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HomeAircraftHelicopterHelicopter Main Discussion › charge 4000mah and 3300mah in parallel
11-15-2014 01:58 PM  4 years agoPost 1
tomtek

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I want to charge my 4000 and 3300lipos together in parallel. If I want to charge at a 1C rate would it be to add the two together which would be 7300mah and a 1C charge rate would be 7.3 amps. Is that correct?

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11-15-2014 02:52 PM  4 years agoPost 2
Al Austria

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Sacramento, CA - USA

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7.3A is correct.

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11-16-2014 04:51 AM  4 years agoPost 3
Aaron29

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Question is, with different size packs, will the electrons know where to go?

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11-16-2014 06:08 AM  4 years agoPost 4
EEngineer

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Aaron, when charging in parallel...as long as the "S" in the same..the charger sees just one big pack...the combo of the total mAH...

But, you knew that....

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11-16-2014 06:10 AM  4 years agoPost 5
EEngineer

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Reminds me of an old joke...

How many sperms does it take to fertilize and egg?

Thousands...because none will stop to ask for directions.

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11-16-2014 11:52 AM  4 years agoPost 6
Retired2011

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So who are they going to ask for directions?

A woman?

I don't think so

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11-16-2014 12:36 PM  4 years agoPost 7
raholek

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Parallel charging
4000 + 3300 together?

www.redstickrc.net ama#: 968515

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11-17-2014 03:52 AM  4 years agoPost 8
Aaron29

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So if you put a 2000 mah in parallel with a 5000 mah all would be well?

I think the MAH difference becomes an issue at some point, no?

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11-17-2014 04:26 AM  4 years agoPost 9
EEngineer

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Yes, the smaller pack will be well charged...and the larger not so well..

Can it be done...yes

Do I do that...no

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11-17-2014 04:50 AM  4 years agoPost 10
Aaron29

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When you say "well charged" do you mean puffing well charged or just nice and topped off?

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11-17-2014 04:58 AM  4 years agoPost 11
EEngineer

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What I meant was that the charger used will "see"....one big "4000+3300=7300 mAh" "X" S Lipo, with no knowledge that one is 4000 mAh and the other 3300 mAh...according to the OP.

So the charger will react accordingly...

And the 4000 pack will be slightly "undercharged" while the 3300 will be slightly "overcharged" when the charger stops.

FWIW

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11-17-2014 05:01 AM  4 years agoPost 12
EEngineer

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It's highly recommended that packs to be charged are of similar capacity.

Batteries are expensive...why beat them up more than necessary?

FWIW

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11-17-2014 10:59 AM  4 years agoPost 13
Retired2011

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+1
I never charge dissimilar packs in parallel...not worth it to me.

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11-17-2014 11:01 AM  4 years agoPost 14
raholek

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Zachary, Louisiana

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Parallel
And... Best if packs are in a similar state of discharge. Also check that balance plugs read each pack. Without them reading voltage you can have a bad day. ***i would advise against parallel charging different size packs all together. Get a two channel charger.

www.redstickrc.net ama#: 968515

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11-17-2014 11:23 AM  4 years agoPost 15
Richardmid1

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Leeds, England

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You can parallel charge different capacity packs no problem. Packs charge by voltage and as all cells are the same voltage they will reach 4.2v/cell at the same time.

60% of the time, it works every time!

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11-17-2014 12:36 PM  4 years agoPost 16
G-Limo

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.....

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11-17-2014 06:10 PM  4 years agoPost 17
dyuen888

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raholek

Parallel
And... Best if packs are in a similar state of discharge.
+1 ... here is an extreme case.. you have a fully discharge 1000mah pack and a 5000mah pack that 90% cahrged... Once you plug the two packs in parallel. The 5000mah is going to start an uncontrolled discharge into 1000mah pack - the bigger the difference in the discharge state the higher the discharge.

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11-17-2014 06:10 PM  4 years agoPost 18
dyuen888

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raholek

Parallel
And... Best if packs are in a similar state of discharge.
+1 ... here is an extreme case.. you have a fully discharge 1000mah pack and a 5000mah pack that 90% charged... Once you plug the two packs in parallel. The 5000mah is going to start an uncontrolled discharge into 1000mah pack - the bigger the difference in the discharge state the higher the discharge.

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11-17-2014 06:29 PM  4 years agoPost 19
Richardmid1

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In the above case the voltage difference between the two packs is probably only 1v/cell. The larger pack will only discharge into the smaller pack enough to raise it's cell voltage by 1v or less as the larger packs voltage will decrease at the same time.

60% of the time, it works every time!

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11-17-2014 06:33 PM  4 years agoPost 20
Aaron29

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It shouldn't be 1V per cell. More like 0.5. A depleted nominal voltage is 3.7V per cell. End charge state is 4.2V per cell.

But this 0.5V difference is still not good. Watch your charger at the beginning of a normal, controlled charge, it isn't pushing very high volts. It only reaches 4.2V per cell charging rate at the end stages of the charge. If that charger tried to push 4.2V from the get go, the push would exceed the charge C rate of the battery. So it doesn't do that. It controls constant Amps until 4.2V is reached late in the charge cycle, then it goes constant V for the final top off.

Plugging a full battery into a depleted battery could exceed the charging amp rate of the depleted battery. The balance wires might not take the amps.

Point is, it's uncontrolled.

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HomeAircraftHelicopterHelicopter Main Discussion › charge 4000mah and 3300mah in parallel
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