# safe to repair battery case?



## TheSGC (Nov 15, 2007)

I'd have to say rather insane. Battery repairing isn't for the untrained and I'll never do it. The problem is that there are so many different kinds of plastics out there that you don't know what kind the case is made of and if you repair it with the wrong stuff, things could go horribly wrong later on. Or immediately. You should really get it replaced, unless someone else has another idea.


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## dtbaker (Jan 5, 2008)

TheSGC said:


> I'd have to say rather insane.


ok, ok, besides Wife agrees and I don't wanna have any KNOWN flaws that might cause lack of trust issues later. 

I did try to weld it just to see if I could.... and made a mess out of it. The case is fairly thin, and without any support behind it, it is easy to push right thru and make a bigger hole. Kinda like trying to weld tin foil with an arc welder. ah well.

d


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## rmay635703 (Oct 23, 2008)

*Re: safe to repair battery case? YES*



TheSGC said:


> I'd have to say rather insane. Battery repairing isn't for the untrained and I'll never do it. Things could go horribly wrong later on. Or immediately. You should really get it replaced, unless someone else has another idea.


What planet are you from? Your statement is well, foolish. What could go horribly wrong? Might he spill acid again, might he put a hole in his new suit or have a short? Oh no that happens anyway at some point! This repair is no more dangerous than putting acid in a new battery.

If you can deal with sulphuric acid you can repair a battery case. 

Step 1.

Get appropriate old clothing you care nothing about and a safe non-paved location, baking soda and some warm water and an acid proof funnel and container. Also a pair of safety glasses and some "acid refill" from a local store

Step 2.

Dump out all of the acid into said container

Step 3.

Clean the broken area then dry with paper towelling or low lint junk rags (obviously if it is REALLY smooshed you may have impacted the plate and broken it, otherwise continue)

Step 4.

Liberally Apply your favorite patch or putty over the entire area. Do as you would to seal a radiator or any other liquid leak. YOU DO NOT NEED TO WELD PLASTIC to seal it. See the videos at the bottom of the page.

http://www.chinadepot.com/batripod.html

I especially like the video showing you how to clear a battery short with a coat hanger.

Also something of interest to the more hardcore
http://members.optusnet.com.au/~weza/

Contrary to what many believe a battery is LESS dangerous than soldering with leaded solder, the acid is biodegradable and normally newer lead acid batteries have minimal amounts of actual physical lead in the acid. Also you are not dealing with lead powder or smoke which is the most dangerous type of exposure.

I have had very strong acid on my hands many times in chem lab and needless to say nothing happened, you just calmly wash them and apply baking soda, if you leave acid on your skin long enough it starts to tingle and burn but it takes much longer than you may think. And obviously don't splash the acid up into your eyes, always wear safety goggles. And obviously don't wipe your eyes with your hands after handling acid and eat/drink during the event, duh!

The main issue with sulphuric acid is its effects on concrete and clothing aka it destroys them, which is why I keep a junky pair of clothing for just such an occasion.

Good Luck


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## dtbaker (Jan 5, 2008)

*Re: safe to repair battery case? YES*

suprisingly, the battery tech guy encouraged me to go ahead and give it a try too... with all proper safety concerns. He did verify that the case was 'plain polypropylene' and should be weldable.

So I did try it... washed case with water, tipped away from crack (other cells are fine), and fired up the plastic welder. I sanded the outside a little in case there was mold release agent or other stuff, and gave it a go.

What I found out was that the case is pretty darn thin, and I had my air a little too hot. I was using a welding tip, and probably should have just used an open nozzle and 'smeared' material with a putty knife. The small welding tip poked right thru the soft case and I made the hole bigger rather than smaller. Sorta like welding tin foil with an arc welder.....

so now I am giving up on it and trying to get a matching replacement. I do think it would have gone just fine with a little lower heat and a putty knife and open tip rather than a welding tip.

ah well, live and learn.


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## TheSGC (Nov 15, 2007)

My problem wasn't really the acid, but what the whole this was as a whole: a 1.2+KWh power source. If the battery ever leaked again and managed to hit some metal, it could send full pack power through the EV and possibly frying components/people. I believe there are people here who had batteries leak some acid and make contact with the battery racks and completely fry the controller.

One battery shorting is one thing, but if its connected to 20+ more, they are now part of the short.


@dtbaker - So how thin were the battery walls? And did you take a look at the plates? I'm just curious about the guts.


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## dtbaker (Jan 5, 2008)

TheSGC said:


> My problem wasn't really the acid, but ... If the battery ever leaked again and managed to hit some metal, it could send full pack power through the EV and possibly frying components/people.


my plan WOULD have been to put the repaired battery in the rear battery case, which will have a sealed polypro tray and sides, and no componnents.... so it might have sloshed a little, but probably not too likely to cause any serious damage.

