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Re: Batteries & concrete (was Battery Chargers ('Maintainers'))

To: triumphs@Autox.Team.Net
Subject: Re: Batteries & concrete (was Battery Chargers ('Maintainers'))
From: Joe Worsley <worsley@ebicom.net>
Date: Wed, 05 Nov 1997 13:40:51 -0800
Organization: Unorganized
References: <c=US%a=_%p=Corporate_Expres%l=USCOBRMFA-SE-971105183844Z-11689@mailgate.cexp.com> <3460E653.55C5@ebicom.net>
Joe Worsley wrote:
> 
> Pelzel, Mark - Broomfield wrote:
> >
> > Dan,
> >
> > I went home last night looking for my records on the battery stuff and
> > couldn't find them (I've since left my position at the nuke site and
> > don't know how much of that stuff I escaped with).  What I was looking
> > for was the failure method that causes the drainage, but I'm positive
> > that regardless of the condensation issue that you brought up - BTW we
> > had environmental condition requirements for this as well, but I
> > wouldn't expect the average TR owner to want/be able to accommodate them
> > - there is still an issue of grounding and loss of charge with concrete.
> >  I'll take another look to be able to provide you with a technical
> > response....
> >
> > <<<<<>>>>>>
> > Mark Pelzel
> > 1979 TR7 BRG DHC
> > pelzelm@tusc.com

 There are a number of reason why a battery will discharge on it's own.
 The cells inherently have a internal circulating current based on their
 chemistry (don't ask).  The lead also changes chemical composition
 between charge and discharge.  There is also leakage between cells due 
to minor container insulation breakdown caused by the salts in the acid
 which are kept conductive on the external surface of the case by 
moisture in the air.  The salts in the acid have a afinity for moisture 
just like table salt or brake fluid.
 
 On the question of operating in water -  If placed in pure distilled
 water there would theoretically be no effect on the battery as there
 wouldn't be any conductive material in the water but that's close to
 impractical.
 
 Even a nicad battery discharges on it's own only quicker.  In 30 days 
you have lost upwards of 30% or more of the charge.
 
 Again on the battery charger for just maintaining stored batteries - 
many of the newer autonmatic charger are based on a current adjustment 
created by controlling the conduction cycle time in a SCR or other 
semiconductor device.  These types will usually allways be on even at a 
very low current output.  The output if looked at on a oscilloscope will 
have a pattern of positive going pulses of varying time.  At full output 
it would probably look like a full half of a sign wave in the case of a 
SCR and partial positive conduction as the current is reduced.  If it is 
a transistor controlling the current the amplitude of the positive halves
 of the sine wave will be reduced.
 
 The point is most of the newer auto chargers will always be on to some
 degree and not allow paralled batteries to all obtain the same terminal
 voltage (they will each have slightly different charging currents due to
 the difference in them) without causing a current flow between batteries
 due to differences.  Many of the differences in automotive batteries are
 due to the different concentrations of acid (specific gravity) in them.
 High current batteries and a lot of northern ones used to have a higher
 SpGg acid in them for higher performance but they wear out faster
 (sulfate and develop internal resistance which limits the current flow
  in and out of them). We use batteries for standby power generator
 starting with about 1225 acid and most car batteries now  have upwards 
of 1280 SpGr. It's not unusual to find one of our the 1225 batteries 
(which spend 99.9% of their lives on periodic automatic charging) having 
a age of 7 to 10 years.
 
 enough again

 Joe Worsley

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