Batteries...

[ozdave]

I bought some 4400 tq batteries from max amps about 6 months ago and had only put 1 or 2 runs through then previously. Well today i toasted one of them! temps by the time i got home (about 5 minutes from when i stopped running) was 132 degrees C! The other battery was fine and about 55 degrees.

Its been a while since i've taken out the emaxx so took her out for a bash today. Its pretty cool outside about 8 degress C. so didnt think id have any problems with heat, it was running a bit hot (both batts and controller) last time i took it for a run.

After about 15 minutes it started to die so i bought it in. When i took the body off i could see one of the batts just melting and expanding! i pretty quickly took it outside and got a door between me and it!

my setup is a bk9920 and 540c 8xl. Now im pretty sure its a result of cheap batteries and brushless drawing too much current, but is the solution here to go to lipo to be able to keep up with the current draw?

thoughts?

[BrianG]

While lipos would certainly be able to better keep up with the current demands, NiMH cells should hold up ok but their voltage will just drop more under load. I run 14 GP3300 cells on my Revo (9xl) and have tons of runs on them.

That is such a difference in temp that I would look at what is specific to that pack. Is it shorting on something on the chassis? Is the plastic sheathing on two or more cells worn so the "cans" touch (which would short out a cell)?

[neweuser]

I would say either loose cell, or loose connection. I had one batt heat up like that before at the bash. Found out my solder job on one cell came apart.

[ozdave]

yeah that makes more sense guys. i've taken a closer look, i pulled it to bits and all the batteries still have their connections in pretty good condition, but there is a small spot on one of the batteries that looks like it could have been rubbing on the motor mount so that might be the cause. i'll have to stick something in there to stop it happening again.

now i have to get a new battery!

[jhautz]

If the lipo was cold when you ran it, the colder temp can have an effect on its ability to deliver the amps you are asking for and posibly stress the cells. Running a cold lipo pack very hard is not the best stiuation for them. When I go out and its cold outside I put one of those chemical hand warmer sacks into my lipo storage bag to keep everything up to a decent temp.

Not sure if this was a problem here, but it could have played into your situation.

[neweuser]

I think he is using NiMh? But still same concept...batteries like it warm.

[glassdoctor]

Does sound to me like a shorted battery.... I've had it happen too.

[hoober]

Sounds to me like one battery (the hot one) didn't charge up all way.