BIG BLAST PLASMA SHORT with LIthium Battery firework style!!

[Doctorbass]

Outch!!

Tonight while i was finishing my third 25V 23Ah battery pack, i accidently shorted the 0V and +25V battery tab with my long nose grip!!!!!!!! the blast hole on those is 2cm long by 1 width!!!

OUch... OUch!... .. OUch!!!!!!

What a blast!!!!!!!!!!

the blast produced a large blue balls with and fireworking all my clothed and work bench.. Many small melting metal balld dammadged all my surrounding working erea.

The melt on my long nose is so incredibble!!!

Believe it or not... i'm freaking now!!!

I now learned how powerfull they are!... and dangerous!!!!!.

probably 200+ Ampere for short burst.. these cells are rated 10C so 23Ah would give 230A.

i'm now affraid to goes back to work on it... :lol:

I would just not immagine the same short on the neg and positive of all 4 pack in serie!!! 100V 230A !!!

That's serious power!!!!


I think i will put some liquid plastic insulator all my hand tools!!!

my battery still work and lost only 20mV after the short and is now showing 24.85V

here are pics of the disaster

 

[TylerDurden]

...my battery still work and lost only 20mV after the short and is now showing 24.85V

A truer scientist, there never was...

 

[slayer]

i bet the legs feels a little weak after that

 

[lawsonuw]

I really doubt that your batteries were producing "only" 200 amps. 1000 amps or more seems more likely given the scale of damage.

Oh yea, steel BURNS if it gets hot enough. I bet more than half your flash was your pliers BURNING.

Marty

 

[Dalecv]

Decent penetration, the bead is a little rough though. Try more flux or inert gas next time. :wink:

 

[jeffkay]

Learning to weld bigger metal than tabs now, Doc?

 

[Jay64]

Good lord. Glad to hear that you came out of it ok.

 

[Link]

LOL I did similar with my 48V 20Ah Ping pack. It was more impressive than a short from a wall socket and sounded like an explosive; yours must have been pretty epic. And yeah, it did the same thing yours did, with the spraying of the bits of molten metal and all. There are a few tiny pockmarks in my tile counter now. 8)

Also my orange shirt might be stained. :?

I'm also betting that your arc was easily upwards of 1,000A. You know the internal resistance of those cells, right? Care to figure out how many amps went through those pliers of yours? :wink:

 

[Iron Yeti]

It didn't melt your nose like it melted those pliers, did it? :|

 

[Doctorbass]

I agrere, i was conservative about saying 200A+.. for suure it's 1000A +

each 18p 1s sub pack have 3.02mohm so 6 in serie give me 18.12mohms. the wires that link subpack together are 10AWG and it has 4 parallel between each subpack so at 1mohm per fti would say 0.5mohm total for the subpack linking..

let say 19mohm at 25V... I =V/R

I=1315A !!

Dooohhh!!!!


Doc

 

[efreak]

I always loved how you have that sign sayning " ANGER " which is actually a Danger sign !

Now maybe there is something there but that jolt must have been something were you wearnig eye protection?
or any other safty gear?

glad that was not more serious

remember ANGER

 

[Tiberius]

Doc,

Glad you're ok, bet you got a fright, though.

Its a reminder that we are dealing with large amounts of stored energy that can be released quickly. Just like a gas tank.

Given that a short in a battery system can be so disastrous, should we be looking for special procedures or construction techniques? At the least, what about insulating materials that are resistant to puncture, wear, heat. Are the things we are currently using, such as duct tape, plastic tape, cardboard, heatshrink, etc, good enough?

I quite like the old style tufnol, paxolin or SRBP available in thin sheets. Eg: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0374395


HTH

Nick

PS. Edited to add: Here's some other options - kapton, mylar, ptfe
http://uk.rs-online.com/web/search/...ount=10&Ne=4294957561&N=4294962344+4294954639

 

[Pete]

Kapton in sheet form... cool. not sure if I would want to use it as a primary insulation material though. I have spent a fair bit of time working on kapton wiring in aircraft. Great stuff in theory, light weight, thermally stable, great insulation properties. But has low abrasion resistance, dislikes hydrocarbons and moisture, and is quite flammable once it starts to burn.

In aviation it has been causing huge maintenance nightmares for a while now because if it's flammability. With normal teflon wiring , when the insulation breaks down through abrasion, flexing or in the military application it gets a hole shot through a wire, you may get arcing. Teflon wiring will rapidly self extinguish. Kapton will burn along the wire, damaging adjacent wires causing a bigger arc, and more burning. There has been several major aviation accidents because of Kapton's failure mode.

Not sure if it is a legal thing, but lots of airlines simply will not buy an airframe if it has kapton wiring, period.

Just trying to offer a different perspective on things.

