Making Amps

[Shack]

If I correctly understand what you are saying, it is that you calculated the required amount of solar amperage to "extend" the battery life to a point that matches my time away from the boat.

However, I would prefer to return to the boat (after an absence) with a full batt bank, and not have to lightup the engine or gen to begin a charge cycle.
To do this it would seem that what I need to do is simply maintain a charge capacity in excess of the draw. An excess charge capacity should charge the bank as well as maintain a floating charge after its topped off.

Wouldn't the critical item here then be a charger controller that can collectively monitor the inputs from charging devices (i.e. solar, and wind) and also change the charging voltage to correspond to the state of the batt bank?

Change Tack - Now, when away from the boat - the math would be fairly simple as the draw would remain fairly consistent from day to day. The tricky part would be the varied draw when using equipment while aboard. I would still need to establish means for replenishing the bank with this higher rate of use. Naturally, amp draw while board would be higher than while away. This now gets into the issue of charging and using simultaneously.

I think I need to jump into the Parrallel Battery thread, too.

[sailingdog]

If you're away from the boat, even a modest solar panel bank should be able to re-charge the batteries, provided the sun is shining brightly with few clouds. A good MPPT charge controller will go a long way to making the panels work to the greatest efficiency.

One thing to watch about many solar-panel charge controllers—they often aren't designed to work with things other than solar panels, because of the way they're designed. YMMV.

[Dawkahab]

Look at the DuoGen water generator

[Rockter]

Serious stuff... a vast electrical demand compared to my olde 36 ft ship.

Poor me... I only run the wee 5A fridge when I am motoring.

[Shack]

Originally Posted by Dawkahab

Look at the DuoGen water generator

Ah HA! I heard about hydro - I'll take a look!
Do you use hydro off your prop? . . . or some other means.
How's the maintenance been on something ike that?

[arghhh]

A good site for all things off the grid is http://www.solar-electric.com/ . I have used them before and they are knowlegeable, friendly and willing to help you design the system you need and of course give a quote.

They might have or know about a charge controller that accepts inputs from multiple systems too.

[SmartCaptain]

Hi Shack,
Here are some numbers from my experiences over the past two years.

I have found the rule of thumb to be true that says you'll get amp-hours equal to about 1/3 of a panels watt rating per day. For example, 300 watts of panels would give you about 100 amp-hours per day.

I've been living aboard for two years now, and have lived entirely on solar/wind power for 7 months. I have four panels that total 400 watts (two Kyocera 125's mounted on a radar arch and two Siemens 75's mounted on the rail). I supplement the solar on cloudy/windy days with a 100 watt Ampair generator. I've had to run my engine three times in seven months to charge the batteries on cloudy/calm days.

I average about 120 amp-hours per day of usage. My amp-hungry items are my laptop computer (about 5 amps x 8 to 10 hours/day) and my fridge (poorly insulated, but keeps the beer cold. 5 amps x 8 to 10 hours/day).

By generating all of the amp-hours I need in a given day, I've been able to survive with a relatively small house bank (300 amp-hour total capacity, 150 usable).

Hope this helps,

Jeff

[sailingdog]

Originally Posted by SmartCaptain

I have found the rule of thumb to be true that says you'll get amp-hours equal to about 1/3 of a panels watt rating per day. For example, 300 watts of panels would give you about 100 amp-hours per day.

Of course, a lot of this depends on where you will be sailing/cruising. If Jeff is in the tropics, where the sun is virtually overhead for a greater part of the day, and the sunshine is more intense, and there are fewer cloudy days, then that will have very different results than if you're in Seattle during the rainy season... where the sun is directly overhead for fewer hours, the light is less intense and there are many more cloudy days.

Jeff- It would help if you put the context of where you were sailing when you calculated these numbers...

[Shack]

That DuoGen is both a wind power gen that san be converted in into a hydro ben for trailing - looks like it puts out some nice amps for only 5-6 knots. Costs a litle less then $2K! Wow.

Dawkahab-
Are you using this right now? Any experiences with it you care to share?


SmartCapt -
Highdraw items - what do use for heat in winter? Cool in summer? Do you cook on gas, alch, or electric? Ditto the "dog" on "what is your cruising Latitude?"