RE: (ET) batteries

["Hazen, Dwight L" <hazen indiana edu>]

 If you need to keep the batteries at full charge all winter you need a
constant voltage charger and set the voltage to a float charge. 
This is not a trickle charger, they are low current low regulation chargers
that tend to increase the voltage to the cells the longer they are 
connected
to the battery. You need a float charger "power supply" that is dead on for
the voltage you set. 40.8 volts maintained over a long term should not gas
the cells. Age of the cells and temperature may cause you to adjust this
voltage up or down a bit to stop gassing. BUT never exceed 41.4  in float
service for 18 cells in series (36 volt battery pack).

 Also you need to think about where to measure the voltage. During fast
charging the best place to measure is at the battery posts. for float
charging you need to measure at the power supply terminals with NO load
attached. That way as the current falls off the voltage drop in all the
connectors and wiring will almost go to zero and you will see the final
float voltage you set on the power supply at the battery posts.

If you try and set the voltage with the battery connected and your meter
connected to the battery you will be trying to hit a moving target. 

 Dwight 



Dwight L. Hazen, Indiana University, UITS 
Bloomington, In. 47408-7378 Phone 812-855-5367 hazen indiana edu
http://php.ucs.indiana.edu/~hazen/ Ham Radio wb9tlh arrl net
IP Phone number 812-856-9251


> -----Original Message-----
> From: Neil Dennis [SMTP:wombat RealNS com]
> Sent: Thursday, August 09, 2001 1:39 PM
> To:   Elec-trak
> Subject:      (ET) batteries
> 
> A comment on "trickle charging" all winter - bad scene -  I even believe
> we had a thread here about it.  A long period of trickle charging will
> cause sulfation and lost capacity.
> 
> On my JD charger, it ran with a auxilary timer that "burped" the charger
> for a couple of minutes each day.
> 
> wombat
> 
> I'll have to look at my tester, it's specailly designed to check either
> 6 or 12 volt batteries, uses the test battery power and reads out to 3
> places behind the decimal.