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HomeRC & Power✈️Aircraft🚁Helicoptere-Electric Battery-Charger-pSupply › New to electrics - charging Q
01-28-2012 03:57 AM  7 years ago
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Scott1115

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Greenwich, CT

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New to electrics - charging Q
How can I figure out how long it will take to charge my 5000mAh packs? Is there a formula for say a 20A and a 30A charge rate if the packs are @25%? I will be charging two 5000mAh packs in parallel with a 306b icharger and balance-board.
Compass 7HV, Trex 550E
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01-28-2012 04:06 AM  7 years ago
TheWoodCrafter

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Costa Mesa, Ca.

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The 20C and 30C refers to the discharge rate not the charge rate.

A charge rate of 1C for your battery is 5AMPS and will take about 1 hour if the pack is discharged to about 20%.

A 2C rate is 10AMPs and take about 1/2 hour.
3C = 15AMPS = about 20 minutes, etc.

You need to know what the manufacturer of your batteries says is the maximum charge rate.
I mark that on my packs.

What voltage is your battery?
That makes a difference in the power that is required.
Thanks, TheWoodCrafter
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01-28-2012 04:08 AM  7 years ago
eggmcmuffinplz

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Los Angeles, CA

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I think you mean 20C and 30C DISCHARGE RATE, not charge rate. And it all depends on how many amps you charge them at. For charging "1C" is equal to the battery's capacity, so in this case ONE batter would be charged at 5000mAh, or 5 amps, which would take an hour.
2C= 10Amps and would take around 30 minutes.

Parallel Adds them up, so you would now have a 10,000mAh battery, so charging at 10amps would take about an hour.

That charger is 1000 Watts, so you could charge 22.2v X 30 amps(the chargers max charge rate, which in this case is lower than the watt limit).

So it all depends on how fast you charge it. Basically divide the ratio of Capacity to charge rate by an hour.

thus ~1Hour/3C = around 20 minutes!
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01-28-2012 04:11 AM  7 years ago
Scott1115

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I meant 20A and 30A, not C, sorryCompass 7HV, Trex 550E
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01-28-2012 04:13 AM  7 years ago
eggmcmuffinplz

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20amps would be around half an hour, 30A about 20. But its not exactly linear.
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01-28-2012 04:28 AM  7 years ago
Scott1115

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Greenwich, CT

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max charge rate = 5C
18.5v
5s 5000mAh packs

So, if I understand this correctly (thanks Ed) the formula is:

(mAh to be put back into both batteries)/charge rate in Amps times 60 minutes.

Therefore, if the packs are discharged to 25%, each needs 3750 mAh put back in = 7500mAh = 7.50A.

Charging at 20A the formula would be: (7.50/20)*60 = 22.5 minutes
Charging at 30A the formula would be: (7.50/30)*60 = 15.0 minutes

I understand the time might be a bit more as it trickles down to balance at the end of the charge. But otherwise, do I have it right?
Compass 7HV, Trex 550E
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01-28-2012 04:40 AM  7 years ago
TheWoodCrafter

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Not exactly.

1C = 1 hour
2C = 1/2 Hour
3C = 1/3hr = 20min.
4C = 1/4 hour
5C = 1/5hr = 12 minutes.

It is that simple.
Thanks, TheWoodCrafter
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01-28-2012 06:05 AM  7 years ago
BladeStrikes

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Shelby TWP,Mi

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For my 700E,I run my two 5000mAh pack's down to 70% and only take's 28min's to fully charge both at 14A.
For my 12S 600E,I run two 3300mAh pack's down to 60%-65% and take's about 35min's to fully charge both at 14A.

Difference is the IR on the 3300mAh pack's is a little higher.
C = HRS/MIN's mean's nothing because it depends on the battery and health of it..
I have a 2S 1100mAh 6.6V LiFe RC pack that take's about 45min's to fully charge at 2C after 2 flight's.Damn thing take's longer to charge than my 6S pack's.
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01-28-2012 01:41 PM  7 years ago
Band1086

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Kennewick, Wa. USA

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1C = 1 hour
2C = 1/2 Hour
3C = 1/3hr = 20min.
4C = 1/4 hour
5C = 1/5hr = 12 minutes.
Those are pretty accurate numbers. Those numbers are based on healthy packs at 80% discharge though, as Lon said.
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01-28-2012 01:50 PM  7 years ago
Scott1115

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Greenwich, CT

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got it, thanksCompass 7HV, Trex 550E
RCRCC
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