Time for a fresh fred on batteries.

[mael]

... I just fitted a 'new' battery to my mini-truck. The truck's standard battery is a 30 A/h job.

My friend gave me two batteries to look at. One was a battery he had sitting in his house for at least a year while he was in prison ... . Er - and that battery's electrolyte was off the end of the float. It took three days to get the specific gravity to the green sone (around 1260) - but the neg side's cell was s-l-o-w. With info I've gleaned recently I suspect that cell's pos plates are in a very poor condition. But it works! Will it crank the car? Hmmm! Well, yes it does, but that sort of battery with a suspect cell would be one I wouldn't feel comfortable about selling - or donating to someone who would be up SCWAP. - I let my friend have that one back - it's a spare one! I told him to keep it charged or the same thing's going to happen again. I wonder if he listened?

The other battery was one from a flood-car. I thought it was a joke ... the initial voltage was about 1.5!

That was a SHELL 65 A/h battery. Again, it had one cell which was moving much slower than the rest, and in the end I decided to adjust the electrolyte somewhat to get the level balanced with the other cells. In (the usual) three days of desulphating, five of the six cells' electrolyte's SG was inside the green.

When I first got the battery the levels in the cells were a little high. I assumed water had got into each cell to some degree. So I took a measured amount from each cell and evaporated it and then put it back in the cells in the ratio it was removed. - The 'slow' cell was way over-filled.

... Now that battery is in my truck. It just fits in the battery compartment and has got lots of cranking power. So it seems apart from a few, I can get almost any battery back to at least 'cranking' provided it isn't shorted.

*

And I have been giving thought to the 'old-timers'' trick of adding mag sulphate to a tired battery and getting more life out of it.

The way I heard it, the mag sulphate would get a few more months cranking, but it would wreck the battery faster because of a chemical reaction.

One point is that wrecking an already wrecked battery is a no -brainer really. If it works then mag sulphate is a cheap fix until you can get a new(er) battery.

Another point is that I gathered when I was informed about putting mag sulphate into the cells to revive the battery was that it works by reducing the internal resistance - thereby increasing the amps it was capable of delivering. -

- But is this simplistic explanation helpful or is it misleading? In my mind, the process worked because (surely) the conductivity of the electrolyte was increased so that it could react with the reduced effective plate size more intensely. -

- BUT! I was wondering whether this is not the case so much as the mag sulphate having the effect of 'bridging' more of the crumbling positive grid - so as to effectively increase the plate area? Does mag sulphate improve the conductivity of disintegrated positive plates to the degree a battery can crank again? T'would be wonderful if this is actually the case - I see another experiment on the horizon.

[SeaMonkey]

Aaaah, the reports of your successes are music to
the ears!

The situations where you've encountered cells with
weak electrolyte (lower than normal specific gravity)
following desulfation and rejuvenation are quite common
in my own experiences.

With continued pulsing the sulfation in those "weak"
cells will usually be converted and the electrolyte will
come back to full strength. It's as if those cells are of
a little less capacity than the others and as a consequence
the sulfation is more severe. Extended and continued
pulsing will in time equalize them unless they're suffering
from some sort of internal defect such as a broken plate
or two.

You ask really good questions about the Epsom Salt
(Magnesium Sulfate) treatment. When it is added to
the weak electrolyte of a heavily sulfated dead battery
it will serve to make the electrolyte (which is nearly
pure water in that condition) electrically conductive.
This will facilitate the beginning of the desulfation at a
somewhat lower voltage than would otherwise be required
to get the process going.

The presence of the additional sulfate ions in the electrolyte
from the Magnesium Sulfate will also lessen the likelihood of
lead sulfate going into solution when the electrolyte is very
weak due to deep discharge. The less lead sulfate which
goes into solution the better as it won't "Plate Out" onto the
negative plates during charging. This will minimize the
formation of dendrites which may in time produce shorts
between the plates;
and it will also minimize the gradual transfer of lead from the
positive plates to the negative plates by this solubility.

The added Magnesium Sulfate by itself will not result in
any great amount of desulfation - the pulsing will still be
needed to accomplish that. But, the addition will be
otherwise beneficial to both desulfation and normal
charging. With periodic desulfation those batteries with
the added Magnesium Sulfate should enjoy longer lives
than would be possible without it.

I prefer to add the Magnesium Sulfate dissolved in
distilled water to top off the cells when the electrolyte
level is low. Or, electrolyte may be withdrawn from the
cells, Magnesium Sulfate added with warming, and the
solution put back into the cells. About two heaping
tablespoons per cell should be sufficient.

Have you tried this yet Mael? If so, what have you seen
in the way of results?