Re: Optima batteries, side posts are not for winching!

["Shubin, Pete" <pshubin@xxxxxxxxxxx>]

I am not familiar with the Optima batteries but could I think the charging
and use of the batteries for winching could have nothing to do with the
posts but rather with the battery design.  I am working with the local fire
authority on getting approval to develop a telecommunications facility that
will have lots of batteries.  Most of the concerns we are up against have to
do with spillage of free acids, hydrogen, and explosive potential.  Aritcles
64 and 80 compliance issues for the engineers and architects out there.  

Charge a battery too fast it gets hot.  Drain it too fast it gets hot.  If
it gets hot it expands.  If the battery expands too much the sealed casing
ruptures and spills acid and releases hydrogen.  I wonder if Optima jsut is
using the post issue as a simple answer for other design aspects of their
batteries.

I found this on the internet in my search for information.  It does not
really apply to my needs for the project but does to the modifications we do
to our vehicles.

CHARGING VOLTAGE VALUE IS CRITICAL

AGM and Gelled batteries require a charging voltage that does not exceed
14.00 volts (summer temperatures may require even lower voltages).
Unfortunately almost all automotive charging systems have a permanently
fixed set point voltage that exceeds 14.00 and this spells trouble.
Subjecting the batteries to (commonly found) 14.6 volts for a prolonged
period will eventually destroy them. Pusher diesel motorhomes normally use
truck-type alternators and voltage regulators and most have internal set
screws which can be fine-tuned (To lower the voltage set point). Automobiles
(pickup trucks) and standard motorhome charging systems can be modified to
accept an exterior adjustable voltage regulator. Your local automotive
electrical rebuild shop can be a lifesaver if you elect to go that route.
For your edification, 14.05 volts is my personal "upper limit" for charging
valve regulated batteries.


THERMAL RUNAWAY

The name "thermal runaway" sounds ominous and when it happens to an
Absorptive Glass Mat battery the results can be dramatic. A curious electro
chemical reaction can take place inside an "AGM" battery if it is overheated
while being charged. The phenomenon can be the result of too high a charging
voltage, which will overheat any battery, too high an environmental
temperature or a combination of both elements. Instead of tapering off, the
charging current actually increases as the battery temperature increases. In
extreme cases the electrolyte and binder material can be forcibly ejected
from the battery vents. Obviously the battery will be destroyed. The point
here is to pay attention to the battery's location and charging voltage
limit.

-----Original Message-----
Date: Wed, 25 Jun 2003 16:41:02 -0700
From: John Hofstetter <hofs@domain.elided>
Subject: Re: Optima batteries, side posts are not for winching!

That reminds me that I was reading a tech sheet from Johnson Controls 
(makers of Optima batteries) that said that they recommend a charging 
rate of 13.8 to 15.0 volts.  Illustrates one more time that things have 
changed in battery charging theory.

John