Got my system working (eventually)

[dlw]

Hi All,

Received my batteries a few weeks ago and after a few issues with settings and cable adjust they seem to be working well but still have to work on bulk and float charge.

I have 3x chinese rack style 125Ah
Voltronic Axpert 8Kw Max hybrid off grid inverter

I am charging the batteries at night with octopus go tariff @90amp and they are lasting between charging, solar helps during some parts of the day to run most of the house at this time of year.

[Caesium]

I have 3x chinese rack style 125Ah

? What are these? Details! Pictures! You can't leave it hanging just like that

[dlw]

? What are these? Details! Pictures! You can't leave it hanging just like that

Lol, not the best pic and I'll be doing a full system tour/thread probably next week when I'm back in the UK



I'm thinking of changing at the max battery charge of 100amp to make sure they are 100% within the 4hrs window because I notice last night they were 0% (43.3v) and only managed to get to about 90% I should be able to setup variable conditions in home assistant to automatically change this, any thoughts on charging at this rate?

[Caesium]

I'm thinking of changing at the max battery charge of 100amp to make sure they are 100% within the 4hrs window because I notice last night they were 0% (43.3v) and only managed to get to about 90% I should be able to setup variable conditions in home assistant to automatically change this, any thoughts on charging at this rate?

Difficult to say without knowing the battery specs, but I will say 43.3v sounds *very* low for a nominal 48v pack. That's around 2.7v per cell if they're 16S, very very close to the absolute minimum cutoff of 2.5v. So that really is genuinely 0% SOC

I'd suggest that for long life, packs like these are best not run below around 48v if possible. That in turn means you keep some buffer of capacity at the low end, so it might be easier to get them back up to 100% using the current you're already charging with? Is this 43.3v a one-off? Were they delivered like that? Really they should arrive at around 40% SOC, which is best for long-term lithium storage.

100A charging rate probably isn't excessive; its common to see 70 - 120A being pushed out of inverters, but the battery spec sheet should tell you what's safe to push into them.

[dlw]

43.3 is slightly above the cut off spec for the battery and 100amp is max for the battery bms input and output just I know sometimes max is not a sensible option
I believe they are 16s
The cut off in my inverter was originally set at 43.5, I think the communication is working between my inverter and battery so it could be all automatic now as the max and min seems to be reported differently in my home assistant

[dlw]

Just looked at the history in home assistant and it looks like the bms is now stopping the battery from going below 46v, my max charge never seems to get to the 57v that is reported back to HA as it only seems to be at 53.4 or there abouts

[nowty]

They are 16S so the voltage per cell would be down to about 2.7V, probably around 2 or 3 % SOC.

I know the sticker on the battery says cut off @ 43.2V but if I were you I would set your discharge cut off voltage on your inverter/charger to about 45V, 46V or even 47V. Thats still down to about 5% SOC.

EDIT - If your BMS is stopping it at 46V, I'd be reasonably happy with that. 57V on the top side is also ok for a 16S pack.

[nowty]

The OP had some details about the batts on an earlier thread.
https://camelot-forum.co.uk/phpBB3/view ... 666#p20669