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knackered lead-acid batteries

Posted: Thu Jul 25, 2013 8:47 pm
by dave45
My lead-acid leisure batteries are 5 years old and are just not holding much of a charge any more. yes I have a proper charge-controller and have not been misusing them in anyway....but after a full charge on a sunny day, they last about an estimated eighth of what they did when they were new.

I did read an e-book from circa 1908 about reconditioning lead-acids, but I rather think they were built a little better a hundred years ago

is there anything I can do to refurb them?

Re: knackered lead-acid batteries

Posted: Fri Jul 26, 2013 2:19 pm
by mamos
I think what happens is deposits collect in the space below the plates and eventually reach a point where they short the plates out. Very old batteries had much more space between the plates and the bottom of the box plus you could strip them down, clean them out and refill with acid but you can't easily do that with a modern sealed battery.

It is called 'Planned Obsolescence' and it is what keeps the battery manufacturers in the lifestyle to which they have become accustomed. It is practiced in most industries I'm afraid.


Re: knackered lead-acid batteries

Posted: Mon Nov 17, 2014 10:55 am
by peat
According to the book 'Do it yourself 12 volt solar power' - A layer of dirt, especially damp dust on the outside of the battery can create a connection between the two terminals, speeding up the self discharge rate.

Also if you have sulphur build up on the plates you can crack it off using a battery pulser.

Or you can charge it for a long time at 14.4v

Or empty all the acid out, fill with distilled water and charge constantly for several days and nights, then discharge fully and top back up with acid, checking the acidity is right

Or you can open the top of the cells, charge at 24v with a resistor for a few minutes at a high current, then discharge fully with as high a current as possible, then immediately charge up fully.

There are lots of safety caveats with this methods:
Do it outdoors, away from naked flame
Use 10mm cable minimum
Fuses between each battery, covered in plastic to prevent sparks
Place batteries outside and have one switch for whole system, inside away from batteries to prevent danger from sparks

Good luck...!

Re: knackered lead-acid batteries

Posted: Mon Nov 17, 2014 11:38 pm
by dave45
What's a battery pulser?

my charge controller does pulsing (PCM) when the battery voltage rises

when you say "charge at 14.4V or 24v" - what do you mean? the voltage is set by the battery surely? if you connect a battery at 11.6V to a source at 12v, 14v or 24v, the battery voltage starts at 11.6v and will slowly rise. if it rises too far (above 13.6v ?) you will get gassing as water is split into H2 and O2 which can be useful in small doses to stir up the acid electrolyte, but will lower the liquid level and in due course expose the plates.

Re: knackered lead-acid batteries

Posted: Tue Nov 18, 2014 5:22 pm
by peat
Sorry Dave, I don't know what it means, I was just paraphrasing from the book. Which is a handy reference, but doesnt go into much more detail than this. I assumed he meant using a variable voltage power supply.

He did emphasis that these methods do not have 100% success rate, but that if the batteries are already knackered.... it doesn't really matter.