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

[Hedges]

I am not familiar with that - I just wrapped the busbars in some heat shrink to keep the double ups together and put them on there with 20mm stainless studs and serated flange nuts

Aluminum oxide and hydroxide are insulators. What current does get past broken parts of the material will be crowded, and things get hot.
For PV grounding there are sharp objects to puncture the oxide.
Aluminum is used in a lot of electrical hardware (busbars, lugs), but that is tin plated.
These terminals are plain aluminum and have been exposed to some extent to the elements.
The torque used gives (by my calculation) 700 pounds clamping force. +/-50% by one guy's measurements.
If the surfaces don't make good enough contact, at high current there will be voltage drop and they will get hot.
Maybe just contaminants as Luthj suggests? But a very fine grit would cut any oxide, without deep scratches.

Check out the threads here where people have sanded, filed, wire brushed, or otherwise removed oxide, then used a corrosion inhibitor.
Much of the conversation has been about corrosion (aluminum with copper, vs. with tin plated copper), but people have gone from hot busbars to stone cold ones with suitable preparation and treatment.

 

[ArthurEld]

My short caused some pitting on some of the other terminals. So I removed all of the studs and sanded the terminals with emery cloth.
Then I put on a small amount of Noalox.

 

[Luthj]

Solar panel frames are anodized, so they have a thick layer of ordered oxide. Bare aluminum that's exposed to the air forms a 1 or 2 molecule thick layer of oxide in a few seconds.

Aluminum thats exposed to moisture forms a thicker layer, but it takes a while.

The thin oxide layer doesn't make a big impact on conductivity, and its not possible to remove outside a vacuum chamber, as it reforms in seconds.

 

[AussieInSeattle]

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?

 

[Luthj]

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?

Thats a hard one. Its not toxic waste in most areas, so you could discharge it completely and landfill? Otherwise you need to search to see if a recycler nearby will take it.

 

[ArthurEld]

I don't think there is anything dangerous in them and it isn't worth the effort to recycle as far as I could find anyway.

 

[ArthurEld]

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.

 

[BoloMKXXVIII]

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.

 

[Steve_S]

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?

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....

 

[ArthurEld]

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.

I think the lesson to be learned here is that short circuits don't care what your charge current or discharge current is.
These batteries have a ton of amps when you short them.

 

[Hedges]

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?

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.

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.

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.

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.

Yikes! ANN-400 is rated 2.7 kA interrupting!

https://www.mouser.com/datasheet/2/87/Bus_Ele_DS_2023_ANN-598373.pdf

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.)

 

[Luthj]

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.

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

I think it may be less than that due to additional resistance in the complete circuit, but its probably at least 10kA.

 

[Luthj]

This is a 480 V system that can deliver 50kA current. Obviously 480V is a bit more energetic.

http://www.b-line.com/content/dam/eaton/products/electrical-circuit-protection/fuses/protective-device-ratings/bus-ele-interrupting-rating.pdf

 

[Hedges]

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.

 

[chops728]

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

 

[Luthj]

The OP shorted the pack externally. I am not sure if a mid pack fuse would have done anything in this particular case.

 

[AussieInSeattle]

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....

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

 

[AussieInSeattle]

It still has as charge.
Time for a You-Tube video!

You are welcome to the battery if you want to make a 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.

Yep - I took my old golf cart batteries to O'Reillys

 

[AussieInSeattle]

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.

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.

 

[ArthurEld]

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.

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.