Electronics > Power/Renewable Energy/EV's

Reconditioning old/dead lead acid batteries.

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vk6zgo:

--- Quote from: james_s on December 08, 2021, 02:59:39 am ---The lead seems to get brittle over time, I've taken apart SLA batteries on a few occasions and every one of them that I took apart pretty much crumbled to bits. I have experimented with reviving dead lead acid batteries a few times and I've found if they don't recover after sitting on a normal charger for a while they are pretty much shot. You might squeeze a bit more life out of one but not enough to be worth the effort.

That Pakistani battery rebuilding video is a crude but effective example of the only way to really truly revive them. They aren't just replacing the guts, they're taking apart the batteries, melting down the plates to reclaim the lead and then forming new plates and bus bars out of the reclaimed lead. In developed nations we do more or less the same process, in a far more controlled and industrial process. I saw a video about that somewhere a while back, they had a huge machine that all the old batteries got dumped into, it would grind them up and separate the plastic, lead and acid for re-processing into new raw materials.

--- End quote ---

Pretty much how they rebuilt batteries in Australia for years.
The plastic (or in earlier years, "hard Rubber") case is the only part that really needs a large factory to make.

Obviously, in Oz, they did it in a proper workshop, not on the side of the road, but the technique would be basically similar.

james_s:

--- Quote from: floobydust on December 08, 2021, 03:38:34 am ---I did not see them recycling the lead, they seem to be using new pre-made plates obtained from somewhere  :-//
Large stationary deep-cycle batteries have tons of room at the bottom for the plate material to accumulate, lots of lead dust at the bottom. They seem to be constantly disintegrating.
If you think about it, how many metals don't mind being in acid for years...

--- End quote ---

They probably process the lead somewhere else, they must use a machine to form it into sheets. It wouldn't make sense to just throw it away though, lead is valuable and easily recycled.

Fflint:

--- Quote from: floobydust on December 08, 2021, 03:38:34 am ---I did not see them recycling the lead, they seem to be using new pre-made plates obtained from somewhere  :-//
Large stationary deep-cycle batteries have tons of room at the bottom for the plate material to accumulate, lots of lead dust at the bottom. They seem to be constantly disintegrating.
If you think about it, how many metals don't mind being in acid for years...


--- End quote ---

Perhaps I posted a wrong link. There are a couple of those videos made by the same team of guys. They are definitely casting plate grids, they are pasting them and they are drying plates on a rack. If it is not in this one there is in another video YouTube shows on the right as "similar videos".

I though those videos were made in different places by unrelated people until I say the bearded guy (in white/grey clothing) that was rebuilding a battery at street side in another video that was showing them manufacturing plates.

It is pretty cool they can do it start to finish. I just wish they were more h&s conscious.

Fflint:
Regarding the battery I showed the picture off. I had to glue the top back together or the recycling guy wouldn't take it. Before I did that I pulled one of the plate packs and I found something very interesting.

The negative plates were in very good condition. The positive plates were practically gone. Few small pieces remained, but the majority turned to dust.

Why, is this interesting? Well, to me it is because after reading lots of online sources one would be justified in thinking the biggest issue with lead acid batteries is sulphation as a problem with negative plate condtivity. It seems with this very old battery that wasn't the case. It is positive plate corrosion that killed it.

As far as I know, short of replacing plates, there is nothing that can reverse or recondition such corrosion :-(

Fflint:
And another data point.

A car battery was purchased 4 years ago. It is a 75ah battery with 750A CCA (the car has a tdi 2.0 engine so requires a pretty large battery).The car is used rarely, maybe once every 7~10 days for short trips of few km. So a pretty hard life for the battery. Specially in winter. After 2 years the battery wasn't starting the car reliability. I bought a new one and I gave the old one to a friend with an off-grid cabin. He used it in his power bank for 2 summers until it wasn't keeping a good charge. Then recently it came back to me.

Surprisingly after few months in storage it still showed a pretty good voltage of 12.6.the electrolyte measured 1.26. When I shorted briefly it gave me 150amps when cold and almost 300a while warm.

I didn't use the magnesium sulphate with that battery, because I wanted it to be a control for the chemical treatment. I just kept it on a trickle charger on and off for the better part of last 2 weeks. Few days ago I discharged if with 55A to 12.0V and I used my newly built pulse charger. I was using 18kHz pulsing frequency, 5% duty cycle and about 23V which gave close to 5A average current (later I changed the frequency to 1Khz, but that's with another battery).

Another discharge to 12V took 25% longer, but this may be due to temperature difference.

However, I decided to test the CCA differently this time, because my clamp on current meter only goes to 400A.I put the battery in my tractor that usually has a set of two 195ah/1000CCA 6V batteries. I know for a fact the tractor requires ~700 amps at minimum to start. I turned the key and it started as if it had the 1000CCA battery in. I let it run for a bit and I restarted it few times later to test it wasn't a fluke.

So there we have it. CCA of one battery was significantly improved by pulsing and trickle charging for a long time. There is also slight increase in capacity.

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