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  #1  
Old 11-23-2008, 07:52 AM
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Default safe to repair battery case?

yesterday as I was schlepping batteries in and out of racks for a test fit, I dropped one... ;( Only about 4" off the floor, but it landed right on the corner, which 'shmushed' a little and cracked. Battery acid all over the floor, no other damage.


so.... now I am one battery short, brand new, and I had to order the set since there is no local distributor. I am looking at the case crack (very small) wondering if I should have a go at it with my trusty plastic welding tool. I do have polypropylene rod and have practiced by repairing my cracked garbage bins.....

So, I'm considering welding the crack and re-filling the cell with fresh acid.
insane, or worth a try?
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  #2  
Old 11-23-2008, 08:02 AM
TheSGC TheSGC is offline
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Default Re: safe to repair battery case?

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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  #3  
Old 11-23-2008, 08:36 AM
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Default Re: safe to repair battery case?

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Originally Posted by TheSGC View Post
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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Last edited by dtbaker; 11-24-2008 at 12:52 PM.
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Old 11-25-2008, 03:18 PM
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Default Re: safe to repair battery case? YES

Quote:
Originally Posted by TheSGC View Post
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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  #5  
Old 11-25-2008, 04:19 PM
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Default 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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Old 11-25-2008, 04:34 PM
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Default Re: safe to repair battery case?

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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  #7  
Old 11-25-2008, 04:37 PM
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Default Re: safe to repair battery case?

Quote:
Originally Posted by TheSGC View Post
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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Old 11-25-2008, 04:51 PM
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Default Re: safe to repair battery case?

Quote:
Originally Posted by TheSGC View Post
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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  #9  
Old 02-02-2009, 08:18 PM
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Default Re: safe to repair battery case?

Quote:
Originally Posted by dtbaker View Post
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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  #10  
Old 02-03-2009, 05:17 PM
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Default Re: safe to repair battery case?

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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