Deciding to DIY my solar battery was one of my worst mistakes ever
- Thread starter kolek
- Start date
WindWizard
Solar Enthusiast
I am sorry that you experienced such extreme challenges on assembling your battery pack. I found it to be a very rewarding experience. First off, the compression thing is not for me. My Cells are not compressed and are doing fine. Top balancing wasn't for me either. It just seemed like a complete waste of time. I have had more years in the electronics field than some of you have been alive, so putting together this system was a walk in the park for me.
My philosophy on putting together my 128 Cell pack was to make it easy on myself. Yes, I had to play whack a mole with the Cells until they were top balanced, but the time spent was a whole lot less than connecting the pack up in parallel. I could not even begin to imagine what it would be like to top balance 128 cells. I can see why you would be frustrated doing it the hard way.
I just connected the pack together in the way that I designed it and then dealt with the Cells that had a bit too much of a charge. Now I look at my data once a week and daily make sure that the pack still has enough power to last the night.
We told CMP to shut off the power in February. Typically, we can run for about 3 days or so without the big bright object in the sky that produces such wonderment in our world.
My philosophy on putting together my 128 Cell pack was to make it easy on myself. Yes, I had to play whack a mole with the Cells until they were top balanced, but the time spent was a whole lot less than connecting the pack up in parallel. I could not even begin to imagine what it would be like to top balance 128 cells. I can see why you would be frustrated doing it the hard way.
I just connected the pack together in the way that I designed it and then dealt with the Cells that had a bit too much of a charge. Now I look at my data once a week and daily make sure that the pack still has enough power to last the night.
We told CMP to shut off the power in February. Typically, we can run for about 3 days or so without the big bright object in the sky that produces such wonderment in our world.
wheisenburg
Independent Solar Consultant
Do you remember punched cards? That's how I learned to program.LOL... lucky you... I had to use a soldering iron to build my first computer. Not just for connecting bits together, but soldering all the components to the PCB... Yes, I am that old
featherlite
Solar Enthusiast
My understanding is that few prebuilt batteries have any "compression". Rather, they just tape the cells together or use foam between the cell and outer case to hold the cells "securely" in place. Consequently, if you are happy with that level of prebuilt "compression", no need to worry about proper "compression".
As for my 4s1p DIY build, in a mobile environment, I fabricated a simple fixture using two 3/4 inch boards and four 1/4 inch threaded rods; with the nuts tightened just enough to keep the cells from falling out when I pick up the fixture.
featherlite
Solar Enthusiast
I hated fortran and punch cards!
Something I don't really follow is that people keep mentioning that DIY batteries are only 10% cheaper than pre-built ones... how is this the case?
For reference, I can get 600ah of pre-built batteries in a rack for $7,700
96 prismatic 105ah cells (16s x6 for 605ah total) is $4,000 shipped. 6x 100amp daly 16s BMSs is a total of $459 shipped.
Grand total to DIY the batteries without any enclosures or racking after taxes and shipping is $4,459
... this is ~46% cheaper for 5% more capacity (630ah vs. 600ah)
What am I missing here?
For reference, I can get 600ah of pre-built batteries in a rack for $7,700
96 prismatic 105ah cells (16s x6 for 605ah total) is $4,000 shipped. 6x 100amp daly 16s BMSs is a total of $459 shipped.
Grand total to DIY the batteries without any enclosures or racking after taxes and shipping is $4,459
... this is ~46% cheaper for 5% more capacity (630ah vs. 600ah)
What am I missing here?
offgrid-curious
New Member
The case/rack, bus bars, fuses, cables, switches, terminals. Perhaps most importantly, your time. I enjoy doing this stuff, but if I take my "hourly rate" into account, I have a really, really expensive battery (and overall solar set up), and it's not even done yet!
Battery prices are dropping quickly so people may be using last year's prices who knows? But yes in my case diy was less than half the price of prebuilt
Wood case $12
Bus bar $50
Breaker $30
Cables you need with either pre build or diy.
My time is free spare time because I would be on this site anyway so it's a quick couple of hours break from the forum
ImAnIdiotPleaseBePatient
Solar Enthusiast
- Joined
- Dec 10, 2022
- Messages
- 423
Man, I was just planning on using no compression and laying the cells out on a HD rack (like that dewalt one). It's gonna look ugly af, but I know I am no carpenter.
hwy17
Anti-Solar Enthusiast
My own build included $150 of additional FR4 separator material and a $70 bench shear to cut it. And I surprisingly to me in the end it's one of the expenses I would repeat in my next build. It felt like a hangup but now I am glad to have heat resistant separation on all 5 sides of every cell (do not shake battery upside down - 6th side is unprotected!).
hwy17
Anti-Solar Enthusiast
As long as you definitely don't get earthquakes.
SilverbackMP
Solar Addict
- Joined
- Apr 4, 2022
- Messages
- 928
And have no mice.
Brucey
Solar Wizard
Four of these, 48V 280Ah for $2156.
Eight of them, 48V 560Ah for $4312.
600Ah $7700 is definitely paying premium pricing for the rack form factor. If you can handle the balancing of the much cheaper 12Vs there's big savings to be had.
hwy17
Anti-Solar Enthusiast
Balancing nightmare though.
Bob142
Build more, learn more.
FWIW, I've never seen any of the plastic case batteries Will or anyone else has torn down with any sort of precisely calibrated compression mechanism in them. I've built several batteries over the years that have run very well without ever sweating over compression. If I were you, I wouldn't worry too much about it. Just my opinion.
Good luck with your build!
Yep, that's mine. I think I mention somewhere that those nuts are hand-tight.
Nothing. You can get to 50% of the price of off-the-shelf by going DIY, and have been for pretty much ever. The last time I made the calculation:
DIY LiFePO4 Cost Analysis - The Cheap November 2023 European Edition
Time to do a another calculation again. (previous posts here, here and here) - but this time, I will go cheap (but with cells available in Europe - I'll do an international Alibaba version at some point). Disclaimer, as usual: I mention vendors below and use them as an example and as reference...
diysolarforum.com
I should do another one soon.
By the way, several people have been able to use the info on this forum as complete newbies, and successfully built their DIY packs. I understand it's not for everyone, but that doesn't mean everyone should abandon the idea. To OP, sorry to hear your DIY journey didn't go as you planned.
As for time - once you built one pack, the other ones after that become a lot easier and faster (and trust me, there will be other ones). For me personally, the flexibility, the knowledge gained, the fun, and indeed the 50% price difference is well worth it.
Brucey
Solar Wizard
Can put a balancer on each series, tho they may emit a 12kHz whine when running.
NCislander
Solar Enthusiast
If DIY is not your thing, pull up your preferred Solar Supply Company on your web browser and fill your Cart with a pallet of prebuilt batteries. SOK, EG4, Trophy, BigBattery...They will happily deliver them with your paid order.
I prefer to pay for mine with improved DIY skills over time. Always learning for me.
I prefer to pay for mine with improved DIY skills over time. Always learning for me.
I just priced some pre-built 48V batteries (because seriously, stringing 4 12V batteries together is a potential balancing mess I do not want to deal with). Even at the old, higher price I got my 230Ah cells for I'm still way ahead, price wise, doing DIY. As long as I find the time...
