Re: (ET) Fw: Lead Acid Battery Question

["David Roden" <etpost drmm net>]

Sulfation is a normal process of discharging a battery.  It's reversed by 
charging.  That's how a battery works.

If you don't charge the battery soon enough, or if you chronically 
undercharge it, the sulfate crystals grow and resist being turned back 
into 
lead.  They'll eventually loosen and fall to the bottom of the cell.  
Enough of this and they short the cell or increase its self-discharge.  
Even if they don't buld up that much, they represent a loss of active 
material from the grids, which is a loss of capacity.

There is no way to reverse this "hard" sulfation, period, end of story.

Some of you other old-timers may recall a well-advertised battery additive 
from the 1950s and 1960s called VX-6.  Its makers claimed it was a miracle 
cure for old batteries.  It contained cadmium sulfate!  That's not 
something you want to mess around with.  

The VX-6 ads suggested this "test": Turn on your car's headlights until 
the 
battery is flat.  Turn the lights off, and add the stuff to the battery.  
Wait a few minutes.  Turn on your lights.  Look, they work again!  Your 
battery is rejuvenated!

What they didn't mention is that if you'd just left the battery alone for 
the same few minutes, the same thing would have happened without the VX-6, 
because that's just how batteries work.  

Cadmium is restricted these days, but the snake oil battery additives are 
still around.  Now they use other chemicals, often various kinds of other 
metal sulfates.  Cobalt sulfate has been used in the past.  Other 
compounds 
have been tried too.  Some of the Home Power magazine guys used to use 
EDTA, with (they said) varying degrees of success.

A temporary fix for a sulfated battery that actually sort of works is to 
charge it, drain the electrolyte, rinse out the precipitated lead sulfate 
with distilled water, and fill it with fresh electrolyte (1.27 - 1.3 SG).  
This will restore some of the capacity, because the sulfation has kept 
sulfate ions from being returned to the H2SO4 in the electrolyte.  

The problem with this method is that you still have less active material 
in 
the grids.  When you use that apparently restored capacity, you over-
discharge the grids.  This leads to further battery degradation and rapid 
decline.  That's why the improvement is only partial, and only temporary.

As for the stuff you're looking at on Ebay, most likely it contains 
magnesium sulfate.  The main benefit of using it comes from the 
instructions that the sellers post, and probably include with the package 
they send.

The instructions will usually tell you to slow-charge the battery for 12 
to 
24 hours.  They may also suggest discharging the battery and repeating the 
slow charge for several days.  Both of those happen to be pretty good 
prescriptions for maximizing what limited capacity a degraded battery has 
left.  So the stuff will seem to work.  When you go back to using the 
battery normally, though, the "restored" capacity will soon vanish.

If you still want to try out this additive, for goodness sake don't send 
$22 to that Ebay seller.  Go buy a bottle of epsom salts at the drug 
store, 
and put a pinch in each cell.   Then slow-charge your battery for 12-24 
hours.  Discharge it and do another slow charge.  Repeat this over several 
days.  

Or skip the epsom salts, and slow-charge your battery for 12-24 hours.  
Discharge it and do another slow charge.  Repeat this over several days.  
The results will be about the same. :-)

To sum it up, the Ebay stuff is going to do a better job of emptying your 
wallet than of filling up your battery.

I'll close this with a little semi-related story.  

There used to be a battery dealer in my area which did a brisk trade in 
"reconditioned" batteries.  I never had much interest in those, but I did  
buy a few new batteries from them over the years.   Their customers for 
the 
"refurbs" were mostly owners of vintage land yachts and used-car dealers.  

One day as another customer left with a $20 reconditioned battery for his 
big old Buick, I asked the guy who'd just fetched my new battery, "So, 
what 
exactly do you DO to a battery when you recondition it?"   

"We charge it,"  he said.

Caveat emptor.


David Roden - Akron, Ohio, USA

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