Short Circuited my 48V 120Ah Build (I'm fine)

AussieInSeattle

Solar Enthusiast
Joined
Jan 2, 2020
Messages
59
Firstly, I'm fine - was wearing safety glasses and gloves at the time and the top of the pack was covered - I do need some new underwear though. In short (no pun intended) I spent the past 3 weeks building my 120Ah 48V pack ever so carefully and managed to short it while hooking the finalized pack up to my golf cart by not having a correctly protected socket handle (left small piece of metal exposed near where you switch direction). On the positive side of the exterior of the pack there was a 400Amp fuse - have not inspected it yet to see if it blew. Disappointed as I was so careful along the way with insulated tools and put a lot of time and effort into the build.

I shorted between the 400A fuse (the nut you see in final pic) and a cable that was connected to the P- of the shunt (not shown in final pic). Only the charging side went through the BMS and relays were in place to cut the golf cart speed controller (white cable) via a relay hooked to the BMS in an overvolt situation.

Pics attached of the carnage - I've since removed all bus bars, covered the pack terminals from the elements and put the pack outside while I work out next steps and wait for my heart rate to lower. Cell #14 is toast and has vented - you can see its + terminal blew molten busbar towards cell #9 - lucky the pack was covered at the time!

The renogy battery meter still read 43.5 volts when I plugged it in before disassembly of the busbars - the pack was 53.4 volts prior to the unexpected arc welding.

What should my next steps be to dispose of cell 14 or all of them? Are all cells toast? Also not sure if I want to proceed with the build at all as it scared the crap out of me.

Note that pic #1 and #5 are from prior to the carnage.
 

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curiouscarbon

Science Penguin
Joined
Jun 29, 2020
Messages
2,293
Glad you’re ok! Sorry to hear about the mishap.

I can’t say whether any of the cells are salvageable, but I can say for sure that there are many more LiFePO4 cells in the world, but only one of you!
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
6,010
Location
Rural NE Ontario Canada
OUCH ! Glad your OK and did not suffer a worse situation. Only takes a second to create major havoc, I'll bet that flash & pop was something else with all that amperage being released. Certainly underwear change time.

On the cells. Good Move to get the busbars OFF. I believe most of the cells should be OK but the ones that popped the cents, absolutely NOT, do not even think about it, the likelihood of internal shorts now is extremely high. Handle these with care, extract them and store them OUTSIDE in a secure fireproof non-metalic box until sent to recycle. Note even squeezing the cells could cause issues, I am serious, Handl;e with Care. From the looks of it, 2 or 3 cells are done.

Once se[parated and cleaned up, check each cell for voltage. You will ABSOLUTELY want to check the Internal Resistance of each cell, any cell with an IR out of whack compared to the rest - do not question it, directly recycle bin. The Yaorea YR1035+ (& other rebranded models) are available on Amazon/Ebay and some shipped from US, I put a copy of the owners many in the resources section a while ago. Gee wiz, my uploaded manual pops right up in google search. How Convenient ! IF THESE ARE EVE 280's the IR should be between 17-19mΩ.
Yaorea YR1035+ Battery Internal Resistance Meter Tester, Manual | DIY Solar Power Forum (diysolarforum.com)

Once you've determined that all the cells are OK by Voltage & IR you can set those aside for individual testing. Yes I know major PITA but honestly, I would do a full capacity test on each cell which should "out" any potential lurking issues. Charge each cell to 100% SOC and discharge to 0%SOC and then recharge to 100%.
LOG the time it takes to discharge & charge for each cell.
Test IR when at 100%, 50% & 0% SOC and log it too.
At the end compare the info you logged to ensure they are all close or not... If any cell comes out "odd" you can retest with a full cycle just in case.
Once all tested, you will know what's good & not and be able to replace any questionable cells aside from the obvious ones that are done.
NEVER Attempt to use a cell with a blown vent valve.

Hope it helps, Good Luck
Steve
 

AussieSim

Solar Addict
Joined
Jul 21, 2020
Messages
252
Firstly, I'm fine - was wearing safety glasses and gloves at the time and the top of the pack was covered - I do need some new underwear though. In short (no pun intended) I spent the past 3 weeks building my 120Ah 48V pack ever so carefully and managed to short it while hooking the finalized pack up to my golf cart by not having a correctly protected socket handle (left small piece of metal exposed near where you switch direction). On the positive side of the exterior of the pack there was a 400Amp fuse - have not inspected it yet to see if it blew. Disappointed as I was so careful along the way with insulated tools and put a lot of time and effort into the build.

