Another interesting site to visit on batteries:
http://www.batteryuniversity.com
All about charging, discharging, storing, maintaining batteries

Jaap
'87 Caravelle diesel
>
> This is basically correct.  Every battery has a specified charge
> voltage, adjusted for temperature.  If you charge with a smaller
> voltage, the battery will not fully charge.  Larger voltage and
> the battery will start to gas after being fully charged.  Here
> is some more info on charge voltage vs temp:
> http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Charging.aspx
> See point 6.  Also, note that Trojan specifies higher charging
> voltages than some other batteries; not all flooded batteries
> are the same.  Most specify 14.4 volts at 80 degrees.
>
> How do I know this?  Because I help take care of a photovoltaic
> light system at a cabin at 10,500' in the mtns behind Boulder.
> The batteries (4 Trojans) drop to about 15 F degrees in early
> December.  Now they are about 35 degrees.  The cabin is used really only
> on Saturday and Sunday, so there is no way to keep the batteries warm.
> We have to raise the charge level of the charge controller to its max
> (15.3 V) to get the batteries fully or almost fully
> charged.  Now as it warms up, we need to decrease it.  That is
> the advantage of a temperature compensated charge controller.  I
> with my screwdriver am the temperature compensator for now.  ;-)
>
>                                 Richard A Jones
>                                 Boulder, Colorado