General questions about charging

Batteries and Chargers Chargers
1

So I studied the manual of the MC3000 and since I understood what most of these parameters do, some general questions about charging Li-Ions came up for me.

1. What is the “standard charge rate” the manufacturers advertise? Charging above or below this has negative effects? It’s the highest rate which is still healthy for the cell? It’s the maximum charge rate before excessive wear?
2. What’s the better way to have a cell with 4.15V resting voltage after charging? 4.20V target Volt and 150mA termination current or like 4.16V target Volt and a very low termination current of like 30-50mA?
3. Are there diminishing returns when using a high charging current in the CC phase? If I use 3A charging current, then my CV phase is obviously going to be longer than if I would use 0.5A charging current. Is there a way to find a sweetspot for this or will more current in the CC phase always be faster?
4. What’s the best way to charge cells if all I care about is longevity? (charging current/ termination current) IIRC a super low termination current actually hurts the cell.

Regards LichtAn

2

The recommended Maximum and typical charging rates are in the Manufacturer data sheets. There is no single number.

For example,

Samsung INR-18650-30Q is 1.5A standard and 4.0A maximum during the constant current phase.

Panasonic NCR18650B standard charge is 1.625A. Max current is 0.5C. There may not be an approved rapid charge rate.

https://na.industrial.panasonic.com/sites/default/pidsa/files/ncr18650b.pdf

3

This is about the best place to read to answer your questions. That have very useful charts and info there.

The column in the middle has the more relevant info your looking for.
And this being the most specific.

4

I also have that same question. I notice the MC3000 will set the charge termination current to 10% of the selected current (so selected 3.0A charge current, termination current defaults to 0.30A. Selecting 1.0A => 0.1A termination current; although the termination ending current is configurable by user)

For some batteries, I notice after they charged to full, the voltage goes down fairly quickly (older batteries), sometimes in these cases, I manually adjust the termination current to something lower — eg. 0.03A or in a few cases, I tried 0.01A, the minimum selectable termination current in MC3000.

I wonder if selecting 0.01A ending current may not be good for the battery? (the charging time can get much much longer for higher resistance batteries when I do this). — will that damage the batteries life cycle?