I’ve been studying adding solar for quite a few years and this summer (2020) I finally purchased two 100 watt rigid panels, two MPPT controllers and the necessary wires that connect the panels to the controllers. Along with the modifications to the lifelines to mount the panels I’ve spent about $600 US.
The goal of the solar plan is to extend our time away from shore power and to avoid running the engine every two days to charge our 420 amp-hours of AGM house batteries. Our major loads are from our electric refrigerator, our diesel hydronic heater that also supplies instant hot water, and the water pressure pump and shower bilge pump. Almost all the cabin lighting has been converted to LED and that helps, along with an LED anchor light. We have added several overhead LED fixtures while installing new plywood overhead panels.
The solar calculator and the estimates and assumptions I used says I will need about 400 watts to maintain decent battery health and 600 watts to really separate from shore or mechanical charging. The need to keep these batteries topped up has been demonstrated by a friend’s experience (no solar) on a long cruise away from everything but water and wooded shorelines. Short motor trips and partial battery charging is not sufficient to maintain long term battery health.
Installation details. I replaced the top lifeline between the stern pushpit and aft gate stanchion on both sides of the cockpit. I used 1” stainless rail and three 1” fittings, making it possible to restore the soft lifelines someday if desired. The panels are about 42” x 22” (Renogy Compact panels) and they fit well alongside the cockpit. I bought 2 pairs of Magma grill rail mounts to securely hold them and to be able to rotate them about 270 degrees. They clear the primary winches when extended horizontally, which will be the normal position while sailing. I can move them forward or aft as needed.
I temporarily routed the wires through the dorade vents on the cockpit coaming and then under the coaming to the left side of the boat where they can enter the cabin high up in the aft quarter berth. Final routing via proper sealed feedthroughs will be decided when I’ve figured out whether more panels should be installed in the cockpit area.
The two solar controllers are installed on homemade brackets in the nav station/quarter berth, on the cabin side bulkhead, behind the fixed port. They should be installed as close to the battery banks as possible to minimize temperature differential between the batteries and the controller. The controllers I chose (Victron SmartSolar 75/15, 15 amp) have Bluetooth communications to a smart phone app and automatic temperature compensation for absorption and float voltage. The difference in temp between the controllers and the #1 pair of house batteries is about 5 deg. C in the late fall with a cold engine. It is warmer where the controllers sit. It is not practical for the controllers to be inside the battery compartments, due to space and wire routing complications. My #2 bank is under the aft dinette seat. Wireless temperature sensors are available to transmit temp info to the controllers. I have not decided to buy those yet. The controllers are very flexible and allow a lot of customization of settings.
Connections to the batteries for charging is conventional. I already have a fine old battery monitor so I have shunts and that means I just connected the negative charging wire to the negative bus bar. The positive charging wire goes to the positive distribution post near my house battery switch, which is usually in the BOTH position. This distribution post is also where the alternator and AC/Shore battery charger are connected, along with the DC panel loads. Note that the LOAD terminals on the solar controllers are not used. The batteries get the charge through the BATT terminals on the controllers. The controllers are paralleled with each other at the terminal strip for their charge output.
Experience so far this fall has been very limited and has been focused on refining controller settings and figuring out whether the solar can co-exist with my AC shore charger. The AC charger does not like the higher (temperature compensated) voltage that the solar can put out. Basically, if the shore charger can’t regulate the battery voltage to about 13.4 volts, it disconnects itself and shows an error. Solar output, compensated, has been about 13.53 volts. I have decided to add a switch and connect the solar output to the start battery during times when AC charging is available. During late fall through early spring, I doubt the panels will keep up with the house batteries anyway. I can disable temperature compensation, too.
I have looked up the battery specs for both the Optima start battery and the Lifeline house batteries. They will accept the temperature compensated voltages as temperature varies. The controllers were clearly designed to be able to closely match typical battery charge voltage vs temperature curves.
