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Old Dec 10, 2010, 02:01 PM
Go Packers!
Lambertville, Mi
Joined Apr 2010
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Need help on figuring size of chrager

How do I figure out what size charger I need? I want to charge 2 3S 2200mah batteries at the same time in say 30 min. Can someone explain how to figure this? Sorry Im just not good at this electrical stuff.
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Old Dec 10, 2010, 02:31 PM
TJin(Guy + Tech)
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United States, NM, Socorro
Joined Jun 2008
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Quote:
Originally Posted by wgregww View Post
How do I figure out what size charger I need? I want to charge 2 3S 2200mah batteries at the same time in say 30 min. Can someone explain how to figure this? Sorry Im just not good at this electrical stuff.
I recommend you do some reading.
https://sites.google.com/site/tjingu...arging-how-tos
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Old Jan 01, 2011, 06:04 PM
Ex AmA mEMBEr
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United States, CA, San Bernardino
Joined Feb 2010
745 Posts
finally

my hats' off to you tjinguy. it's refreshing to see someone steered in the right direction without a lot of chest beating and overly technical answers that some poor bright eyed shmuck won't understand anyway. i wish every category here had a first page of pertinent info that you had to read before venturing inside that area. it would make me feel better about asking questions. don't get me wrong, this is the best site going, it just gets tiresome reading through miles of stuff and not quite finding what you need. the 2 search features are great but not perfect due to pilot induced oscillation. it's nice finding a link with all that related info in one spot.

uh oh, was i ranting or what?
excuse me i've got a link to read
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Old Jan 01, 2011, 11:16 PM
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Melbourne, Australia
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Quote:
Originally Posted by wgregww View Post
How do I figure out what size charger I need? I want to charge 2 3S 2200mah batteries at the same time in say 30 min. Can someone explain how to figure this? Sorry Im just not good at this electrical stuff.
"1C" charge rate will charge a battery in approximately one hour.
The 1C rate is equal to the capacity in mAh divide by 1000. Hence for a 2200mAh battery it would be 2200/1000 = 2.2A

To charge in half that time you double the rate, in the example: 2 x 2.2 = 4.4A

To charge two 3S 2200 batteries at the same time you can connect them in series to make a 6S 2200 or in parallel to make a 3S 4400. Parallel charging is safer, easier and often faster.

Assuming you parallel the packs, the 1C rate becomes 4400/1000 = 4.4A.
To charge in 30min you have to charge at about 2C = 2 x 4.4 = 8.8A

Charging a 3S lipo at 8.8A requires approx 3 x 4.2 x 8.8 = 110W

So to charge two 3S 2200 lipo packs in parallel at 2C you need a lipo charger rated for at least: 3S, 8.8A, 110W.

In today's market there are many, many 6S, 5A/50W chargers but they won't do the job. There are also plenty of 6S, 10A/200W chargers which would certainly be suitable.

Don't forget that once you select a charger you need to ensure you have a suitable power supply. Since chargers are typically around 80% efficient, you need 25% more DC power input than the full rated output. Hence a 200W charger needs a 250W power supply to deliver its full output. Also note that high power chargers usually cannot deliver their full rated output from a 12V supply, needing 15V, 18V, 24V or some even 28V.

A good combination is the iCharger P350 (15V/23A, 350W) power supply and either the 106B+ (6S, 10A/250W) or better, the 206B (6S, 20A/300W).
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Old Jan 02, 2011, 01:32 AM
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AWESOME !!!!!!!!! reply kgfly.
very informative and you even suggested potential chargers, excellent excellent reply.
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Old Jan 02, 2011, 03:55 PM
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Melbourne, Australia
Joined May 2006
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Thanks Meebo,

If you want an Aussie vendor for iCharges I can recommend Aiden at arkrc.com.au
Otherwise both progressiverc.com and epbuddy.com are highly regarded US vendors that ship to Oz and provide great backup.
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Old Jan 02, 2011, 06:41 PM
Go Packers!
Lambertville, Mi
Joined Apr 2010
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Quote:
Originally Posted by kgfly View Post
"1C" charge rate will charge a battery in approximately one hour.
The 1C rate is equal to the capacity in mAh divide by 1000. Hence for a 2200mAh battery it would be 2200/1000 = 2.2A

To charge in half that time you double the rate, in the example: 2 x 2.2 = 4.4A

To charge two 3S 2200 batteries at the same time you can connect them in series to make a 6S 2200 or in parallel to make a 3S 4400. Parallel charging is safer, easier and often faster.