I shorted between the 400A fuse (the nut you see in final pic) and a cable that was connected to the P- of the shunt (not shown in final pic). Only the charging side went through the BMS and relays were in place to cut the golf cart speed controller (white cable) via a relay hooked to the BMS in an overvolt situation.

Pics attached of the carnage - I've since removed all bus bars, covered the pack terminals from the elements and put the pack outside while I work out next steps and wait for my heart rate to lower. Cell #14 is toast and has vented - you can see its + terminal blew molten busbar towards cell #9 - lucky the pack was covered at the time!

The renogy battery meter still read 43.5 volts when I plugged it in before disassembly of the busbars - the pack was 53.4 volts prior to the unexpected arc welding.

What should my next steps be to dispose of cell 14 or all of them? Are all cells toast? Also not sure if I want to proceed with the build at all as it scared the crap out of me.

Note that pic #1 and #5 are from prior to the carnage.

Glad to hear you're okay. I accidently shorted the parallel busbar (18p) during top balance to my charger lead, instantly melting/welding the lug.

48v is alot more pop than 3.5v
 

AussieInSeattle

Solar Enthusiast
Joined
Jan 2, 2020
Messages
59
OUCH ! Glad your OK and did not suffer a worse situation. Only takes a second to create major havoc, I'll bet that flash & pop was something else with all that amperage being released. Certainly underwear change time.

On the cells. Good Move to get the busbars OFF. I believe most of the cells should be OK but the ones that popped the cents, absolutely NOT, do not even think about it, the likelihood of internal shorts now is extremely high. Handle these with care, extract them and store them OUTSIDE in a secure fireproof non-metalic box until sent to recycle. Note even squeezing the cells could cause issues, I am serious, Handl;e with Care. From the looks of it, 2 or 3 cells are done.

Once se[parated and cleaned up, check each cell for voltage. You will ABSOLUTELY want to check the Internal Resistance of each cell, any cell with an IR out of whack compared to the rest - do not question it, directly recycle bin. The Yaorea YR1035+ (& other rebranded models) are available on Amazon/Ebay and some shipped from US, I put a copy of the owners many in the resources section a while ago. Gee wiz, my uploaded manual pops right up in google search. How Convenient ! IF THESE ARE EVE 280's the IR should be between 17-19mΩ.
Yaorea YR1035+ Battery Internal Resistance Meter Tester, Manual | DIY Solar Power Forum (diysolarforum.com)

Once you've determined that all the cells are OK by Voltage & IR you can set those aside for individual testing. Yes I know major PITA but honestly, I would do a full capacity test on each cell which should "out" any potential lurking issues. Charge each cell to 100% SOC and discharge to 0%SOC and then recharge to 100%.
LOG the time it takes to discharge & charge for each cell.
Test IR when at 100%, 50% & 0% SOC and log it too.
At the end compare the info you logged to ensure they are all close or not... If any cell comes out "odd" you can retest with a full cycle just in case.
Once all tested, you will know what's good & not and be able to replace any questionable cells aside from the obvious ones that are done.
NEVER Attempt to use a cell with a blown vent valve.

Hope it helps, Good Luck
Steve
Thanks Steve. I think only 1 cell popped a vent (#14) but looking closely at my high resolution photos it may only be molten metal from the bus bar that melted the plastic cover to the vent and it didn't actually vent. No smoke from any cells after I removed the cover. Just the molten metal remnants. Will provide a link to the high resolution photos tomorrow.
 

AussieInSeattle

Solar Enthusiast
Joined
Jan 2, 2020
Messages
59
Joining in here to say I too am glad you are ok but also to thank you for sharing. It's unfortunate what happened to you, but it's a very valuable lesson for everyone, myself included.
Thanks Gazoo. Appreciate it. I thought about not posting as it's a bit embarrassing but hopefully someone else can learn from it.

