Cause of Battery Fire

[MrM1]

My biggest fear with lifepo4 in the RV...

I'm surprised HDPE 'starboard' isn't used more often. Impervious to everything and non-conductive. It's used a lot on boats and I suspect that many are unaware of its existence due to that.

I liked this build so much I'm copying its overall design parameters with a few modifications.

Thread link:

560ah 12v Battery with Clean, Modern Case

This is my first post here, but I wanted to share my DIY battery bank. This forum and Will's videos were so helpful that I wanted to share a few things I learned, as well as a few things I created that I haven't seen before (specifically the asthetics of the case). I'd also appreciate any...

diysolarforum.com

@Browneye ,Hard to tell. Is that 3 lugs coming off the BMS to the battery or 3 cables in 1 lug?

If 3 wires into 1, Any issues with that? NEC code ?

I'm about to build 2 16s packs. Wanting to do it "Code-ish" (not inspected) . Will have 2 cables each side of the BMS. Can't decide if I want 1 lug or 2 per side. Issue is the cable is 7 awg. 1 fits too tight in a #8 and loose in a #6. But I do have a hydro crimper. If I go 2 cables in 1 lug a #4 is just right before crimp.

 

[Hedges]

I know code doesn't allow two wires in one lug/terminal. Except for lugs/terminals listed for two wires. Like split-bolt? I've found ferrules for two wires, not sure they are listed.
I never could see what was wrong with it.

There are a variety of lugs for two wires. Maybe mostly screw type, not crimp, except battery terminal?
I've also threaded a wire through a single lug (wire stripped in middle and both ends) to connect two circuits to a single lug (output of knife switch.)

 

[Alloy]

I found white acrylic rod/tube extrusion for the compression rods I’m pretty excited about. And various thicknesses of clear lexan for shields and covers.
I’m debating on blue or green led strips to light it up.

When I worked with acrylic we would score it with a knife and snap it. The pieces broke if dropped and fastening was a nightmare. Quarter turn to much would break so we started to use foam washers.

 

[Browneye]

@Browneye ,Hard to tell. Is that 3 lugs coming off the BMS to the battery or 3 cables in 1 lug?

If 3 wires into 1, Any issues with that? NEC code ?

I'm about to build 2 16s packs. Wanting to do it "Code-ish" (not inspected) . Will have 2 cables each side of the BMS. Can't decide if I want 1 lug or 2 per side. Issue is the cable is 7 awg. 1 fits too tight in a #8 and loose in a #6. But I do have a hydro crimper. If I go 2 cables in 1 lug a #4 is just right before crimp.

I assume so. Check out the thread - it's not my build.

The Overkill bms does have two or three feed wires to it from neg post - I guess you're supposed to crimp them into a single lug for output. I dunno. I ordered mine with two screw posts on each side - -B and -C on the board - I made up two 6awg wires into a 4awg lug and crimped them, double shrinked. Seems solid. It was tough to get all the strands into the lug, but I managed. The other ends can have a lug on each lead, put them together on the outer negative post to connect the neg cable to ground. I actually have a shunt to install, so that will be my outer battery post. The plus side has a huge class T fuse - I had no idea those things were that big!

The acrylic rod/tube I got is just to protect threads on the compression rods. They don't have to be tight between the end panels, and they'll have no stress on them.

I also got 1/8 medium density rubber sheeting for the bottoms to rest on. I'm still trying to decided if I'm going to turn my cells on their narrow side - under the sofa in the motorhome doesn't have much vertical clearance. It's probably still going to work out okay with the lugs up.

I'll link over to finished pics in one of my build threads when I get done. In the meantime, I'm STILL waiting on the top-balance - they're taking forever to come up to full charge. I had the power supply on 3.4 for two days, then on 3.5 for a day, and the cells are still sitting at 3.359 and not budging. I may shut it down, let them rest for a day, then try again at 3.6V to complete the top balance. The power supply says it's putting out a few amps, but gee, seems like I've pumped a couple of hundred amps into them, and they're only 230A cells!!

Class T...

 

[edcoopered]

The power supply says it's putting out a few amps, but gee, seems like I've pumped a couple of hundred amps into them, and they're only 230A cells!!

Remember if you have 16 230Ah cells paralleled up thats a 3680Ah pack, a power supply at 2A could take two months to fill that up.

 

[S Davis]

I assume so. Check out the thread - it's not my build.

The Overkill bms does have two or three feed wires to it from neg post - I guess you're supposed to crimp them into a single lug for output. I dunno. I ordered mine with two screw posts on each side - -B and -C on the board - I made up two 6awg wires into a 4awg lug and crimped them, double shrinked. Seems solid. It was tough to get all the strands into the lug, but I managed. The other ends can have a lug on each lead, put them together on the outer negative post to connect the neg cable to ground. I actually have a shunt to install, so that will be my outer battery post. The plus side has a huge class T fuse - I had no idea those things were that big!

The acrylic rod/tube I got is just to protect threads on the compression rods. They don't have to be tight between the end panels, and they'll have no stress on them.