Assuming you parallel the packs, the 1C rate becomes 4400/1000 = 4.4A.
To charge in 30min you have to charge at about 2C = 2 x 4.4 = 8.8A

Charging a 3S lipo at 8.8A requires approx 3 x 4.2 x 8.8 = 110W

So to charge two 3S 2200 lipo packs in parallel at 2C you need a lipo charger rated for at least: 3S, 8.8A, 110W.

In today's market there are many, many 6S, 5A/50W chargers but they won't do the job. There are also plenty of 6S, 10A/200W chargers which would certainly be suitable.

Don't forget that once you select a charger you need to ensure you have a suitable power supply. Since chargers are typically around 80% efficient, you need 25% more DC power input than the full rated output. Hence a 200W charger needs a 250W power supply to deliver its full output. Also note that high power chargers usually cannot deliver their full rated output from a 12V supply, needing 15V, 18V, 24V or some even 28V.

A good combination is the iCharger P350 (15V/23A, 350W) power supply and either the 106B+ (6S, 10A/250W) or better, the 206B (6S, 20A/300W).
I can say I bought the P350 and 206b and love them both. Excellent customer service at Progressive as well.
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Old Jun 21, 2012, 08:07 AM
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United States, IL, Chicago
Joined May 2012
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Quote:
Originally Posted by kgfly View Post
Charging a 3S lipo at 8.8A requires approx 3 x 4.2 x 8.8 = 110W
Awesome reference guide, even if it was started a while ago.

I was wondering if you can help me figure out the math in the above equation.
3 = S rating?
4.2= ?
8.8= The above listed Amps result

I am trying to figure this out for a 3300 mAh 3S1P 11.1v 25c lipo battery, where I would need to charge two at the same time, and also checking for a charge rate of 1C vs 2C.
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Old Jun 21, 2012, 08:29 AM
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Joined Mar 2002
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4.2 = volts needed to fully charge one LiPo cell. Your other guesses are correct.

For your specific example:
1C: 3.3A x 3 x 4.2V = 41.6W per battery, or 83.2W for two of them
2C: Twice that, of course, ie. 166.4W total.

Of course it won't hurt anything if your charger/psu is capable of supplying more. They will be operating at lesser stress level and you just might need to do bigger packs in the future.
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Old Jun 21, 2012, 08:34 AM
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United States, MN
Joined Feb 2011
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The ProgressiveRC calc seriously needs to be a sticky somewhere:
http://www.progressiverc.com/chargingdemand

Easiest way to do it, no math required for the lazy people!
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Old Jun 21, 2012, 10:23 AM
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Good link ,,,,,I'm the lazy guy
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Old Jun 22, 2012, 02:16 AM
Registered User
United States, IL, Chicago
Joined May 2012
26 Posts
You all are fantastic! Thank you for clearing this up.

I was originally going to get a quad charger, then realized I could do with a duo charger, but then figured a decent iCharger would do the trick for me just starting out (still haven't purchased my first plane or anything else yet, but have been hitting the simulators and researching for several weeks). ProgressiveRC seems to have their act together on the iChargers and I will be looking to purchase from them.

Great support in the forums, I appreciate it!
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Old Sep 04, 2012, 12:45 AM
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AWESOME AWESOME AWESOME SITE! Thanks a million sir!
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Old Sep 04, 2012, 07:40 AM
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Barbados
Joined Jan 2011
1,890 Posts
Just remember that you cannot charge 2cell batteries and 3 cell batteries at the same time on a para board you will need a dual output charger or two chargers in order to do it similtaneously,the batteries would be different voltages therefore incompatible to charge in paralell format, if using a single charger you will have to do two charging cycles.I have not purchased from Progressive but like you have only heard good things,EP Buddy i have and all i can say is he's also a very very good vendor.
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