RCU Forums - Lipo question

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Can someone refresh my memory on how to find the amp draw with the mah and c rating for lopo batterys.

RE: Lipo question

Battery Capacity in Ah multiplied by the C rating.

Example: 2000mAh LiPo @ 20C

2000mAh = 2Ah
2Ah * 20 = 40

The LiPo would be able to provide 40A constant. What I do is then multiply this value by 80-85%, to be on the safe side. This would be about 35A of continuous discharge.

Ryan

RE: Lipo question

So mah stands for milliamp hour and there's 1000mah in 1 ah?

RE: Lipo question

here is my question, i have both 3700 mah 25 c 2s packs and 3200 mah 20 c packs, should i be seeing such a drastic difference between the two? When i had my jet boat set up i would run the 3700's just fine but then the 3200s i would always cut short because of one thing or another. I always charged them though even if i only used em for like 2 min, could that have affected them? When i checked the voltage on them after today's run it read 7.6 where as the 3700's read 6.8 but it seemed like the 3700s had more left at the end when i stopped it then the 3200s. I hooked up a brushed motor to one of the 3200s and when i put a load on the motor the voltage would drop quite a bit, about a full volt. Are my cells damaged somehow? anyway to re boost them or something of that sort? Also the 3200's seem to struggle lasting 5 min but the 3700's easily last 10 min plus. anybody have any ideas? oh yeah here is the link http://www.youtube.com/watch?v=Rvbd_DrABZM you should be able to get to the 4 videos i took today and see the one i took when i was using the 3200's that are in question. Posted this in the super tune you sv thread but no response so i'm trying again

RE: Lipo question

Quote:

ORIGINAL: asupervee72

here is my question, i have both 3700 mah 25 c 2s packs and 3200 mah 20 c packs, should i be seeing such a drastic difference between the two? When i had my jet boat set up i would run the 3700's just fine but then the 3200s i would always cut short because of one thing or another. I always charged them though even if i only used em for like 2 min, could that have affected them? When i checked the voltage on them after today's run it read 7.6 where as the 3700's read 6.8 but it seemed like the 3700s had more left at the end when i stopped it then the 3200s. I hooked up a brushed motor to one of the 3200s and when i put a load on the motor the voltage would drop quite a bit, about a full volt. Are my cells damaged somehow? anyway to re boost them or something of that sort? Also the 3200's seem to struggle lasting 5 min but the 3700's easily last 10 min plus. anybody have any ideas? oh yeah here is the link http://www.youtube.com/watch?v=Rvbd_DrABZM you should be able to get to the 4 videos i took today and see the one i took when i was using the 3200's that are in question. Posted this in the super tune you sv thread but no response so i'm trying again

It sounds like you are answering your own question..
3700mah 25c packs = 92.5amps cont.
3200mah 20c packs = 64amps cont.
that's almost 30amps difference

RE: Lipo question

i know there is a big amperage difference but i was thinking since the esc is only rated for 45 amps and it barely even gets warm both sets of batteries would supply enough amps to get pretty much the same speed but just a little shorter run time with the 3200s but they seem like they die in less then half the time of the 3700's. guess that's what i get for buying more expensive cells in usa, the cheap china ones out perform them for less coin

RE: Lipo question

the esc does not limit what the motor gets. [:-]
the motor will pull how many amps it needs at anytime, the esc supplies the volts and amps the motor needs from the batteries..

RE: Lipo question

After a run, how many mAh are you replacing the 3200 pack vs the 3700 pack

Ryan

RE: Lipo question

unfortunately i could not tell you that because the three dollar multimeter i got from harbor freight only reads up to 2000 mah and my charger is very basic and does not tell me any of that

RE: Lipo question

Quote:

ORIGINAL: asupervee72

unfortunately i could not tell you that because the three dollar multimeter i got from harbor freight only reads up to 2000 mah and my charger is very basic and does not tell me any of that

What SR10 was trying to say was you will only get 2/3 the amperage (power) from the smaller battery - if the motor asks for it. And it will (also) run down sooner - maybe a lot sooner, depending on the motor draw and age of the battery.