I need help choosing a lipo battery
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I need help choosing a lipo battery
Right now I have a ecx circuit with a viper rc coper head in it right now I am using a 7cell 4200mah Nimh battery but later I will get a 3s lipo for speed runs and I was wondering what should the c rating be?
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At a glance, I can't find the wattage that motor wants (or amps), so let's assume you need a battery that can supply the 100 amps your ESC can handle.
In that case, C rating x amp-hours gives you amps. (so yes, capacity of the pack comes into play).
For example, a 4000 mAh pack is 4 amp hours. If that 4000 mAh pack had a 25 c rating, then it's 25 x 4 = 100 amps the battery can supply (in theory).
So for you, make sure that your C rating is high enough so that when you multiply by the capacity, you are well over 100. Maybe shoot for 140+ or so to be safe? I know no one wants to over spend, but you don't want your battery working all that hard.
Does that help?
Hopefully others will chime in.
In that case, C rating x amp-hours gives you amps. (so yes, capacity of the pack comes into play).
For example, a 4000 mAh pack is 4 amp hours. If that 4000 mAh pack had a 25 c rating, then it's 25 x 4 = 100 amps the battery can supply (in theory).
So for you, make sure that your C rating is high enough so that when you multiply by the capacity, you are well over 100. Maybe shoot for 140+ or so to be safe? I know no one wants to over spend, but you don't want your battery working all that hard.
Does that help?
Hopefully others will chime in.
Last edited by Eman77; 08-20-2013 at 06:09 AM.
#9
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I understand your math, Eman, but I think the word "theory" is the salient point. Theory is good, experience is better. In my experience, 20-25C rated packs tend to get hot, even in my "little" 35A EZrun system. Now I suppose it's possible that Gens Ace over-rates their batteries, but I have found that 20C or even 30C 2S LiPos get well over 110F, where 40C or 50C packs stay below 95F. Based on that, I would suggest the OP get higher C-rated packs for his 100A ESC.
FOXY, what do you say?
FOXY, what do you say?
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I understand your math, Eman, but I think the word "theory" is the salient point. Theory is good, experience is better. In my experience, 20-25C rated packs tend to get hot, even in my "little" 35A EZrun system. Now I suppose it's possible that Gens Ace over-rates their batteries, but I have found that 20C or even 30C 2S LiPos get well over 110F, where 40C or 50C packs stay below 95F. Based on that, I would suggest the OP get higher C-rated packs for his 100A ESC.
FOXY, what do you say?
FOXY, what do you say?
I guess maybe the motto is "overkill is better". You don't need a 90C pack or anything, but a 35c 3300 pack seems a bit low. I'm sorry I don't have a solid answer to the question, but maybe we could suggest something where the math puts him at 160+ amps? (example, a 40C 4000 mAh pack)?
Fortuantely, there are plenty of mid-level C rated packs that are inexpensive to choose from. That's why it doesn't make sense to try and save $5 and get a much lesser pack, for instance.
#15
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Cool mate. And it'll probably be fine. All I'm sayin' is be aware of it. Pick up an Infra-red thermometer (Duratrax has one for $25) and monitor battery, motor and ESC temps. I've had that Castle system. Monitor temps. Try an keep the battery under 100 (measured after a hard run), the motor under 180 (IMO under 170 for safety-margin) and the ESC under 125 or so. If your motor can be opened, first be careful not to loose any shims on the rotor, but inspect it once in a while, blow it out with canned air and clean and lube the rotor bearings.
#19
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Yeah, I know, it gets bloody hot here too. Generally, I don't run on days where it's over 100. Hell, I don't even go outside!!
3S is going to be a BIG jump from 7-cell NiMh!!! Hope you have a good bumper on the thing and you've got some wide open space.
Shoot, you're in Texas! It's all ABOUT wide open space! So have fun!
3S is going to be a BIG jump from 7-cell NiMh!!! Hope you have a good bumper on the thing and you've got some wide open space.
Shoot, you're in Texas! It's all ABOUT wide open space! So have fun!
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