Setting LFP to AGM batteries on Growatt

[kashxpert]

Hi,

I have Growatt SPF5000ES Off Grid inverter with 2 x 5.12kw 48V Jakiper batteries.

Ever since I installed them, every few weeks the batteries suddenly die, sometimes 40% straight to 0%. Sometimes 60% straight to 0%. I noticed this happens when there has been fair bit of usage during the day but sun keeps the batteries full going into the evening.

Anyways, I have contacted Jakiper support and after looking at batteries logs, they advised to change batteries from lithium to AGM and manually setup below parameters.

Set in AGM mode
Bulk charge 57.6V
Float 54.5V
Cutoff 44V

I'm bit confused, I thought this could hurt the batteries, is that safe to do?

 

[sunshine_eggo]

The jakiper batteries are likely not top balanced due to suboptimal battery/inverter communication and/or are suffering from an erroneous SoC value.

You are simply cutting off comms and telling the inverter to charge at certain voltages.

57.6V = 3.6V/cell - generally safe for a balanced battery
54.5V = 3.41V/cell - generally safe for float.
44V is a bit on the low side, but LFP can go as low as 40V.

Note that the battery BMSs will still protect the batteries if anything goes out of range.

The idea is that you'll force the batteries to work in upper voltage ranges where the batteries will work to recalculate the SoC accurately and to top balance the cells to maximize usable capacity.

This is a very common practice. Some folks prefer to run with comms disabled to avoid this kind of behavior. @timselectric

It is also important that you have sufficient power to regularly attain the bulk voltage. If you are consistently operating in lower SoC ranges, this may not resolve for some time.

 

[kashxpert]

The jakiper batteries are likely not top balanced due to suboptimal battery/inverter communication and/or are suffering from an erroneous SoC value.

You are simply cutting off comms and telling the inverter to charge at certain voltages.

57.6V = 3.6V/cell - generally safe for a balanced battery
54.5V = 3.41V/cell - generally safe for float.
44V is a bit on the low side, but LFP can go as low as 40V.

Note that the battery BMSs will still protect the batteries if anything goes out of range.

The idea is that you'll force the batteries to work in upper voltage ranges where the batteries will work to recalculate the SoC accurately and to top balance the cells to maximize usable capacity.

This is a very common practice. Some folks prefer to run with comms disabled to avoid this kind of behavior. @timselectric

It is also important that you have sufficient power to regularly attain the bulk voltage. If you are consistently operating in lower SoC ranges, this may not resolve for some time.

Thank you for your input, it makes sense. Our batteries usually stay above 50% and being a holiday home usually stays 100% charged except over night goes down to 85% due to fridge running.

Good to know if it's safe to use in that settings, do you think this will sort out the balancing issues?

 

[sunshine_eggo]

Good to know if it's safe to use in that settings, do you think this will sort out the balancing issues?

This is a common practice to restore batteries' top balance. In some cases with some brands of server rack type batteries, firmware updates improve the batteries' ability to maintain balance with comms enabled.

If your batteries are healthy, it should work; however, it will likely need to be repeated periodically.

 

[kashxpert]

This is a common practice to restore batteries' top balance. In some cases with some brands of server rack type batteries, firmware updates improve the batteries' ability to maintain balance with comms enabled.

If your batteries are healthy, it should work; however, it will likely need to be repeated periodically.

Do I need to set it back to Lithium on the Inverter or its okay to leave it as AGM with those settings permanently?

 

[wattmatters]

Why not set it to user specified (USE) and set the custom voltages according to your battery's charging specs?

 

[sunshine_eggo]

Do I need to set it back to Lithium on the Inverter

Nope.

or its okay to leave it as AGM with those settings permanently?

Yes, or this:

Why not set it to user specified (USE) and set the custom voltages according to your battery's charging specs?