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HelicopterMain Discussion › LiPO Basic Charging questions
08-07-2011 01:57 PM  6 years agoPost 1
ssmith512

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Indianapolis, IN USA

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OK, I am a nitro junkie, but am seriously thinking about getting at least one electric bird to play around with (max 6S so maybe a 500), but I am little confused about LiPO charging and could use a simple primer, especially if I decide I like eletric and get into the larger birds (700 size and 12S setups)

My main confusion stems from knowing what is a safe "charge rate" for a LiPO (whether it be a 2S 2500mAh RX pack OR a 6S 4500mAh flight pack.) For the sake of this discussion, let's say I have a power supply that is capable of an output of 15V @ 700W. Let's say my charger is capable of 30A and 1000W.

I want to charge my no name brand 6S 4500mAh pack. V x A = W says my charging setup will allow me to pump 27.7A into my 6S 4500mAh pack. As I understand it, that is a charge rate of 6.15C (27.7/4.5), is that safe??

Now I want to charge my no namebrand 2S 2500mAh RX pack. My charging setup will allow me to pump 83A into the battery, BUT the charger can only handle 30A, so we will only charge the RX pack at 30A. Can I really safely charge my 2S 2500mAh RX pack at 30A (assuming I wanted to)?? How do I know what the maximum "charge rate" of a liPO is? I know 1C is safe, but is 12C safe?? (assume a no name brand LiPO that doesnt advertise a "max" charge rate)

Please help me understand what the max amp charge rate I can pump into LiPo's is (no mater the cell count or capacity of the liPO).

Thanks in advance!

Steve

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08-07-2011 02:39 PM  6 years agoPost 2
inkspot1967

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Cranston Ri

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you have to go by what the battery company says is the highest c rate is.

a 5000mah pack 1c is 5amp
a 5000mah pack 2c is 10amp
a 5000mah pack 3c is 15amp
a 5000mah pack 4c is 20amp
a 5000mah pack 5c is 25amps

a 2500mah pack 1c is 2.5amps
a 2500mah pack 2c is 5amps
a 2500mah pack 3c is 7.5amps
a 2500mah pack 4c is 10amps
a 2500mah pack 5c is 12.5amps

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08-07-2011 05:49 PM  6 years agoPost 3
AirWolfRC

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Charge away . . .
Keep close tabs on the battery temperature
Back off if it gets uncomfortably hot

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08-07-2011 06:03 PM  6 years agoPost 4
fenderstrat

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Aston,Pa

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as I have posted before this site is a MUST read for anyone serious about elec rc helis.everything you need to know about batts,chargers,charging in series/parallel ect

https://sites.google.com/site/tjing...arging-how-tos/

edit.there is also a how to on building a 24V power supply on the cheap

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08-07-2011 06:27 PM  6 years agoPost 5
fenderstrat

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Aston,Pa

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How do I know what the maximum "charge rate" of a liPO is? I know 1C is safe, but is 12C safe?? (assume a no name brand LiPO that doesnt advertise a "max" charge rate)

Please help me understand what the max amp charge rate I can pump into LiPo's is (no mater the cell count or capacity of the liPO).
unless you know a max charge rate given by the manufacturer,you MUST assume a 1C charge rate for safety's sake.

Now,having said that, since the days that 1C was the norm,charger technology has advanced significantly.meaning all modern lipo chargers have dedicated lipo charging firmware with most having integrated balancers.(as opposed to the "old" days where guys were charging with chargers not designed for lipo and using seperate balancers).

If you do not know the actual spec for the battery and you feel comfortable doing so,charge at 2C and watch the battery during the charge.if there are no issues or puffing ect.You should be ok.

Most of the horror stories and "old" rules come from the days when a 18-20C discharge lipo was considered high discharge.With todays insane discharge rates,and chargers,2-3C charging is nothing to worry about

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08-07-2011 06:28 PM  6 years agoPost 6
AirWolfRC

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I like that 80% rule. Now if some manufacturer would just come up with an on board module that monitors mah consumption (the same circuit that monitors mah discharge on your bench) and lets the RX telemeter it back to the TX, you're all set.

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08-07-2011 06:39 PM  6 years agoPost 7
fenderstrat

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Aston,Pa

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I like that 80% rule. Now if some manufacturer would just come up with an on board module that monitors mah consumptio and lets the RX telemeter it back to the TX, you're all set.
I think we are going to see this in the VERY near future

EDIT: I believe units like the EAGLETREE data logger can track MAH used(can any owners confirm this?),telemetry is here now(Futaba is supposed to be releasing its first tx with telemetry this year, with upgrades for existing models.The DX8 is out now)

All we need is someone to put it all together in one small package

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08-08-2011 02:09 PM  6 years agoPost 8
ssmith512

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Indianapolis, IN USA

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Thanks for the help friends! Much clearer understanding now.

Steve

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