Mark,

depending on the type of battery 14.5 may or may not be a good
voltage for long term charging. I am just pulling numbers form my
leaky head, but I do recall gel cells having a fairly high (14.5 -
14.7 V) charging requirement, and a lower "float" charge. Often those
numbers are printed on battery.

As for rate of charge, correct me if I am mistaken but if voltage
fixed, then current is self limiting. I have a hard copy of a very
good doc made by dynasty that goes into various aspects of battery
theory, and charging, including schematics for various battery
chargers you can make at home. I will see if I have  a pdf version,
if not I can scan it and send it on.

alistair

On 20-Apr-10, at 3:11 PM, mark drillock wrote:

Today I was able to fire up my 3 battery system for the first time. A
dedicated 125 amp hour deep cycle was added for the Vitrifrigo fridge
only. With the Zetec it fits easily in the engine compartment and is a
foot from the alternator. I used short #6 wires with a Surepower 1314
between the alternator and the battery, and ran #6 between the neg post
and the engine block.

As part of this setup I added an amp meter for the fridge battery so I
could see how fast it was charging and then know how long I needed to
run the engine to get another night of camping. I was surprised to see
the meter reading over 60 amps going into the battery when I first
started the engine even though the battery was fairly full. This quickly
tapered down over a few minutes to a steady 25 amps. I wonder if maybe I
have too much charging?

I have not been able to pin down the capacity of this Ford alternator. I
have seen it listed as 105 amp, 115 amp, and 130 amp. I don't care much
either way as 105 would be plenty but it would be good to know. I am
measuring 14.5+ volts at the alternator which I believe is pretty common
with modern vehicles but I wonder how good it will be for the battery
long term.  I could slow down the charging rate by switching to longer
and thinner battery cables but this would not drop the voltage much
after the battery was full. That seems too high for a "float charge" but
I don't know how it will be in practice. Anybody know? Suggestions?

Mark