Rolls - a safe battery when shorted...

[Simen]

I just got a Rolls S-4000, 6V, 530Ah for free from my supplier, because the previous owner had connected the batteries the wrong way... He had 2x 2 batteries in series which he connected together in parallel the wrong way, and the result can be seen below...




That lead rod are 1/2" thick, and was melted clean off. It seems that Rolls have dimensioned those rods according to how much amps the battery can deliver for 5 seconds; over that, and the rod melts instead of exploding the battery...

All 3 cells seems ok, and measures 1.13 SG; resting voltage are 5.95V, and the battery takes charge just fine...


Now, anyone have suggestions to how to get a proper connection to that remaining tap? And what material to use? (I do not have the equipment to solder lead back on, and heating up that lead with all that acid are probably not a good idéa...  )

[TomW]

I knew a guy who fixed a similar problem by building a clay mold right on the post to extend the lead post  and then just poured molten lead into this mold. It worked for a long time. It was a car battery with a normal post. The extra hot lead melted the old stub enough to bond to the molten lead. After it cooled he whittled it until it was the shape he needed for the battery clamp.

He did this all in a remote location when the battery tipped over and shorted the + post to frame and melted it out  under the clamp.

He only used a wood fire a soup ladle, fishing sinkers and some clay from the river bank. He only expected it to get him home but he used it a couple years before it died from probably old age.

Might work here and no open flame near the battery? I don't think the acid itself is very flammable.

Battery dealers do something similar when building some of the forklift batteries. The bore a hole into the lead lug and pour molten lead in that to attach interconnects.

Good luck with it.

Tom

[Simen]

That's actually a good idéa Tom! Thanks!

My mind was set completely on the wrong track; thinking of 'soldering' lead onto lead, or mechanically fasten a cable down there in the acid pool... Ofcourse one casts a new post; that's how they're originally made!
The old post are rather large, so if i melt that one down, it might be enough to make a standard round 'car-battery' post.

[taylorp035]

I somehow doubt that the acid would be very flammable, considering that 1000's of high school and college chem labs have kids+bunsen burners+acid...

 

[Simen]

No, i know that the acid will not burn, but if one heats it up; what do you get?!
A gas that burns very rapidly...

[Mr_T]

Evening.
Lead acid batteries use 30%ish sulphuric acid which indeed is non flammable. If you heat it up to it's boiling point all that happens is that the water mixed with the acid will slowly boil off and hence the acid becomes more and more concentrated. Only when you got rid of most of the water and reach very high concentration (98% I believe) the acid will actually give off SO2 which is rather nasty.

Personally, I'd either try drilling a hole in the piece of rod that is left and then bolt something to it, or much rather solder another piece of lead to it using standard tin/lead solder. Casting a new bolt with molten lead as mentioned before should work just as well but might be a little harder to accomplish.

Cheers

[madlabs]

What about a combination? Drill a hole and tap it, thread in a bolt with nut and washer, maybe a couple of 'em (nuts and washers, not bolts). Then cast the lead on top. That way you would get some mechanical strength as well as a connection. I'd also groove what is left of the lead to increase contact and meltability when you pour the molten lead.

Jonathan

[Simen]

I don't think i want to introduce any other metals than lead into that acid; even if it will be encased in lead...
But i am going to drill some holes and grooves on the remaining lead tap to get a better bond...

[TomW]

I don't think i want to introduce any other metals than lead into that acid; even if it will be encased in lead...
But i am going to drill some holes and grooves on the remaining lead tap to get a better bond...

High grade stainless threaded into a tapped hole in the stub might be a good "core" inside the post and add strength. You could let it protrude from the lead as a connection stud?

Just thinking into the keyboard.

Tom

[Simen]

I've tried some 'A4' stainless steel that should be acid resistant, but when dipped into the acid; small bubbles started to form around the steel.... It's probably not 'high grade' enough...

The battery are going to live out it's life standing very still in my basement, so i'm not worried about mechanical strenght, only electrical... As long as the joint get solid, i'd think 1/2" thick led post should be solid enough; besides, the rod will have horizontal support in the lid...

As soon as i find some clay, i'll start casting. I'll try to get som photos of the process...

[madlabs]

On second thought, I think you are right. Two disimilar metals plus acid does equal galvanic corrosion. Let us know how it turns out.

Jonathan

[TomW]

Do be aware that well melted lead is water thin or lighter maybe? I never cast a battery post but have cast a few hundred pounds of sinkers, jigs and bullets.

Got a hotfoot a time or two when the mold leaked in a weld pinhole in the ingot mold for storing cleaned lead.

Just tossing that out there.

Tom

[Simen]

I'm planning to put a collar of clay around the post beneath the mold to catch any leaks from the mold. Any liquid lead leaking into the acid would be lively, so i'd do what i can to avoid that...

I'm not unfamiliar with clay, since my mother are a potter and a teacher of the subject at university level...

