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

[AussieInSeattle]

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.

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.

 

[chops728]

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

As usual I misread the initial post ---

 

[BiduleOhm]

The +ve terminal however did not fare very well as you can see from the pics - I assume its stuffed.

Sadly yes. At least it's the only one who has a problem, all the others ones are fine.

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.

Yes

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?

Yes, this connection was probably not great and had a high resistance.

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?

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.

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.

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.

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.

Yep, see this thread: https://diysolarforum.com/threads/introducing-the-new-improved-shenzhen-luyuan-technology-co.15880/

 

[AussieInSeattle]

Yep, see this thread: https://diysolarforum.com/threads/introducing-the-new-improved-shenzhen-luyuan-technology-co.15880/

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.

 

[ArthurEld]

I did a google search and saw quite a few options.
Basen on Alibaba
RJ Energy on Amazon. crappy seller though
This one looks like it has fast shipping but I never heard of them - https://www.alibaba.com/product-det...igee-120Ah-Lifepo4-Battery_1600109854135.html

 

[Burke]

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.

 

[Gazoo]

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.

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.

 

[ArthurEld]

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.

 

[ericgrand]

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...

 

[AussieInSeattle]

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...

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?

 

[AussieInSeattle]

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.

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.

 

[ericgrand]

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?

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.

 

[DerpsyDoodler]

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 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.

 

[ArthurEld]

I expect it would have been less explosive without the short.

 

[Hedges]

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.

 

[AussieInSeattle]

I expect it would have been less explosive without the short.

Have been avoiding this question as I'm not sure I want to know the answer, but if that bad connection at cell #14 had not been there, what would have happened to the socket handle I was holding onto and to me (was wearing rubber lined gloves)?

 

[AussieInSeattle]

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.

Not sure at this stage as I dont think I can test that without the 16 cells - the BMS was still showing up in Bluetooth list after the short and no obvious damage to it. I found that weird since cell #14 had no BMS tap connected and the full pack voltage would have been off due to the "break" at cell #14. Might get an additional BMS as part of my order from XUBA.

 

[Surferdudemi]

Is this how "Bussman Fuses" got their name?

 

[Luthj]

but if that bad connection at cell #14 had not been there, what would have happened to the socket handle I was holding onto and to me (was wearing rubber lined gloves)?

The fuse probably would have blown. However if there was another high resistance point, it may have started arcing before then.

 

[ArthurEld]

The fuse probably would have blown. However if there was another high resistance point, it may have started arcing before then.

Is that because his short was outside of the battery?
Also, sould the fuse blow if terminals within the battery are shorted?
I shorted the busbar from one cell to another cell busbar and my fuse didn't blow. The fuse was on positive terminal of the cell next to the one I shorted.