Battery management system BMS

[Mauri Meere]

Hi
I got a real deal?? on a used 24 volt 270 amp-hr LiFePO4 battery bank, 8 cells 3.2 volts each.
Can anyone recommend a battery management system (BMS) at a reasonable price for this battery bank.
I estimate the load at my cabin is 1.3 kwatts-hrs per day (50 amp-hrs) or a weekly load of 2.6 kwatts-hrs per week (100 amp-hrs for weekend use).
If all appliances were running at the same time the maximum current draw from battery bank would be 113 amps dc.
Any suggestion/advice re:BMS is appreciated.

[Rob Beckers]

There are a number of open-source BMS projects floating around the Internet. This one, OSBMS, seems interesting (https://endless-sphere.com/forums/viewtopic.php?f=14&t=63863).

The various Chinese sources also sell ready-made BMS systems (Aliexpress etc.).

-RoB-

[Mauri Meere]

Hi Rob
After our chat this afternoon, I thought I should send you the full picture.

After much thinking, I plan to replace my old system as follows:

2 Hanwha 310 watt 60-cell modules (620 watt array in series)
Samlex PST-2000-24 pure sine wave inverter (2000 watt 24 volt)
SBMS0 Electrodacus solar battery management system
1 DSSR20+diversion Electrodacus charger
24 volt 270 amp-hr LiFePO4 battery bank, 8 cells 3.2 volts each….purchased from China

The load at our cabin is 1.3 kwatts-hrs per day (50 amp-hrs) or a weekly load of 2.6 kwatts-hrs per week (100 amp-hrs for weekend use).
If all appliances are running at the same time the maximum current draw from the battery bank would be 113 amps dc or 2.7 kwatts.
Here is my usage:
DEVICE-------WATTS-------HRS/DAY-------W-HRS/DAY
pump-----------504------------0.2--------------101
lights----------- 60-------------6.0--------------360
vacuum cleaner-1140---------0.2---------------228
kettle------------1000----------0.3--------------300
inverter----------15------------20.0-------------300

TOTAL.----------2719---------------------------1289

s this a balanced set-up, do the components match well? I am assuming the SBMSO can control the Samlex through the remote connection?
Is the Samlex sizing correct?
Is there enough room for expansion?

My old system is 25 years old and is as follows:

8 Trojan 6 volt 225 amp-hrs batteries (battery bank 24 volt 450 amp-hrs)
EP Solar 2215BN mppt controller (20 amps 150 volts dc)
Trace U2624 inverter (2.6 kwatts 24 volts)
4 Kyocera 12 volt 3 amp 50 watt panels (200 watt array)

I will use the old system for our sleeping cabin and hopefully, in the winter, to also warm the lithium battery bank in the new system.

Any advice/suggestions would be appreciated.
Thanks, Mauri

[Rob Beckers]

Hi Mauri,

Vlad pointed out that you were looking for an answer to your post. So here goes...

The 2kW inverter would be marginal. It may work, or not, depending a little. A pump would draw about 4x rated power to get started (unless it has 'soft start'). The inverter can deliver twice rated power for a short time. With 2kW continuous available you would have to manage your 2.7kW in loads, obviously you can't switch everything on at the same time. That is complicated by the pump, which I presume switches on/off based on the water pressure and can switch on at any time.

With that in mind you may want to think about a 3kW inverter.

The rest looks OK. Two panels should bring in around 1.6 kWh per average day between spring and fall. The battery bank stores over 6 kWh in energy, so with just 1.3 kWh in daily use you have plenty stored.

Hope this helps!

-RoB-

[Mauri Meere]

Hi Rob
As you suggested, I am now looking at 3000watt inverters for my new set-up. You carry two inverters that I think should suit me.....the Victron Multiplus 3000w and the Samlex PST-3000-24 in the same price range. Which do you think is more suited to my off-grid application?....also which is quieter, more reliable etc?
Thank for all the good advice