Figuring out what current you should charge your LiFePO4 battery is easy.

There are two factors to consider:

- The recommended charge current of the cells
- The maximum allowable charge current from the BMS (battery management system)

Let’s explore the first.

## Recommended charge current of the cells

If we take a standard 100Ah 3.2V EVE Lithium cell (we need 4 of these to make a 12V battery). We can see it has the following specifications:

- Typical Capacity: 100Ah
- Typical Voltage: 3.2V
- AC Impedance Resistance(1KHz): ≤0.5mΩ
**Standard Charge/discharge current: 0.5C/0.5C**- Operating Voltage: 2.5V~3.65V
- Maximum continuous charge/discharge current: 1C/1C
- Maximum pulse charge/discharge current(30s): 2C/2C

As we can see, the standard charge/discharge current is 0.5C.

Now, what is C?

C stands for C-rate. To know more about C-rate, I recommend watching my video about it.

The battery capacity (in Ah) multiplied by the C-rate gives you the recommended charging current.

In the case of a 12V 100Ah battery, the maximum charge rate is as follows:

100Ah * 0.5C = 50 Amps

If you have a 12V 200Ah battery, the maximum charge current is as follows:

200Ah * 0.5C = 100 Amps

Now if you have a 48V 100Ah battery (5kw server rack) the charge current is the following:

100Ah * 0.5C = 50 Amps

We can see that the maximum recommended charge current depends on the battery capacity (Ah), not the voltage.

If we use a larger battery cell, the 280Ah EVE cell for example, we can see that the recommended max charge current is 1C.

Let’s calculate the recommended charge current for this cell:

280Ah * 1C = 280Amps

We see that the c-rate is double. This is because the cell is much larger and can dissipate heat better.

The higher the cell’s capacity, the higher the charge current can be.

## Maximum charge current of the BMS

Another limiting factor will be the charge rate of the BMS.

Each battery management system (BMS) has a maximum charging current. Take a popular Chinese BMS brand, for example.

If we take a 100A BMS, we can see in the datasheet that it can only charge at 50 amps.

If you have a 100amp charger, it won’t work. The BMS will shut down to protect the battery. This is because too much current gets sent to the battery cells.

Charging at a lower C-rate is not bad. It is better for the battery’s lifespan. Refer to my article about my recommended chargers for LiFePO4 batteries.

**Conclusion**

Figuring out at what amp you should charge your LiFePO4 battery is straightforward.

Multiply the C-rate of the battery by the capacity of the battery.

C-rate (usually 0.5) * Capacity (in Ah) = Recommended max charge current of a LiFePO4 battery.

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Newbie⚡Recently acquired a LFP12.8V400AH.

I would like to know what charging parameters to use before placing the battery in service.

I have an ADJUSTABLE CHARGER

DC Output: 0-15Vdc (Adj.)

DC Current 0-60A (Adj.)

My inclination is setting:

⚡DC Voltage: 14.6Vdc

I am Questioning BEST or OPTIMUM DC Current for initial charge rate? (Listing possibilities below)

50A for 8 hours

40A for 10 hours

20A for 20 hours

10A for 40 hours

other RECOMMENDED❓

Obviously, I must choose one method; If I am wrong about this, Please let me know.

The battery State Of Charge is about 15% in my estimation;

But I don’t know how to check the TRUE status except for the built-in digital meter that indicates 12.8Vdc and a battery symbol with 2 bars on the low side. Is there another way to check the actual SOC❓

Thank you for your answers or Recommendations on the above (?).

Charge at 14.6V and the maximum charging current is 200A depending on the BMS inside the battery. You need a shunt