Photo cell charger for Battery

[jismith44]

Hello,

I was interested in a method of using a photo panel to charge my onboard battery.  If anybody out there has an installation/diagram that I could use, I would appreciate it.

Thanks

Jismith44

[curtis]

Hello,

I was interested in a method of using a photo panel to charge my onboard battery.  If anybody out there has an installation/diagram that I could use, I would appreciate it.

Thanks

Jismith44

I don't have a diagram but here's how you do it in words.

The battery is already in series with the loads.  There is usually one wire to the circuit panel where it goes to the fuses then switches, then the loads.  There is sometimes a separate wire going to an electric bilge pump.  In larger boats the one wire going to the circuit panel goes through a large fuse first, then a battery switch, then the panel.  The closer the fuse is to the battery the safer.

The first thing you need to do is size the panel to the  battery and the expected usage.  If you plan to run a refrigerator, you can't get enough solar panel without covering the boat so forget that.  If you occasionally use the NAV lights and only for a few hours when you do use them, then you should be OK with a small panel.  Figure your current draw times time.  That gives you some number of AMP-hours.  For example if worst case you sail 4 hours with NAV lights on after 8 hours daytime sailing and the whole time the VHF and a depth gauge and knotlog are running then its 4 time the NAV light draw plus 12 times the VHF and instruments.  Typically you'd be conservative enough to estimate 4 AMPs and 1 AMP, yielding  4*4 plus 12*1 for a total of 28 AMP-hours.  Solar panels only produce near full output with direct sunlight almost directly overhead.  A rule of thumb is 1 AMP hour per 3 watts of solar panel on a sunny day.  To get 25 AMP hours in a day you need a 75 watt panel and a sunny day.  You'd need a little over a day for your battery to recover in this case.  If your usage is light, for example using the radio and instruments rarely or rarely sailing more than 5 hours a day and rarely sailing at night, and leaving the boat for the whole week to recharge, then a really small panel might do.  A lot of people use 6-10 watt panels if they normally have near zero battery usage.

If you have a really small panel then you can get away without a charge controller.  I'd use one anyway.  The really small panel is almost only useful for a float charge (it can not bring the battery back from a deep discharge before the battery is damaged by being left discharged too long).  Wire the battery positive to a separate fuse, then a blocking diode, then the charge controller, then panel positive, then panel negative back to ground.  The panel should have a separate pair of battery connections so you could never blow a fuse or remove the battery terminal and end up with 17 volts on your electronics (which could fry a VHF or other instrument and might blow a light bulb).  The charge controller will have its own wiring diagram.

Hope this helps.

Curtis

[jismith44]

Curtis,

Thanks for the info..  I am just charging the battery for nav lights an anchor light so the 6-10 watt panel should be ok.

Thanks,

Jerry

[john walker]

run your engine, if you don't have a charging engine, you aren't a serious cruiser!

[patch]

west marine has a thin 6 amp solar panel that roll up.you can put it on top of your bimini you can plug your cell phone into it and your computer gps.it has 4 grommets to attach or you can use double sided tape. $220.with a deep cycle marine battery should work well.