Advice for a neophyte

[Frog french]

I need advice. I should be able to recharge batteries quickly. I would prefer to use 18650 if not 21700.
Charge them with a 'classic' device (xtar over4 slim) (4.1 amps)
I had thought of
30Q in 18650 or 40T in 21700.
On the security side, since I am not a specialist can I use 18650 for this or is it too dangerous?
Thank you

I know that Mooch has been studying performance loss for Samsung 30Qs.
6.1 / 100 capacity loss after 50 cycles.

 

[amberwolf]

How fast do you have to charge your pack?

How large a pack do you have to have?

Those will tell you how large a charger you need.

But you have to check the specs for the cells you wish to use, and see what their max charging rate is, and under what conditions (temperature, etc).

Then see what your pack configuration is, and figure it'll be hotter in there both under discharge and charge, and derate their usage / charging rates to whatever the spec sheet chart says for those conditions. If it doesn't say, then you'd have to guesstimate, and doing it on the safe side (lower rate) is better.

If you charge a cell too fast, it heats it up too much, and what happens then depends on the cell quality / design, and the pack size / configuration, and the age of the cell and it's condition. If it's all good stuff, cna disspate the heat, etc., then it'll probably jsut prematurely age the cell. If it's not good stuff, can't get rid of heat so it builds up, etc., then there is a chance of fire.

So....you should check the numbers, first.


Some cell brands/types/chemistries can take a much higher charge rate than others, so look around at the various cell threads to see what others have found, for a bit easier work on that part.

IF you have the space and weight capability, LTO (lithium Titanate) probably has the highest safe charging rate...but possibly the lowest energy density.

 

[john61ct]

What is the use case? Need high-C discharge as well?

Charge them with a 'classic' device (xtar over4 slim) (4.1 amps)

To me, this implies no pack at all, just swapping individual cells in and out?

Why do you want to charge so fast, over 1C every time?

Buying more cells to allow slower charging will likely work out cheaper in the long run.

 

[e-beach]

Check the datasheets for your cell choices to see which suites your need.

 

[Frog french]

Normally the charging speed is not a problem. I can change to 1 amp. But I'm going hiking and I would have loved recharging very fast when I'm going through villages. The Q30s have a maximum charge of 4 amps, and a maximum allowed temperature of 50 degrees.
I do not know what temperature it goes up ...
if they lose their abilities it's not a problem. But I do not want them to explode ..
At what temperature do you think it can go up?
would you rather recommend using 40Ts that have a maximum charge of 6 amps.
I would prefer to take 18650 but good ..
And 40T can they also exploded at 4.1 amps of charge?

 

[Frog french]

for the discharge it will be low

 

[Frog french]

samsung 40T
standard charge 2 a
maximum load 6 a
maximum temperature charge 50


Samsung 30Q
standard load 1.4 a
maximum load 4a
maximum temperature charge 50

 

[e-beach]

samsung 40T
standard charge 2 a
maximum load 6 a
maximum temperature charge 50


Samsung 30Q
standard load 1.4 a
maximum load 4a
maximum temperature charge 50

Either of these would work with your 4 amp charger.

 

[john61ct]

Yes not dangerous long as they're healthy.

Just use a charger lets you scale down to 1-2A when not in a hurry.

 

[Frog french]

Thank you for your answers