24Ah 48V 13S5P Samsung INR21700 50E battery. What amp charger should I use?

[Harrdy]

So Ive been checking out multiple chargers and I am currently using a 4amp charger. I have been reading a lot and some people say charge at 1amp, some at 8 amps.
I was thinking of buying an adjustable charger but unsure if I need one.

I saw a post where is stated:

"C is a factor for expressing the current flow rate for a battery based on its capacity:
For a 10Ah battery 1C = 1 x 10 =10A
For a 20Ah battery 1C = 1 x 20 = 20A
For a 5Ah battery 2C = 2 x 5 =10A
For a 34Ah battery 0.2C = 0.2 x 34 = 6.8A."

From here:

Test of Samsung INR21700-50E 5000mAh (Cyan)

"

• Standard discharge capacity: 4900mAh (0.2C discharge)
• Rated discharge capacity: 4753mAh (1C discharge)
• Charge voltage: 4.2V
• Nominal voltage: 3.6V
• Charging method: CC-CV
• Maximum charge current: 4900mA
• Maximum continuous discharge current: 9800mA
• Maximum pulse discharge current: 14700mA
• Discharge cut-off voltage: 2.5V
• Cycle life: 500 cycles to 3802mAh (80%)
• Operating temperature: Charge: 0°C ~ 45°C, discharge: -20°C ~ 60°C
• Storage temperature: 1 month: -20°C ~ 60°C, 3 months: -20°C ~ 45°C, 1 year: -20°C ~ 23°C

So what is the C rating? 0.2 x 24 = 4.8 amps. (is this correct?)
Would a lower amperage be better for charging?

 

[saneagle]

So Ive been checking out multiple chargers and I am currently using a 4amp charger. I have been reading a lot and some people say charge at 1amp, some at 8 amps.
I was thinking of buying an adjustable charger but unsure if I need one.

I saw a post where is stated:

"C is a factor for expressing the current flow rate for a battery based on its capacity:
For a 10Ah battery 1C = 1 x 10 =10A
For a 20Ah battery 1C = 1 x 20 = 20A
For a 5Ah battery 2C = 2 x 5 =10A
For a 34Ah battery 0.2C = 0.2 x 34 = 6.8A."

From here:

Test of Samsung INR21700-50E 5000mAh (Cyan)

"

• Standard discharge capacity: 4900mAh (0.2C discharge)
• Rated discharge capacity: 4753mAh (1C discharge)
• Charge voltage: 4.2V
• Nominal voltage: 3.6V
• Charging method: CC-CV
• Maximum charge current: 4900mA
• Maximum continuous discharge current: 9800mA
• Maximum pulse discharge current: 14700mA
• Discharge cut-off voltage: 2.5V
• Cycle life: 500 cycles to 3802mAh (80%)
• Operating temperature: Charge: 0°C ~ 45°C, discharge: -20°C ~ 60°C
• Storage temperature: 1 month: -20°C ~ 60°C, 3 months: -20°C ~ 45°C, 1 year: -20°C ~ 23°C

So what is the C rating? 0.2 x 24 = 4.8 amps. (is this correct?)
Would a lower amperage be better for charging?

0.2c is the recommended charging rate, so for 24Ah, it's 4.8A. The maximum charge rate for the cells is 1C, so 24A, but when you charge at high current, the cells don't have such a long life, and they can become hot, which is dangerous if the battery hasn't been designed to let the heat out. Also, you need to know the maximum charge current that your BMS allows, and maybe leave a bit of a safety margin.

There no exact answer to your question apart from the limit in your BMS and some batteries include a charge fuse. It's just a case of the lower the charge rate, the safer it is and the longer your battery lives, but the longer it takes. Always charge an ebike battery to 100% to avoid balance issues.

 

[Harrdy]

Thank you.
The reason I wanted an adjustable charger was to lower the charge rate to 1amp or lower as its better for the battery? Is that right or it's not really worth it buying a new charger?
( I only have a 4 amp charger and may buy a 1A to 5A so I can lower the charge)

Also reading form multiple posts it says to never charge is at 100%, only to 80% but I think thats only if its not going to be used? (Ive edited this post)

(I also have a bluetooth BMS but I cant change any charging parameters there)

 

[saneagle]

Thank you.
The reason I wanted an adjustable charger was to lower the charge rate to 1amp or lower as its better for the battery? Is that right or it's not really worth it buying a new charger?
( I only have a 4 amp charger and may buy a 1A to 5A so I can lower the charge)

Also reading form multiple posts it says to never charge is at 100%, only to 80% but I think thats only if its not going to be used? (Ive edited this post)

(I also have a bluetooth BMS but I cant change any charging parameters there)

I can't say for certain because I've never tested it. I would have said that a 4A or 5A charger would be fine. You can use a 2A one if you already have one. I can't see any advantage in using a variable one, nor charging at 1A.

 

[Harrdy]

Got it. I need to buy a backup one anyway (home/work) so I'll get a 2amp one for home. Thanks again.