I also got 1/8 medium density rubber sheeting for the bottoms to rest on. I'm still trying to decided if I'm going to turn my cells on their narrow side - under the sofa in the motorhome doesn't have much vertical clearance. It's probably still going to work out okay with the lugs up.

I'll link over to finished pics in one of my build threads when I get done. In the meantime, I'm STILL waiting on the top-balance - they're taking forever to come up to full charge. I had the power supply on 3.4 for two days, then on 3.5 for a day, and the cells are still sitting at 3.359 and not budging. I may shut it down, let them rest for a day, then try again at 3.6V to complete the top balance. The power supply says it's putting out a few amps, but gee, seems like I've pumped a couple of hundred amps into them, and they're only 230A cells!!

Class T...

Yes but you have four at 230ah cells so 960ah charging at 3.6 volts.

 

[Hedges]

People produce videos of "dendrites" growing across a PCB in real time.

Tin whiskers.
One looks like an insect leg in the air, other like "alien" coming out.

This one, well, I'll refrain from saying what it looks like:

Now those were "tin whiskers" growing in the air.

As for dendrites where voltage across PCB is too high (and there is surface contamination & moisture), this is what I was talking about:

That's something a vendor shows us a few decades ago. Easy to find now on YouTube if you know what to look for.


And finally, "Treeing" high-voltage failure in insulators.

 

[Browneye]

As promised...a twelve hour build session yesterday - Eve LF230's with 120A Overkill for the RV house:



It lives under the sofa:

 

[HRTKD]

Nice looking build you have there. Did you run the washing machine unbalanced with the battery on top as a shakedown test?

 

[Browneye]

Nice looking build you have there. Did you run the washing machine unbalanced with the battery on top as a shakedown test?

Thank you for your patient help Jim. You were a big inspiration to go for it. @time2roll too, you guys and the old guard here are a wealth of information. Three months ago I had never even heard of lifepo4 batteries.

I winced when I turned the cutoff switch on...the silence was deafening. LOL
Overkill bms BT app is just killer. It's in and working. ?

 

[12VoltInstalls]

I winced when I turned the cutoff switch on...the silence is deafening.

I imagine

An electrical code inspector made me throw and reconnect a humongous spring loaded legacy 1971 800A three phase disconnect that my electrician had “field repaired” once. I was quite scared especially when the two state inspectors suddenly backed up ten feet as I reached for the disconnect release.

I’ve imagined playing with batteries would have a similar scary gut.

 

[HRTKD]

An electrical code inspector made me throw and reconnect a humongous spring loaded legacy 1971 800A three phase disconnect that my electrician had “field repaired” once. I was quite scared especially when the two state inspectors suddenly backed up ten feet as I reached for the disconnect release.

Did you ask the inspectors to hold your beer? LOL.

 

[Alloy]

As promised...a twelve hour build session yesterday - Eve LF230's with 120A Overkill for the RV house:



It lives under the sofa:

That's a nice build. With the length of the plexi there won't be an issue with the PE bending.

Countersunk screws and hole saw holes in plexi isn't the best....here's some info.

Repairing a Crack in Plexiglass

Your Plexiglas is cracking. You're thinking... hey, it's the Plastic Genius, there must be a solution to this! Well, there is and here's the...

www.plasticgenius.com

....fuse goes after the disconnect
...a double cable crimp on the battery neg vs. two single crimps on the shunt?

 

[Browneye]

That's a nice build. With the length of the plexi there won't be an issue with the PE bending.

Countersunk screws and hole saw holes in plexi isn't the best....here's some info.

Repairing a Crack in Plexiglass

Your Plexiglas is cracking. You're thinking... hey, it's the Plastic Genius, there must be a solution to this! Well, there is and here's the...

www.plasticgenius.com

....fuse goes after the disconnect
...a double cable crimp on the battery neg vs. two single crimps on the shunt?

Thanks!
My thoughts...as a noob:
It's lexan - polycarbonate, three times stronger than acrylic. I can replace it with non-countersunk if it becomes an issue, but wanted a flush appearance. It would have been just as easy to use round-head screws, considered it. I build a lot with wood - boats, cabinets, etc., and it's natural to countersink and plug. Old habits die hard.

Everywhere I searched said fuse comes before switch. Everywhere. It was a quandary. I even asked and got no replies. It's really there to protect the battery, and really that's the BMS's job. The only other thing on that leg is the charger and it has it's own 70A fuse. If the feed wire shorts when the battery switch is off it will blow the fuse to the charger if it's on, I suppose.

Yes, double crimp. Fits better on those smallish 6mm posts. I bought SS 8mm adapters but they're too tall and didn't like the way they fit over the very small contacts on the cells. Overkill/JBD actually recommend TRIPLE crimps to the cells. I was going to buss the two posts on the bms and use a single 4awg wire, then decided it would be easier and cleaner to utilize two 6awg leads. Spec calls for 3@10awg or optional 8awg. Pos is 2awg all the way to distribution blocks. BMS build options are: no wires, 3@10awg,3@8awg, 12 or 24" leads, or 6mm screw posts. I figured I could make my own custom leads, hence....

