Xmod RSX with 7.2v Li-Ion battery pack

pbmax · #1 12-25-2003, 07:34 PM

So I had a bunch of li-ion cells sitting around that I bought from a surplus place. What better to do with them than stick them in an xmod?

I made a 2-series pack that is roughly 7.2v and 1050mAh capacity. This is about the same as 6 NiCd / NiMH AAAs voltage-wise, but with much more capacity.

They do weigh a bit more than the stock 4 AAA pack, but wow does the xmod scream with 7.2v!

Seems that the electronics can handle it, but I'm not counting on the motor lasting too long (thank goodness they're pretty cheap). It was really hot after I got done running it for about 10 minutes earlier (high speed passes on my hardwood floor).

Here are some pics:

pbmax

Bad Company · #2 12-25-2003, 07:43 PM

Nice work! Does it weigh more than 6-AAA cells? Faster than a 6-AAA mod?

pbmax · #3 12-25-2003, 08:12 PM

Quote:

Originally posted by Bad Company
Nice work! Does it weigh more than 6-AAA cells? Faster than a 6-AAA mod?

I'd say it weighs a touch more than 6 NiMH AAA batteries, but that's w/o plastic holders and all. The pack consists of 2 AT&B 1050mAh 3.6v Li-Ion cells, a bit of shrink, some 18 gauge wire, a deans ultra connector, a bit of velcro, and now (not pictured above) some electrical tape over the top to help hold the batteries in place.

The speed should be about the same, since both a 6-AAA pack and this pack are rated at 7.2v. Actual fully charged voltage will be a bit higher for both.

You will get longer run times with these (at least I think so...I haven't measured current draw yet; too high and it'll prematurely drain the Li-Ions).

pbmax

pbmax · #4 12-25-2003, 09:17 PM

Unloaded current draw (wheels in the air) with the stage 1 motor is .7A, well within the 2C safe current draw. Under load this will be higher, but still probably within safe discharge rates.

Made another pack for my Skyline. I think I'll cut some of the electrical tape to allow better cooling on the first pack.

pbmax

R33E8 · #5 12-26-2003, 11:32 AM

Looks nice

. I have some nokia batteries that look thing enought to go inside. Never tired but I might soon.

#6 12-26-2003, 09:00 PM

i was gonna take some batteries out of my zip zaps an hook them up with an on/off switch and use them for quick boost in a drag race or somethin like that maybe take 4 of the zips zap cells
an put in adding an extra 4.8 vlts in one race they would be shot cuz there only 120mah but i think it would be worth it because of the weight ur saving

pbmax · #7 12-27-2003, 11:52 AM

Quote:

Originally posted by Lucid Dreams
i was gonna take some batteries out of my zip zaps an hook them up with an on/off switch and use them for quick boost in a drag race or somethin like that maybe take 4 of the zips zap cells
an put in adding an extra 4.8 vlts in one race they would be shot cuz there only 120mah but i think it would be worth it because of the weight ur saving

In order to get a "boost" from the little zipzap cells, you'd have to wire them in series with the other batteries. It would take two physical switches or some smart IC switching to do it.

Electrically this would be a bad idea because you'd be mixing discharge rates. You will end up destroying your batteries eventually.

I'd also be worried about feeding 9.6v to the electronics and motor.