10kWh LifePO4 DIY Battery Addition..... Here is my write up.

tnegun

I'm still missing a few bits, but I have my box built, test fitted the cells and powered up the BMS. I hope to go live in the next couple of weeks!

kevinr7213

https://www.boards.ie/discussion/comment/123018970#Comment_123018970

Thanks for the info, il look into that a bit more.

Bawnmore

Going to pick up the bits for this soon - is there any reason not to go for Seplos V4 over the V3? Assuming it's a progression of it so should be better, but just want to make sure there's no gremlins to be aware of. Only an extra £100 so assuming it's worth getting to futureproof if no major drawbacks.

...Ghost...

https://www.boards.ie/discussion/comment/123037696#Comment_123037696

The V3 is a recent enough board and there is more info available on them. I have 3 V3 packs myself. I would check what the difference is between them and if it's little or nothing, I would save myself the £100.

Bawnmore

https://www.boards.ie/discussion/comment/123038237#Comment_123038237

Appreciate it - I'll check out the differences, but that's good to know.

Cyrus

some stupid questions coming up,

We are a high usage household (A2W heatpump and large battery EV), last year we used circa 14,300 units (4,300 for the car all at night, 2,700 or so for the HP). Am on Flogas BWG D/N tariff.

I dont have solar and we probably dont have the roof set up for it (nor am i sure we will be in this house longer term) but a large 15-20kwh battery to fill at 12c at night appeals.

I have an external shomera which is wired for power and has its own fuseboard.

Ideally id like to have the battery out there, would that be possible or do i need electrical work done on the main fuseboard (which is pretty near at capacity now with EV charger, power to shomera and a few shelly ems!) Who can install the invertor and where can that go? what does one cost?

What would i be looking at all in if i go with one of those nice looking ali express cabinets and say 15KWH or so of capacity incl invertor and elec work?

graememk

https://www.boards.ie/discussion/comment/123038328#Comment_123038328

If the supply cable is good enough you can put it out there.

Say you went with the solis hybrid, about 1.2k

15kwh battery in a case, 1400-2k depending on if you get the whole kit or buy stuff separately.

Install could suck up half a day pretty easily.

The inverter will need to get a CT back to the consumer unit or meter box, this is usually done over a cat6 cable.

mjatkey

https://www.boards.ie/discussion/comment/123038237#Comment_123038237

I have the V4 and a V3 other than the fact that the V4 it is narrower than it is deep they are similar to look at.

The V4 has 250A breaker built in and another difference is on the connections to the balance boards (as I call them).

V4 has the two side connections that go back up to the balance board as well as the two top connectors (black and white) which go to the BMS, V3 only has the top ones.

Cables on the V4 are also nicely wrapped in some cloth like material, looks neat and tidy.

V4 video https://www.youtube.com/watch?v=MJ-RMxj66CA&t=994s

And ghost has a great collection of video's including V3 build and balancer setup.

That said I think the actual BMS in the V4 is same as V3, maybe the balance board is different. (I've not watched the whole of ghosts V3 video).

tnegun

Does this voltage profile look right? I'm using a JK BMS and Andy's settings. The battery is set to charge overnight from 11pm, with charging disabled at 8am. There wasn't much load from 8am to 9am, but there was a significant voltage drop before recovering when the solar kicked in. It came back to 55v and dropped to 53v again under load.

graememk

https://www.boards.ie/discussion/comment/123064212#Comment_123064212

Perfectly normal.

When under load the cells immediately drop to 3.3/3.2 depending on the load

tnegun

Thanks, I've been babysitting it I found a warm connection and discovered I'd left a washer under the lug rather than on top so was worried there might be something else up!

tnegun

One more question! What do you set your minimum SOC to?

graememk

https://www.boards.ie/discussion/comment/123064717#Comment_123064717

10% These batteries are here to work!

tnegun

Thanks I had 15%, 10% it is so!

SD_DRACULA

https://www.boards.ie/discussion/comment/123064940#Comment_123064940

If you manage your batteries so that they get emptied and then immediately charge then you could safely go to 0% as well, Andy mentioned this in his vids. It's just bad for them if they stay "empty" for long, but if they drop to 0% at 10:50pm and then you start to charge at 11pm all good.

The devils

https://www.boards.ie/discussion/comment/123064823#Comment_123064823

😁😁

tnegun

https://www.boards.ie/discussion/comment/123065683#Comment_123065683

Nice I will stick with 5-10% for now until I get comfortable with them, annoyingly my smart meter has stopped uploading so I can't see the impact/success of grid shifting for the last week.

Noela2025

I’m looking at getting the Seplos V4 and have a string inverter but will probably get something like a SOFAR ME3000 SP Solar PV AC Controller to cut out the need of having to replace my inverter. The problem I have is I can only find an AC battery controller around 3kWh discharge and was hoping for around 5kWh to take advantage of the EV rate. Can anyone recommend anything or am I best just cut my losses and replace the inverter to a hybrid one?

paddy236

https://www.boards.ie/discussion/comment/123068585#Comment_123068585

For a diy battery the soc % is relative.

We set the 100% and 0% voltage in the BMS. So if we have conservative numbers set in the bms then it's safe to go below 10%, especially as Dracula said if we are recharging them straight away.

graememk

https://www.boards.ie/discussion/comment/123328438#Comment_123328438

Id set the 100% high even maybe to 3.6.

What would your total charge voltage be?

slave1

https://www.boards.ie/discussion/comment/123328168#Comment_123328168

Is your concern with battery charge or battery discharge? If battery charge, you can just get a rectifer

Noela2025

both I suppose! Would the rectifier replace the need for the SOFAR ME3000

championc

https://www.boards.ie/discussion/comment/123329760#Comment_123329760

Not really. It's a way of adding an additional 3kW charging without getting a 3kW inverter. But it's a charger, one way, into batteries.

So it can be added to a 5kW inverter to bring charging up to 8kW, and the inverter would do 5kW discharging

Look on AliExpress for an "Emerson R48 3000e3"

fearrchair

I have a Sofar HYD-6000-EP that is connected to 4 Fox LV5200 100Ah 48V batteries in parallel (they are linked input to output to each other with the master connected to the Inverter. I have EPS 230V sockets setup as well.

I measured the output socket of battery 4 the other day and it was reading 57V during a charging period.

The batteries currently appear on the Sofar inverter as Pylontech 400Ah although I have not been able to change the DOD to less than 20% but its not so bad.

If I was to purchase this cable (Inverter to Master Battery), would I be able to connect a Seplos etc or similar DIY batteries onto the last battery.

https://etronixcenter.com/en/8176212-se295-fox-ess-fox-lv5200-battery-cable-pack.html?gad_source=1&gbraid=0AAAAAC0HnafOtrL2gmSrhmBzbuv5bCiz2&gclid=CjwKCAjw--K_BhB5EiwAuwYoynuuvdXnvy_-bLJ6QGWbl42cxNYlRJj7EP7ufzGi0o2CPuYXmL7myBoCkrkQAvD_BwE

I know you can't mix batteries if theres different BMS but could it work if the Seplos appears as a similar setup on the inverter or does it.

Another option I had was to use a DC charger and power the large DIY battery off the EPS sockets, might not be ideal.

I suppose a cleaner setup would be to have the DIY battery on there own unless I could run the two canbus bms together or have them share the same Inverter connection.

Am i correct in understanding that its down to physical weight / cost per kWh of a battery or another reason why you would chose a 280Ah over a 314Ah etc or I have seen some batteries showing very large 600Ah - 900Ah but they are probably very heavy as well. Is there an advantage to having 4 boxes of 100Ah over a 400Ah single box ….