Replace 1 bad cell in a 7 cell NIMH pack?

[circusfreak]

Hi gang,
My buddy is new to electric and I have a nitro. I know a little about batteries, but not a ton. He recently had a pack start acting weird, and I determined that one of the cells went bad and is totally dead.
The pack is almost new (Venom 4200), and has maybe seen a half dozen runs. Can we just solder a new 4200 cell in there to bring it back from the dead? Or will there be a problem with cells not matching voltages or something. Please let me know if there is any way to save the pack.

Mucho Appreciato!
Rob

 

[RC Addict]

Yes, you can remove the bad cell and replace it with a like mAh Sub C rated at 1.2 volts.

 

[circusfreak]

Thanks! Do I need to do anything as far as balancing it to the voltage of the other cells? If so, how?

 

[RC Addict]

Naw, they won't be matched in a Venom Sport Pack anyway as far as cells go. If it were a more expensive matched pack then I would worry a bit. They will level themselves out. You might want to fully discharge the cells in the pack first though.

Just make sure to get a 4200 mAh cell!

 

[destrucktomaxx]

You might as well rebuild the entire pack and save yourself the hassle, while increasing performance.

 

[Lessen]

Venom batteries are junk. I wouldn't even waste my time, but that's just me.

 

[RC Addict]

I have had good luck with their Sport Packs. But that is just me.

 

[destrucktomaxx]

Venom has done me right, so I have no complaints. When my 3000 6 cell pack esploded in the revo, a supervisor not only offered to replace BOTH packs, but replace them with the 4200 7 cell packs, for free. So I got not beef. But you will see a helluva a difference if/after you rebuild the entire pack. Good luck bud.

 

[ohmygahitscoby]

I'm not sure if you could do this with a stick pack. Stick packs are weirdly put together. They aren't soldered on, and I'm not sure how they do it, but you can easily twist the tabs off the battery with some pliers. So you may have to replace that tab with a battery bar, but If you were to do that I would recommend doing it to all the cells. Just my opinion though. It's probably not worth it too. I agree that Venom makes some bad packs. I had one of their 1800 batteries, and it died out on me on maybe the 11 charge.

 

[Lessen]

I just tossed a couple Venom packs becaus they were junk. Well, it's no wonder they get so damn hot... the sticks are basically encased in a cardboard tube. Replaced 1 cell is going to be a PITA and not with the effort for a sub-par battery pack IMO.

Venom = Spotty reputation and overpriced (sometimes overpriced)

I say junk that pack and purchase a quality sport pack like Intellect. Generally more expensive, but the consistancy and predictability is right on the money. Intellect is the only type of Nimh cell I buy now.

 

[MotoGod]

I ordered some Tenergy 3800s maybe 2 months ago and have stellar luck with them thus far. I caught one of their weekly specials and paid like $26 for both batteries.....and I bought 16 AA Rechargeables while I was at it. Great prices.....seem like great batteries thus far as well. No issues whatsoever.

 

[circusfreak]

Thanks for all the info guys!
One thing : This is a 7 cell pack, and luckily the end cell (that is oriented perpendicular to the others is the one that is out, so getting to it to replace would not be a problem.
Also, I agree these packs are not good, but we are just trying to get him going for a little while until he buys some lipos, so that's why I suggested this is a stopgap to keep running until he gets those. The thing that sucks is that he runs a e-revo, and 3 of his packs are working well, but that still only gives him 1 run.

Thanks again for the info!