Who is still building DIY batteries

JJJJ

Aspiring apprentice
Joined
Feb 25, 2021
Messages
845
Ok. There are plenty of discussions on UL ratings and cost comparisons of DIY vs prebuilt batteries.

What I want to know is who is still doing DIY and the reasons you chose this approach.

I will go first. At first it was the only thing going. Later it was for the challenge and satisfaction of building something from scratch.

The prebuilt versions are nice and my mouse has wandered towards the purchase button more than once. However for me there is just something about the creative process which has me strongly considering DIY for the next battery. An added advantage is that I can jump from 24 to 48v with a simple reconfiguration and BMS if I want.
 
2P4S in 230ah cells with 200A JBD, going to 8S buy just picking up a 200a JK BMS. This is in an off grid cabin, no inspections needed.

Eventually I’ll add another 230ah 8S battery to the system and use that 4s BMS for another 12v emergency spare.

If I’m DIY assembling my components for the OV system why not DIY the battery.
 
I was so torn I decided to buy one server rack as my first 48v battery to play with.

Pretty instantly I found I am completely unsatisfied with not having total control over BMS settings and functionality, and that settled it. I am assembling the parts to set up my own contactor BMS on the 16s pack out of the server rack battery. I will use these cells as the test bed for BMS systems and then move the BMS over to larger cells later.
 
What I want to know is who is still doing DIY and the reasons you chose this approach.
I have three DIY 16S, two DIY 8S, and four 14S-5P DIY EBike packs.
I got into the DIY batteries long before solar, building EBikes for my grand-kids from scrap 5 & 12 speed bikes I got for free. Was a hobby, something the GK looked forward to working on while they visited, gave us something to talk about (to bridge that 50plus year age gap) and once built, we would go out riding - without killing myself. (yeah my own Ebike got a double battery pack).
If I’m DIY assembling my components for the OV system why not DIY the battery.
Ditto! and what better way to understand how everything works then to actually have a hand in putting it together.

It's cheaper and if one cell ever fails, I only need to replace one cell.
I sure liked the cheaper part! and as Tim says, easy to have a spare cell on a shelf that could be used in any similar battery. I have (so far) three DIY 16S packs all built on the same 280K cells, although my next two packs in the process will be built with 304A cells, so I should actually have a 280 and a 304 cell spare - I can steal a 304 from one of the 8S packs in a pinch.
I was so torn I decided to buy one server rack as my first 48v battery to play with.
I was too, but clearly I was not as courageous as you, I bought two factory server racks first, then moved on to DIY packs - LOL.

The cells in the factory packs do not look too easy to remove or replace individually, but I know exactly how to remove and replace a single cell in my packs.

Playing with the packs taught me a lot about balancing, both in one pack, and between various packs, even when the packs are very different capacity - 100Ah factory racks and 280Ah DIY packs, this was good to learn and I am happy to know now a lot more than I did a couple years ago.
 
About 210kWh total, all but a Trophy 220aH are diy. 10kWh diy in my work van with 26 ga sheet metal cases. I like to know how it’s built, how to troubleshoot, repair-ability is important to me so NO welded cells, easier to take apart if I need to move it, better cooling, easy to check for hot spots/loose connections with an IR camera.
 
About 210kWh total, all but a Trophy 220aH are diy. 10kWh diy in my work van with 26 ga sheet metal cases. I like to know how it’s built, how to troubleshoot, repair-ability is important to me so NO welded cells, easier to take apart if I need to move it, better cooling, easy to check for hot spots/loose connections with an IR camera.
What is your go-to cell for these packs? did you try to standardize them across all these packs?
 
What is your go-to cell for these packs? did you try to standardize them across all these packs?
James at 18650 Battery always does well. I get the 304aH (or 100aH for my work van 24V) grade A cells on the last 100kWh or so. I wouldn’t go anywhere else. No communication necessary. Grade B’s from Aliblabla 280’s, 304’s, all work fine together. Those with higher IR, charge and discharge slower. Not a big deal. I’ve ran 100aH’s with good success with them too. No standardization for me. Five different BMS brands, JK is the most used and only one I buy now. Eight different pv arrays with different angles/azimuths.
 
About 100,kWh semi DIY..
(Use seplos Mason boxes) and EVE / envision cells

Will keep doing so.
Boxes have CE mark (needed for inspection) and I control cell quality and active balancer ( although hasn't been running yet)
Given the box esthetics gives me the best of everything.
 
DIY is all but necessary for our setup.
Our 4 cell Sinopoly 300Ah battery has survived 9 years of full-time travel both powering the motorhome and starting the Canter 3.9l TD truck engine often multiple times a day.
I recently paralled a 4 cell EVE 280Ah battery.
This is why I would never trust an affordable commercial BMS. Fail open or shorted could be catastrophic for the direct connected alternator 80A charging. No smoke yet.

1.jpg
A poor 3 year old photo of the peak currents involved.
 
2 48v 304ah so far. Cheaper, got to pick the components, serviceable, enjoyed making them.

Next battery is also going to be a 48v 304ah, but it's going to be a 4 segment stacker. Reason for this is to make it easier to move. Going to be used in my camper when camper is in use, but in the home when not.
 
DIY is all but necessary for our setup.
Our 4 cell Sinopoly 300Ah battery has survived 9 years of full-time travel both powering the motorhome and starting the Canter 3.9l TD truck engine often multiple times a day.
I recently paralled a 4 cell EVE 280Ah battery.
This is why I would never trust an affordable commercial BMS. Fail open or shorted could be catastrophic for the direct connected alternator 80A charging. No smoke yet.

View attachment 166685
A poor 3 year old photo of the peak currents involved.
Man what kind of cables are you using for 700 amps?

Pulling 10kw on a 12v system.
 
still DIY for battery. designing/manufacturing the case has been slow. want robust, not an ME.

no interest in DIY BMS/SCC/inverter/charger for myself.

just some extra DIY for Interfacing between BMS and Other Devices.

some really great development efforts on this forum about DIY communication between BMS for DIY battery.

i've chosen JBD MOSFET type BMS for my design, but many visitors here have been reporting nice experience with JK.

being able to programmatically read details about the inner workings of the battery like cell voltage and history is important to help me diagnose any eventual issues. some prebuilt batteries have that, and many lack it yet.

one day there will be a much better Ecosystem of BMS/Inverter Communications where many devices are compatible with each other (like ethernet RJ45), but for now the weakness of compatibility lock in motivates me to just DIY it and keep the independence of being able to fix it myself locally when something fails. make the features you want to see in the world takes extra time :)
 
James at 18650 Battery always does well. I get the 304aH (or 100aH for my work van
I have been watching these cells. Should work well with the CATL 302s I already have on board.

My neighbor is also my mechanic. He can field strip an engine down to the smallest components and fix things others can't. While others might simply replace the modular components he is able to take these apart and repair them as well. He has been watching my project and has recently made a purchase of a grouping of these cells to be used as a UPS. Yesterday he was talking with someone who was without power for 8 days because of a recent storm. I could see the wheels turning.

I also have control of the battery alignment in my builds. They are upright and not stacked on each other. For me this is piece of mind.
 
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