 

[Tiberius]

Hi Pete,

Well kapton is probably not a good choice then. I have only ever come across it in some very high voltage cables for high energy physics instruments. Not really relevant to ebikes. Yet....

Nick

 

[Toorbough ULL-Zeveigh]

yeah, blue balls is never good under any circumstances.
you got off lucky, both the battery & your pliers are still functional.
Tell me, do you ever wear the goggles in your pic not just on your forehead? :wink:

 

[Pete]

Hi Pete,

Well kapton is probably not a good choice then. I have only ever come across it in some very high voltage cables for high energy physics instruments. Not really relevant to ebikes. Yet....

Nick

I reckon the Doc is already breaking new ground on the high energy physics

 

[docnjoj]

Glad You are OK! It must have been "quite a shock" to stress test batts that way. Welding gloves now for soldering?
otherDoc

 

[efreak]

and rubber mat for the work area ( from one of the posts)

 

[Doctorbass]

yeah, blue balls is never good under any circumstances.
you got off lucky, both the battery & your pliers are still functional.
Tell me, do you ever wear the goggles in your pic not just on your forehead? :wink:

Usually, i wear safety google when using my drewmel or cutter.. but now i will wear them all the time i work on battery!!

With that serious power i have no choice now! 8) 1300A at let say 20V is 26 000 Watts!! and the duration was like 100ms so it's like 2600joules!

 

[Ypedal]

wooooo. good one !;

I was nervous as hell when i first started working on he duct-tape pack... then the theaded lug cells.. but over time you get comfortable .. sometimes a bit too comfortable with the work and start to get careless.. Yes.. i've caused sparks lol.. but nothing like that !

Where is the " blown up parts thread " ? this is perfect addition

 

[Doctorbass]

About safety,

My bench table have a non conductor ESD rubber that i use to protect my table from scratch.

taking time to built them and doing some ingeneering
All battery i build have the maximum safety material. That's one of the reason why it take me so long time to built every unit. I Always keep in mind the worst situation that could happen with these battery like crash, acident, fall to the ground.. etc.

I use kapton tape and high density and thick white tape recovered from the original makita pack to seperate the cells.

Friction and vibration
I also seperate each subpack that are in serie with fiberglass for PCB that is very strong but that i can bend. it have 0.006" thick. That's the best insulation and strenght compromise to protect against friction and vibration that could dammage normal tape and the plastic enveloppe of the cells.

Also, i use 0.060" thick fiberglass from PCB to surround each entire battery pack. that protect them from poncture or any parts ofd the bike that could perforate the pack and creat a short.


here is hoe i proceed:

1-each subpack are created and parallel cells are soldered together to form the subpack. I use large cooper wire (11AWG) that i removed the insulation and i solder each nickelstrip of each cell pair to it.

2-i place a 0.006" thick fiberglass between each subpack to make them in sandwich.

3- i press all subpack together using a press to make it the more compact i can to bend correctly the fiberglass between each cell (in "S") so the fiberglass become a sinusoidal shape along the subpack.

4 - I put strong nylon tape to fix and hold all subpack together and to keep all them pressed together the best as i can.

5- I put kapton and white strong tape to strategical place where some edge could create problem like shorting wires in case where vivration could make some dammages

6- i solder all negative and positive pair 10 AWG wires and all 7 charging/balancing 14AWG wire on the battery tab.

7-I put Strong nylon tape on the entire pack again to fix «l wire and subpack together.

8- i put the first large heat shrink envelope on the pack to make it solid and to protect it against wather and dust.

9-I put duct tape to every open part that the shrink can't hide and seal.

10- i put a layer of 0.060" fiberglass to every side of the pack and i fix them with strong nylon tape.

11- I cover each edge of the fiberglass with duct tape

12- I put the final thermo shrink enveloppe.
( the space between both thermo shrink layer that include the fiberglass make a kind of insulation to help heat to stay homogene and protect against mecanical shoc.)

13-Done !

the pack should be safe and insulated against temperature differences, mecanical shoc, vivration and some abrazive part of the ebike frame.

Even though, the pack keep a small and compact shape and have a great energy density.

4.8kg and 540Wh = 112.5Wh/kg

Doc

 

[Microbatman]

Glad to hear you are OK.

I heard someone else refer to the pack making process as

Handgernades with the pin pulled out.

 

[Link]

Glad to hear you are OK.

I heard someone else refer to the pack making process as

Handgernades with the pin pulled out.

Eesh. Yes, indeed. It feels much more accurate after you short a pack out a few times. Believe me. I don't have any batteries that haven't experienced a short at some point. :?

 

[dirtdad]

Updated avatar:

 

[deecanio]

lol @ avitar

glad to hear you are ok Doc
be careful man!!! this is exactly the reason i dont try to build packs myself, gulp!!!!



cheers


D