## 22 cell charger can charge 20?

masagero   1 W

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### 22 cell charger can charge 20?

I ask for an expert opinion: I have a charger for 22 lion cells, can I charge 20 cells?

UKebiker   10 mW

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### Re: 22 cell charger can charge 20?

masagero wrote:I ask for an expert opinion: I have a charger for 22 lion cells, can I charge 20 cells?

What is nominal voltage of the pack ? And the charger is what voltage ) Just I can't see how 22 cells and 20 cells can be arranged to have the same nominal voltage (unless it's to make a 3.7 or 7.4v pack)

Which would make the answer - no

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eee291   10 kW

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### Re: 22 cell charger can charge 20?

If your Charger looks something like this then there is a good chance that you can change the output voltage to match your battery.

amberwolf   100 GW

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### Re: 22 cell charger can charge 20?

masagero wrote:
Dec 04 2018 8:05am
I ask for an expert opinion: I have a charger for 22 lion cells, can I charge 20 cells?
If you mean it's a 20s battery, and your charger is for 22s battery, and it's for a common 4.2v-fully-chargd cell chemistry, then that means it's mroe than 8 volts above what your battery would be fully charged at.

If your battery has no BMS, it's going to shorten it's life, or damage it, or even potentially start a fire depending on the condition of the battery and it's cells.

For 20s, that means each cell would be overcharged to 4.6v, instead of 4.2v, assuming it's perfectly balanced.

If it's not well-balanced, then the overcharge will be greater on some cells than others, especially if some of them have less capacity than others, and/or higher internal resistance. If it's bad enough, it could start a fire at worst; at best it would damage the cells and potentially make the battery unusable (at least unsafe to use).

If there is a BMS on the battery, and it is set to stop discharge once any cell reaches it's full voltage, then as long as teh BMS works correctly it will protect against the overcharge. But if the BMS fails or does not have that kind of protection, then the previous stuff still applies.

Alternately, you can check with the charger manufacturer to see if it is adjustable.

Or there are quite a few threads about opening up chargers and adjusting them; if you're willing to risk damaging it while experimenting, you can look them up and see if they help you adjust yours.

masagero   1 W

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### Re: 22 cell charger can charge 20?

This is the charger. I have smart bms programmable 300A
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amberwolf   100 GW

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### Re: 22 cell charger can charge 20?

The answers are still the same.

masagero   1 W

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### Re: 22 cell charger can charge 20?

So there will be no problem charging this charger after I have bms?

amberwolf   100 GW

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### Re: 22 cell charger can charge 20?

amberwolf wrote:
Dec 04 2018 11:49pm

If you mean it's a 20s battery, and your charger is for 22s battery, and it's for a common 4.2v-fully-chargd cell chemistry, then that means it's mroe than 8 volts above what your battery would be fully charged at.

If your battery has no BMS, it's going to shorten it's life, or damage it, or even potentially start a fire depending on the condition of the battery and it's cells.

For 20s, that means each cell would be overcharged to 4.6v, instead of 4.2v, assuming it's perfectly balanced.

If it's not well-balanced, then the overcharge will be greater on some cells than others, especially if some of them have less capacity than others, and/or higher internal resistance. If it's bad enough, it could start a fire at worst; at best it would damage the cells and potentially make the battery unusable (at least unsafe to use).

If there is a BMS on the battery, and it is set to stop discharge once any cell reaches it's full voltage, then as long as teh BMS works correctly it will protect against the overcharge. But if the BMS fails or does not have that kind of protection, then the previous stuff still applies.

Alternately, you can check with the charger manufacturer to see if it is adjustable.

Or there are quite a few threads about opening up chargers and adjusting them; if you're willing to risk damaging it while experimenting, you can look them up and see if they help you adjust yours.

eee291   10 kW

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### Re: 22 cell charger can charge 20?

masagero wrote:
Dec 19 2018 6:18am
So there will be no problem charging this charger after I have bms?
Once you have it open there should be a potentiometer near the DC wires that you can turn to adjust the voltage.

masagero   1 W

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### Re: 22 cell charger can charge 20?

I do not find a potentiometer

masagero   1 W

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### Re: 22 cell charger can charge 20?

eee291   10 kW

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### Re: 22 cell charger can charge 20?

You should hook up a voltmeter to the output wires (while powered on of course) and try turning the potentiometer closest to you.
You'll need a tiny flathead Screwdriver or something similar. I made one from some wood so I don't risk a short circuit if I miss.

Try to change it only by half a turn or so just in case it was the wrong one you can return it to its original position and try the next one.

In case you are wondering what each Potentiometer does, one is for Voltage the other for output Current and the last one is for cut-off Current.

Also, you can lift the top cover off to gain access to the Pots.

TommyCat   100 W

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### Re: 22 cell charger can charge 20?

Look closely on the circuit board and see how they are labeled. May give a good clue as which does what.
But most importantly read thru this thread first to have an idea of what your doing and how to do it...

See my completed Magic Pie V5 rear hub E-Bike build Here!

masagero   1 W

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### Re: 22 cell charger can charge 20?

Thanks for the advice, but nothing happens. I rotate them all three potentiometer, but nothing changed.BMS cut off the connection by passing over 58v. Think about whether to put some resistance? What do you say about it? I found a problem with one of the capacitors - I will change it.
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eee291   10 kW

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### Re: 22 cell charger can charge 20?

Do you not have a Multimeter?

I suggested changing one Pot at a time until you see the voltage change on a Multimeter.
Half a turn corresponds to about 0.2V increase or decrease, so it's not like you changed it by a significant amount.

You really need a Voltmeter connected on the output wires.

masagero   1 W

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### Re: 22 cell charger can charge 20?

as far as I know, there must be a load. How do I simulate a load?
Of course I have a multimeter

eee291   10 kW

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### Re: 22 cell charger can charge 20?

You don't need a load connected to it.

You could try 2 turns and see if there is a change in voltage.

999zip999   100 GW

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### Re: 22 cell charger can charge 20?

That caps cooked. Pop. Look at the board to see if you burn the traces. Bad idea to charge with a over voltage charger. It only takes one missteak and you can't go back. Danger.
You also blow a cap by turning to far up to fast.

masagero   1 W

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### Re: 22 cell charger can charge 20?

So ... I changed the capacitor and I measured the voltage and I found something strange the voltage was not constant, but we have progressed the charger without problem. With one of the potentiometers I was adjusting the voltage, but with the voltage changed the amperage. From the beginning, as the battery was charged giving with 12A after almost charging the battery dropped to 3A. I need to understand the other two potentiometers what they are changing and to fix the problem of voltage play.
https://youtu.be/b7DDnhmBUOU

TommyCat   100 W

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### Re: 22 cell charger can charge 20?

TommyCat wrote:
Dec 24 2018 4:08pm
But most importantly read thru this thread first to have an idea of what your doing and how to do it...

See my completed Magic Pie V5 rear hub E-Bike build Here!

eee291   10 kW

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### Re: 22 cell charger can charge 20?

It doesn't seem too strange.

It's just that at 84V the current is supposed to start dropping until it hits 0.1A or so.
So maybe you need to lower the voltage some more.
You usually don't have to mess with the other two Potentiometers.

masagero   1 W

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### Re: 22 cell charger can charge 20?

So after yesterday we have made great progress thanks to eee291 for which I thank him. It remains to balance the battery. For now everything works well. Special thanks to Eee291.
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eee291   10 kW

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