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

AussieInSeattle said:
And one other question I forgot to ask. Where do I recycle the damaged cell 14 ? I assume my local auto parts store that takes FLA's won't take it?
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It still has as charge.
Time for a You-Tube video!

Not wanting to give away valuable old LA car batteries, I did a google search, found that some auto stores pay for them.
Winchester Auto doesn't, but O'Reilly's pays $10 for car batteries, $5 for motorcycle.

BoloMKXXVIII said:
Glad the max theoretical draw on my 24v system is only 86a and have a 100 amp fuse. Most of the time the draw is much less. Those photos are scary.
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How much current do you think the max they can produce into a short would be?

My math was 3.7V/0.00017ohms = 21,764 amps

So Class T fuse seems good. For a single string of lithium batteries.
AussieInSeattle said:
Yes there was a fuse in place that I had on my old FLA pack a ANN-400 fuse which did not blow - have since learnt I should have had a much lower fuse like a ANN-250.
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Yikes! ANN-400 is rated 2.7 kA interrupting!


I suggest something like class T that is rated to interrupt 20 kA. Some fuses are rated to 50 kA.


I've started to wonder what the fault current carrying capability of your busbars (and bolted connections) actually is.
Of course they can't carry 20,000 amps continuously. But can they carry it long enough for a fuse to blow? Or are they unable to, and that was the actual problem here? (Safety switches can carry 200,000A fault current)
What if all your busbar connections were done right, it's just that at 20,000 amps I^R this one happened to enter thermal runaway first.

16 cells x 0.00017 ohms (+ undetermined wire and wrench resistance) = 0.0027 ohms.
48V/0.0027 = 17,647A

Matched impedance occurs when one bad contact rises to 0.0027 ohms, a point where power dumped into the contact is maximum.
48V/(0.0027 + 0.0027 ohms) = 8824A
48V x 8824A = 424,000W
424,000W x 0.001 second = 424 joules deposited in 1 millisecond.

That's about the muzzle energy of a 9mm bullet. Enough to blow apart that bit of aluminum. (Although a considerable amount goes into heating that metal, so probably more than 1 millisecond melting it, and a sudden impulse as resistance increases.)
 
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For those wondering what the AIC (Amperage Interrupting Capacity) is. AIC is the max current level that a limiting device can safely and effectively interrupt.

If the short current exceeds this value, the device could fail, sometimes spectacularly. Breakers and fuses can throw minor shrapnel. In some cases the device cannot extinguish the arc in a timely fashion.

The inability to extinguish the arc or too slow a response time can result in a long enough duration to cause other parts of the circuit to be damaged. This is why some applications specify fast acting current protection (Class T for example).

I have seen ANL fuses arc for half a second and blow bits of molten metal out of their glass windows for example.

In some cases you will see a fast acting Class T fuse followed by a breaker for main or brank protection, often of similar ratings. This is typically on applications with big motors where fault conditions (other than short circuit) can cause an overcurrent event occasionally. In this case the breaker is sizes to trip before the fuse. The fuse protects the slower and lower AIC breaker from a dead short. The breaker performs the fault isolation for lesser faults without the hassle/cost of changing the catastrophic fuse. I am not saying thats necessary in this application, but picking the right overcurrent protection is a bit more involved with higher voltage systems which can easily delivery 20kA+ of fault current.

Hedges said:
My math was 3.7V/0.00017ohms = 21,764 amps
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I think it may be less than that due to additional resistance in the complete circuit, but its probably at least 10kA.
 
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Interesting explanation in the linked Cooper/Bussman paper about Interrupting Rating Vs. Interrupting Capacity.
Circuit breaker standard test conditions have a length of typical gauge wire, adding impedance such that they aren't actually tested at the fault current in their spec. Plan carefully where you will have short circuit fault.

Also, (some?) tests don't include closing onto a short, just opening if a short is applied.
We hope the main breaker opens first, or fast enough, in the case of a dead short. It is rated 22kA, while the branch breakers are rated 10kA.

The paper gave as an example "20A, 240V, 2-Pole Circuit Breaker marked 22,000 A.I.R." which sounds like it is for commercial applications. Standards are somewhat different for residential.

I've acquired 400A class T fuses I'll be using in series with 200A (22kA interrupting) main breaker. My intention is that they are "coordinated", interrupting fault currents but not overloads up to 5x breaker rating. If the utility grid could deliver up to 100kA or 200kA, the "current limiting" fuses don't actually reduce peak current but reduce time so breaker gets hit with energy less than a 20kA fault. Current/time curves for class T are such that in the event of a 20kA fault (more likely the capability of a smaller transformer feeding a few houses), it may not actually lessen damage to the breaker. One of my goals had been to save the breaker if something goes wrong.
 