Tiny mistake with big ramifications after being so careful putting the thing together.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
6,010
Location
Rural NE Ontario Canada
Please examine the vents closely with a Magnifier Glass because they may not necessarily fully pop or blow or whatever you want to call it. It's not worth the risk to skip a Very Close Inspection. I know PITA but personal safety is worth some PITA. Personally, the only PITA I like involves a Sandwich.
 

Gazoo

Dumb Dumb
Joined
May 12, 2020
Messages
2,794
Location
Texas
No need to feel embarrassed although I understand where you are coming from. It took me awhile to admit I had stripped a screw in one of my cells. You did exercise much caution during your build and in the end had an accident. Main thing is you are ok. I understand your hesitancy to repair the pack...I know I would be hesitant too. Think it over. You know you have the support of many of us no matter what you decide to do. It's always sad to see this kind of stuff happen.
 

AussieInSeattle

Solar Enthusiast
Joined
Jan 2, 2020
Messages
59
Please examine the vents closely with a Magnifier Glass because they may not necessarily fully pop or blow or whatever you want to call it. It's not worth the risk to skip a Very Close Inspection. I know PITA but personal safety is worth some PITA. Personally, the only PITA I like involves a Sandwich.

Advice noted. I'll take a close look tomorrow (2am here) at the vents.

The bus bar on cell 14 to 15 was the weakest link in the short circuit and dissolved. Will take a pic of it tomorrow but the end of it is gone and you can see the bms lead for 14 has disintegrated too.
 

Solarfun4jim

Solar seduced :-)
Joined
Sep 22, 2019
Messages
743
Location
Sunny Scotland
Glad your safe mate, that's number one. Appreciate you posting this, as it is a reminder that one cant be too careful. I cant offer any advice on the cells, but i will say your whole set up looked very neat and tidy. Yes, you have been unfortunate/fortunate at the same time, but i'd give it some reflection time, then get back on the horse as they say.
 

Johnson

Solar Addict
Joined
Nov 21, 2020
Messages
715
Glad you are ok and thank you so much for posting this.

Mistakes are bound to happen and that is how we learn. By sharing, you have made this is a lesson for all of us tthat mistakes can easily happen. I suggest you don't give up, clean up what you can, check there is no vapourized metal that condensed on the wires or anywhere else it can be harmful, replace the parts that need to be replaced, feel good by persevering and completing the task you set out for yourself.
 

ArthurEld

Photon Sorcerer
Joined
Aug 3, 2020
Messages
2,082
Location
Palm Harbor, Florida
I shorted one of my 48V EVE batteries and it was an eye opener for sure.
With all the sparks and pieces flying, I was glad to be wearing glasses.

Mine wasn't as bad as yours but I still haven't finished checking all of the cells. None of my vents released but one terminal was melted off.
Sorry I didn't take any pictures. I was embarrassed to show the spiders nest I got tangled up in that caused me to fumble.

Your battery is much neater than mine and you have more covered than I did.

It is pretty scary to admit my ignorance but I don't even understand what is more likely to cause a short and what is not. I'm used to the negative side being safe. But the busbars confuse the heck out of me. I assume they can't be shorted to each other or anything else.

I have been very slow to proceed and thinking about how I can cover as much as possible.
 

BoloMKXXVIII

Fully Charged
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Sep 23, 2019
Messages
276
Location
Somewhere on or near Earth
Thank you for sharing. It is a good reminder to everyone here what the potential is for the amount of energy we are working with. It also shows that even if you are being careful bad things can happen. Definitely a "code brown" event. Glad all the carnage was of the non-human variety.
 

Luthj

Photon Sorcerer
Joined
Jul 1, 2020
Messages
956
Take any non vented but suspect cells, and inspect for bloating or obvious damage. If they inspect good and show reasonable voltage, you can likely reuse. Internal damage will certainly show up in a load test. Put a load on the cell and see if the voltage drop matches the other cells. If its much higher, the anode backing or internal connections are compromised.

Open circuit voltage can also be used to detect damaged cells. Assuming the pack was balanced beforehand, you likely didn't remove more than a few percent SOC from any of the cells. Given you are showing low pack voltage It seems likely a cell may be zeroed.

I am not clear on what the load path was. Evaluate what cells were actually in the short circuit path. Any cells outside that do not need to be evaluated.

