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Battery blew/shorted

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yantruocmot

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Feb 12, 2022
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I had the unfortunate experience of thief's stealing out of my trailer and in the process breaking part of my solar setup and appears to have shorted my batteries. I had four 100ah LiFePO4 batteries in my passthrough setup in a parallel configuration. When the thief's did this two of the batteries spewed some gel like substance out and some carbon (prob some decent smoke as well). Thankfully they didn't catch fire but by the time I found them they were REALLY hot and swollen. This short blew up everything inside our trailer that had a circuit board. No wires however were burnt including some very small 18ga for USB ports, but the ports no longer work..

What did I do wrong with my setup on why this type of surge was not protected against? I have a 250amp T-Class fuse, along with multiple other mega fusses in a lync distribution for other circuits. The trailer is currently at the shop having the components fixed. Once I get it back I want to make sure I also put in some better protection. What can or should be added to a system to stop something like this from happening again?

Also how do you dispose safely of multiple 12v 100ah batteries that have been shorted?

Thanks for the help!
 
Would have to know more about your setup to answer what went wrong. Clearly there was a short that caused some cells to vent. The vent hydrogen and a number of other less than good substances but nothing as bad as the heavy metal LiPo cells do.

For disposal - I would call the hazardous waster for your county/city/etc and ask what they want you to do - some cities take all forms of batteries in at the same place they take old oil, paint, and other chemicals.

Personally I have MRBF fuses on the posts of my 12v batteries. In your case I would have used 125a fuses on each battery post then if the wire was longer than 12" another MRBF on the bus bar end of the cables. Then the class T between the bus bar and inverter.


Do you know where the short happened? Was it battery cables or inverter or whatever he stole and left the cables touching?

Looking at your other thread pictures it looks like you need to also add rubber boots to every cable end with exposed metal to prevent shorts.
 
Different locks on the pass through. There's only a few standard RV keys that will open a door unless the locks are changed. That's cheap.

Maybe a light turns on inside when the door to the pass through is opened. That may be fairly cheap.

For not shorting the batteries out, putting them in a box. As having a looked for battery boxes, that is easier said then done. Could be pricey.

I bought these battery terminal covers to help prevent accidental shorting for a homemade battery.

Only get Busbars with covers. Again easier said than done, not all bus bars have this, and some were surprised when trying to use hose that some hose conducts electricity.

I'd like to know what you do with the batteries. There may be one recycling facility in all the US, so I would like to know what this proper procedure is. I've
 
Locks were changed out and more added when be purchased the trailer a couple years ago. The problem is those types of locks can just be twisted and opened....

As for how it shorted, all of my solar equipment is mounted on the ceiling of the passthrough. They appeared to have tried prying off the panel and then tried with the shunt. I believe that moved over and connected with the main positive from the batteries. I did not have rubber boots over the shunt connections, but since those other pics were posted I did have them over all of the battery connections. I also had the plastic cover over the class-t fuse.

My main concern now is did I over size the fuse i.e. it didn't burnup when it should have on the short? Or should I use a breaker or a MRBF like suggested above to alleviate this potential from happening in the future? Im not so worried about the battery as I am about the rest of the circuits in the trailer (TV, Fridge, Microwave, some lights, fan, heater, AC, and water heater).


In the future Im going with fewer but bigger batteries.

This is the shunt where they tried to break it off...
IMG_9555.JPEG
 
I accidentally shorted one of my batteries and I was surprised a fuse didn't blow. It looked and sounded like an ark welder.
You can operate an ark welder from batteries without blowing a fuse.
 
yantruocmot said:
Locks were changed out and more added when be purchased the trailer a couple years ago. The problem is those types of locks can just be twisted and opened....

As for how it shorted, all of my solar equipment is mounted on the ceiling of the passthrough. They appeared to have tried prying off the panel and then tried with the shunt. I believe that moved over and connected with the main positive from the batteries. I did not have rubber boots over the shunt connections, but since those other pics were posted I did have them over all of the battery connections. I also had the plastic cover over the class-t fuse.

My main concern now is did I over size the fuse i.e. it didn't burnup when it should have on the short? Or should I use a breaker or a MRBF like suggested above to alleviate this potential from happening in the future? Im not so worried about the battery as I am about the rest of the circuits in the trailer (TV, Fridge, Microwave, some lights, fan, heater, AC, and water heater).


