I've been in the electronics and telecommunications industry for over 40 years, as well as an extra class amature radio licensee since our transmitters had tubes. Overall I've built six 48 volt batteries and have found top balancing to be important but cell compression, not so much. I trust my DIY packs to be completely safe and reliable. From what I've seen, commercial built batteries are getting better and it's just a matter of time until I'll probably have to concede the mass produced offerings are superior. But since I'm a hobbyist and 15 minute engineer, I have enjoyed building and refining my battery builds.
Deciding to DIY my solar battery was one of my worst mistakes ever
- Thread starter kolek
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kolek
Inventor of the Electron
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Ok, but the parts don't order themselves. You knew every product you needed to buy and where to buy it, and that process took you zero time?
I've spent 40+ hours just figuring out which cells, busbars, BMS, Anderson connectors, switches, fuses, breakers, cable, torque wrench, wiring, battery charger, fuse, fuse block, circuit breaker, battery shutoff switch, ring terminals, crimpers, wire strippers, electrical contact grease, heat shrink tubing .... etc. to buy. A couple of the components I had to buy twice because I screwed up the first time, like I bought the Daly BMS before I figured out that JK-BMS was a better choice. Same with the busbars. Literally every component from large to small I needed to research and find from scratch.
Also I needed a wiring diagram, that took a good 8+ hours to come up with.
Needed to flash the BIOS on the BMS.
Needed to learn the BMS software and settings.
Every step took longer than I expected.
Also in my case I need to add the time I spent worrying. Probably a good 60 hours spent worrying. And time spent procrastinating. At least 200 hours of procrastination time. Time spent building the boxes. Probably 30 hours for that.
And how many hours did you spend to "research and gain confidence" ?
I'm trying to take my research time into account. That all has to be amortized into the cost if you want to accurately calculate the true cost of DIY vs. buying off-the-shelf.
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That's fair, but then you also have to consider the value of the knowledge and experience you've gained. Plus, how do you place a dollar value on the satisfaction of being able to say "I built that".
OP, I am much like you. Fortunately my obsessions tend to become pleasurable hobbies so I don’t feel out the time financially.
In the last 4 months I’ve acquired 64 cells. Because I was overwhelmed with other facets of my power system, I chose to take the easy route and purchase a Seplos/EEL box for each battery. It contained all pertinent parts required, Seplos/Pace BMS (which seems only outdone by the REC and Orion types of the world and on par with others), the flexible bus bars, the cell separators, the pre fabricated design, it was all there and took the guess work away.
Now, I can feel more confident in the future should I want to broaden my scope and fashion my own case and acquire individual pieces as well.
In the end I did cut my losses in this regard. I found it more fruitful to concede my time and buy the box.
I still chose to obsess and over analyze my wiring, breakers, fuses, mounting hardware, utility shelf, bench, DC charging, tools, gloves, thickness of plywood, aluminum or steel, crimp my own wire or don’t
Each of these caused a domino effect as I then had to figure out “well who makes the best fuse, what kind of enclosure, should I build my own enclosure, do I need SPD, do I need to rate to 1.25 or 1.56, do I even need breakers in this situation, where can I get a fuse holder with a clear cover”
“If I make my own cables what size hydraulic crimper should I get, should I get two sizes, how will I hide another purchase from the wife, maybe I’ll just order prebuilt custom lengths, no that’s dumb i can make wire forever”
I think I’m rambling at this point, but sometimes it’s best to cut one’s losses and trust in the skills and judgement you have developed over your life, make the gut choice and not overthink it.
I have to do this sometimes and while it can bite me, I often have the most satisfying projects come to fruition
I find myself turning more into the Chad all the time, as I will think myself to death if I don’t and I’d like to see the fruits of my labor before I die
In the last 4 months I’ve acquired 64 cells. Because I was overwhelmed with other facets of my power system, I chose to take the easy route and purchase a Seplos/EEL box for each battery. It contained all pertinent parts required, Seplos/Pace BMS (which seems only outdone by the REC and Orion types of the world and on par with others), the flexible bus bars, the cell separators, the pre fabricated design, it was all there and took the guess work away.
Now, I can feel more confident in the future should I want to broaden my scope and fashion my own case and acquire individual pieces as well.
In the end I did cut my losses in this regard. I found it more fruitful to concede my time and buy the box.
I still chose to obsess and over analyze my wiring, breakers, fuses, mounting hardware, utility shelf, bench, DC charging, tools, gloves, thickness of plywood, aluminum or steel, crimp my own wire or don’t
Each of these caused a domino effect as I then had to figure out “well who makes the best fuse, what kind of enclosure, should I build my own enclosure, do I need SPD, do I need to rate to 1.25 or 1.56, do I even need breakers in this situation, where can I get a fuse holder with a clear cover”
“If I make my own cables what size hydraulic crimper should I get, should I get two sizes, how will I hide another purchase from the wife, maybe I’ll just order prebuilt custom lengths, no that’s dumb i can make wire forever”
I think I’m rambling at this point, but sometimes it’s best to cut one’s losses and trust in the skills and judgement you have developed over your life, make the gut choice and not overthink it.
