Re: Batteries don't stay charged
The following possibilities may be at play here:
1. Your batteries are old, and have greatly reduced capacity.
2. You have a short or hidden load somewhere, draining the batteries.
3. No, the solar panel doesn't act as a "load" on cloudy days, it simply doesn't produce any output. Also, most panels have a diode to prevent current from flowing back to them. If the diode is damaged...maybe, but unlikely.
4. Shore power is not relevant to the state of your batteries unless you have an onboard charger. Is the charger on or off when you connect shore power?
Buy a cheap voltmeter or multi-meter. Set it for Volts (DC) or VDC.
With the engine off, but with the switch ON, observe the battery voltage.
Is the voltage dropping?
Now, set the battery switch to OFF. Does the voltage continue dropping?
Next, with a fresh charge on the battery(s), turn on a couple of lights.
Does the voltage drop precipitously?
Try cranking the engnie.
Does the voltage crash?
The answer to these questions will help determine if you have a short, or if your batteries are toast.
S/V Old Shoes
1973 Pearson 30 #255