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

championc

https://www.boards.ie/discussion/comment/120180623#Comment_120180623

Remember, DC amps are higher with the lower voltage.

3kW is about 60A, so 100A is about 5kW

graememk

https://www.boards.ie/discussion/comment/120180623#Comment_120180623

Fuses protect cables (and possibly batteries) not equipment.

So the fuse isn't to protect the inverter it's to protect the cables going to the inverter.

If you have the solis id be going for the 150, as the solis can pull 100 amps

munsterfan2

Happy enough to accept this.

poker--addict

storage again.

how much room do these cells need? They should not swell all things being normal right? But probably wise to leave some space so as not to make one problem become 16 problems?

that Homebase box looks to be 60cm internal while the 16 cells are basically 58cm

championc

So which cells ? The CALB's (which won't swell) or the 280Ah Aluminium boxed cells ?

poker--addict

Calb

slave1

You have the Calb cells, you are fine, no need to compress or anything, just put the busbars on when they are in their final resting place

poker--addict

Progressing

slave1

I didn't put my temp sensors on the terminal, I put them between the battery casings, not sure if that is the most correct approach (what I did)

poker--addict

Yes temp sensors i plan to stick between casings, they aren't pictured.

need to figure out solis settings and connection order now.

jasgrif11

Hi All,

There are many threads on the DIY battery configuration and optimisation. Before accepting the order within Alixpress after delivery, what are the essential steps I should take? Ideally would be great if we could build up an initial guide here for Noobs with some supporting pictures, videos and links.

Ha Long Bay

https://www.boards.ie/discussion/2058282276/lifepo4-battery-diy-arrive-what-are-the-next-steps

Dedicated thread and great write up here.

https://www.boards.ie/discussion/2058246061/10kwh-lifepo4-diy-battery-addition-here-is-my-write-up

ELM327

https://www.boards.ie/discussion/comment/120183105#Comment_120183105

Following with interest. You're doing exactly what I intend to do in the next 6-12 months. (Even down to the plastic box!) but especially interested in the connection to Solis

slave1

Just look back to OPs first posts on this thread, excellent summary with pictures

Geeyfds53573

https://www.boards.ie/discussion/comment/120182241#Comment_120182241

Looks good “really useful” as it says

don’t forget to measure the voltages at the end of the the harnesses before you connect anything

unkel

I would tidy up those balance wires, wee accidents with them can easily happen. (I've sinned against this myself in the past) Also I would have P16 and the last wire of the JK BMS crimped together into the one ring terminal

And of course double and triple check the balance wire connector block for voltages, before plugging it into the BMS. Get it wrong and the BMS might get fried within seconds!

poker--addict

https://www.boards.ie/discussion/comment/120184699#Comment_120184699

Good idea on p16 and last BMS cable.

And yes the BMS cables are fragile to say the least. Actually one got pinched today between two cells. I think I rescued it, and got some insulation tape all over it to protect but the red insulation on it was well damaged (and is not much better than butter anyway). will test tomorrow.

I will tidy everything again once I have everything in final position and working.

johnbk

Thanks again for the diagram @championc

Made bms wiring easy to follow. Checked with multimeter and all ok. Put the thermocouple between cells.

Didnt extend any

but a little tight to cell 9.

I’ll get the laptop fired up tomorrow evening and turn on the battery for the first time.

poker--addict

Where do I start with teeing up the inverter? Anyone a YouTube video they recommend?

championc

Not sure what you mean by teeing up ???

slave1

@johnbk interesting you are putting the BMS wires on the busbars, how will the BMS know if it’s truly monitoring the positive or negative cell?

graememk

https://www.boards.ie/discussion/comment/120185472#Comment_120185472

Doesn't matter where on the busbar, it's the same voltage no matter where you put it.

slave1

I get the voltage will be the same but if you look at the bottom photo from the post above, which cell is being monitored, genuinely interested here...

graememk

https://www.boards.ie/discussion/comment/120185803#Comment_120185803

Each bms wire does double duty.

I know how it works in my head, just need to put it into words!

The bms can measure the voltage of each cell

The first cell is straight forward, from the most negative to cell 1.

For cell 2, the bms measures the voltage between the positive of cell1(which is also the negative of cell 2) and the positive of cell 2. And then it steps up the pack.

As you know my pack is split on two rows, and I've replaced the joining cable with a copper bar. And was getting a falsely high reading on charge and a falsely low on discharge.

My bms was measuring the voltage from the positive of cell8 to positive of cell 9, including any loss on the cable (when calculated out was 1-2w at 100 amps) but it was enough to throw that reading off by about 0.05-0.06v at high currents

johnbk

Off grid garage is my guide for the way I’m putting it together. Very similar too to Ray builds cool stuff. (Both on YouTube) These two guys are away more advanced than I ever will be. Both put bms onto the bus bars and not the terminals. The idea being that you don’t interfere with the connections on the battery terminals.

As the Solis won’t ever pull the amps these batteries and BMS are capable of then I don’t think it really makes that much difference. Both these guys are pulling more amps than I will be. They use contact paste and torque the terminals too which I am not doing.

The positions I took with BMS connections might not be optimal but they tested fine on the multimeter. I am a bit confused on the final battery positive and negative and the connection between cell 8 and 9 so I screwed to the lugs.

I also threaded a points for an active balancer if I fit one in the future.

As ever, really appreciate suggestions on the build.

slave1

Your build is looking great so far, if only I had the vertical and horizontal space you have, I'm bet into a corner with my 32cells

graememk

https://www.boards.ie/discussion/comment/120187998#Comment_120187998

To the solid bus bar is good, as it doesn't annoy the terminal connections.

As for position it doesn't matter, Because its connected via a bus bar, The negative of one cell is the positive of the next, no matter where its measured on the bus bar.

johnbk

All connected and up and running. Had a few minor issues getting the software to run on my PC with compatibility but once I got it running connection was instant. Only setting I changed was the amp hour to what I tested. 238ah in my case.

The single pole isolator snapped as soon as I turned the knob - very annoying!

Ill clad the three sides to close in and that will be it.

Next thing is mounting the Solis inverter which I am looking forward to and panels after that (which I am not as I have to scaffold the side of my house first and lift floor boards to run the dc cable). A few weeks to go so.

johnbk

By the way, what a thread and thanks all to those that share their experiences and subsequent knowledge. Such an enjoyable diy project.

unkel

Did you top balance your cells @johnbk? There's already some imbalance and the Seplos is not going to fix that for you.

Sweet build though. And plenty of space for more.