I have to do this sometimes and while it can bite me, I often have the most satisfying projects come to fruition
I find myself turning more into the Chad all the time, as I will think myself to death if I don’t and I’d like to see the fruits of my labor before I die
kolek
Inventor of the Electron
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My goodness, that is EXACTLY the kind of thought processes I've been having non-stop since this whole nightmare project started. You nailed it.
timselectric
If I can do it, you can do it.
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A couple of clicks on my phone. (5 minutes)
Reading threads on this forum.
Watched a few of Andy's videos. (Off grid garage)
And seen how simple it was.
A few hours, divided over all of the batteries.
Could add 10 minutes per battery.
Could also be counted as entertainment.
I do enjoy the time I spend here and on YouTube.
It’s a blessing and a curse. I often don’t make a foolish purchase. On the other hand the store may sell out before I decide to buy.
And it seems to be with every.single.thing
kolek
Inventor of the Electron
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Right, the store may sell out, or the company may introduce a new model before I'm finished researching the current model.It’s a blessing and a curse. I often don’t make a foolish purchase. On the other hand the store may sell out before I decide to buy.
And it seems to be with every.single.thing
I used to say that. Let me tell you about the classic
timselectric
If I can do it, you can do it.
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I over think every single part of my projects.
My OCD forces me to. Some projects take years to begin. Because I won't start until I have everything worked out in my head. But most of my projects are one of a kind.
My batteries are basically copy and paste of others.
So, it was easy to just do it.
My OCD forces me to. Some projects take years to begin. Because I won't start until I have everything worked out in my head. But most of my projects are one of a kind.
My batteries are basically copy and paste of others.
So, it was easy to just do it.
I put engine valve springs on my compression threaded rods. Measured how much squish I needed to get on the springs to get 150lbs of force, assembled the compression system, then cranked down the nuts on the threaded rods to get to that same measurement. 150lbs x 4 threaded rods and springs = 600lbs compression. Close enough.
I used silicone and fiberglass BBQ mats for cell separators.
Edit: Photo added, springs visible at far end.
kolek
Inventor of the Electron
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Interesting approach. I guess by using springs you didn't need to concern yourself with torque, but do you happen to know the torque your setup required to get to 600 lbs?
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No clue. Very little.
I wouldn't go with torque at all. That's a measurement of rotational force, and only bears a relationship to clamping force under very specific and controlled conditions. Completely unsuited to applying compression to battery cells which will expand and contract as they go through their normal charge and discharge cycles. The slightest variation in thickness in the batteries will induce huge differences in compression force in a fixed or rigid compression system.
The springs were cheap too. $3/ea or something like that from Summit.
ImAnIdiotPleaseBePatient
Solar Enthusiast
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ill shoot em if they get close to the batteries or the inverter
ImAnIdiotPleaseBePatient
Solar Enthusiast
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no earthquakes. just clumsy people with well-conducting wrenches
I completely agree with this. Because of strong interests, we will carry out this tedious and interesting project no matter how complicated it is.
But if it is just a temporary interest, I suggest to buy the finished product, because the temporary interest may be exhausted when encountering various problems during the DIY process, and then you will only be left with deep fatigue and regret!
But also think about the opportunities it can bring, when you invest time into this and become good at it and how valuable that knowledge can be. Because I started doing this, I've been able to join projects I wouldn't have been able to otherwise. I'm currently designing a battery pack for a datacenter, I've joined Batteries Europe to help shape future battery legislation in Europe and have made tons of contacts that can lead to future projects, I've met and am able to have conversations with people in the industry that are currently the top experts in battery research and I've been able to expand my field at university to include among others a course I teach in solar power systems and related energy projects at university.
While I was building my house, I also got local electricians interested, started a company to deliver batteries and solar for cottages where all I had to do was play middle man setting up the supply chain and train some people how to do it, and in general I think I played at least a small part in getting solar adoption going in this region in Finland - including these guys.
In other words, the time I've invested in this paid for itself, and those batteries I built have already brought their return on investment several times over.
shadowmaker
Solar Addict
Some people can buy premade batteries under 130e/kWh (it was 130e/kWh about three months ago and prices have gone down since). So 600ah (51,2V) =30,72kWh is under 3994e ($4352) all included (delivery and 24%VAT). With 60kWh you get rack for free (nothing fancy, but a rack on wheels nonetheless). With every battery you seem to get a working warranty also.
I guess you are missing a nice vendor.
Pi Curio
Rim Tim Tagi Dim
It's probably a good idea to build something smaller first, the principle is the same and there's a lot to learn, just on a smaller, more manageable scale. There'll be much less on your plate if you have some experience before building a bigger battery.
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Oh, ive built some computers where the complexity DEFINITELY compares with the complexity of building battery packs...No I get that, building a computer is easy, I didn't mean to compare the complexities, but the broad strokes of it all. But with the amount of time you've spent, I bet you've learned some stuff along the way, so maybe not a complete waste of time
Neon, and water blocks, and hard tubing heat formed around obstacles, mounting the paralleled video cards, and getting all the drivers to cooperate...
Yeah, ill build batteries all day long before doing THAT again...
Anybody build a pc when windows Me was the operating system of choice?
Remember building pc's when windows 95 was first out?
Or BEFORE 95? Vista anyone?
Yeah... i love solar!
