[sailingdog]

PWM-chargers should do a pretty good job of charging the batteries...but a 10 W panel is probably not going to give you enough output to CHARGE the batteries, as it is probably just enough to keep them from discharging any further. What you need is a larger panel. Deep cycle wet-cell batteries really need to be recharged to near 100% on a regular basis or they will sulfate and die. Equalization can sometimes help, but they NEED TO BE RECHARGED REGULARLY.

A 10 W panel is only going to generate less than 3-4 Amp-hours on a good day (10 W = 14.4 V * .7 amps; 5 hours * .7 amps = 3.5 amp hours.).

This isn't enough to re-charge the batteries after your day out—much less what your anchor light is using up...and they're going to be sitting there at a partially discharged state for a long period of time. If you don't get a larger solar panel or bring the batteries to the dock and charge them up to 100%, you won't get much more than two years out of them...since you're basically killing them.

What you really need is a 60-80 Watt solar panel that can properly charge the batteries. A 80 Watt panel would give you about 25-30 amp-hours of charging per day. This is probably enough to replace what your VHF, Depth Sounder, and Anchor Light use and keep the battery nearly fully charged...greatly prolonging its life span.