KS18XL First charge one or 2 chargers?

[Spinner]

Hi everyone, 

Apologies if this has already been discussed. I received my 18XL today (yes!) and the battery was below 50%. I have a fast charger (ewheels) and the stock charger. The wheel has 2 ports. 

In order to maximise my batteries' lifespan: 

-Should I only use one charger for the very first charge? I set the fast charger on 2 AMP, not 4 and 5, but set the goal at 100%.

-Should I leave it charged for a while after it reaches 100%? 

Apologies again, I know nothing of Lithium-Ion batteries...

Thanks in advance

 

 

 

 

Edited August 24, 2020 by Spinner

[TomOnWheels]

For the 1st charge, I will use original charger delivered with the wheel. Slow charge is less stressful for batteries. It's probably a good idea to use it for 2 or 3 first charge cycles. For 1st charge you can go to 100% then it's a good idea to keep it between 20% and 80% most of the time. You also need to recharge it to 100% sometimes for cells balancing. I do it about once every 2 month... Remember also that discharging under 15% is not a good idea, and should be avoided as much as possible...

 

[Chriull]

16 hours ago, Spinner said:

Should I only use one charger for the very first charge? I set the fast charger on 2 AMP, not 4 and 5, but set the goal at 100%.

Should be of no concern. With the KS18XL's 21Ah battery your amperages (2-5) are about 0.1C to 0.25C charges - everything quite slow.

If the KS18XL uses the NCR18650GA cells the manufacturer recommended charging current for this 6p pack would be ~8.8A. (which already could be too much for the used connectors wirings).

42 minutes ago, TomOnWheels said:

You also need to recharge it to 100% sometimes for cells balancing. I do it about once every 2 month...

That's unfortionatelly a "quite unknown topic"- never found a real serious study or mass longterm test showing "balancing needs".

So i'd tend to recommend proper full charges - a unbalanced pack can render quickly unusable and even dangerous.

A properly charged pack staying balanced maybe degrades a bit faster, but stays usable and safe...

49 minutes ago, TomOnWheels said:

Remember also that discharging under 15% is not a good idea, and should be avoided as much as possible...

+1! I'd guess/have the gut feeling that emptying the batteries supports imbalances.

Especially with the high burdens the cells have to take with EUCs.

16 hours ago, Spinner said:

Should I leave it charged for a while after it reaches 100%? 

Li Ion cells are charged in two stages - first C(onstant) C(urrent), then C(onstant) V(oltage).

Around the end of the CC stage the wheel already shows 100%.

While the CV stage most of the balancing occurs. It's end is more or less shown by the charger led turning green. But about noone really knows at which current threshold the chargers are set and how well this fits the battery.

For NCR18650GA (as example again) 67mA are recommended/used in the spec sheet. So 67mA*6~0.4A would be a nice threshold for the green charging light to go on.

If this was not already too much information you can go on reading

Pand

 

[TomOnWheels]

@Chriullfor balancing cells, I guess it depends on BMS and how it manage cells... So indeed 100% charge should not be mandatory for cell balancing if BMS manage it properly... I just remember that on a electric scooter app showing per cell voltage, sometimes it was becoming unbalances and the way to fix it was to keep the battery charging for 2h after 100%.

[Chriull]

36 minutes ago, TomOnWheels said:

@Chriullfor balancing cells, I guess it depends on BMS and how it manage cells... So indeed 100% charge should not be mandatory for cell balancing if BMS manage it properly... I just remember that on a electric scooter app showing per cell voltage, sometimes it was becoming unbalances and the way to fix it was to keep the battery charging for 2h after 100%.

But that's how most and especially the KS18XL BMS works - they apply the balancing resistor at about 4.2V. They don't show single cell voltages. And they cut off charging once a cell reaches about 4.25V.

So i tend to recommend some 90% to 100% cycles for intensifying balancing - leaving the pack on the charger could just cut off and do nothing...(1)

Edit (1) not really true - the 4.25V cell gets discharged by the balancing resistor, charging resumes, cuts off again, cell gets a bit discharged, charging continous... Maybe...

And at least this one cell is kept in a very stressy voltage range.

 

Edited August 25, 2020 by Chriull

[Spinner]

On 8/25/2020 at 5:47 AM, Chriull said:

Should be of no concern. With the KS18XL's 21Ah battery your amperages (2-5) are about 0.1C to 0.25C charges - everything quite slow.

If the KS18XL uses the NCR18650GA cells the manufacturer recommended charging current for this 6p pack would be ~8.8A. (which already could be too much for the used connectors wirings).

That's unfortionatelly a "quite unknown topic"- never found a real serious study or mass longterm test showing "balancing needs".

So i'd tend to recommend proper full charges - a unbalanced pack can render quickly unusable and even dangerous.

A properly charged pack staying balanced maybe degrades a bit faster, but stays usable and safe...

+1! I'd guess/have the gut feeling that emptying the batteries supports imbalances.

Especially with the high burdens the cells have to take with EUCs.

Li Ion cells are charged in two stages - first C(onstant) C(urrent), then C(onstant) V(oltage).

Around the end of the CC stage the wheel already shows 100%.

While the CV stage most of the balancing occurs. It's end is more or less shown by the charger led turning green. But about noone really knows at which current threshold the chargers are set and how well this fits the battery.

For NCR18650GA (as example again) 67mA are recommended/used in the spec sheet. So 67mA*6~0.4A would be a nice threshold for the green charging light to go on.

If this was not already too much information you can go on reading

Pand

 

Thanks to everyone. I also asked my vendor and followed his advice (down below) since I was eager to charge my wheel and it was before you guys answered me. What do you think: 

"Speed of charge isn't really a concern related to the long-term health of your battery packs; they are comprised of so many cells that even splitting 5A of input current is well below the max charging specs for these. I would charge at 5A with the fast charger alone until the charger's LED flips to green. To maximize the lifespan of your packs we suggest you routinely charge to 80-90%, which can be done with the fast charger, as well. This is the single most important parameter that can extend the usable life of your packs."

 

 

[TomOnWheels]

7 hours ago, Spinner said:

Thanks to everyone. I also asked my vendor and followed his advice (down below) since I was eager to charge my wheel and it was before you guys answered me. What do you think: 

"Speed of charge isn't really a concern related to the long-term health of your battery packs; they are comprised of so many cells that even splitting 5A of input current is well below the max charging specs for these. I would charge at 5A with the fast charger alone until the charger's LED flips to green. To maximize the lifespan of your packs we suggest you routinely charge to 80-90%, which can be done with the fast charger, as well. This is the single most important parameter that can extend the usable life of your packs."

 

 

Yes it makes sens... The most important is not to overcharge and not let your batteries to discharge to low... As said, it's all question of how the BMS manage batteries, and I have no idea of its algorithm.