In the future Im going with fewer but bigger batteries.

This is the shunt where they tried to break it off...
View attachment 224625
Click to expand...


Well, the shunt is typically connected close to the negative lead of the battery. The main positive of the battery is before the fuse. So your short wouldn't have blown it. The MRBF on the post would have probably blown verse vent the battery.

I use a boot over the MRBF and battery bolt. I also painted the exposed parts of my shunt with liquid electrical tape. I don't connect the tape all the way across, mostly just the brass bolts and block area after attaching things. Then I booted the cables. I am a bit paranoid.
 
yantruocmot said:
I have a 250amp T-Class fuse
Click to expand...
yantruocmot said:
My main concern now is did I over size the fuse i.e. it didn't burnup when it should have on the short?
Click to expand...
IMO, if your fuse was 250 amps and the wire had ampacity for it, the fuse is right sized and fine. This is a picture of the class T fuse chart:
1719360845170.png
If you look at the trip time and % of rated current, the fuse will blow at quite a bit more amperage than rated. I would think if you undersized the fuse, then you're at a point where since these fuses melt, then the fuse could get hot if ran at the higher amperages and did not burn out. I don't know if this heat is a factor or not.

Use the chart for what you want. Maybe you see that a 150 amp fuse is actually 225 amps. THe only thing bad I see is now perhaps this fuse would run hot, and perhaps if you ran it for an hour at 175 amps, maybe it would blow.
=================
FWIW, you have to at some point just take reasonable precautions and then be able to enjoy yourself. I found myself boondocking at some nice places, but did not leave the trailer because I was afraid someone would break into it. This last boondocking season I got out more and enjoyed myself.

I am glad you posted your experience. I wonder how many others here have had something like that happen.
 
Yes the chart shows Class-T passing 200% rating for about a minute. That is 500 amps for a full 60 seconds. Put down a nice bead in half that time.
I prefer to keep these tight and no extra size for surge performance of less than 5 seconds.
 
A class T blows in under a second when shorted. Anything over 6x rated capacity.

But from the normal layout of things I still do not see how it was in the path or current?
 
I’ve worried about the “less than class T” shorts. I think the MRBF on the terminals is a good idea.

It would be nice to have some sort of arc fault protection in the BMS but their programming is beyond me. Or a cap for the battery with arc fault detection circuitry built in.

On security, here’s a pretty good tip. Get a 12 volt siren, cheap in amazon. And a trailer break away switch. Have it arranged so you can reach in and unhook it with the door open about 4 inches. When the door is opened too far, it pulls the breakaway switch and activates the siren. Loud as heck. Hard to approach when the siren is going off.

You can also power it off 8 little AA lithium batteries in a 12 volt holder. Lasts forever in standby.

I hate thieves.
 
robbob2112 said:
I also painted the exposed parts of my shunt with liquid electrical tape.
Click to expand...
Great idea. My bussbars are partly covered in shrink tubing but the liquid tape sounds like a much better idea.

For what it's worth, I nEveR trust anything other than a class-t fuse to break a LiFePo4 battery bank.
 
Bluedog225 said:
I’ve worried about the “less than class T” shorts. I think the MRBF on the terminals is a good idea.

It would be nice to have some sort of arc fault protection in the BMS but their programming is beyond me. Or a cap for the battery with arc fault detection circuitry built in.

On security, here’s a pretty good tip. Get a 12 volt siren, cheap in amazon. And a trailer break away switch. Have it arranged so you can reach in and unhook it with the door open about 4 inches. When the door is opened too far, it pulls the breakaway switch and activates the siren. Loud as heck. Hard to approach when the siren is going off.

You can also power it off 8 little AA lithium batteries in a 12 volt holder. Lasts forever in standby.

I hate thieves.
Click to expand...
Was thinking something more along the 9mm size, but 100% agree, I hate thieves.
 
Kornbread said:
Great idea. My bussbars are partly covered in shrink tubing but the liquid tape sounds like a much better idea.

For what it's worth, I nEveR trust anything other than a class-t fuse to break a LiFePo4 battery bank.
Click to expand...


Add the MRBF on the battery post as well, and keep the class T - the main difference is AIC. A MRBF would protect against shorts directly on the battery post since you can't get a class T right on the post.

