Keeping Spray Charged

Spray has 2 large 4D 12 Volt batteries. The house battery is #1 and the start battery is #2. The start battery is only used to provide juice to start the diesel. It only gets used for a few seconds at a time (although many amps for those few seconds) and easily stays fully charged. The house battery supplies juice to everything else: the fridge, lights, water pressure pump, etc.

 

When we are traveling the house battery stays pretty well charged by an alternator driven by the diesel, but when we sit at a mooring for a month (as we are now) we need other means to charge the house battery every day. We have 2 systems for that - solar panels and a small gasoline powered generator.

 

Three years ago I mounted 3 solar panels to the front of Spray's flying bridge. When these are in bright sunlight they provide enough power to run the fridge plus some leftover to charge the house battery. The idea is that the hotter the sun is, the colder the beer gets. Here's a shot of the solar panels :

You may notice 2 problems here. The solar panels are in the shade and one of them is missing. They are in the shade because we have north winds today so Spray is pointed north while the sun is to the south. Since its winter, north winds dominate, which is a problem. This explains the missing solar panel, which I recently moved to the aft end of the flying bridge :

See how its in nice bright sunlight? This helps but can't keep up with the fridge as its only a 40 Watt panel best case (which means when aimed exactly at the sun, at noon, on the equator, on an absolutely clear day), and the fridge draws about 50 Watts.

 

Which brings us to charging device no. 2 :

 

Many of the boats here in Marathon have a small Honda generator just like this, unless they have a 'real' marine generator built in. We run ours for 2-3 hours per day, usually while we are on shore walking the dogs so we don't have to put up with its noise. It's actually not that noisy as nearby boats can barely hear it (and we can hopefully barely hear their generators). It lives outside in the cockpit so that any possible gasoline fumes don't end up in the bilge creating a possibly explosive situation.

The Honda makes 120 V AC power and we have a battery charger that converts that to 12 VDC to charge both batteries.

 

We haven't gone for the 3rd possible charging option which is a wind-powered generator. Many sailboats here have them and they must make good power in these winter winds. Many of them make noticeable noise.

 

Anyhow, between our modified solar panel setup (replacement panel for up front is on order), and our Honda generator, we can reliably make enough power to run the fridge 6-8 hours per day which keeps things cool enough (we keep a few beers in the freezer so they are nice and cold), plus all the power we need for lights and other things.

 

We monitor the battery charge states with this little number :

It monitors Voltage and current for each battery. As seen here it is telling us that the starting battery (no. 2) is fully charged, and the house battery (no. 1) is about half charged, and is charging at 1.8 amps. (from the aft solar panel).

 

If we want to be able to power the fridge 24/7 we need 2 upgrades : more house battery capacity (add a 2nd battery in parallel with the existing one), and a more robust battery charger. Maybe someday.

 

By the way, 4 years ago when I was here, there were no solar panels nor Honda generator aboard. This meant warm beer plus every few days a short journey around Boot Key to let the diesel do some recharging of the batteries. So the setup we have now is a great improvement.

 

 

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