Has Anyone Built their own FogStar Battery ?

[Raul]

Here’s my homemade Fogstar bought batteries. I made these around April 2023. I made two 280amp approx batteries, I was making one 560amp but the JK bms didn’t allow each cell to be monitored separately and it was bloody heavy. So I made two with two BMS’s. Glad I did as one bms did fail in the first year while camping and fortunately that meant I had one working battery left!
The cells were B grade eve of which I didn’t balance as they were all pretty even already. The only so called special tools I used was a cable crimper and volt meter. I made my own flexable busbars from 28mm copper tube as there were non available at the time and two boxes from ply. I added a sponge type foam tape to the cells and the boxs to allow expansion and separation also 20mm insulation at the ends.
Cost at that time was about £900 I think.
These batteries do not like the cold so bear in mind if they do get cold you can’t charge them, you can still use what’s left in them but that’s it until they are warmed up.
If I were making them now I would buy A grade cells although ours have been fine but the cost difference is really not worth it.



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Couple of things:
Why didn't you go with the nickel plated copper bars? They are better against the aluminium terminals, compared to the bare copper.
Secondly, why no cell separator/insulator between the cells? That shrink wrap is not enough, needs additional electrical insulation.
Also, bms on top of the cells open terminals without insulation is a no no, a separate compartment on the side will be better as the bms produces heat, and those middle cells will get enough heat from neighbouring cells as it is.
Just my thoughts.

 

[tezza-alli]

Couple of things:
Why didn't you go with the nickel plated copper bars? They are better against the aluminium terminals, compared to the bare copper.
Secondly, why no cell separator/insulator between the cells? That shrink wrap is not enough, needs additional electrical insulation.
Also, bms on top of the cells open terminals without insulation is a no no, a separate compartment on the side will be better as the bms produces heat, and those middle cells will get enough heat from neighbouring cells as it is.
Just my thoughts.

Not a problem to advise me.
I wanted bridge type busbars but there were non at the time and yes I had the flat nickel ones but I wanted the flex. So I made a jig and used some 28mm copper that I had. The idea was to get some later. Obviously they have not been replaced.
The tape is a solid insulated tape not bubble wrap and it has worked fine. I've only just had them out the other week to keep them warm in the house and check them out and all was good. Many people don't separate with anything between the cells!
Yes, the terminals are bare but they are well separated and where these fit in our motorhome nothing can touch them and I'm the only person who works on our van. If I sell the van I'll remove them!
When in use being charged or discharged with our inverter the cells nor the BMS have any real heat build up as I often reach in to have a feel of the cables and cells etc.
I don't pretend to be an expert but they work well and these were my first build and to be honest at the time I thought I'd probably rebuild them at a later date.

 

[McLouis]

I made a battery with 4 off EVE MB30 great HSEV cells. With epoxy sheet and Eva separation and applied the recommended compression, which the better boxes enable. I actually used a load cell to get the torque on the 6 off 6mm rods right. That torque was virtually 5/16 of sweet FA. I used a JK bms with blue tooth and no heater couldn't see the point. I put the bms on the top as many folks do. I tested all cells with the same charge./discharge power supply that the manufacturers use. I used the Ni plated flexi bus bars and torque all nuts to 6Nm. I did spend a fair bit of time top balancing, all cells came in at 332=334Ah. Giving a battery of just over 4kW. The bms has active balance, but I haven't turned it on in the 8months of use. The cell delta is typically 1-2mV. Max with 120A discharge was 8mA. I never leave connected to a mains charger just letting the m/h drain keep the battery being crammed at 100% SoC.

I built a plywood case and epoxy coated it.

Would I do it again.... Too right.,I know what I have and how to fix it. My only problem is the shipping costs from China have increased a lot. The euro shipping is less but the cell cost is higher. I might build another with A graded cells in prep to build a 48V battery for Energy storage for the house.

 

[wfdTamar]

I would rather use Fogstar grade B cells than some unknown rebadged/respecified cells from China. The grade B are carefully explained by Fogstar.
My 230Ah grade B Fogstar EVE cells have been fine. They are seldom out of balance by more than 5mV whilst using a JK BMS.

You do know that Fogstar would be buying cells from China too? They might think they can trust their Chinese supplier. The cell market (out of China) is the wild west. Counterfeiting is rife. You basically can't trust what any of the Chinese wholesalers say (that has nothing to do with their nationality, but the industry). All you can do is hope and test the cells you buy, which takes a long time - no business has that amount of time. They might test samples from a batch, but not every cell. The wholesalers will provide 'test reports', certification passes and spreadsheets with test results, but they mean sod all.

BTW - this in no way is a suggestion that Fogstar or any other reputable battery assembler is dodgy or has these attitudes.

Also the whole Grade A, Grade B (and I've seen mention of Grade C) is fiction. There are only EV/storage certified and all the others that have failed that testing and get auctioned off to Chinese resellers/wholesalers (which generally is what is available to small scale storage buyers). They might do a simple resistance check and grade them from that.

The other issue is the warranty. Sure if a battery melts or dies you'd hope that will be covered, but there's no way the number of cycles stated will be covered as there is just no way to prove how you've treated the battery.

 

[mikash]

The other issue is the warranty. Sure if a battery melts or dies you'd hope that will be covered, but there's no way the number of cycles stated will be covered as there is just no way to prove how you've treated the battery.

It's actually the manufacturers problem to prove you have mistreated the battery, not the other way around, if they want to dispute the warranty case. If your installation and BMS (whiuch typically prevents the easiest ways of abusing the battery) are as manufacturer recommends, you have a pretty strong case.
Overall I do think most people are overly worried about the cycle life - for a 200Ah battery, 4000 x 80% cycles is about 80Ah of energy consumption every single day, for 20 years straight, assuming it degrades relatively linearly from 100% to 80% capacity during those 20 years. The 4000 or 8000 cycles is a nice big and impressive number to advertise, but not really very relevant in recreational use.

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