Len wrote in message . ..
I experience a very short battery-life and I want to know the cause
before I install anything new.
The fridge / freezer and other consumers constantly draw power
(between 4 and 11 amp)
I have a 3-stage 120 amp charger (bulk at 14,4,absorption at 13,6 and
float at 13,0)
My batteries are 18 months old. 6 x 180 Ah. They were called
"Maintenance-free". As I understand now that means you can't add
destilled water later on, don't see any advantage of that.
At present my battery-capacity is very low. As I look at it now I'm
confronted with replacing my batteries after 18 months.


Anyone familiar with such problems that (maybe) arise from using the
charger as a power supply during float-charging?

Do I bourdon my batteries by creating a lot of small
discarge/charge-cycles?

Any advice is welcomed for this (surely not unique?) liveaboard-
stuation with 220AC shore-power and use of 12-v appliances.

Thanks in advance, Len.


Most battery chargers will boil away water in lead acid batteries and
shorten their life when 12 volt refrigerators are left on. Over
charging is even possible with many of the expensive step chargers.
Only a charger that will hold the battery voltage in the float stage
when the refrigerator runs will prevent excessive water loss.
Examples, A Heart inverter/charger will remain in float phase when the
charger is set for 100 degree battery temperature voltages and the
refrigerator draws less than 6 amps., A 10 amp GUEST smart three step
charger with only one side used producing only 5 amps., causes minimal
water loss.
The best advice is not to use maintenance free lead acid batteries and
install a sacrificial battery for the refrigerator when at the dock. I
have one boat where the Adler Barbour has been running steady for 8
years on a old battery with the small Guest Charger. For more
information on Battery Stress from chargers click on BATTERY STRESS on
my web site http://www.kollmann-marine.com

From the author of four books on boat refrigeration