48VDC LiFePO4 bank with TS45 and Victron 375W 48VDC inverter

[John Gorman]

have a 900W of PV connected to a Morningstar TS45 (PWM) charge controller connected to a 48VDC pack made up of (4) 12V LiFePO4 batteries in series. Also have a 48VDC 375W Victron inverter attached to this battery bank for AC loads. It was working fine, but possibly it is a set of very sunny days but the Low Voltage Disconnect (LVD) feature which is enabled now seems to keep triggering a lot. does anyone have advice on the TS45 settings to avoid this? Thanks

[Rob Beckers]

John, what are the settings you're using for the TS-45?

-RoB-

[Rob Beckers]

The "series" remark just registered: Did you balance the 4 batteries lately? Lithium-ion batteries do not self-balance at all (lead-acid does, making it easy for lead-acid to be connected in series). Did you at least check each individual battery Voltage to see if they're all still doing the same thing at the same time?

-RoB-

[John Gorman]

Hi Rob, the batteries are really off the shelf LiFePO4 lead acid replacements so they have some kind of circuitry to protect them I think - are not 3.4V cells or anything with an external BMS.

https://www.jaycar.co.nz/12-8v-100ah-lithium-deep-cycle-battery/p/SB2215

so just wired in series and the only thing I think that is new is that we're using the "battery sense" terminals on the TS45 which report a different (lower by around 2VDC) value for the battery voltage than battery voltage when you look at it on MSView. Also I think important given your question: there is a small load on only one of the 4 12VDC battery to run a monitoring computer for the system, possibly a 1A 5W device. could that be messing with the balancing? I could power that off AC but had wanted to keep it monitoring through inverter shutdowns. it uses a buck converter to take 12VDC and convert it to 5VDC to run a Orange Pi Zero SBC that does a lot of Modbus and weather and camera capturing to the cloud.

[Rob Beckers]

John, please see https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/
It has a section on all the peculiarities the BMS introduces.

I'd say yes, your issues may very well have to do with the batteries being unbalanced. That would be the first thing to check or rectify. Further to your info, you absolutely cannot have ANY load that is on just one of the batteries, when you have series-connected lithium-ion batteries (unless you have some external means to keep them balanced).

Best regards,

-RoB-

[John Gorman]

OK that makes sense then - I believe that the batteries were drained and the bank went below 48VDC so the TS45 stopped operating. but we're bringing them back up and I have removed the 12VDC load on one battery and isolated the inverter so there should be no load on them whatsoever at the moment.