Are you certain the cell vented? Below the plastic film is an aluminum rupture disk structure. Its possible the arc blast or molten material compromised the plastic, but the cell itself didn't vent.

Rapid venting in a few short seconds is typically caused by the internal connections vaporizing. Though with enough current/duration its possible to get boiling electrolyte. However there is a fair bit of mass so that's not instantaneous.

The other possible venting cause takes 30 seconds or more, and results from the cell separator breaking down during the brief shorting event, causing the cells to rapidly discharge into itself and overheat, even after the external circuit is broken.

If I am correct and that cell didn't actually vent (you may have had a small burp of flame if there was an ignition source). Then its possible all the cells are fine internally. That one cells terminal may be beyond recovery though. The testing I have seen shows these cells are quite robust in a low duration short circuit event. Though with the low pack voltage one or more cells may be toast.

PS: Why a 400A fuse? That seems excessive for a 120AH bank, especially given the fuse would need 500A+ to trip.

PSS: All us electron wranglers have been here/there. You rarely forget the first major short circuit. The good news is the vehicle is still intact, and you are uninjured. I was 14 and not wearing safety glasses when I dropped a 1/2" box end wrench onto a golf cart pack. That wrench was 3/4 vaporized, and I had holes in my shirt.
 
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AussieInSeattle

Solar Enthusiast
Joined
Jan 2, 2020
Messages
59
Take any non vented but suspect cells, and inspect for bloating or obvious damage. If they inspect good and show reasonable voltage, you can likely reuse. Internal damage will certainly show up in a load test. Put a load on the cell and see if the voltage drop matches the other cells. If its much higher, the anode backing or internal connections are compromised.

Open circuit voltage can also be used to detect damaged cells. Assuming the pack was balanced beforehand, you likely didn't remove more than a few percent SOC from any of the cells. Given you are showing low pack voltage It seems likely a cell may be zeroed.

I am not clear on what the load path was. Evaluate what cells were actually in the short circuit path. Any cells outside that do not need to be evaluated.

Are you certain the cell vented? Below the plastic film is an aluminum rupture disk structure. Its possible the arc blast or molten material compromised the plastic, but the cell itself didn't vent.

Rapid venting in a few short seconds is typically caused by the internal connections vaporizing. Though with enough current/duration its possible to get boiling electrolyte. However there is a fair bit of mass so that's not instantaneous.

The other possible venting cause takes 30 seconds or more, and results from the cell separator breaking down during the brief shorting event, causing the cells to rapidly discharge into itself and overheat, even after the external circuit is broken.

If I am correct and that cell didn't actually vent (you may have had a small burp of flame if there was an ignition source). Then its possible all the cells are fine internally. That one cells terminal may be beyond recovery though. The testing I have seen shows these cells are quite robust in a low duration short circuit event. Though with the low pack voltage one or more cells may be toast.

PS: Why a 400A fuse? That seems excessive for a 120AH bank, especially given the fuse would need 500A+ to trip.

PSS: All us electron wranglers have been here/there. You rarely forget the first major short circuit. The good news is the vehicle is still intact, and you are uninjured. I was 14 and not wearing safety glasses when I dropped a 1/2" box end wrench onto a golf cart pack. That wrench was 3/4 vaporized, and I had holes in my shirt.

Thanks for the detail. Answers to your questions:

The pack was balanced beforehand - although I only charged to 53.4 pack voltage (resting) and I had a cell range of 3.337-3.343 (.006v diff) only minutes prior to installation.

You asked about the load path - the path was from main pack positive on the exterior of the pack, through the fuse, through a socket and socket extension to a "post" on the golf cart that had a 2awg cable hooked to it - that 2awg cable then went to the P- of the renogy shunt that is in turn connected to B- of the main pack on the exterior. You can see the internal connections of the 16s pack in the above pics.

I'm not certain that the cell vented - will take a better photo today when I dismantle but from the hi-res photo I took last night it looks like just the clear plastic on top has a hole in it from molten material - the aluminum disc beneath appears to be in-tact although has a "copper spec" on it - am guessing that is part of the bus bar - also based on the attached photo of the foam (yes not the best choice of material) that was covering the top of the pack you can see the burn hole from where the cell #14 busbar blew - the "line" along the side of the hole is the channel where my cell taps were running. Other cells in the pack have molten material on top of their clear vent caps or are discolored black from the flying bus bar material.

