Axpert/Mercer 3KVA SOL-I-AX-3M24 Li-Ion settings help

[Rolf Bartels]

Sup,

I am looking to understand the bulk and float charge settings I need to set I. My 24v inverter, I have connected it to DIY Powerwall made up of 7s80p 18650 cells, I want to have the max voltage 4.05 and the Min voltage 3.4v

I have set the following setting

05 - use

26 - 28v

27 - 28.35v

29 - 23.8v

29 I get as that's 3.4v per cell cut off, 26 and 27 I'm not sure do I set the float to 4.05v per cell and the bulk to 4.1v ? At the moment my Blick is at 4v and the float at 4.05, I'm not really sure if bulk need to be less than my desired end volt or more, and I assume float is my desired 4.05v ?

Also is there fireware available somewhere ?

Thanks in advance

[Coulomb]

5 hours ago, Rolf Bartels said:

26 and 27 I'm not sure do I set the float to 4.05v per cell and the bulk to 4.1v ? At the moment my Blick is at 4v and the float at 4.05, I'm not really sure if bulk need to be less than my desired end volt or more, and I assume float is my desired 4.05v ?

I'm surprised that you want to set the float setting higher than bulk, and even more surprised that the inverter lets you do that.

The idea with the float stage for lithium batteries is a voltage to aim for with fluctuating loads and usually fluctuating charging power, so that the battery remains full or nearly full. I don't know much about non-LFP lithium batteries, but I imagine that for good life, you still want to stay away from the higher voltages (more than 4.05 VPC) if possible, but want to hit 4.1 VPC until the charge current drops to a certain level to make sure that the battery is fully charged. So I would think that you'd want something like 4.1 VPC for bulk, and 4.0-4.05 VPC for float.

What do other non-LFP lithium battery users do? I imagine there aren't many of you; it takes a high level of dedication to build and maintain a DIY battery made from hundreds of cells. Personally, I'd never be comfortable with the safety of such a battery, but I think I understand the appeal.

Edit: I forgot to add:

Quote

Also is there firmware available somewhere ?

Firmware for 24 V Axperts is very hard to find. The 48 V models seem to be considerably more popular, so there tends to be more firmware available.

I'm not aware of any recent 24 V firmware update files at all.

Edited July 22, 2020 by Coulomb

[Rolf Bartels]

Hey Coulomb,

 

Thanks you for the response so that was exactly what I wanted to understand so bulk to 4.1 and once it stops charging the voltage will settle down, then setting the float to 4.05v will have the inverter maintain the 4.05v per cell.

 

Appreciate the help !