx with a very recently installed Titan 775 with 19/68 gears.

I have been running nimh batteries but bought 2 a123 racing 2s1p packs and two a123 sonic chargers from a guy for a decent price. When i got them i check voltage and they were at around 7 volts each. Still waiting on my 3s1p packs, i wondered how it would run on the 2s1p packs hooked up like normal at 13.2 volts.

I ran it around the yard for a few min and took it in and charged them up.

Later i ran it again and got about 5-6 min run time. Checked voltages and one was around 6.4 and the other was low 5s. The lower one was out of balance badly, I was stumped.

I put them on the charger and let them charge again and balance and set over night. I checked voltage and it was around 7 on each.

I ran them hard, and got a good 6 min run time and checked voltage and it was 6.45 on one and 5.4 on the other. The low batt was on the bec side which powers the reciever and servos. I let them charge again and stay on for a while and voltage was 7.35 of each pack.

I am wondering of the bec circuit is draining that battery a lot faster then the other. I will try running them together tomorrow on the bec side and see if it happens again.

Redrocket6.0

Just check the batts and both are 7.15v

Redrocket6.0

I just ran the truck with the batteries together on bec side and when it got ran down I checked voltages. One pack was 6.3 and the other was 4.4, one cell was 3.1 and other was 1.3!!! ***. It is on the charger now. Been there for about an hour. Will let it keeP peaking and balancing.

Now what?

Goldenduff

If a lipo is showing 1.3v on a cell I would say its broken beyond repair.

Redrocket6.0

I just wonder if it's taking that one pack longer to balance out right? These batteries haven't got but maybe 5 charges on them

Redrocket6.0

Are you kidding me? Do you know anything about the a123
Cells?

bgosselin

While the BEC side will drain one pack faster, I am surprised there is that much difference. Usually A123 cells are near bulletproof. I wonder how many cycles they've seen and how they were (ab)used before you got them? Unless there is something else going on with the BEC, they seem to be acting like cells near the end of their life.

Goldenduff

I know a little about a123 cells but as I wrote and you quoted I mis read the original post and thought they were reading 1.3v on a lipo. Which would more than likely be broken. Also 1hr charge time would be quick for a LIPO but not for an a123

Redrocket6.0

Sorry for the confusion!

Each consecutive run has the same outcome. 5 min run time and it's flat, all cells but one are well over 3 volts. The one is less then 2. The seller said he would reimburse me.

Goldenduff

No worries, my apologies also.

Redrocket6.0

I bought two a123 racing 2s1p packs and two hypersonic chargers for 85 shipped. He is giving me 16 dollars back for the pack. I found a123 packs on eBay for 26 shipped for a 2s1P pack and i ordered two 3s1p packs from the same place for 62 shipped. Does anyone have experience with the eBay a123 packs

bgosselin

No experience personally, but you have to watch out for prices that are too good to be true because they could either be "B" stock, or counterfeit cells. In either case, they wouldn't handle the abuse that real "A" grade cells would.

If you want to build your own packs, individual cell prices range from ~$10 minimum (this price is usually a bulk price) to ~$16.50 per cell - just don't solder to the cells, but rather get the kind with the solder tabs (you don't want overheat the cells or cover the vents). Pack prices would be a bit higher than the per-cell price to account for assembly labor and such.

Redrocket6.0

These Show to be a123 racing packs, I guess I will find out!