Re: Extending battery life

[ptimmerm@mashtun.JPL.NASA.GOV]

Sachelle Babbar Writes:

>I've seen new products  that charge the battery (tenders) while using a
>new technology that reduces or eliminates plate sulfation. What type of
>charge is preferred by the battery 

Most of these tender use a simple constant potential limit.  You can't
get a really accurate constant potential limit without remote sensing
(4 wires total), but you don't need it really accurate.  You also don't 
need to go as high in voltage as your alternator.  You can use 13.8 volts
regulation at the power supply and everything will be very happy, 
tapering to a very small current, exactly equal to your self discharge 
rate (equillibrium).

>In NiCd batteries, a similar thing happens.
>After some time, a salt bridge forms and shorts the internal terminals.

That is not a salt bridge, that is a cadmium/cadmium hydroxide dendrite.
Sorry to be nit picky, but they are different, and enough confusion 
exists already.

>The battery can be reconditioned by the use of a high pwered capacitor.
>Just dischage the battery, charge the cap and shock the battery. Monitor
>the battery's voltage until it rises. Shocking it will break the salt
>bridge and you're done. I wonder if the the lead acid is much thesame. I
>am running a 3200 microfarad cap acrros the terms ofthe battery rightnow
>(not shocking it). I get .01 more volts, but the thing ischargingvoltage
>doesn't fluctuateas much and the battery is seeing more smoothinstead of
>pulsed power. I really don't know if this is good or not. Info would be
>appreciated.TIA!

There are some pulsed chargers out there, and I have reviewed all the
applicable patent literature and done simulation and testing.  Perhaps
the ONLY benefit for Pb-Acid comes in when doing VERY fast charging.
Your application did not mention this, and it is a topic far out of 
scope so I will drop it and suugest you do the same.  keep it simple 
and reliable.  You can't burn out the shorts that occur at the bottom
of the stack of a SLI automive battery effectively.  Keep it topped
up to 13.8 and replace it at the first sign of problem.  I bought
my 3 amp / 13.8  charger for less than $20 at the local electronics
emporium.  It was not made for autos, but works great.  Not worth 
doing it yourself atthose prices, and little/no benefit to adding 
bells and wistles will be gained.

Paul Timmerman