I'm not CRAZY.


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## rmay635703 (Oct 23, 2008)

TheSGC said:


> My problem wasn't really the acid, but what the whole this was as a whole: a 1.2+KWh power source. If the battery ever leaked again and managed to hit some metal, it could send full pack power through the EV and possibly frying components/people.


Now what you described above is crazy, good reason to design your ev well like the op above, so that cannot happen, my boxes are isolated with bed liner and disconnects.


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## dtbaker (Jan 5, 2008)

dtbaker said:


> my plan WOULD have been to put the repaired battery in the rear battery case,


ok, I am a little crazy... and was having trouble getting a matching battery so I gave repair another try after practicing with the plastic for the rear battery box. Turned out that with the 'speed weld' tip, and additional welding rod instead of smushing existing material, it WAS possible to fix up the casing even after my failed first attempt.

I laid in several rows of welding rod for form a new case, and then filed a little bit with a rasp to flatten it out. filled the cell with acid, and it holds fine.... So, away we go! I will post pix of repair on my website next time I empty the camera....


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## rmay635703 (Oct 23, 2008)

What brand type of plastic welder do you have?

I was looking for a cheap alternative to harbor freights hot air blower

Thanx
Ryan


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## dtbaker (Jan 5, 2008)

rmay635703 said:


> What brand type of plastic welder do you have?
> I was looking for a cheap alternative to harbor freights hot air blower
> Thanx
> Ryan


I got a Leister 'Triac S' kit used on ebay... it STILL was expensive for $300! But apparently the good ones are pricey. I have a picture of the tip at
http://envirokarma.org/ev/gallery/090127_plasticwelding.htm
and a shot of the repaired case at
http://envirokarma.org/ev/gallery/090125_battery.repaired.htm
and a shot of the battery rack panels at
http://envirokarma.org/ev/gallery/090119_rrack03.wdone.htm


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## dirtfarmer (Jun 13, 2008)

I have repaired battery cases many times. I used to rebuild wrecked cars and batteries were often broken. I have never had any problems with any of them. I just took a repaired one out of my own car that I used for seven years. I usually take any old junk battery and break off small pieces of plastic. I put the pieces into a vegetable can and apply heat slowly using a small propane torch. Once the plastic is molten I pour the material into the damaged area. You can smooth it up and blend in the edges with a hot piece of steel so you can barely tell it. If you use the correct color of plastic often you can't tell it at all especially if you sand the area with extremely fine sandpaper and the polish the finish. I have even fixed batteries with large pieces missing by splicing in a similar piece from a junk battery. You do need to be careful to find out if the partition between cells is broken. That has to be repaired while the hole is still open.


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## mizlplix (May 1, 2011)

FWIW: I have repaired battery cases. I worked in a battery shop during high school. 

Small cracks can be sealed by a small soldering iron. That is to avoid your problem of the thin case. I used common zip ties for any filler I needed.

The other patches were sealed with polyurethane window sealant. 

No magic. No danger. 

Having said that.....new build.....take your lumps, buy another one.

Miz


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## poprock (Apr 29, 2010)

Been there; done that. Used a soldering iron to weld the case and it was a top job visually. However, some weeks later a short developed between pack & chassis. The repair was a different density to the rest of the case and electolyte tracked through.I scrapped the battery.


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## V96400A (Mar 13, 2011)

To clear the air with battery welding:The battery in my old chevy S-10 was not properly seated and hit a pulley while driving and acid went everywhere.
I cleaned everything up and my dad showed me how to repair a battery case. We did not even match the plastic. Certain plastics of different types can be welded together (the plastic bags from the grocery store are a mix of different types of PE). You don't really need plastic welding equipment. I used and regularly use a torch to heat a piece of aluminum and use the aluminum to melt the plastics. Your wife may not like it, but you might even get away with using her clothes iron. 
Since I first learned about plastic welding, I spent a few years fusing natural gas pipeline, got some serious plastic welding training. 

Another side of me says a good epoxy resin could have worked, but that side of me also would have tried a hot glue gun.

Back to serious, the trick is the right amount of heat, just enough to get a good enough portion of the plastic heated to the amorphous (gooey) state, while leaving enough in the crystalline state (solid). If you need the plastic to cool, you can usually get away with water cooling to avoid damage on the post repair section.


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## kingpower (Nov 24, 2011)

hi i have traded in car batteries for 35 years and have not known about a permanent plastic repair to a battery? i think you have had it ? eric www.batteriesontheweb.co.uk


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