Discharge test of 24V LiFePO4 with grid tie micro inverter

FrankB

New Member
I was looking for a good method to measure the discharge capacity of my Battery. First I started with a normal 24V/230V inverter with connected heater. This was not so greatful, becouse it was also very noisy and generates heat.

So I decided to by an Solar panel inverter to do that. the inverter uses MC4 solar plugs for DC-Connection.
IMG_20210902_194556.jpg

This inverter has a rated power of 700W. In my measurement it uses 20A discharge, this is about 500W. The discharge got over the whole night. The inverter is complete noiseless.

blue: voltage, left scale
red: current, right scale
time in hours
chart.png
The main advantage here is, that this inverter stops discharge automaticly at 24.5V. So the minimum cell voltage was 3.0V. So it was not necessary to supervise the inverter the whole time.
The capacity of the discharge test was 270Ah with 280Ah cells. I think, this is a good result.
 
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