Why the flying fu(k is my battery pack melting?!
 

Here's the deal. I've got a dual 150 mah battery setup with a 3.5 motor in a bit and made a stand alone charger for it. Just a standard pack that holds 4 double A batteries that I got from Radio Shack. Every time I hook it up to my bit to charge it gets really really REALLY hot and the metal spring that holds in the (-) side of the AA battery melts through the plastic. I dunno if I wired it wrong or what but can somebody please help cuz I can't even run my bit anymore!:mad: BTW- I think I wired the batteries right but correct me if I'm wrong. I went from the (+) end of one battery to the (-) end of the other battery.:confused: :confused: :confused:

either you are charging too long or you wired wrong

I just edited the title of this thread...Keep it clean skater.

Well I know I'm not charging too long cuz doesn't a 2.4 volt bit take like 2 to 4 minutes to fully charge. Anyways It starts melting after about a minute at most. BTW, sorry bout the title Namuna.:D Anyone else know what's wrong?

it depends on your charger. 4aas going straight to it is quite a bit of power. my 4aa charger has a timing capacitor.
if it runs after you charge for a minute its not the wiring. id guess you are overcharging.

So let's get this straight - you've got 6 volts (unregulated) dumping into a 1.2 volt cell, and your wondering why things are getting hot?

Just use the charger that's built in the transmitter until you've done a little more research on charging NiCd or NiMh batteries.

I use a 1/10 scale RC battery charger to charge my Bits at a lower charge rate than the built in charger. It takes longer to charge, but the cars run over 15 minutes, and the batteries will last longer.

Arceeguy- Alls I know is that I've read at least 5 different instructions on how to modify a bit to use dual 150's, and all of them have said to use a battery pack that holds 4 AA batteries. And I'm not sure if this matters or if it's correct, but isn't it dumping into the eqivalent of a 2.4 volt cell? I'm no electrician here you know lol. BTW, supposedly you can't get enough power outta a standard transmitter charger to charge up the dual 150's.

i think you are overcharging.

As I understand it, the controller regulates the voltage normally, and can charge dual cells if you rewire the charger past the regulator and timing circuit...

http://tinyrc.com/qfm/racing/img/conversion.jpg
(From Quest for Madness)

My standalone charges dual cells fine with only 2 AAs in the charger, and I believe the theory is to charge at about the same voltage as the rating of the batteries, which is why the stock charger is stepped down. The heat, I imagine, is caused by overvolting the batteries. Try charging with just 2 batteries and see if that works...

I somehow failed to see the "dual cell" in your original post. Anyway, the "if 2AA batteries charge 1 cell, then 4AA batteries can charge 2 cell" thinking is not valid. Anyone else doing this must be melting battery holders too!

If you want to do a "professional" job, check out page 14 of this pdf document from National Semiconductor. Look at the "simple 1A current regulator" circuit. Using this simple circuit will allow you to charge a 1-3 cell Bit at 1 amp regulated charge rate. It won't shut off automatically, so you'll still have to time it - but it will regulate current and prevent melted battery holders! I think all of the parts are available from RS for less than 3 bucks! (You can use a LM317 regulator instead of a LM117 regulator)