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› Charging Formula Confusion????
05-13-2011 08:40 PM  7 years agoPost 1
Noobyflyer

rrVeteran

Clearwater, FL

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Hey All,

I recently decided to step up and order a quality charger to charge my packs. I have had too many inconsistent charges and balance issues with my 50watt ACDC charger.

I charge 6S 4200 mah packs for my 700--2 to a flight, and 6S 3000 mah packs for my 500.

My question is the charge rating. Turnigy says that I can go 2C. I can only charge at 2amps on the 50watter (It won't let me choose 5amps) and that is 2/3 C. My confusion is that the Icharger 1010b is 300watts and the power supply I ordered is 350w. It says that I can charge up to 10amps which is a little over 3C. The charger is 6 times the wattage of my Passport right?

So, I should charge the lipos at 6amps (3000mah packs) and 8amps (4200mah packs) with the new charger to yield 2C???? and that would mean that since it takes me 45 minutes to charge a 3000mah pack from 80% down on the Passport, the icharger would bring the same pack up in around 20 minutes????

3000mah divided by 1000= 1amp per 1C and 4200mah divided by 1000-4.2amp per 1C

......and what does the wattage of a charger have to do with the equation??? Why does the 50watt charger not allow me to select the 5amp setting on it???? I have had it for a year but never understood that????

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05-13-2011 08:51 PM  7 years agoPost 2
TJinGuy

rrProfessor

Socorro, NM - USA

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Watts = Volts * Amps

so rearranged it looks like

Amps = Watts / Volts

so now to find the max charge rate for 6s packs.

Amps = 50W / 25.2V = 1.98A

or when using the 1010B+

Amps = 300W / 25.2V = 11.9A

but the charger is limited to 10A, so 10A is the max.

- Chris

Team New Mexico
TJinTech

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05-13-2011 08:59 PM  7 years agoPost 3
Noobyflyer

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Clearwater, FL

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Man I am slow on this.

So the bottom formula is the max amperage that the charger can supply. Where does mah's factor into that in determining what c to charge at if the max rated C is 2C on my packs.

4200 mah 6S and 3000 mah 6S????

and thank you for the help.

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05-13-2011 09:38 PM  7 years agoPost 4
TJinGuy

rrProfessor

Socorro, NM - USA

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C is equal to the size of the pack in mAh divided by 1000 and dropping the time, the h. So

3000mAh 6s pack has a C=3A
3000mAh 2s pack has a C=3A
4200mAh 4s pack has a C=4.2A

1C charge rate is 1*C, so if C=3A, the 1C charge rate is 3A. The 2C charge rate would be 2*C or 2*3A = 6A.

1C charging takes about an hour. 2C takes almost half that but usually a little longer than half at 35ish minutes. 3C drops it to like 25min. 4C to maybe 20min. All those numbers depend on many factors including the charger, settings, pack quality and condition, discharge level, etc.

- Chris

Team New Mexico
TJinTech

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05-13-2011 09:52 PM  7 years agoPost 5
Rafael23cc

rrKey Veteran

Junction City, KS

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Noobyflyer
......since it takes me 45 minutes to charge a 3000mah pack from 80% down on the Passport, the icharger would bring the same pack up in around 20 minutes???? .....
How can your charger, working at 2/3C charge a pack in 45 minutes? Are you balance charging or are you just pumping electrons into the battery? My batteries take a little longer than 1 hour at 1C when balance charging. You might be doing somehting that is not correct. (Or I might be doing somehting that is not correct )

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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05-14-2011 01:12 AM  7 years agoPost 6
Noobyflyer

rrVeteran

Clearwater, FL

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Now I get it. Thank you TJ!!

I really don't know why it only takes 45 minutes, sometimes less. That is kind of what is so confusing to me. It is a 50 Watt AC/DC charger. I have no choice but to balance while charging. It only lets me charge at 2amps for a 6S pack. So, if 3amps would be 1 C, then that would be 2/3rd C. I fly the batteries in a Trex 500 for 6:30 minutes and show an end voltage of 3.82-3.84 per cell.

It only takes about 40-45 minutes to bring the pack back up to full--or atleast it beeps and says its full. I check with a volt tester and usually get variances of 4.18-4.2 accross. So I am assuming the charge is kind of crappy and that's why I am banking on the new charger to do a better job.....and I will have the ability to discharge if the weather is crap on the planned day to fly. I am kind of sick of keeping a running clock in my head of "How long have the packs been charged.....crud, now I HAVE to fly."

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