All this talk about Fuses ---But if your fuse is on either pole + or - and you short out the battery midstream to the non fused pole they are useless -Seems like in these big packs or any pack there would be a way to fuse cell to cell --In his case It's a good thing that Buss Bar blew out instead of something worse
 
The OP shorted the pack externally. I am not sure if a mid pack fuse would have done anything in this particular case.
 
Steve_S said:
Getting *lithium' batteries of any sort into the Recycling Stream is Haphazard at best in North America, largely due to the Lagtard mentality towards EV's and such up until recently. Fortunately this is changing fast & on a large scale but it's not quite there yet.

Auto-parts suppliers will not likely take Lithium cells. Their deal for Lead Acid batteries is a different best. (BTW most don't know, but that is legislated, not entirely voluntary, pending where.)

Recycling Departments in your locality "should" be able to direct you IF they do not take them directly. Contact your County, Town, City they should know.

Hazardous Waste sites generally have facility for all sorts of batteries as well as chemicals & such. Virtually every City/Town/Village has at least one such waste site. Sometimes they are open regular hours, in some cases may only be one day a week or so... Your local municipal waste department should know the hours, sites and materials accepted.

NEVER EVER chuck used batteries into the garbage, regardless of type. They are responsible for a LOT of Dump Fires aside from toxic leakages over time in landfills. Even Ikea Stores have battery stops for collecting used batteries of different types in many places where allowed. Yeah, in some places, the localituies do NOT permit such collections... believe it or not....
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Thanks Steve_S - I found a local hazardous waste collection place that says they take rechargeable batteries - assume mine falls into that category:

Households | Hazardous Waste Management in King County, WA

Find out what you can and cannot bring to a household hazardous waste disposal location in King County, WA.
kingcountyhazwastewa.gov kingcountyhazwastewa.gov
 
Hedges said:
It still has as charge.
Time for a You-Tube video!
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You are welcome to the battery if you want to make a video :)

Hedges said:
Not wanting to give away valuable old LA car batteries, I did a google search, found that some auto stores pay for them.
Winchester Auto doesn't, but O'Reilly's pays $10 for car batteries, $5 for motorcycle.
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Yep - I took my old golf cart batteries to O'Reillys
 
ArthurEld said:
Maybe moving the battery pack caused busbars to loosen.
Cells could move around or like Hedges said you could push against wires and not realize something is unscrewing.
I'm shocked that could cause so much damage.

Glad you only lost a cell by the way. You'll probably be able to find a suitable replacement fairly easy.
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Any idea where I could get another 120Ah quickly? These were Higee cells - have contacted the original supplier but have not heard back yet and assume that will be 30-60 days shipping.
 
AussieInSeattle said:
Any idea where I could get another 120Ah quickly? These were Higee cells - have contacted the original supplier but have not heard back yet and assume that will be 30-60 days shipping.
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I have heard of people getting small numbers of cell by air. I don't personally know who sells those cells.
But if you can't make a deal with your supplier, I would check with Michael B Caro. He probably could locate one for you.

I think you will find that your original supplier will work something out for you. Could cost $200 but it's better than waiting 2 months

edit: maybe check to see if buying 2 or 3 is a better deal. spares are good to have.
 
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ArthurEld said:
I have heard of people getting small numbers of cell by air. I don't personally know who sells those cells.
But if you can't make a deal with your supplier, I would check with Michael B Caro. He probably could locate one for you.

I think you will find that your original supplier will work something out for you. Could cost $200 but it's better than waiting 2 months

edit: maybe check to see if buying 2 or 3 is a better deal. spares are good to have.
Click to expand...

I just found an email from Amy who seems to have started with a new company and they appear to have the same cells. Have contacted her for pricing on 2 cells so I have a spare.
 
AussieInSeattle said:
The +ve terminal however did not fare very well as you can see from the pics - I assume its stuffed.
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Sadly yes. At least it's the only one who has a problem, all the others ones are fine.


AussieInSeattle said:
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.
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Yes ;)


AussieInSeattle said:
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?
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Yes, this connection was probably not great and had a high resistance.


AussieInSeattle said:
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?
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That's what I would do. I'd test the whole pack once re-assembled with a new cell just to be sure, I don't really see the need to test each cell one by one.


