RE: (ET) batt's

["Elie, Larry (L.D.)" <lelie ford com>]

Harry, Neil, etc.

Sorry Harry, but I vote with Neil.  12.66V just isn't a normal voltage for 
an auto charging circuit.  It is even a bit low for a battery several 
hours after charge for a old battery.

I work for Ford Research.  I know the people who design the charge 
circuits in today's cars.  I have worked on the design of charge circuits 
in the past.  I have inventions in the area.  We typically set the voltage 
of the regulator at 14.2V no load and 13.8V at load.  We see very large 
droops at times due to wire length and gauge picked for load and weight, 
but these are the targets.  Typical voltage for the batter after soak (car 
off, several hours to return to room temperature) is 13.2 to 13.6 
depending on age of the battery and how hot it was under hood when it was 
'charged'.  It isn't quite that simple (I know someone who wants to add a 
wire for <$1/car that would improve battery life by measuring without the 
lead resistance drop at under hood temperature and he can't get it 
approved) but it's basically the truth.  Now, having said that, the ET 
does NOT have an automotive battery.  It is a deep-discharge design, so 
these values are probably not exactly right.  However, !
2.4V per cell is not unusual for a car, and most 'trickle' chargers exceed 
that under some conditions, without instant damage.  Remember too, 
automotive batteries do NOT last more than 4 to 6 years (under hood and 
vibration are the bad actors, as well as cheap regulator design and warped 
plates) and the values we use are certainly not the 'best' ones you can 
come up with.  The people doing Ranger electric chargers do a much better 
taper on their charge (but they didn't like my charge equalizer as well as 
theirs... mine ended up bookshelved!) than the alternator guys do, and 
that may be represented too; charging series batteries is a bit harder to 
do and most people (like the Ranger guys above) tack on a few volts to 
make sure every cell gets enough.  This is what we call cell equalization. 
 But again, FAST charging is a selling feature; battery life is secondary.

Now, my best assumption is that GE knew what they were doing 30 years ago. 
 Batteries may have changed, but the VOLTAGE at the meter probably is 
still 'safe'.  In other words, charge MEANS charge.  If you only charge 
into the green range, you are not getting the full charge the ET is 
capable of.

The bottom line:  42 to 45V at the end of a charge is the minimum I 
accept.  If the cells didn't start out equal (the lift used a lot like 
with the tiller or the headlights were used) I go 45 to 47V.  I never 
leave it above 45 for long periods.  I have NEVER got good performance at 
39V, period.

Larry Elie



-----Original Message-----
From: Neil Dennis [mailto:wombat RealNS com]
Sent: Thursday, August 09, 2001 9:31 PM
To: Elec-trak
Subject: (ET) batt's


Harry, sounds like an interesting idea on the voltage measurements.  I
worked for years on auto and marine charging systems (alternators and
regulators), for the average use, we aimed at 14.4 +-.2 as a correct
charging level.  One trucking co used 12.6 as they wanted to increase
lamp bulb life.  Some tractor co's wanted 132 / 13.6 as their batteries
were in a hot location.

Agree on the "pulsing" maintainence rather than trickle.

wombat