View Full Version : battery amp draw ?

09-30-2007, 12:32 PM
i am trying to understand amp draw with the set up i am going to build this winter its a cat 9xl hex 120 if i was running a 438 on 10c it would be pulling 33 amps. the same set up on 12c would pull 44 amps the later would be to hot for batteries if they were3500 10c or even 4200.is this correct ? batteries are the only thing i have not destroyed yet.the warmest i have ever got them was on the charger.sorry so long trying to be thorough.

09-30-2007, 12:43 PM
Those packs can not be run unless 2 are in parallel. If they are getting hot on the charger you may have it set up incorrectly. What charger are you using, what brand packs? As I understand it..it goes like this. 3500mah to 3.5x10c=35 amps constant. If you parallel a set you should be able to safley draw @ least 50amps from the set. I would not push them any harder.

09-30-2007, 01:21 PM
the batteries are not getting hot on charger was using as example to say i have never really pushed batterys. was never looking for high amps as i have been running600's on 10 cell . so am i correct in thinking 10s 2p should handle this with room to spare. because the amp draw does not increase on this set because it running on10s with the amp out put increasing.i am charging at 1.8 amps on a smart charger with peak detect.thanks for reply.

09-30-2007, 01:32 PM
You are talking about Nimh's when you say s10-2p correct? s10 lipos would be almost 40 volts....lol. I thought you where on lipo.

09-30-2007, 04:43 PM
yeah nimh i have 14 cells and was going to pick up some more with same rating but didn't want to if they cant handle setup.

09-30-2007, 05:29 PM
Heat. The way I understand it is heat is the enemy. You can draw 100amps from the C cells if you want....but they may heat up to damaging temps in only 1 minute. So you would be killing them running them harder.

The way I do it is run the packs, and when I know (from checking) they are starting to get warm....I bring them in. they are almost always about dead anyway. In my experiance most of the heat comes from the last bit of run time people try to get out of there cells.

just don't run them dead, make sure they do not get to hot and you should be all set.

09-30-2007, 07:15 PM
My setups pull 60-70 amps continuous from my nimh cells. To keep the temps under control I can only run about 2/3 of their capacity before bringing the boat in. If I go beyond that (way before the boat begins to slow down) the cells get REALLY hot. You can pull more amps from these cells, but as FEChris stated, your runtime will decrease.

09-30-2007, 09:54 PM
so would you say you 65%of capacity to stay safe.do you peel hatch tape every 30 seconds to feel heat. i never run cells to dumping .

10-01-2007, 05:32 PM
Naaa man...I check it every minute or so....when I am testing new batteries that is. But I mean heck, they are ment to be run, so run them. They are gonna ware out...sooner or later..... Just find out where the sweet spot is. They will last longer if you don't juice'em down all the way.

I try to keep nimh cells in good shape, but you can only do so much. Just keep checking the temps every minute or so till you get used to it, then you'll know....it's not a bad idea to have a timer with you either. Then when the buzzer goes off you know to bring it in.

again, all this IMO.

10-01-2007, 05:55 PM
i gut ya. i have seen and read about batteries blowing up. i would cry my eyes out if that happened.lol.thanks for the info.

10-02-2007, 02:30 AM
hi there,
I have a 8XL pulling 70amp constant on a cheap 80amp BL ESC, under 12x4000mAh Nimh cheap cell, battery is getting pretty warm, but run time does not exceed 3 minutes, plus I always charge them at 1/10C.
For sure this setup pulls a bit too much for the max amp battery rating, having 2 pack in parallel would be better but heavier, the really best would be Lipo's that are lighter at higher amp rate, it's a question of budget!!!