Flex v Fixed frame Solar panel

[smckean (Tosca)]

Someone in this thread mentioned that they don't bother charging their batteries with solar panels or a generator, but instead just use the engine alternator because it's fast.

During two consecutive months of cruising last summer I played with this concept. I concluded that recharging via a modern, well designed, high output (20+ amps) battery charger (power supplied via shore power) was preferred.

I think the reason is that a battery charger, using "smart" programming with stages, really tops off the battery well. The alternator only charges in bulk, and doesn't use higher voltages (e.g., 14+ volts) to top off. My batteries held their voltage much longer when charged via the battery charger rather than with the alternator (even if I ran the engine 8 hours that day). True, the alternator was fast, but I concluded it only charged to maybe 80% (or even less) of capacity. Sure the alternator gets the voltage up to 12.6 or even 12.7, but I found that the batteries dropped in voltage much quicker during my at anchor evening use if the batteries were charged up with the alternator rather than when I had used the battery charger on shore power the night before. I suspect that this would also be true if I powered the battery charger with the generator (but it is unlikely that I would ever run the generator long enough).

I don't understand enough about battery chemistry to explain all this, but the results were very noticeable.

 

[DayBreak]

True, the alternator was fast, but I concluded it only charged to maybe 80% (or even less) of capacity. Sure the alternator gets the voltage up to 12.6 or even 12.7, but I found that the batteries dropped in voltage much quicker during my at anchor evening use if the batteries were charged up with the alternator rather than when I had used the battery charger on shore power the night before.

I don't understand enough about battery chemistry to explain all this, but the results were very noticeable.

I found what Sandy mentions to be the same for us while on shorepower and using a smart charger. We often use a 100 watt Renogy Solar Panel https://www.renogy.com/100-watt-12-volt ... gJyAvD_BwE when on buoy or the hook. With using the refrigerator on low setting on a full sunny day, the solar panel keeps our 24 series flooded cell house battery fully charged as if we were using a smart charger and holds the 'better charge overnight'. In using the 100 watt Renogy Solar Panel, make sure you are using the proper solar charge controller, otherwise you may cook your battery.

 

[daninPA]

I found what Sandy mentions to be the same for us while on shorepower and using a smart charger. We often use a 100 watt Renogy Solar Panel https://www.renogy.com/100-watt-12-volt ... gJyAvD_BwE when on buoy or the hook. With using the refrigerator on low setting on a full sunny day, the solar panel keeps our 24 series flooded cell house battery fully charged as if we were using a smart charger and holds the 'better charge overnight'. In using the 100 watt Renogy Solar Panel, make sure you are using the proper solar charge controller, otherwise you may cook your battery.

I bought the same panel and the Renogy MPPT controller. I’m waiting on the inline fuse and extension cable to connect and test the setup in the basement (we have a large window that lets in a bit of sunlight on a sunny day) before installing it on the boat.

 

[daninPA]

I’m encouraged to hear the single 100w panel provided sufficient charge to sustain the refrigerator overnight. Except for anchor light, a small fan, and PED charging I wouldn’t expect much else to require power. I’m planning on testing the load once I put the batteries back on board.

 

[colbysmith]

True, the alternator was fast, but I concluded it only charged to maybe 80% (or even less) of capacity. Sure the alternator gets the voltage up to 12.6 or even 12.7, but I found that the batteries dropped in voltage much quicker during my at anchor evening use if the batteries were charged up with the alternator rather than when I had used the battery charger on shore power the night before.

I don't understand enough about battery chemistry to explain all this, but the results were very noticeable.

I found what Sandy mentions to be the same for us while on shorepower and using a smart charger. We often use a 100 watt Renogy Solar Panel https://www.renogy.com/100-watt-12-volt ... gJyAvD_BwE when on buoy or the hook. With using the refrigerator on low setting on a full sunny day, the solar panel keeps our 24 series flooded cell house battery fully charged as if we were using a smart charger and holds the 'better charge overnight'. In using the 100 watt Renogy Solar Panel, make sure you are using the proper solar charge controller, otherwise you may cook your battery.

Hi Gary,
Where do you store the solar panel when not in use? I'm thinking seriously of adding 200watts of solar power. This week I'm at Mackinac Island Marina. Great deal in that the marina is still under construction, so not officially open. They are allowing use of about 10 slips along the shore for free, but without power or bath houses. While I've been able to discretely run my generator to bring the batteries back up to a full charge daily, I've been told generator use is not allowed. (I'm playing the C-pap card and need for bringing my batteries back up to a full charge!) So this is one of the rare times solar may have come in very handy. Also, now that I have the composting toilet with the tiny fan, even having the solar available while sitting on the trailer between trips would allow me to skip plugging the boat in. Colby