diy solar

diy solar

When a solar enthusiast and a welding enthusiast really love each other (Warning - Photo heavy!)

Rednecktek

Solar Wizard
Joined
Sep 8, 2021
Messages
5,672
Location
On a boat usually.
So I needed a 24v case capable of 300Ah cells and Seplos wanted about $800 for their case and the special cables but no low temp cutoff, no heaters, no active cooling... weeeelllll... I have a welder!

So first I got out the paints and painted them up real pretty... then drilled them like they'd never been drilled before!

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Then I swung my hips for a little bumping and grinding...

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I wasn't sure until I played around a bit if it was even going to all fit in there...

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Yup! It all stuffed in there nicely! Blew some slag all over it and I needed a cigarette and a nap!

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Day More! Time to start getting things accomplished!

So I wanted something that would be durable and non-conductive, so I got a few cans of truck bed liner and started hosing it down. After getting a new piece of steel and re-designing the face plate (Class-T fuses are HUGE!!!) the test fit looked pretty good.

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Wiring was a little time consuming but the neat package was going to be worth the effort. I used some threaded nylon standoffs to mount the BMS so it was electrically isolated from the case.

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Waitaminute... why the F#@K are there 10 wires on an 8s BMS?!?!?

So evidently JK is stupid and can't count, so my 19v battery... Grrrr.... :mad:

But I mounted the face plate on hinges for access to the guts (fuses, etc) and some welded nut tabs to hold it closed. The fans draw plenty of air through the hole in the front when the lid is on which goes around both sides of each bank and over the top, that ought to work well.

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The cooling fans will be run off the existing 12v system up at the camp so it'll still cool when it's Stupid Hot and nobody's around. Cut in at 34c and cut off at 24c and tested good! The heater pads won't arrive until the end of October which is why the keen eyed observer will notice holes in the side walls and a little gap.

Next steps are to:

Replace the STUPID harness!!
Extend and mount the STUPID start switch.
Install the heating pads when I get them and get back up there.

I'll have to transport this assembly to the camp in 5 pieces, 4 shipping boxes of cells and the case itself. Looking back, I've learned a few lessons though:

Use thinner steel. I'm so used to the industrial side that I used nice "thin" 10AWG steel... the box weighs about 60lb! EDIT: Just did the math and the box is 95lb of steel alone!
Get another brand of BMS. This JK has been a real hassle!
Order parts sooner. The heating pads are 2-3 months to arrive from time of order.
Use lighter weight steel. This thing is heavy!
Mock up in cardboard first. Save money on buying extra steel plates.
Build it with THINNER METAL!!
Have the World's Strongest Man on speed dial to help move it.

Ssssoooo.. anyone want to go camping in NE Washington in a couple weeks? Anyone strong with a good back? ;)

Final Specs:
8.5Kwh
8s 304Ah EVE cells
JK 8s 200a BMS with Heater
3x 120mm IP65 Noctua exhaust fans
Digital temperature relay
24v relay between BMS and heating pads
4x 20w 24v heating pads*
160a DC breaker
Aili Shunt
150a Class-T fuse
3.22 Metric Assload-a-grams!!
2AWG wire on positive leads
2x 4AWG on negative leads
Copper bus bars where applicable
3/8" isolating terminals

Whew! Still slightly cheaper than a Trophy or the Seplos case, AND 30% more capacity, active cooling, real shunt, heaters, built in Class-T fuse!

Hey @Will Prowse , you want to do the teardown review? You just need to pick it up. :ROFLMAO:

I think this counts as "DIY", right?
 
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And yes, it's just sitting on a table in the open carport. If anyone tries to pick it up and run off with it, I'll just call 911... for an ambulance. ;)

Now I just gotta wait the couple days it's going to take my little 10a bench power supply to charge and balance it all. Good thing I'm still waiting on parts!
 
Whew, I was a bit scared to click on the title.
Wasn't sure what pictures I was about to unsee. lol

Nice project
 
Is that a technical term lmao ?


What's the actual final weight?
It's a nautical technical term yes and I have no way of getting an exact weight. Even if I could find a scale big enough around here to fit it, there's no way I'd be able to move it and I only want to disassemble and reassemble it once.

If I can find the original steel receipt I might be able to get a rough calculation though...
 
What's the actual final weight?
So rounding up to account for screws and terminals and the little things:

Steel - 10Awg 16.9sq ft = 95lb
Batteries 8x Eve 304 cells = 97lb
Fuse & breaker - 3lb

So around 200lb total if you round up for all the little things rather than trying to add up all the ounces here and there.
 
It's a nautical technical term yes and I have no way of getting an exact weight. Even if I could find a scale big enough around here to fit it, there's no way I'd be able to move it and I only want to disassemble and reassemble it once.

If I can find the original steel receipt I might be able to get a rough calculation though...
Cmon it’s simple. You take your bathroom scale outside and stand on it. Then you pick up the battery with a few quick grunts and look at what the scale says. Math the difference.
Should be no problem, I’m sure it’s only a couple hundred pounds ?
 
;) Great work, nice post - lots of good pics.
So...
instead of 10ga, would you go thinner steel just above the base plate or the whole box?
What gauge would you use next time.
 
I don't think the stitches in my chest would hold very well and I like my doctor, I don't want to piss him off. ;)

As an update I needed to relax so I decided to mount the button. Big mistake! I think my blood pressure is in Anime Nosebleed range now!

I had to install the button in the face, THEN connect the heat shrink red butt connectors with about 2" of tiny-ass-awg wire right next to the breaker. The connectors together were larger than the button retaining nut so no other install option.

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instead of 10ga, would you go thinner steel just above the base plate or the whole box?
What gauge would you use next time.
The whole box was massively overbuilt. Being as that it's going to sit on a shelf forever I'm thinking somewhere in the 20-24awg range would have been plenty with some angle iron welded in special places to strongback a few places.
 
Nice job, are you going to release DIY drawings??

If you build another, I'd look at 1.0mm (20 AWG) steel, once welded up it should be plenty strong enough (maybe retain the thicker stuff for the base?)

Last year I ordered a bunch of 1mm wall-thickness box section for a new chook house / shed. It was delivered whilst I was at work, Madam checked the sizes and count and signed for it.
When I got home I nearly did myself a mischief when I picked up a 6m length of inch and a half square! Looked a bit closer, it was 3mm wall thickness!
Check the delivery note - definitely supposed to be 1mm. Called the man, next morning the chaps arrived with the correct steel and took away the rather thicker stuff.
 
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So rounding up to account for screws and terminals and the little things:

Steel - 10Awg 16.9sq ft = 95lb
Batteries 8x Eve 304 cells = 97lb
Fuse & breaker - 3lb

So around 200lb total if you round up for all the little things rather than trying to add up all the ounces here and there.

Twice the weight of LiFePO4 alone.

I could'a had an AGM! ?‍♂️
 
Nice job, are you going to release DIY drawings??
Have you seen my krappy MSPaint drawings? Nobody wants those. The parts list is readily available in multiple posts though and I'm available for Q&A if needed but that's about as far as I'm willing to go.
If you build another, I'd look at 1.0mm (20 AWG) steel, once welded up it should be plenty strong enough (maybe retain the thicker stuff for the base?)
Yeah, looking back 1mm is still a happy range for the welder and would have been plenty. I don't foresee myself doing this ever again but if I did I'm sure I can stack the new one on top of the old one just fine. ?

This is one of the many times I wish the USA was a properly metric country. Trying to convert 75mm to inches left quite the gap in the boxes that I needed to fill with mouse pads. Fractions SUCK!
 
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