I appreciate those who have posted their solar experiences and installations here at EY.o and elsewhere. I’m happy to have finally made my first move.



The goal of the solar plan is to extend our time away from shore power and to avoid running the engine every two days to charge our 420 amp-hours of AGM house batteries. Our major loads are from our electric refrigerator, our diesel hydronic heater that also supplies instant hot water, and the water pressure pump and shower bilge pump. Almost all the cabin lighting has been converted to LED and that helps, along with an LED anchor light. We have added several overhead LED fixtures while installing new plywood overhead panels.
The solar calculator and the estimates and assumptions I used says I will need about 400 watts to maintain decent battery health and 600 watts to really separate from shore or mechanical charging. The need to keep these batteries topped up has been demonstrated by a friend’s experience (no solar) on a long cruise away from everything but water and wooded shorelines. Short motor trips and partial battery charging is not sufficient to maintain long term battery health.
Installation details. I replaced the top lifeline between the stern pushpit and aft gate stanchion on both sides of the cockpit. I used 1” stainless rail and three 1” fittings, making it possible to restore the soft lifelines someday if desired. The panels are about 42” x 22” (Renogy Compact panels) and they fit well alongside the cockpit. I bought 2 pairs of Magma grill rail mounts to securely hold them and to be able to rotate them about 270 degrees. They clear the primary winches when extended horizontally, which will be the normal position while sailing. I can move them forward or aft as needed.
I temporarily routed the wires through the dorade vents on the cockpit coaming and then under the coaming to the left side of the boat where they can enter the cabin high up in the aft quarter berth. Final routing via proper sealed feedthroughs will be decided when I’ve figured out whether more panels should be installed in the cockpit area.
The two solar controllers are installed on homemade brackets in the nav station/quarter berth, on the cabin side bulkhead, behind the fixed port. They should be installed as close to the battery banks as possible to minimize temperature differential between the batteries and the controller. The controllers I chose (Victron SmartSolar 75/15, 15 amp) have Bluetooth communications to a smart phone app and automatic temperature compensation for absorption and float voltage. The difference in temp between the controllers and the #1 pair of house batteries is about 5 deg. C in the late fall with a cold engine. It is warmer where the controllers sit. It is not practical for the controllers to be inside the battery compartments, due to space and wire routing complications. My #2 bank is under the aft dinette seat. Wireless temperature sensors are available to transmit temp info to the controllers. I have not decided to buy those yet. The controllers are very flexible and allow a lot of customization of settings.
Connections to the batteries for charging is conventional. I already have a fine old battery monitor so I have shunts and that means I just connected the negative charging wire to the negative bus bar. The positive charging wire goes to the positive distribution post near my house battery switch, which is usually in the BOTH position. This distribution post is also where the alternator and AC/Shore battery charger are connected, along with the DC panel loads. Note that the LOAD terminals on the solar controllers are not used. The batteries get the charge through the BATT terminals on the controllers. The controllers are paralleled with each other at the terminal strip for their charge output.
Experience so far this fall has been very limited and has been focused on refining controller settings and figuring out whether the solar can co-exist with my AC shore charger. The AC charger does not like the higher (temperature compensated) voltage that the solar can put out. Basically, if the shore charger can’t regulate the battery voltage to about 13.4 volts, it disconnects itself and shows an error. Solar output, compensated, has been about 13.53 volts. I have decided to add a switch and connect the solar output to the start battery during times when AC charging is available. During late fall through early spring, I doubt the panels will keep up with the house batteries anyway. I can disable temperature compensation, too.
I have looked up the battery specs for both the Optima start battery and the Lifeline house batteries. They will accept the temperature compensated voltages as temperature varies. The controllers were clearly designed to be able to closely match typical battery charge voltage vs temperature curves.
I appreciate those who have posted their solar experiences and installations here at EY.o and elsewhere. I’m happy to have finally made my first move.


