Solar panel charging

[Joel]

On my H23, the former owner used a small rigid solar panel to keep the battery topped off. Since he was in a slip at a marina, occasionally he would remove the battery, take it home and recharge it fully with a battery charger.Since I'll be at a mooring as opposed to a slip, I'd rather not be lugging a battery back and forth in a small dinghy.Can / should a solar panel be left connected for charging for long periods of time (2-3 days)? Any possible damage to the battery when doing this?The solar panel is "directly" connected to the battery with a 2 prong plug which has a fuse inline. Any other safety devices which should be inline with the solar panel? Some seem to come with a controller whichthis one does not have.

 

[Miles]

General rule...

Is that if the output of the panel is less then 1% (some say .5%) of the amp hour capacity of the battery it doesn't need a regulator. For example a panel which puts out 2 amps could be left connected to a 200 amp hour battery indefinately. Remember that you'll be lucky to get maximum output for more than a few hours a day, and a night there will be no current. Having said all that you might consider getting a regulator anyway, especially if you're close to the spec. above. A good three stage solar regulator is around 20 bucks. Pretty cheap compared to batteries and panels, very easy to install. Like everything else connected to a battery the panel (and regualtor if you have one) needs to be fused to prevent a dead short and potential fire.

 

[Anthony Bavuso]

don't you need a diode also?

I don't know much about this subject, but have heard that sometimes the solar panel can act as a load and power will be drained from the batteries unless a diode is installed.

 

[Miles]

Yes...

Yes, but many of the panels have built in diodes. Also most of the regulators do too. Without a diode somewhere in the system the battery will discharge through the panel at night. Since there is a voltage drop across the diode you probably don't want to add an extra one though...

 

[Ron Mehringer]

Two diodes

Since many panels (like UniSolar) already have a diode, I wonder if regulators can be purchased either with and without a diode? The voltage drop across two diodes would have a significantly detrimental effect on the panels charging capability.RonM