If the batteries are 100% charged when I move to the mooring, is the 1-2 amp (25 or 50w) panel with the regulator enough to meet the trickle charge and keep them at 100%? Something like this image?
Yes, 50 watt would be better, however you are not accounting for use of the battery. What every energy you use on weekend sailing adventures will need to be replaced and 50 watts probably won't do it, especially if you fire up the refrigerator. A 50 watt solar panel will produce about 4 amps at 12v. Using the estimate that Calder suggests in the earlier referenced article, you can expect 12 ah a day of output on average. There are formulas to make the actual calculation, however a perhaps only 9 or 10 ah a day will actually be returned to the battery. With this estimate only about 45 to 50 ah will be replaced or about 25% of the battery bank capacity. Bad weather and cloud cover will reduce the amount returned.
We have a blue-top AGM in a 20' Whaler that is going on 4 years old and we have taken pretty poor care of it based on what I have read here. At the marina it's had a AC trickle charger, but during the winter the battery was fully charged before storing it in my garage and then pulled out 6 months later - charged up and installed in the boat. Seems like it should be on the smart-charger all winter in the garage.
You may not be abusing those batteries as much as you think you are. The Optima probably has an capacity of about 50 ah and the alternator on the outboard probably puts out at least 6 amp or more. If that is the case, then the battery is being recharged at a rate of more than .1C. On the Whaler the engine will be running more than on the sail boat so there is more charging time at closer to an optimal charge rate. The one important variable that you didn't mention is how much energy is being used when the engine isn't running, or another way, how depleted is the battery when you head after a day on the water. Unless you have a mega stereo with huge speakers and several hundred watts of amplifier, you probably don't use much electricity. Thus when you get back to the dock, the battery is near a full charge and the trickle charger brings it the rest of the way up. Over the winter, a fully charged battery in a cold environment will have a limited self-discharge as cold reduces self-discharge rates.
It seems like my uneducated assumptions that the AGM was a better choice, was a fool's decision. Sounds like some basic flooded (cheap) batteries might have been a better choice given how the boat and it's batteries will be used.
If you read enough of MaineSail's articles you will learn lots and one thing you'll learn is that you are not the first (nor probably the last) to learn this the hard way. We learn best from our mistakes.
Is spending $200 more for a solar system worth doing or should we just treat the 2 banks badly like the Whaler and hope we get 4+ years of use out of them by only charging when the Honda is running for the summer ?
In life there are seldom dichotomous choices. Without additional charging capacity, I doubt you will get 4 years out of the AGMS, if you use them much at all. There are some alternatives. It is essential to have a good idea of how much energy you actually use and and the current SOC of your batteries. Without this information, you will be guessing a lot and guessing induces errors and those can be costly. A battery monitor is essential for knowing the health and charge state of your batteries. Balmar makes a couple of good ones. Victron makes one that gives more information, however, it requires programming which can be a bit tricky. Check the HowtoMarine.com website for articles on battery monitoring.
Limit electricity use when you go sailing. The less you use, the less you have to put back.
Every few weeks sail to a marina and spend the night. Plug into shore power and get a good charge back into the battery. This will not be as good as a full charge every day, however, it should help extend the batteries life. Not as much fun as swinging on a hook in a quiet cove, but the crew might enough the marina's showers and nearby restaurants.
You have some time before the boat goes to a mooring, spend it learning about Solar power and electrical systems. In the spring, you can make a good informed decision and find a decent quality panel and controller. The
Alt-E website has good information and products that are a good balance between cost and quality, MaineSail often recommends the company.
