Stus-List re solar panels

Eric Frank efrank03 at
Fri Sep 27 12:31:38 EDT 2013

I agree with Bill on that.  A proper charge regulator for solar cells will do just that.  I have a similar arrangement that has been running for 5 years with a semi-flexible 20 watt solar panel over the forward hatch.  At first I just used one regulator, running the panel output to the two batteries through diodes so that one battery would not charge the other.  That's a mistake, because the voltage drop on the diode is about 0.4 V, so the charger thinks it's done before that batteries are fully charged.  So either use two one-battery regulators (I use the Morningstar ones and have had no problems in the 5 years) or one regulator with two separate outputs, as was mentioned earlier on this list topic.

The panel is now down to about 0.6 Amp max in bright sunlight (used to be about 1.4 A) - apparently the panels age.  But it is still plenty to top up the batteries when I am not aboard (pretty much only weekends).

Eric Frank
Cat's Paw
C&C 35 Mk II
Mattapoisett, MA

> Date: Fri, 27 Sep 2013 11:59:06 -0400
> From: Bill Bina <billbina at>
> To: cnc-list at
> Subject: Re: Stus-List Solar panels
> Message-ID: <5245AB4A.3040201 at>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
> I have a single 20 watt (nominal) panel laying on top of my sliding 
> hatch. What it does, and does very well, is top up the charge of my 
> batteries during time when I am not on the boat to 100%, and hold them 
> there. Most people are never aware, but their batteries seldom get 
> charged that last 5-10% of capacity. Charging is far more complex than 
> just stuffing amps into the battery as fast as you can. Running the 
> engine for 20 minutes with batteries that are at 90% charge already, 
> won't do much at all. That last 5-10% requires a long slow charge to 
> achieve.
> Bill Bina

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