Hi Folks,
I'm looking for some good advice as to what seems to work best in terms of a permanently mounted location for a very small (approximately 14"X12" / 10 watt) solid solar panel on a 311/323 or even a 331.
What do you expect from this panel? Is it a "maintainer" to keep your batteries that were at 100% state of charge, at 100% state of charge, or are you expecting to actually re-charge them?
I'd like to be able to easily remove the bimini, so that's not a great location for me.
Under the boom on the cabin top seems the best location, but seems like a lot of holes to drill, and wiring might be a challenge in the headliner?
Under the boom on the cabin top is one of the absolute worst locations for a solar panel, performance wise. Convenient, sure, but for performance terrible... Shading even a small portion of a panel can rather drastically cut your output. It does not matter how much sun you have, if you have shading. Keep in mind that even in the best conditions you'll only have about 5 hours of full output per day BUT this is ONLY if your panels are aimed at the sun and this 5 hour number is derrived from fixed shore based solar arays. On boats they usually sit flat and are not sun oriented for optima performance. I have yet to measure any boat panels at 5 hours of full rated output unless they were larger panels that could utilize the benefit of an MPPT controller.
Leads me to wonder about stern rail, but far enough from the ladder not to interfere.
For performance this is a MUCH better location but you're talking about a panel that puts out next to nothing to begin with. Keep in mind, the bimini can still shade this panel if it is in the arc but you will experience less shading than you will on the cabin top....
Bimini/boom shade are not a concern - plenty of sun here, and this is just for a trickle charge.
Even worse if it is just a "trickle charge" as the shading will take your output to a performance level so bad you may not even keep up with the natural self discharge rate. I have plenty of installations I've "fixed" where the net solar gain was zero..... Most of these were panels sub 15W that also had shading issues. Basically these owners paid for something, and then, got nothing...
Here's some math based on a 100Ah battery bank. I would guess yours is at least double that...
You're talking about a panel with roughly a 0.45A - 0.5A output.
You can plan on about 4-4.5 hours per day at full output (in PERFECT weather) with the panel flat.
MATH = 0.45A X 4.5 hours = 2 Ah's per day returned to the battery (in PERFECT weather)
So a 100Ah battery at 50% state of charge would take nearly 30 days (accounting for charge inefficiency and natural self discharge) to go from 50% to 100% with near perfect conditions.
To go from 80% state of charge, where your alternator leaves off, would take about 11+ days in perfect weather with NO shading. Any shading could easily turn this into 20 to 60 days, if at all, to get full....
If your bank is 200Ah it will take about 22 days + to go from 80% state of charge to 100% state of charge in perfect conditions with no shading..
I find the bare minimum for a 30+ foot boat, with a 30+ foot boat house bank, is around 30W panel....
If you can't go from 80% to 100% in a week then the cost, to benefit, is pretty negligible. If your not getting to full in 5-6 days you're still going to be suffering from bank sulfation and battery life issues.
