Tiny Home DIY System Help!

[Rhodzy555]

Hey all, first thread, thanks for any and all help.
I built a tiny home over the last year and built it to be off grid. Wired half the house in 12v and the rest in 110v. I hired a guy to build a power wall and help me size and wire my solar power system. Long story, short, he burned up a good chunk of the batteries, didn't fix the problem, gave me all of it incomplete, including the burnt batteries and didn't help me with what to do with it. So it's up to me to build the system. I have only a beginners knowledge of electricity. I understand volts, amps, and watts, as well as wire sizing, a little bit of fuse sizing and somewhat of a grasp of all the components of a solar power system. But I have no idea how to finish this system. First thing is the batteries, I don't know what they are, the guy found them for a really good deal. Each pack has 9P3S of Panasonic NCR18650. Please correct me if I'm wrong. Which if I am right is, 12.6V, 26.1ah and comes with it's own BMS. Supposedly it was used for medical purposes. Here's a picture:

And the BMS:

Bit ugly, but you get the idea.
Here is a picture of the battery box built by the guy.

One of these batteries almost caught fire when he hooked them all up, in parallel, to balance charge them. His guess was that the BMS malfunctioned and kept the voltage lower, so all the other batteries began to send too much current to this one battery, thus fire, or almost fire. Damaged 11 of the 32 batteries. I'm wondering if that is correct or not. Could he have somehow hooked up the batteries wrong? The connectors plug goes into +1 -2 +5 -6:

Yet if you look at the solder joints, it say Red Pack + is 1 and 2, and Black pack - is 3 and 4. I don't know how BMS's work so maybe it doesn't matter, but with a multimeter I wasn't getting any voltage getting a reading of .35 volts from terminals 1 and 2, as well as 5 and 6. If I tested the solder joints, it says this battery has 10.5V. So was the fire caused by a malfuctioning BMS or the way the batteries were hooked up? And what would be the solution to prevent this problem from reoccurring? I can provide pictures or more tests if needed. Thanks for any and all help. I will have many more questions, but starting at step 1.

 

[Forbisher]

Your Lithium ion batteries are dangerous as you found out. How much did you pay for them?
That's why most solar installs in houses and RVs use safe LiFePO4 batteries.
Catching your house on fire is not worth any kind of deal.
LFP batteries can be DIYed quite easily or bought assembled at a decent price.

 

[Craig]

I agree run as fast as you can from those batteries. Feel free to ask questions here about how to build and deploy new systwm

 

[snoobler]

Best thing I see is the wooden box - great for getting the fire started or keeping it going when it starts on its own!

Start over. The design approach was shit. 3S NMC makes for a shitty 12V.

I'm going WAY back to the very beginning. Do you know your actual power needs? How much solar and battery you need? If not...

Link #5 in my signature to obtain your available solar for your location, panel orientation and tilt.
Link #1 in my signature to conduct an energy audit - what you want to run, how much power it takes and how long you want to run it per day. In your case, you should distinguish between 12VDC and 120VAC items.

If you haven't done the above in some way, then you're just guessing. This is your chance to do everything right and meet your needs rather than just toking on the hopeium pipe.

If you've already done the above, share your results.

 

[Rhodzy555]

Thanks for the responses. Hard news, but I agree, would rather not burn down my house. Payed $780 for 32 of the battery packs. The guy who built it, said he's been using them for a long time with no problems for other builds and never had problems. But I think ours was the biggest he ever built. Would fusing the individual packs prevent a fire? Or is the problem more so with the BMS? That's what burned up. I wondered about taking them apart and testing them and building my own wall like I've seen lots of youtubers do, but that seems like a long arduous process. Right now we're hooked up to the grid via extension cord from a house, 12 volt converter for 12VDC. I've been monitoring the energy usage. About 1.5 to 2KW on week days and 2.5 to 3KW on the weekend, over the course of about 5 months. I think about a quarter or less of the power is the 12VDC. I have 1.5 KW of panels on the roof, 6 250W panels. Separated into two runs. 3 panels each in parallel, going to two separate charge controllers. Although I only have one right now, I got an Epever 60amp MPPT Charge Controller. They are 30V Panels, I think. I can give more specs if needed. They are south facing, with little to no shade. And I got a 4000w inverter. Overkill for our house, but wanted to have the ability to run the occasional power tool here and there. I live close to Vancouver, WA in the PNW. I'm pretty sure our system is more than large enough for our needs, correct me if I'm wrong. Thanks for the help!
Pictures:
Culprit battery on right:

Solar Array:

 

[Forbisher]

3.7V x 3 in series is only 11.1V nominal so that pack was too low a voltage for 12V.
Sell those NMC batteries.

Looks like you already bought a large 12V 4000 watt inverter.
Your tiny home should be 24V battery.
What kind of 12 volt loads do you have?

1500 watts on a 24V battery is 62.5A
You would not need to buy another Epever 60A

 

[snoobler]

Right now we're hooked up to the grid via extension cord from a house, 12 volt converter for 12VDC. I've been monitoring the energy usage. About 1.5 to 2KW on week days and 2.5 to 3KW on the weekend, over the course of about 5 months. I think about a quarter or less of the power is the 12VDC. I have 1.5 KW of panels on the roof, 6 250W panels. Separated into two runs. 3 panels each in parallel, going to two separate charge controllers. Although I only have one right now, I got an Epever 60amp MPPT Charge Controller. They are 30V Panels, I think. I can give more specs if needed. They are south facing, with little to no shade. And I got a 4000w inverter. Overkill for our house, but wanted to have the ability to run the occasional power tool here and there. I live close to Vancouver, WA in the PNW. I'm pretty sure our system is more than large enough for our needs, correct me if I'm wrong. Thanks for the help!
Pictures:
Culprit battery on right:

Solar Array:

If you're confident your peak usage is 3kWh/day, then you should be fine.

You have ZERO plans of EVER running A/C, correct?

As @MBR mentioned, 1500W is a tall order for 12V. 24V would have been a better choice for the number of panels. It's also tough for 4000W. You're going to need MEGA battery cables to support that current.... 4000/12 = 333A

You could build your own 7.2kWh 12V LFP battery for about $1200.

 

[Dusterdubs]

If you're confident your peak usage is 3kWh/day, then you should be fine.

You have ZERO plans of EVER running A/C, correct?

As @MBR mentioned, 1500W is a tall order for 12V. 24V would have been a better choice for the number of panels. It's also tough for 4000W. You're going to need MEGA battery cables to support that current.... 4000/12 = 333A

You could build your own 7.2kWh 12V LFP battery for about $1200.

If you're confident your peak usage is 3kWh/day, then you should be fine.

You have ZERO plans of EVER running A/C, correct?

As @MBR mentioned, 1500W is a tall order for 12V. 24V would have been a better choice for the number of panels. It's also tough for 4000W. You're going to need MEGA battery cables to support that current.... 4000/12 = 333A

You could build your own 7.2kWh 12V LFP battery for about $1200.

build your own 7.2kWh 12V LFP battery for about $1200? I searched in the forum and only find your statement. Do you have a link to a safe reliable build on this?

 

[snoobler]

build your own 7.2kWh 12V LFP battery for about $1200? I searched in the forum and only find your statement. Do you have a link to a safe reliable build on this?

Start with the "280Ah cells" thread. So many.