Taking the Plunge into DIY Battery

[Drunkin Solar]

Well I gave lots of thought to the pros and cons of a DIY battery bank and decided to dive in.

Went with the Seplos Mason kits purchased directly from Seplos. They went out the door last week and I should see them in about five weeks from across the pond.

My system is a 24V system so I am putting together 3 units 8s for approximately 21kwh of storage using Eve 280k grade A cells.
This should give me about 3-4 days of power as my off grid consumption is generally in the 4-5 kwh a day which should cover most bad weather runs without firing up the generator. The rest of the gear is Victron and 3.1kw of panels backed up with an Onan 7.5 kw generator.

Looking forward to the journey!

 

[Drunkin Solar]

Geez.... the three Seplos boxes are here. Was not expecting them for another month. I'm astounded how fast they got here.

Also they have way more factory pre-assembly than what their assembly video shows and the printed out instructions show.
The BMS is mounted to the faceplate along with the screen. Also the balancer boards are mounted. And the handles are pre-installed. Finish looks great. Nice !

Now the work starts

 

[Drunkin Solar]

Just finished opening everything up and trying to do an inventory on all the little pieces. As best I can tell without opening up all the little bags of screws and whatnot all looks present and accounted for. The boxes all arrived in pristine condition very well packed. Shipping was lightning speed.

Must say kudos to Seplos....well done!

Can absolutely recommend a direct purchase from them. My sales rep quickly answered every question I had and there were many over a two week period while making my decision to take the dive.

Happy with the purchase

 

[740GLE]

You have a link to the seplos 8s cases?

Did you buy your cell from them too or you source them somewhere else?

 

[Drunkin Solar]

Hey 740GLE
I can give you a link that connects you directly to my sales guy. PM coming your way...

The cells I'm purchasing locally at Battery Hookup. Eve LF280K v3 and grade A.
Lucky they are about a 25 mi drive for me at the moment.

 

[Drunkin Solar]

Contemplating the next steps to get these up and running once I get my cells and put it together.

I do not have a charger to top balance the cells and I'd rather not buy a benchtop power supply for a onetime operation and then having it laying around taking up space. Already own more junk than I know what to do with.

A suggestion from another was to just assemble the whole thing and program the BMS and let it charge because the cells are already really close from the factory. I have a spare 370w panel and a little 100/20 Victron SCC and have no time constraints requiring a fast setup and commissioning of the batteries. I know this method will be slow at that rate of charge and would hope that if I leave it setup when it gets to float. My question is will the cells balance out within a week or two? This assumes they are very close out of the box.

All thoughts are appreciated

 

[rustyrotors]

if you dont have a power supply, you can use a 12V automotive headlight to pull about 2 amps out of the higher cells

 

[BenQ]

Contemplating the next steps to get these up and running once I get my cells and put it together.

I do not have a charger to top balance the cells and I'd rather not buy a benchtop power supply for a onetime operation and then having it laying around taking up space. Already own more junk than I know what to do with.

A suggestion from another was to just assemble the whole thing and program the BMS and let it charge because the cells are already really close from the factory. I have a spare 370w panel and a little 100/20 Victron SCC and have no time constraints requiring a fast setup and commissioning of the batteries. I know this method will be slow at that rate of charge and would hope that if I leave it setup when it gets to float. My question is will the cells balance out within a week or two? This assumes they are very close out of the box.

All thoughts are appreciated

This will work perfectly fine. The amount of time it takes to balance depends on your BMS. Does it have an active or passive balance on it? 1A or 2A balancing? Hopefully you didn’t go with a seplos BMS…

 

[Drunkin Solar]

It is a Seplos BMS. It is passive balance at the moment. Figure if I wind up with balancing issues down the road a Neey could be added later if necessary. Just wondering if I will get some decent balance initially if I let it sit at float.

I've read about the issues with the Seplos BMS v3 and also saw the video you referenced and it seems that they have been taken care of with firmware updates so I'm okay with that. The passive balance issue has been solved.

I almost ruled out the Seplos until I found out things were being taken care of. Seems to me they launched that product prematurely last summer.

Thanks

 

[Rednecktek]

Just remember to hit the switch in the app to turn OFF the "balance while charging" so it will continue to balance all night when there's no sun out. That'll speed things along.

 

[Drunkin Solar]

Thank You @Rednecktek

This is exactly the type of info I was hoping to receive while working on this project

 

[740GLE]

Also set the SCC to float 8*3.45v and let it bake.

If you’re not in a rush let the BMS do its job.

 

[Drunkin Solar]

Also set the SCC to float 8*3.45v and let it bake.

If you’re not in a rush let the BMS do its job.

That was my thinking. If you give it time, which I have plenty of, at some point (hopefully) things are good enough to commission it into the system

Okay then float at 27.6v. That number sounds familiar because I think that is where it's already set at. Won't know till I return to Tenn.

Thanks Again