How to determine ideal 0.xC Charging Current for EG4 Lithium?

[Old_Skewler]

I've read a few posts about charging current and it seems like most commonly recommendation is around 0.2C to 0.5C.

Could someone point me to a brief explanation on how this is determined? I would like to understand the science behind this. And more specifically, what should be the optimum charging current for a 48V 100Ah EG4 battery? And lastly, what would be the safest max current to charge these batteries, as I charge them off a propane gas generator and runtime has a cost.

Here is the EG4 battery recommendations from the manufacturer, which does not cover much:

 

[Old_Skewler]

This is my current understanding, which is based on reading different posts on the forum only:

"C" is the max battery discharge current. The battery charging current seems to be always a fraction of the Max discharge current "C".

For lithium batteries, the ideal charging current rule of thumb seems to be a range from 0.2C to 0.5C.

So for the EG4 lithium battery with a discharge current of 100A, this would mean:

0.2 x 100A = 20A charging current
0.5 x 100A = 50A charging current

Am I at least on the ballpark here?

 

[Substrate]

Yes, you are correct. We get into efficiency vs practicality here very quickly though.

LFP "intercalates" well anywhere from 0.1 to about 0.15C. Longest life. But that might be impractical in a solar application.

Some very smart AC chargers, will track the voltage/current ratio of LFP while charging, and automatically adjust either one to stay within the best part of the established LFP charging curves. When you watch and measure them, you'll see them usually end up at about 0.1 to 0.15C. But from a time standpoint, this too may not be practical.

The safest max charge current many use is generally use is 0.5C, or two-hours from empty to full. Do you really need it to be faster? Some energy/storage cells are easily charged at 1C, but cycle life suffers because of that. Some BMS's may purposely limit the input current rating to 0.5C, even though the cells themselves are capable of more. Helps prevent a customer from just wiping out his bank really quick.

So unless you are a motive-power drag racer, who purposely uses high-C "power cells", 0.5C max for the "storage / energy" cells is quite common. Go lower in charge current if it fits your needs when time is considered.

 

[Old_Skewler]

Yes, you are correct. We get into efficiency vs practicality here very quickly though.

Thanks for the feedback.

The safest max charge current many use is generally use is 0.5C, or two-hours from empty to full.

Okay, I am currently set to charge the EG4 at 35A and it seems like a good number for my setup. I will be adding a second battery soon and my charger is rated for up to 45A.