Solar battery chargers

[Izzy1414]

Anyone with experience with solar battery chargers? I am charging two 12 volt deep cycle marine batteries. I am thinking flexible panel would be more practical. Is more output always better?

[chuck5499]

Izzy - not sure of what your power consumption is or what you are using the boat for but i can only tell you what i am doing
first - flexible panels are more expensive and can only provide smaller amounts of power vs the hard panels
second - i am in the process of outfitting a jeanneau ds40 for some long term cruising - i have 740+ amps of power from 6 golf cart batteries and one starter - i have a reefer and all the gadgets one needs plus a few - i am in the process of install 2 130 watt solar panels on my bimini top - i do not plan to use any wind generator nor do i have a genset - these should be able to more than keep up with my needs and if it gets cloudy for a few days i will run the iron genny that has a 160 amp alternator attached
- so in summary - what are trying to gain and how much power do think you need
chuck and svsoulmates
ki4sry

[Izzy1414]

My power consumption is relatively small on our 26 foot pocket cruiser. Just depth sounder, stereo, nav lights, etc. There is just not that much chance to charge the batteries with the motor when the wind beckons.

[camaraderie]

IZZY...welcome. It sounds like you are just looking to recharge your batteries during the week rather than have a charging system for daily cruising use. Correct?
Flexible panels are OK for such use but it is the wattage output of any panel that will matter. I suggest no smaller tha 20 watts for keeping batteries recharged during the week. To be of better help we need to know more about your use of the boat and the SIZE of the battery bank.

[Izzy1414]

We use our boat for a couple days at a time on a mountain lake with it moored on a ball in between uses. The down time ranges from several days (typical) to several weeks (unacceptable).

[camaraderie]

Izzy...for on the mooring use a 20watt panel should put in 6-8 amp hours per day or roughly 30-40 amphours a week.
Your radio,cabin lights, anchor light, bilge pump etc. probably use about that many amp hours per day you are on board so 20 watts is really pretty minimal.
You can get a much more precise idea of your electrical use by clicking on the spreadsheet link on this page:
Southeast Marine Services :: Technical Information :: Battery Bank Sizing
Hope this helps.

[sailingdog]

Izzy-

The flexible panels are amorphous silicon and have a much lower power generation capacity than a hard polycrystalline panel of the same surface area. IMHO, you'd be better off getting a 40-60 Watt polycrystalline panel and mounting it. However, you may need a charge controller for a larger panel, but it depends on your battery bank size.

[camaraderie]

Dawg...are you saying that a 40 watt panel of amorphous does not give the same output as a 40 watt panel of poly? My understanding is that more AREA of panel is needed to produce the 40 watts from amorphous but that the output is the same (or slightly better in low light/low angle of incidence) with amorphous.

[sailingdog]

CAM-

That is why I said:

much lower power generation capacity than a hard polycrystalline panel of the same surface area.

Many boats are going to have trouble finding the space required by a 40 Watt amorphous panel, but might be able to fit a 40 watt polycrystalline panel fairly easily.

A polycrystalline 40 Watt panel is about 26" x 21", where a 40 Watt amorphous silicon panel is going to be about 48" x 21"...almost twice as large.

[camaraderie]

OK...so you're saying get a 40w poly panel instead of a 20w amorphous panel of the same surface area. No problem with that other than price and complexity of installation...but a longer life and more power too.