Remember, this is a 120A bms, a 600w inverter is the highest load - the rest is lighting, fridge board, water pump, furnace blower. It replaces two GC2's.

Adapters from Pegasus racing I didn't use:

 

[12VoltInstalls]

Did you ask the inspectors to hold your beer? LOL.

>grin<
The senior electrical inspector used to be a master sparky for a big commercial electric outfit who knew me from years before. Big guy, 275ish.
The guy with him wasn’t an electrician but when big john moved so quick he jumped back.
Comical in hindsight but I honestly was more than a little scared.

The last recorded disconnect was something like 1987 when the powerco threw it and it wouldn’t reconnect. A brilliant electrician disassembled it and fixed it. Coincidentally his son was my electrician- he said “do not open that! If you hit that you’re on your own.” And hurriedly left. I had no choice… needed the CO signed off for Level 5 compliance.

I lived.

 

[Alloy]

Thanks!
My thoughts...as a noob:
It's lexan - polycarbonate, three times stronger than acrylic. I can replace it with non-countersunk if it becomes an issue, but wanted a flush appearance. It would have been just as easy to use round-head screws, considered it. I build a lot with wood - boats, cabinets, etc., and it's natural to countersink and plug. Old habits die hard.

Everywhere I searched said fuse comes before switch. Everywhere. It was a quandary. I even asked and got no replies. It's really there to protect the battery, and really that's the BMS's job. The only other thing on that leg is the charger and it has it's own 70A fuse. If the feed wire shorts when the battery switch is off it will blow the fuse to the charger if it's on, I suppose.

Yes, double crimp. Fits better on those smallish 6mm posts. I bought SS 8mm adapters but they're too tall and didn't like the way they fit over the very small contacts on the cells. Overkill/JBD actually recommend TRIPLE crimps to the cells. I was going to buss the two posts on the bms and use a single 4awg wire, then decided it would be easier and cleaner to utilize two 6awg leads. Spec calls for 3@10awg or optional 8awg. Pos is 2awg all the way to distribution blocks. BMS build options are: no wires, 3@10awg,3@8awg, 12 or 24" leads, or 6mm screw posts. I figured I could make my own custom leads, hence....

Remember, this is a 120A bms, a 600w inverter is the highest load - the rest is lighting, fridge board, water pump, furnace blower. It replaces two GC2's.

Adapters from Pegasus racing I didn't use:

I've had Lexan crack (allot).
For the counter sunk screws you may have some luck with Nylon Shoulder Bushings to keep the screw threads away from the Lexan

https://spaenaur.com/wp-content/uploads/2018/02/Sealing-Insulating-Washers-D71-D73.pdf

Disconnect first so nothing / zero / zip is live when working on it.

I hate those terminals. Would be better if there's a battery clamp that fit. For decades 3M has tried to come up with a long term connection that allows bare copper and alum to be in contact with each other. At this point crimping (excludes O2 and H2O) is the only method that works.

Tin plating works but the aluminum and copper are not in contact with each other.

Shoot it with a thermal camera when it under load every so often to keep an eye on it.

 

[Batvette]

Me too. But I'm getting better. Back in high school they kept telling us everything was going to switch over to metric. Gee, that was fifty years ago!

Some things converted well some did not. C for temp measurement is awkward unless its all you know.
"Its a hundred degrees out there" isnt the same.
The foot and yard will always be superior to metric because nothing human visually relates to a meter. For most males at least, a foot is their foot, a man is two yards tall so we can easily visualize a distance. The way military binoculars have reticles, the vertical line is the height of a man.
Maybe 50,000 years in the future when the average man is 6'7"+ tall the meter will be accepted.

 

[Batvette]

I've had Lexan crack (allot).
For the counter sunk screws you may have some luck with Nylon Shoulder Bushings to keep the screw threads away from the Lexan

https://spaenaur.com/wp-content/uploads/2018/02/Sealing-Insulating-Washers-D71-D73.pdf

Disconnect first so nothing / zero / zip is live when working on it.

I hate those terminals. Would be better if there's a battery clamp that fit. For decades 3M has tried to come up with a long term connection that allows bare copper and alum to be in contact with each other. At this point crimping (excludes O2 and H2O) is the only method that works.

Tin plating works but the aluminum and copper are not in contact with each other.

Shoot it with a thermal camera when it under load every so often to keep an eye on it.

I thought lexan doesnt easily crack, only acrylic. Not saying it doesnt I just havent seen it .

 

[Alloy]

I thought lexan doesnt easily crack, only acrylic. Not saying it doesnt I just havent seen it .

That's what I used to think too. After using it for 1-2 years the pieces I made started to crack/spit at the mounting holes. The worst pieces were outside so I assumed it was stress from expansion contraction so I drilled the holes bigger. This reduced the cracking but still had issues with the holes at the bottom. I figured it was the threads cutting into the Lexan so I started to use rubber/plastic inserts around the bolts or clamping it.

 

[12VoltInstalls]

started to use rubber/plastic inserts around the bolts or clamping it.

Yes. Oversized holes, nylon sleeves, and surprisingly: finishing washers under oval heads works ‘better’ than screw heads on plastic or flat washers.