Cracked battery case

[lifer]

Hello,

I've just discovered that one of my batteries has a pretty ugly crack just bellow the top lid (it has two long and flat lids, each of them covering three cells at once).

The lid was sealed by the manufacturer with a sticker (covering the whole top of the battery) thus I couldn't check the battery integrity when I bought it (due to warranty terms).

Most probably, the damage has been made by throwing another battery on top of it (for stacking purpose) at the dealer shop. The lid has been pressed too much and it pushed against the top surface.

The battery performance isn't affected (it doesn't spills out any water/acid) but I want to seal the crack to avoid any dust contamination.

The crack is 5cm long and 1-2mm wide. May I use a sealant or a PVC adhesive to cover that crack? 

[dbcollen]

use a soldering iron and some milk jug plastic to weld it shut

[hiker]

Epoxy. Stick....buy it a Home Depot...or lowes..industrial store?   Strong and really rock hard..no cracking...

[TomT]

There is a product at Home Depot.
Is is called Plastic Welder. 2 part epoxy.
 It is in a dual tube dispenser.
Works on just about any plastic. Sets pretty quick too.

[Frank S]

It was hard for me to believe but this stuff they advertise on TV actually works well for repairing several things
 I've used it to repair a chipped piece on my laptop the plastic grill on a Mack truck and a couple other things
 It gets pricey for large repairs though.
 http://www.ebay.com/itm/221949279239?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[Mary B]

I cleaned the case on one in an old truck, sanded it to rough the surface, tossed some RTV on and drove it like that for 8 years... at the top of the case there isn't much liquid and the acid won't attack most plastic glues. Since RTV is acid activated I didn't think it would matter! It was still on there when I sold the truck for parts! They hit the battery with a booster and started the truck, guy drove it for a year before the cab fell off the frame(why I sold it, cab mounts were all rusted bad)

[lifer]

Thanks for your suggestions, pals! Sorry for this late reply, I was celebrating Christmas away from home.

I see that everybody recommend some sort of epoxy or plastic bond. Anyway, I am not sure what kind of plastic (PVC, ABS, polyester) the battery case is made of.

I guess I need some sort of elastic filler as I can't pull the lower side in place to bond it (the crack has a 2-3mm gap side to side).

What about this product: UHU plus endfest? I have used it to bond the neodymium magnets for my axial flux generator and I still have some syringes left. Don't know about its elasticity though.

[dnix71]

I second Mary B's suggestion. RTV silicone. Scuff up the surface and wipe it clean with a damp rag and let it dry before squeezing on the silicone. Push it into the crack and let it set up overnight before moving it. Don't make it too think, it doesn't need to be.

Silicone is made for custom engine gaskets. It's flexible, water, heat and petroleum proof once set up. Cheap, too. A medium size tube is only abouy $4. It will set up in the tube if you aren't careful to replace the cap tightly when done.

[lifer]

Thanks for your confirmation.

I will look up for a RTV silicone tube and I'll let you know the results. Seems like the best solution, indeed.

Once again, thanks everybody for your time!

[Mary B]

If the RTV peels in a few years then redo it... simple fix. Make sure to degrease the case first!

[Johann]

Just use a 2-part plastic epoxy which will have a beige to white color and cost about $4 US dollars.
If you have a black battery just use one drop of black paint when mixing the 2-part epoxy. It uses very very little paint.....just use one drop to start with.

Clean the crack and surrounding areas of the plastic with brake-cleaner that is sprayed on a rag really good. You want a cleaner that has no oil, fat, soap or wax in it.
Then mix your plastic epoxy (equal parts) and if wanted one drop of paint to match the battery color.
Fill your crack and let cure according to your epoxy instructions on the package.
This fix should last for years to come.
I am a maintenance man and the last battery I fixed that way lasted for years until it died on natural causes.

I never had much luck with silicon, it never lasted long enough for me.

Uhu? I remember Uhu as a kid and I used it back then, but at the time they had only one kind of glue. I guess they are coming up in the world.

If you still have warranty, I would see if they would exchange it.

[lifer]

Thanks for your very informative post, @Johann!

I'll begin with the last question: yepp, the battery it's still under warranty but I couldn't prove that the damage was done before I bought it (and that's a big frustration).
That is, I will never buy a battery again if I could not check its whole integrity. Like I said, this one had a large sticker (label) covering the entire top face of the battery and the damaged area was beyond it (and the lid). Nevermind, I have to live with that and that's why I'll take good care of it.

I did not repaired it yet as I'm looking for a method to pull the lower plastic wall in place to reduce the gap. Seems like I have to insert a hook or something in the filling hole and pull it up. My main concern is to avoid any contamination of the battery fluid while doing such a manoeuvre.

I'm not concerned about it final look either (by adding black paint - but thanks for the tip for a further use). I just want to seal the crack to avoid any dust contamination or acid spill during bubbling.
 
I'm going to try both RTV silicone and bicomponent epoxy resine on a "healthy" battery region to check for the best adherence.

[Johann]

Regular epoxy most likely will crack on flexible plastic.
Use a plastic epoxy like this http://www.homedepot.com/p/Loctite-0-85-fl-oz-Plastic-Epoxy-1360788/100371824

[lifer]

The epoxy you have suggested seems a good choice.

My only concern is the following statement: "the components react to produce a tough, rigid, high strength bond". The battery case is made of a hard plastic and the actual crack has a 2-3mm gap. I would try to put both crack sides in place (by pulling up the lower side) but I'm afraid there will still remain some mechanical tension trying to push back (enlarge) the gap.

That's why I thought that an elastic bond could be more appropiate. Moreover, every time I'll have to replace the filling hole lid I need to push it hard thus more mechanical stress on that bond.

Btw, in the product description there's no mention of (vapour) acid resistance. Could that be a problem? 

[joestue]

Battery cases are polyethylene and epoxy will not stick to it, other than surface roughness, there is no chemical bond. Use a hot gluestick , heat it with a propane torch and melt the plastic together.

[Frank S]

Not to toss water in the mix but using a propane torch around a crack that is open to the acid can be risky.
 I've built up the posts on a lot of batteries using a torch to melt the lead back in place but I always had a wet blanket covering the filler vents. it would be far better to use a large Weller soldering gun when doing any plastic welding.