The arc/short was very quick.

400A fuse was in place as that was what was on my FLA pack - I have a 500 amp controller in the cart - cells were rated for 2C continuous (240A) and 3C for 30 seconds so I figured the 400A fuse was right.

Will dismantle the pack later today and inspect cell #14 vent and terminal more closely along with all other cells for issues including bloating and report back.

Thanks again for your detail - didn't sleep much last night as I thought about the what ifs and also due to constantly checked my security camera to make sure the pack wasn't doing bad things in my yard. Responses like yours and members own stories have helped me a lot.
 

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AussieInSeattle

Solar Enthusiast
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Messages
59
Ok, I had some time this afternoon to look at the pack.

Cell Voltages:
All cells tested at 3.340-3.341 volts on my DMM including cell #14. Prior to the mishap they were reading 3.337-3.343 in the BMS app.

Not sure why the Renogy battery meter still read 43.5v (3 cells short of full voltage) when it was still plugged in just after the incident before I removed the busbars - maybe that was its memory from just prior to the issue.

Condition of Cells 1-8, 9-13 and 15,16:
No swelling of any of the cells including cell #14.

Cells 1-8 even look fine with no shrapnel damage from cell #14+ busbar as they were "behind" the wire raceway in the middle of the pack. No issues with the vent caps or anything else.

Cells 9-13 have progressively worse shrapnel damage to the top plastic sticker and some have marks where the molten metal fell between the batteries - very minor though and only cosmetic. Same for cells 15 and 16 although they are not too bad as the busbar liquified away from them and towards cell #9. Vent caps all still in place for all these 7 cells too.

Cell 14
That just leaves cell #14 which I've attached pics of. I was mistaken in original post - it did not vent, however a piece of molten busbar melted the clear plastic cap and made a mark on the aluminum disc beneath it. The piece of molten busbar was still in the little space between the two and you can see it in the pics (I fished it out carefully with a plastic golf tee). The +ve terminal however did not fare very well as you can see from the pics - I assume its stuffed.

All attached pics are of cell #14 - first pic is the busbar from cell #14+ to cell #15-

Storage of the cells:
Do you think its safe to store all cells except 14 inside my garage still? Meant to get below 32 (0c) this weekend. I've left cell #14 outside.

Is this what happened?:
Could it be that the short "found the weakest" part of the circuit I created which was the #14+ to #15- busbar (doubled up busbars) on the #14+ post - essentially that particular part of that busbar couldn't handle the huge current and spat hot metal everywhere when the short occurred - mainly towards cell #9?

Where to from here?:
I see a few options:

1. Maybe just buy a single cell from the original distributor (Amy but I think she left XUBA?). Any other testing I'd need to do on the remaining 15 cells?

2. Sell 12 of the cells in packs of 4/12v or 8/24v locally in Seattle - are they even worth anything? (I paid $55 per sell including shipping) I guess it comes down to the level of effort someone would have to do for option #1 above. I'm leaning towards this option as I think I need to take a step back from this experience. I'm also in the middle of a house remodel that I need to spend time on as the family is living in half the house - I'm essentially "time poor" at the moment and cant commit a lot of time to option #1.



Thanks again everyone for their support through this - feel much better this afternoon about the situation and my heart t
 

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Luthj

Photon Sorcerer
Joined
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956
Are you sure you didn't short to that damaged busbar? That damage shows an arc blast, which typically occurs when you short directly via loose contact.
 

AussieInSeattle

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Joined
Jan 2, 2020
Messages
59
Are you sure you didn't short to that damaged busbar? That damage shows an arc blast, which typically occurs when you short directly via loose contact.
The pack was covered at the time of the incident - I definitely shorted the pack outside of the pack as there is a large arc mark on my socket handle. There was a bms lead on the same post and from a previous pic it may have been loose (not much thread showing out top of nut as other terminals), so not sure if that somehow contributed to things?
 

Luthj

Photon Sorcerer
Joined
Jul 1, 2020
Messages
956
I guess you just had a high resistance connection there then. The small ring terminal is totally gone, but the other terminals look fine So it would have been a fair bit higher than its neighbors. Even then I think it would have had to be loose to arc like that.
 
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