For example - a 100ah battery - 125amp MRBF on the post - 150amp class T at the inverter end of the wires -

A bad connection or other fault that hits 200amps - the MRBF will blow first and the class T will survive. They both have similar curves for time/current - in a 6x current situation they both blow in 0.01 - 0.1 seconds - the class T just has higher AIC so it will extengiush an arc if present.

at 12v - class T AIC is 40ka - MRBF 12ka - Mega 2.5ka - ANL 2ka

In a short situation on the post only the MRBF blows. In a dead short situation at the inverter you would probably blow both fuses.

Make sense?
 
Last edited:
robbob2112 said:
Add the MRBF on the battery post as well, and keep the class T - the main difference is AIC. A MRBF would protect against shorts directly on the battery post since you can't get a class T right on the post.

For example - a 100ah battery - 125amp MRBF on the post - 150amp class T at the inverter end of the wires -

A bad connection or other fault that hits 200amps - the MRBF will blow first and the class T will survive. They both have similar curves for time/current - in a 6x current situation they both blow in 0.01 - 0.1 seconds - the class T just has higher AIC so it will extengiush an arc if present.

at 12v - class T AIC is 40ka - MRBF 12ka - Mega 2.5ka - ANL 2ka

In a short situation on the post only the MRBF blows. In a dead short situation at the inverter you would probably blow both fuses.

Make sense?
Click to expand...
Yeah, good idea, I see what you're trying to do, but is the aic of the mrbf enough to quench the arc of a LIFePo4?
 
You would do both - just add the MRBF on the post and the class-t in the line before the inverter.

There is a 58v MRBF I have seen as well now - but at the higher voltage instead of 12ka it is only 2ka


1719418509494.png
 
Thanks for the suggestions! I will have to grab some of the MRBF's. Would this amperage go up if the batteries were feeding into a 2000w or 3000w inverter or would it stay the same since its per battery?

For the replacement battery I'm looking at potentially going with one of the Epoch 460ah 12v batteries, it has a T-Class built into it.
www.epochbatteries.com

12V 460Ah LiFePO4 Battery | Group 8D Size, IP67, Heated, Bluetooth & Victron Comms

www.epochbatteries.com www.epochbatteries.com
 
Do you have a 12v AC on top of your trailer? Other high draw 12v equipment?

If your high draw operates from an inverter and the lights and the rest operate from 12v then it makes more sense to skip up to 24v or 48v than buy a massive 12v battery. Then for your 12v items you use a dc-dc converter.
 
What is the real benefit of going to a 24 or 48v system? I know the wires would be a smaller gauge etc.. however wouldn't I need to get a new solar controller or other components? I know the inverter would also need to be 48v.

But does anything else change? I know 48v is a bit more dangerous than 12. But 12 needs the larger gauge wire etc.. which I already have 4/0 even with my 2000w inverter. I know battery wise you can get the same amount of power/time usage with fewer, but from what I have seen I believe the physical size of them is the same as the 12v versions.

Is there some other reasons to make a jump like this that I am not understanding or is it mainly the ease of wiring/heat etc..?
 
I would say the real advantage of higher voltage battery setup is the amount of voltage slump from loading is less. The more voltage slump you get the higher current must rise to feed the load. W=VA
 
The major benefit is smaller wires and lower current in the wires so less heating. 48v is no more dangerous than 12v. Both should be treated with care. With LFP batteries there is a tremendous amount of energy stored no matter the voltage. Your are very lucky your damage was not a total loss.

With 48v batteries the mppt are cheaper and can also transfer 4 times the energy into the battery. You can't transfer more than what panels you have you you can use higher voltage panels and push more watts in. I.e the smaller victron mppt max out at 600w to 800w on 12v, but 2400w on 48v.

The downside is you do have to use a different inverter. Depends on your current mppt if that needs upgrading. I am using a victron 250/100 that does all 4 voltages. This is on a 12v UPS for my server. I know in future 48v will be the house sized install so everything I can buy that is both I do.

I only asked because large 12v batteries are expensive and if you are replacing your dead stuff it is worth thinking about voltage.
 
Some SCCs support 12/24/36 and 48V, it would be model specific.

More charging output (100A at 48V versus 100A at 12 or 24A) from each SCC.
 
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