LiFePO4 charge vs discharge

[Solarguy]

Hi,
I recently upgraded lead acid battery pack in my parents home to LFO. However I noticed that for example if the battery discharge 4 (2.5kwh today +1.5 yesterday) kwh then during the day it took 5.85kwh to charge back to full.
Is this normal? I do understand chargers and batteries generate heat but wanted to make sure.

 

[400bird]

Your system isn't tracking some loads or there is some miss understanding of what those stats are saying.

If I add up battery load and inverter load I get approximately the same as solar power.

Lifepo4 is something like 99% efficient round trip. Most inverters are going to be in the 90% range.

So, the 70% numbers you've got above (4kWh/5.85kWh) is either 1.85 kW of heat or energy usage that isn't tracked by your system.

What component provided the screenshot? What all do you have in your system? Can you provide pictures?

 

[callmeburton]

Are you sure the pack was top balanced before you got the information above? My system is still trying to find the top and set a proper 100% SoC benchmark ... early on when I hooked everything I assumed the SoC and that lead to more amps going in then out and the SoC reading "full" at different times ... if that makes sense.

 

[400bird]

That's a good point, if the pack was out of balance and the old 100% SOC wasn't actually 100% due to one cell hitting the high cells cut out (3.65 volts?)
Then with more balancing, that high cell burned off some of that and is closer to the remainder of the cells, you'd gain some capacity. But, that would require both a significant imbalance between cells and lots of balancing from the BMS to gain 1.85 kWh of capacity.

 

[Burke]

Yes I would guess that the pack wasn't fully charged. If it starts to balance out over time, that is likely why it took on more initially. There could also be something wrong with your settings, shunt, etc also. You should verify everything is set right also.