Replace solar panel on R25 SC with larger panel

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A

Al Spencer

Member
Joined
Oct 14, 2021
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15
Fluid Motion Model
C-26
Hull Identification Number
FMLR253D617
Vessel Name
Sapphire
I would like to replace my factory installed solar panel with a larger 365 watt panel and controller will the current wiring be large enough for the new panel.
Thanks Al
 
You'll need to determine the number of AMPs the panel puts out and size the wire to your controller, the controller, and the wire from the controller to the battery bank appropriately. The specs for the panel should be available from the manufacturer. HTH, Gary
 
I just completed the upgrade from the factory 145 watt Kyocera panel to a 335 watt LG panel. I found in my 2017 Cutwater 28 that the factory used 10 AWG copper from the panel to the Morningstar SunSaver Duo controller. No fuses or breakers between the panel and the controller per a factory admin person. Then from the controller to the house batteries it was 10 AWG used with a 30 amp fuse near the battery connection. The wires from the controller to the engine battery seemed smaller than 10 AWG but I wasn’t going to use those so, I capped them off and ignored them.
Your boats solar system installation may be different than mine!
My 335 watt panel has an open circuit amperage just under 10 Amps. I’ve used the factory 10 AWG wire from the solar panel to a 15 Amp resettable breaker near the controller with 10 AWG from that breaker to my Victron Energy 100/30 Smart controller. I installed the 15 Amp breaker between the controller and the panel to have a way to shut the system off before electricity reached the controller as well as protecting that wiring from overload. I used the factory 10 AWG from the VE controller to a resettable 30 Amp breaker next to the battery. The wire runs were about 15 feet from the panel to the controller and 10 feet from the controller to the battery.
Your panel will be likely be putting out more Amperage than mine. The first step is to look for the max open circuit amperage from the spec sheet. Then confirm the AWG used in your install and the wire run distances. With that info, come back here and ask the real experts about your upgrade.

PS: If you tow your R25 make sure the bigger panel is secured to the sports rack AND that the sports rack is secured to the roof. Folks have lost panels and sports rack from the higher wind load’s encountered during towing.
 
Thanks for the information. I will start doing my research while it is cold outside.
 
The wire size depends on amperage and length. You have to determine the amperage, as @scross mentions, but you also have to know how far the current has to travel. Here is a chart you can use for reference to make sure you get the right size https://thirdgens.com/wp-content/uploads/2018/02/DC_wire_selection_chartlg.jpg

So I had have a 30 amp charger with the battery about 9 feet away, so I used 10 AWG wire.
 
Doug,
Thanks for the link to the table. I would assume for the purposes of charging a battery we are not in a “critical” situation and can live with more than a 3% voltage drop.
Asking for clarification on one thing you mentioned. You said you had a 30 Amp controller and had sized the wire gauge based on the 30 amp max output of the solar controller. Wouldn’t you just use the wire run distance from the controller to the battery as the criteria for the calculation? You wouldn’t use the wire length getting from the panel to the controller would you?

PS: With my 335 watt panel and the controllers charging profile set to about 14.6 volts, I don’t think I ever get more than 25 amps out of the controller even though it’s rated at 30 amps.
 
Hi scross,

Yes, my example was the controller to the battery. You have to do the same on the panel side, determine how many amps are going to be delivered and size for that. I've found that the 10 AWG that comes with solar panels to be more than enough for most. I have 2 340W panels in series at 76V max for the two, so 8.9 amps max. Making 10 AWG more than enough for the 10 feet I needed to run. This works for any wiring that you are doing.

This can be used for any wiring that you are doing. I did some upgrades and the wiring could no longer handle the voltage drop that resulted, so I had to upgrading wiring as well.

Series means higher voltage and lower amperage, so you can use smaller wiring. This is the reason larger boats use 24v DC vs 12v DC. It's also why solar panel installations when they get to higher wattages have the solar panels run in series. You just have to watch out you don't go over the max voltage of the controller on the panel side.

If you ran my panels in parallel, they would be 36 v, so the amperage would be 18.9 amps. 10 AWG would work for up to about 15 feet, but then you'd need to bring in thicker, more expensive wiring if you went any longer. This is also why you'll see more than one controller for large, multi-panel solar banks. The cabling can be extremely expensive otherwise. They have mini-controllers (one per panel) now as well for the reasons above, they also help with shading (not really an issue on most power boats) too.
 
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