T&T: Battery Charging

[Peter Bennett]

You will need a 1500 - 2000 watt generator (perhaps more if you want
to run a heater at the same time.

I know the Honda 700W generator won't run a TrueCharge 40, despite what
a simple calculation may show.  The  TrueCharge 40 (and probably most
chargers) has a poor power factor, so the current it draws (which is
what the generator cares about) is much greater than the power
calculation would indicate.  The TrueCharge 40+ manual indicates that
it wants 8.5 amp, typical, with 120V input.

The Honda EU2000i should be fine for this task.

Friday, December 14, 2007, 11:10:59 AM, Key wrote:

KS> I am in a bit of a quandry about my batteries.  Here in Maine, we
KS> are in the midst of a cold and snowy
KS> winter.  My Lord Nelson Victory Tug is on the hard and
KS> "winterized".  The yard has no electrical power,
KS> so I thought that once a month or so I would simply hook up my
KS> external power to a portable generator
KS> and let the Xantrex Tru-Charge 40 do its thing with my two Group
KS> 27 AGM house batteries as well as the
KS> Group 27 AGM starting battery.  Maybe even heat up the cabin with
KS> a space heater drawing 850 watts or so
KS> from time to time as well until the Spring thaw.  But, I cannot seem to figure out Ohm's Law to
KS> intelligently choose how big a portable generator I would need. 
KS> The TruCharge 40 sends out 14.5 V at 40
KS> amps.  Since watts equals volts times amps, do I only need 580
KS> watts input (14.5 times 40), or do I need
KS> to figure 120 volts times 40 amps for a power requirement of 4800
KS> watts?  I would not use the space
KS> heater at the same time as the battery charger, so in essence,
KS>  what is the minimum power output from a portable generator that I would need to charge my three
KS> batteries once a month over the winter?  I have been eyeing the
KS> Honda EU2000, but I am afraid it might
KS> be too small?  Many thanks, and my apologies for my electrical ignorance!



-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca