"Shaun Van Poecke" wrote in
:

What im
thinking is probably a single 100Ah AGM battery, a 2000watt generator
hooked up to a 30A charger. I dont really have a lot of power needs,
just lighting (flourescent), a cd player that gets used a couple of
hours a day, Nav lights, and power for my GPS/notebook as needed.

Im hoping to get 2 to 3 days use without charging.



100AH isn't much of a source. You can only discharge it 50AH, if you
know what's good for it. If you discharge it further, you'll be
replacing it too often.

Whatever power you THINK you'll need is never enough. You'll soon get
bored sitting with one little flourescent light and a flashlight
listening to those same CDs all the time or the waves slapping the hull
and want more, which will drain that little battery really fast. If you
run a 2A anchor light for 15 hours, this time of year, that's 30AH of
your 50AH safe content, each day, right there. The GPS draws 1.5A,
unless it has a depth sounder, then it draws 3A times the number of hours
you're sailing. Notebooks consume their 3AH internal battery in 2 hours,
so that's 1.5A plus the inefficiency of the inverter to run its AC power
charger, let's say 2A. Sailing with GPS/notebook for nav with sonar is
about 5A times the number of hours sailing, without turning anything else
on. 10 hours sailing = 50AH drain. You'll be charging that little
battery twice a day for 3-4 hours at a time if you sail then anchor out.

Batteries charge SLOWLY. That will never change as long as we're using
inefficient lead-acid batteries, no matter how they package and hype it
or what fancy color the plastic case is. To fully charge a discharged
battery...FULLY CHARGE, not just until its voltage rises trying to stuff
50A into it at 16V to charge it in minutes instead of hours. It's a fact
of physics and chemistry, not sales and advertising. Plan on C/10 amps.
100AH/10 is 10A....for the first few hours. Then, it drops off to 5A,
3A, 1.5A after 4 or 5 hours charging from 50% drain. Jokers telling you
they can recharge their superdooper AGM in 30 minutes are dreaming. It's
STILL a lead-acid battery with lead-acid chemistry.... You have plenty
of charger, plenty of genset.

But, let's add some more heavy house batteries to extend the runtime.
That charger will standard charge 300-400AH of house battery capacity.
300AH of supply will take 600AH of battery capacity. I'd think two banks
of L16H 6V golf cart batteries will do the trick, but you could start off
with one bank and add the second one later, but not too much later. It's
not nice to parallel a new bank with one 3 years old. Two batteries in
series to get 12V then two banks in parallel to add up the AH to 660AH is
more sensible. The anchor light will run all night without draining them
dangerously low and leaving you some headroom to make breakfast in the
microwave you haven't discovered you really need, yet. To run the
notebook and microwave, get a 1000 watt Tripplite inverter and mount the
inverter right next to the house batteries through its own 100A fuse with
#4 fine stranded flexible wire from the car stereo shop (or Radio Shack).
If you open it up where the power switch is, you can parallel the tiny
power switch with a remote one with two little wires putting the inverter
control in a more convenient place. Put a neon bulb next to the switch
hooked to the AC output so you can see it's running and looks about the
right brightness. You'll only be drawing 45-50A for a few minutes as the
microwave heats breakfast. I like Tripplite because of its $70K
insurance guarantee I know is honored. They make great inverters that
don't cost an arm and a leg like "marine" inverters, which is nonsense.

Now, where you're going to put the battery boxes for these beasts is YOUR
problem. Being tall, L16H don't take up a lot of deck real estate, but
are more vertical. 100AH little AGM is not near enough. The golf cart
beasts won't cost you much more for 6 times the supply. You'll be able
to replenish their electrolyte with DISTILLED WATER ONLY, please, saving
you lots of replacement costs. They will survive an inversion as their
caps seal. Golf carts flip over, so the caps seal and have a water trap
in them. Remember you MUST LASH THEM DOWN in case the boat broaches!
Way too many battery banks are just sitting there like the boat will
never flip over. How stupid that is.....

POWER is our friend!
In the anchorage, it's not good form to be a smartass showoff and leave
all the deck lighting on for hours standing out like a beacon while your
poorly-planned neighbors with 100AH AGM batteries sit by their candles
trying to find the head with a flashlight...(c;