On a 50A charger, it'll hardly notice the drain from a 12V fridge.
Leave the fridge running on the charger all the time....works great.



On 13 Jun 2003 01:44:06 GMT, (Bobsprit) wrote:

Alien has a 12 volt fridge. There is also a 50 amp charging system and 2 group
27 batteries with a third group 27 on a seperate switch in case they fail. The
two mains are isolated.
While underway I've been able to run the 12v with no trouble and everything
stays cold, but there is no A/C mode for the unit when docked. Is the practice
to just shut these down in the slip or run them with the charger on
continously? It would be nice to leave the fridge on for the weekends at least.


Thanks,

Robert B
C&C 32 "Alien"
City Island, NY


Larry W4CSC

"No, NO, Mr Spock! I said beam me down a WRENCH,
not a WENCH! KIRK OUT!"

Most 12 volt boat refrigerators today have Danfoss compressors with
brushless motors inside and an electronic motor control as a separate
unit or Swing compressors which are pulsed on 12 volts by
electronics. Running these units direct from the battery charger
without a battery as a buffer can be a $300 mistake. To learn more
about refrigerators running off battery chargers go to
http://www.kollmann-marine.com and click on BATTERY STRESS.

Richard Kollmann
Author of books on boat refrigeration.

Larry,

I think the issue is that if you have a smart battery charger it
will sense the current draw of the fridge and kick the voltage
up to the "charging" voltage instead of the "float" voltage. This
will result in your batteries being overcharged while the fridge
is running.

Don W.

Larry wrote:

Why not just run the fridge off the battery with the charger on it.
There's no danger at all this way....I wasn't trying to tell him to
operate it off the charger without the battery online.

On 31 Jul 2003 05:31:27 -0700, (Richard
Kollmann) wrote:

Most 12 volt boat refrigerators today have Danfoss compressors with
brushless motors inside and an electronic motor control as a separate
unit or Swing compressors which are pulsed on 12 volts by
electronics. Running these units direct from the battery charger
without a battery as a buffer can be a $300 mistake. To learn more
about refrigerators running off battery chargers go to
http://www.kollmann-marine.com and click on BATTERY STRESS.

Richard Kollmann
Author of books on boat refrigeration.

Larry W4CSC

"No, NO, Mr Spock! I said beam me down a WRENCH,
not a WENCH! KIRK OUT!"

On Fri, 01 Aug 2003 15:39:58 GMT, "Don W."
wrote:

Larry,

I think the issue is that if you have a smart battery charger it
will sense the current draw of the fridge and kick the voltage
up to the "charging" voltage instead of the "float" voltage. This
will result in your batteries being overcharged while the fridge
is running.

Don W.

For 8 years, I had a remote ham radio packet system running on a nice
330' tower about 40 miles from home.

When it was receiving, the packet modem and little radio drew about an
amp off a WalMart deep-cycle marine battery (about $60). When it was
transmitting with its 170 watt linear amplifier, it drew about 30A
during the packet transmissions which were used by all the area
amateurs on the mode to make digital contacts out of town and to hams
too far for their stations to contact directly.

For all those years, that battery was maintained by a Schumaker
SE-50MA-2 10A car battery charger (automatic shutoff) which shared the
little green cabinet sitting on the deck next to the huge paging
transmitters belonging to my friend Robert's paging company. It
replaced whatever power the ham station drew off the marine battery,
then shut down at 14V like a good boy, even after a lightning hit took
out most of the paging equipment and the antenna I shared with one of
Robert's 350W Motorola Monsters on 152 Mhz!

Your fridge running off ANY marine automatic battery charger hooked to
the house batteries, permanently, will run just fine.....cycling the
charger on and off as necessary to replace the power you use....just
like that light over the chart table.

The charger (about $42 at WalMart, not $899 at West Marine) is humming
away under my desk next to this keyboard. I crawled up under there to
get the model number for you. Today, it's charging two marine
batteries with dual purposes. The batteries are just in parallel with
some bus bars. The loads on them include my ham radio HF station,
which draws about 130A at 650W output RF power (Yaesu FT-900 and a
highly modified TenTec Hercules II 12V linear amp), a couple of 50W
2-meter transceivers and my kilowatt UPS this computer is plugged
into, but doesn't switch until the power blinks in milliseconds. It's
still providing great power for the whole station, but it does hum a
bit because of its steel case and magnetic leakage from the
transformer. It's cheap, you know.

There's another one buzzing away in my work truck, a surplus USAF blue
stepvan I use as a mobile electronics shop for my mobile music,
PA/organ repair business and toy truck. It keeps up 2 Optimax diesel
starting batteries on the 6.2L diesel and 2 6V 225AH golf cart
batteries in series I use for "house batteries" when the Honda EU1000i
isn't running.



Larry W4CSC

"No, NO, Mr Spock! I said beam me down a WRENCH,
not a WENCH! KIRK OUT!"