T&T: Specific gravity of Batteries

[Candy Chapman and Gary Bell]

GARY FIRST MAINTAINED IN AN EARLIER POSTING:

> <>
> Robin also said <no snipping here>
> I also have read that some manufacturers use different mixes of acids and
> acid concentrations so specific gravity can vary among brands....
>
> REPLY: Interesting. Could you suggest where you found that? My
> understanding is that automotive and marine wet cell batteries all share
> exactly the same chemistry, which has evolved over a very long
> time to produce the same specific gravity vs. charge state curve for 
> everyone.
>
>  
>
AND ARILD JENSEN REPLIED TO ME:

>REPLY
>Gary I too have heard the bit about altering the specific gravity of the
>sulphuric acid.
>I heard it direct from a battery manufacturer.
>The rationale being that a stronger acid concentration means more free
>electrons to give more current flow.
>
>To the end user it means a given size /weight of battery  would rate more
>Amp-Hours as a specification.
>That would be important in tne specmanship  marketing game.
>There is never a free lunch. There has to be a trade-off somewhere.
>Perhaps it gives more amps but less service life time.
>  
>
GARY'S REPLY:  I quite agree.  The way I see it, flooded cell technology 
has as we both said, been through a very long evolutionary 
development.   Any objective observer should see the  present state of 
the art as the best of all the available trade offs.  Simply changing 
one item in the current recipe, like  different  specific gravity, 
without  accompanying changes in  plate  or electrolyte chemistry  seem 
likely to cost  us in some other traded -off  aspect.   Seems a pretty 
bad case of specmanship to me too. 

ARILD AGAIN:

>A stronger acid also poses more of a risk to the people handling it.
>  
>
GARY'S COMMENT:  Gee, the regular stuff is already pretty hot.  You are 
of course technically correct, but I wonder how much more hazardous one 
could make today's battery acid (and I have the shirts and jeans to 
prove it!)

ARILD ONCE MORE:

>If lead sulfate is the end result of stripping away the electrons during the
>conversion from lead oxide and acid to create lead sulfate, might the lead
>sulfate be of a kind that is harder to reverse?  
>
GARY'S COMMENT:  Yeah, I guess it may come down to how much water is 
bound up in the precipitated sulfate, its hydration, or perhaps they 
have slipped in some secret herbs and spices that allow this 
improvement.  I have no idea how the various levels of hydration would 
affect solubility (among the numerous topics I have no valid ideas 
about!  ...but that has never stopped me from pontificating my 
opinion!).   As to 'secret improvements' I expect they would be hyped in 
headlines if there were even the suggestion of any real success involved.

ARILD: 

>That being the case, a
>stronger recharge current would be required. Until recently this kind of
>amperage was difficult to create in a cost effective manner.
>
><snip out some interesting speculation and a question/challenge...>
>  
>
AND GARY'S CONCLUSION:  Apparently, from your comment above,  there may 
well be a flooded cell lead acid battery maker who has increased the 
traditional acid concentration, in hopes of 'improving' an already 
pretty well evolved technology.   Given that there are so very few 
actual manufacturers (each putting out numerous labels) it would be very 
interesting to learn which manufacturer you talked with, how much they 
increased the specific gravity, and how many of their lines of batteries 
this affects.  Of course, the shift may not be substantial, but we 
consumers sure need to understand if there is a significant change in 
our traditional means of assessing battery charge. 

I do wish them luck finding substantial improvements in flooded cell 
lead acid battery performance (we could all use better batteries), 
although I have several reasons to suspect that they are merely dabbling 
in the irresponsible 'specmanship' you suggested.   It does mean that we 
the consumers would need to be aware of the nature of the juice in 
whatever batteries we use.  Hydrometer testing is the best commonly 
available means of testing the charge status of any flooded cell lead 
acid battery, and if some outfit is intentionally tinkering 
significantly with the acid concentration we would certainly want to 
know how to properly interpret our tests. 

 We haven't discussed the ever present but slight possibility of errors 
in the preparation of the acid solution -- as you know, flooded cell 
batteries are shipped from the factory dry, and the acid added by the 
retailer, usually just as the buyer's credit card processes.  That way 
the industry doesn't have to deal with heavy batteries that are full of 
liquid acid, and the customer gets a fresh battery.  There are of course 
also a few cases where some uninformed person (definition:  doesn't 
agree with me) added something other than clean water to their battery.  
You can buy acid advertised to be added to an old battery -- probably 
intended to counteract sulphation's immobilizing sulfate ions or perhaps 
some instance where electrolyte leaked out of a cracked case (hope they 
fixed that crack first!).  Naturally the automotive aftermarket retail 
system also provides examples of miracle battery mender remedies, but 
since few boaters I know would even consider buying a used battery, and 
few would think to add goop to a new one, that risk probably is 
insignificant here.  I feel confident that the noble boaters wise enough 
to hang around on this list only buy new batteries and that they would 
know better than to add anything but really clean water to them.  I'll 
pass on restarting the circular discussion of precisely which clean 
water is best, thanks -- depends on how clean your local tap water is 
and whose advice you trust, but for me, the chemistry in today's flooded 
cell battery is pretty robust, it takes a significant contamination to 
hurt it much.  In case anybody cares, I use fresh grocery store 
deionized or distilled water, whichever is handy. 

Cheers,
Gary