Luthj said:
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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Connection heated up, melting the aluminium which increased the connection resistance which increased the power dissipated in the connection, which heated up more, ... in the end when enough metal is eroded you have an arc.


AussieInSeattle said:
I just found an email from Amy who seems to have started with a new company and they appear to have the same cells. Have contacted her for pricing on 2 cells so I have a spare.
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Yep, see this thread: https://diysolarforum.com/threads/introducing-the-new-improved-shenzhen-luyuan-technology-co.15880/ ;)
 
Wow glad you are ok. A reminder about how much energy we are dealing with and how easy it is to have that one unplanned moment... A reminder to be deliberate, careful and think through every move. I have found myself doing an absent minded movement with a tool or lead a couple of times. Hope you get it back up and running ASAP.
 
AussieInSeattle said:
Unfortunately Amy doesn't have any stock of the Higee 120Ah cells - anyone else have a good experience with another ali seller of those cells? Amy recommended Dongguan Huanhuan Energy Technology Co., Ltd. who seem to have the cells in stock but I don't see any good reviews of them on this forum.
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Her recommendation is surely better than nothing. I say go for it but as we all know by now it's taking a risk. And as has been suggested order a spare or two.
 
If you use a major credit card, I don't think anyone can outright rip you off. Especially if you get fast shipping and report problems quickly.
I'm not saying to be haphazard but a CC gives a little extra assurance.
 
Maybe one good thing anyway...Imagine you installed the pack in your golf cart and use it with this bad connection? You may have ended with a toasted battery and a burnt golf cart...
 
ericgrand said:
Maybe one good thing anyway...Imagine you installed the pack in your golf cart and use it with this bad connection? You may have ended with a toasted battery and a burnt golf cart...
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Was wondering the same thing but the cart only has momentary spikes of 400amps (can set in the controller) and should generally be around 100 amps during normal driving - maybe a max of 200 amps sustained for 30 seconds going up a hill. Far less than the amps generated from a short.

Based on the above numbers and assuming a bad connection, would the result have been the same or would the busbar merely have warmed up? The electronics (relays etc) and the BMS inside that black box is wired in such a way that it cuts the speed controller on the cart if there is a LV (from amp draw) or HV (from regen) situation for any of the cells. Based on that I don't think the same thing would have happened?
 
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Gazoo said:
Her recommendation is surely better than nothing. I say go for it but as we all know by now it's taking a risk. And as has been suggested order a spare or two.
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ArthurEld said:
If you use a major credit card, I don't think anyone can outright rip you off. Especially if you get fast shipping and report problems quickly.
I'm not saying to be haphazard but a CC gives a little extra assurance.
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XUBA got back to me (Selina) and a quick search on here seems to show that all is fine with her/them. They are the same price ($36.80) as when I purchased plus a 3% discount for this forum and $132 for air freight so about $203 all in.

She also mentioned the minimum weight for sea freight is 22kg (two batteries is only 7kg) and costs $108 which might be useful to others.
 
AussieInSeattle said:
Was wondering the same thing but the cart only has momentary spikes of 400amps (can set in the controller) and should generally be around 100 amps during normal driving - maybe a max of 200 amps sustained for 30 seconds going up a hill. Far less than the amps generated from a short.

Based on the above numbers and assuming a bad connection, would the result have been the same or would the busbar merely have warmed up? The electronics (relays etc) and the BMS inside that black box is wired in such a way that it cuts the speed controller on the cart if there is a LV (from amp draw) or HV (from regen) situation for any of the cells. Based on that I don't think the same thing would have happened?
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Not the same, but definitely a very hot point in your pack. Depending on the surroundings, it could lead to a fire. Most probable scenario is that you would have had such resistance that the overall voltage of the pack would have fall below LVD, or you would have had a low cell voltage under high load for the cell with the bad connection on the busbar.
 
AussieInSeattle said:
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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Glad to know you are alright and have this sorted. Also glad to see you’re persevering and moving forward. Thank you for sharing! This is a huge reality check for everyone in the DIY community.
 
With external load limiting it to 400A vs perhaps 20,000A, 50x smaller, power = I^R only 1/2500 as much. 400A x 50V = 20kW. Seriously heavy duty arc welding, but no "arc blast" explosion.

"Only the charging side went through the BMS and relays were in place to cut the golf cart speed controller"
Reasonable way to wire it, and in the case of this fault (so long as not through charging side), the relays were not involved in the fault current.

Is the BMS confirmed OK?
With individual cell connections wired to BMS and one connecting going open, the voltage between those two wire would have gone outside the intended zero to 4V range, I think to -50V or so.
 
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