wrote in message
news
On Mon, 18 Sep 2017 09:53:20 -0700, Gunner Asch

wrote:

On Mon, 18 Sep 2017 06:20:24 -0700, Larry Jaques
wrote:

............
He said "charge the battery", not "battery bank". I was thinking a
simple 80w for LED lights, radio, and laptop. One battery ought to
handle that. BUT, if he had a larger boat, solar panels could be
utilized to replace the sail while the batteries replaced a
significant portion of the ballast. VBG.


He said 800 watts load as well. (2) Deep cycle batteries will give
him
far more than 800 watts if he is on a 145 watt solar charging
system.


That depends on how many watt hours he needs. with 8 hours od
sunlight and a tracking panel sysyem he will get a MAXIMUM of 1160
watt hours of power from the panels - so 1150 watt hours out of the
battery if he is very lucky. That is 800 watts for about an hour
and
15 minutes. Yes, he can get more out of the battery, but the battery
will not recover it's charge unless charged with more than the 145
watt panel, or charged for a few days with no load.

There are several multifunction DC wattmeters available to monitor the
system's condition and performance. Unfortunately I haven't found one
that does everything necessary. The ones which are powered by the
system battery measure current with a ground-referenced shunt and read
only shunt voltage higher than ground, ie they display current of one
polarity and ignore the other, so you'd need two to show both charge
and discharge current. They can be different, one matched to the
higher voltage and lower current from the panels and the other sized
for the maximum load current out of the battery.

The type that measures current in both directions with differential
inputs needs its negative supply to float below the system negative,
meaning they require batteries or a separate isolated power supply,
like a cheap obsolete miniUSB phone charger. I've suggested to DROK
that they should offer an isolated 12VDC - 5VDC converter for meters
that need it.
https://www.amazon.com/VAC1030A-wire.../dp/B01JD6ZN8A

The low-cost analog panel ammeters aren't too bad.
https://www.amazon.com/uxcell-Analog..._89%3Au xcell

I have only more accurate digital meters on the batteries.

-jsw