If my generator is a 1000 watts and I have a 1500 watt inver

[sailingdolphin]

ter and my hot water heater is running at 1500 watts. Does that mean that only 500 watts is being sucked out of my batteries?

If so how many amps would that be?

# 171

[David Sanner]

Well if there was such a thing as a perpetual motion machine...  

There is loss in your battery charger and inverter (and wiring). Lets say each puts out about 90% of what is put into them.

So...

1000 watts from you generator puts 900 watts into the batteries.  (roughly 70 amps - but you charger probably can't charge at that rate anyway)

1500 watts out of your inverter requires 1666 watts from your batteries.  (roughly 120 amps)

So the difference is 766 watts that your battery is losing
which is roughly 60amps.

However there's another problem since I doubt your charger can put 900 watts into your batteries as that would require near 70 amps going into your batteries.  If you have a 40 amp charger and you're drawing 120 amps you've got to make up the other 80 amps by running your generator after you've made hot water.

If you can make hot water in 20mins you'll likely have to
run your generator for an hour or more (with a 40 amp charger) to break even with your batteries.

Seems to me this would be a good time to run your motor for 20-30 minutes, you'll get hot water and with a decent alternator you'll charge up your batteries as well.  Either that or get a 1500 watt generator.

-d

ps. AMPS = WATTS / VOLTS  (WATTS = AMPS X VOLTS)

[sailingdolphin]

I have a heart 1500 I am not at the boat and therefore I am without the manual.  I am looking at this 4stroke 1100 watt generator to buy its only 38 lbs and 59 decibals.  

Do you know if i use an extension cord from the generator with a conversion plug of 110 to the 30 amp shorepower and plug it into the boat will that be enough to run my battery charger? I have seen my battery charger pumping in between 45 to 80 amps before.

Why does it start out pumping in 80 amps and then it starts coming down to 50 or so?

away from shore I like to run the hot water heater with battery or generator rather than engine.  If I use battery it sucks them dry quickly even with 4 trojan 105's.  So I am trying to figure the best solution.

[Stu Jackson]

Doug

It starts pumping out 80 and then goes down to 50 because of the acceptance of the batteries.  If they're fully charged, they just won't take any more amps.

[Stu Jackson]

This also seems to be an extension of this earlier post

http://www.c34.org/phpbb/viewtopic.php?t=2129&highlight=shower

[Ron Hill]

Doug : If you look at the March 2005 issue of Practical Sailor you'll find a review of 5 portable gen sets.  
You might want to compare you future purchase to these that were tested.  
My Honda 1000 does the job, is lighter in weight, quiet and thru my Zantrax 20 recharges the house bank at an average of 14 amps.  

BTW, the input of you Heart system may not correlate directly to the output of your gen set.  Read the manual your Heart system and see what kind of power it need to run.  When indoubt call the manufacture rather than posing the question to the internet!!!  Back to my old rule that you don't know which end of the "horse" is speaking!!!  

[Stu Jackson]

Just another thought:

I recall that Hal Devera did a thoughtful couple of posts on sizing of generators to loads.  I believe he recently sold his boat in Benecia, CA.

Try here, it's on the third page of this long thread:

http://www.c34.org/phpbb/viewtopic.php?t=1563&postdays=0&postorder=asc&start=30

Look (search) for his posts - try hdevera.