[Hilltopgrange]

I had to do this many years ago on a forklift battery. I made a mould from a short length of aluminium tube with an inside diameter the same as the post, split the tube down its length and clamp in place with a couple of hose clamps, you can seal the split with exhaust paste to stop the tube leaking. After the lead cools the tube should just pull off.
This worked really well for me and lasted for years. Good luck with it!

Russell

[Simen]

Now the deed is done!

First, i cleaned the tap for dirty lead, and then drilled some 3mm holes at an angle at the top. The holes meet in the center about 1cm down; i hope the molten lead will flow into those holes and make a good grip/bond.


What i found of clay, was some porcelain clay; it was a bit soft right out of the bag, but i managed. I formed the clay around a long socket wrench which was 16mm in diameter, which are perfect for the negative round battery post.


Melting the lead was done in a tin can over a camping gas cooker. I was almost out of gas, so i was a bit worried about the temperature, but it worked ok.


After the lead melted, i scraped off the slag on the top of the melted lead, and took it out to the battery quickly, and poured...


One can see that the clay cracked a little in one place, but not enough to leak any molten lead out. The molten lead made some crackling noise for a few seconds before solidified, due to the moist clay. Next time, i'll use more clay to make the sides a bit more robust.

I'm satisfied with the result. The post sits firmly onto the old tap, and doesn't look to bad either. A thicker mold would probably have avoided that slight bulge in the middle, but it doesn't hurt, since i had enough lead, and the hole in the lid fits snuggly over the post.


All that needs to be done now, are to glue the lid back on, and put some sealant around the post.


(More and larger pics at my gallery: http://mwlmf.net/gallery/brokenrolls )

And now; charging... The only 6V charger i have are at 2A, and will take decades... I'll think of something i guess...

[bj]

   Well done!  No fancy tools, just good use of what you have.

[tanner0441]

Neat job, and you were lucky that the top blew off so it could be salvaged. The last battery I managed to destroy using an angle grinder near it blew the end out, it took a lot of convincing the young lad with me to bin his clothes not put them in a washing machine.  He realised I was serious when I stripped my overalls and shirt off and put them in the skip (dumpster).  As for charging can you borrow another one to make 12 V and use an engine driven alternator, once charged you can keep it topped up with a small charger.

Brian.

[madlabs]

Good stuff! Thanks for the pics and congrats!

Jonathan

[Simen]

Thanks guys.

The top didn't blew off; the negative post just melted off inside the cell. I had to pry open the lid and break it off... The Rolls S-4000 series batteries are good batteries, but the casings are not so robust. It's easy to pry loose the lid with a chisel and hammer. These batteries are designed to stay put in a shed/basement/whatever, and doesn't handle rough handling very well...

[SparWeb]

Simen,
Great story!  It may come in handy some day, too, for those who have the same problem.

[Simen]

Yes, i hope this will be useful for others too. The melting of the led, forming a form and casting was actually easier than i thought.

To wrap up the story...
My supplier was kind to me, and sold me another 6V, 530Ah battery that had a slight transport damage, for 1/3 of new price, so now i have a 2S2P 12V bank 1060Ah @ 100hr (800Ah @ 20hr).

The repaired battery charged nicely with my 25A worth of solar together with the other 6V battery, and the sg ended around  1.280 @ 18deg. C. for all 3 cells.

[Madscientist267]

Always wondered if this kind of surgery was possible... My introduction to the 8D class involved the exact same scenario, the only difference was the "system" voltage, erroneously available as 24V and I'm sure that every available electron was flowing at full throttle (the interconnects were 00 apparently), and if I recall, the CCA rating was 2500A or so. Posts left to connect to? What posts?

They still had 12.5V on them by the time I acquired them, but with no way at the time to really connect anything worthwhile to them (charger or otherwise), they succumbed to sulfation and shorted cells after sitting in the shed for months. By the time I decided WTH, I couldn't get them to respond worth two doodoos, and gave them up for recycling.

Glad to know that if the opportunity ever arises again, I can just pour a new set of posts and be done with it.

Any problems with current flow or heat from resistance at the joint or anything?

Steve

[Simen]

I haven't really checked properly for heat from resistance, but last week i performed an equalize; 25A for 2 hrs. after the batteries was fully charged, and all posts was cold to the touch. (I checked if i could feel if the batteries had heated up at all, because i was at the time fiddeling with my dumpload controller with temp. compensation, and i hadn't fastened the temp sensor... )

Before i poured the cast, i cleaned and scraped the post-tap to a shine, and also roughed it up a bit. when the lead was poured, it took 4-5 seconds before it solidified, so i think the lead had time to melt the post-tap a bit and bond properly.

[TomW]

Before i poured the cast, i cleaned and scraped the post-tap to a shine, and also roughed it up a bit. when the lead was poured, it took 4-5 seconds before it solidified, so i think the lead had time to melt the post-tap a bit and bond properly.

That was what I kind of expected that they would marry together by the old melting when the new was poured.

I am far from an expert but have melted and cast a fair bit of lead for bullets, sinkers and decoy weights.

Tom