[jbondy]

I'm looking into a solar system to serve two purposes: (1) is to try to keep the batteries fully charged and ready to go during the sailing season. We don't motor long enough to get the charging system into its third stage (float), so probably the only time the batteries are close to 100% is at the beginning of the season when they are topped off "on the hard" and connected to 110v. (2) is to keep them topped off during the off-season.

My question is related to the charge regulation. I assume I'll need a multi-stage charger so that the solar panel can apply a float voltage to the batteries. Otherwise, it would be no better a charging system than my too short motoring regimen. Is there a way to use the same regulator that is connected to the alternator, or do I need a separate three-stage charger for the solar panel?

A recap from an earlier thread: I have a Pearson 323 with a 90A Balmar alternator and a 3 stage Balmar smart regulator (ARS III) to charge my two banks connected by a Blue Seas ACR relay. When at a dock (exremely infrequently) or on the hard, charging is via a TrueCharge 20+ multi-stage charger. The 3 group 27 house batteries and single group 24 starter battery seem appropriate to the loads we put on them/support our electronics addiction (Sea Frost reefer, radar, plotter, stereo, etc.).

TIA

 

[negrini]

Joel, keep in mind your solar panel provide very small amount of power daily, and any waste will deter its efficiency. Such regulators like your Balmar, are very inneficient in terms of power loss (what is OK considering the source can generate 90A!!!), also, avoid it going to your batts through ACRs, as they will also take some toll. At the end, summing up cables and connectors, very little solar energy will get into your batts, so consider highly efficient regulators that will drain little amount out of your panel to operate, and straight connections. This should be your major concern ....

 

[camaraderie]

joel...you first need to calculate the wattage of the panels you are going to use to replace your weekend amp hour usage. without knowing that, it is difficult to recommend a regulator.
But for kicks I am going to make an assumption that a typical weekend might cost you 200 amp hours of battery use...with about 3/4 of that in the fridge....and that the fridge will be turned off during the week with only an occasional cycle of the bilge pump providing any drain for those 5 days.
I will also assume you put 100amp hours back in during around an hour of motoring during the weekend leaving you with a net deficit for your panels to provide 100ah's during 5 days on the mooring. That would require around 400 watts of panels if you wanted to put it back in one SUNNY day but lets call it 100-150watts toget you through a 5 typical days of sun and clouds and rain with a typical solar regulator.
Panel output at 150watts will be 17.5V and about 9 amps in full sunlight...and a conventional regulator will strip about 35 watts off keeping the voltage in line....which would still leave you with plenty of wattage to keep topped up. A cheap ($40) but effective 10 amp controller like this one will do the job.
Amazon.com: Sunsei SE-CC10000 10 Amp Solar Charge Controller: Home & Garden

Now if you want to minimize the size of the panels and maximize charging efficiency you could go with an MPPT controller like the $200 BlueSky 2512ix. You could buy 120watts of panels with this instead of 150 watts and still get the same charging performance PLUS get a 3 stage controller WITH an EQ cycle to keep your batteries in better shape.
Blue Sky Solar Boost 2512iX 25A,12V 3 Stage Charg - Blue Sky Solar Charge Controllers (MPPT) @ AltE


Now...Your actual panel size wattage needs may differ from my example but hopefully you can extrapolate from my suggestions. For keeping topped up over the winter...I'd suggest a 40watt panel and a cheap regulator if you decide not to go the full blown route.

 

[billyruffn]

To regulate or not to regulate, that is the question.

Negrini's right about small amounts of power. My solar panels (measuring approx 25" x 50") deliver ~2 amps at ~19V (they're 15 years old).

If you're going to get a regulator, get one specifically designed for solar applications. They run between $40 and $80 depending on the amperage they have to regulate.

I said, "if" because you may not need one as I explain below.

When I first got the boat there was no regulator -- panels were directly wired to the largest battery bank (~400 amp hours in size). The PO had lived aboard the boat continously for five years and said he didn't think a regualtor was necessary. After I bought the boat we kept it at a dock, and I decided to avoid shore power and to use the panels to keep the batteries charged. One weekend the first year we owned BR, I arrived at the boat to find the batteries at 15 V. Obviously we'd had a very sunny week and, with no load on the battery banks, the panels had overchardge the batteries in spite of the fact that I had connected both large banks (totaling 800 ah) together. I bought a regualtor and used it until it failed (for reasons unkown). At the time it failed were living aboard in the Caribbean I decided not replace it. My rationale was that if you're using the batteries everyday and if you keep at least some load on them 24/7 you don't need a regulator because you're not going to overcharge them. Now that we are not living aboard, I have installed a new regulator. Last summer the panels kept the batteries charged to the proper voltage and the frig cold while we were away from the boat.

PS - I see that while I was writing this post Cam has done one with much more specific info on regulators. I now use a 7amp $40 regulator, but if I ever get around to replacing my panels with newer technology and higher W output, I will consider one of the new high tech chargers that claim to boost your amps to the battery by 25% or so. Neither of these events will occur, however, until the DJIA reaches 12,000.

 

[aquatooth]

Buy a Solar Regulator and wire it with a manual changeover switch.

Never hook up the panels without one otherwise you run a high risk of damage to those expensive batteries...

2x 80w panels would give you around 800 watthours per day (assuming an average of 5 hours)

Better to use 2 small panels rather than one big one as it gives you a little failsafe.

Simon