Marine battery and solar panel questions

rgranger · Jul 9, 2016

Fred
Your power needs are not too demanding so....
I'd size the panel to the physical space you are willing to devote to it then get the biggest panel that fits in that space conveniently

Chief RA · Jul 9, 2016

I have a pair of size 24 batteries and 2 ea. 80 watt solar panels. In your case the same would be fine for your batteries but probably one 80 watt panel and controller would be fine. Hang it on your stern rail and you can use plastic pipe for props to put it up to a decent angle. Basic concepts to start. Chief

Meriachee · Jul 9, 2016

Charge controller. Don't forget the charge controller, and don't cheap out on it. It will save your batteries.

Ron20324 · Jul 10, 2016

31 is the largest of the three, amp-hour-wise. Get the largest you can fit in.

Chief RA · Jul 10, 2016

Ron: He has a small boat like mine. Huge batteries are not practical due to weight plus he needs to select a battery the same basic battery type /size he has installed now. One more caution; if existing battery is old just get 2 new matching batterys.
Hello Meriachee! Chief

sesmith · Jul 10, 2016

The difference is physical size and capacity. Here's a link with info on capacity and size of the various battery groups:

https://www.batterystuff.com/kb/tools/bci-battery-group-sizes.html

As far as what you need, try adding up what you expect to use in a day in amp hours, and use that to judge what you might expect to need for battery storage. Do the same to size the solar. Browse Mainesail's forum and his website (compass marine). There's a lot of good and accurate info on batteries and solar systems there.

sesmith · Jul 10, 2016

And just a data point for you. We used to own a Hunter 23.5. It had one group 24 battery in it. We only had lighting, fishfinder, charging of our tablets and phones to worry about. Motor was manual start. We used a 15 watt solar panel to keep the battery up when at our slip. We just put it out on deck when needed and could move it around...no permanent mounting. This worked fine at our marina. When we traveled with the boat, it wasn't quite enough for daily use. The boat also had shore power, so we just planned on doing a full charge at a slip, every few days. Current boat has refrigeration, and no shore power, diesel motor, so our battery and solar installation is much larger and more involved.

FWIW, you can get a big bang for the buck by changing out all your interior lighting to led (likely, you can just swap incandescent bulbs for led replacements). Swapping the mast light for led would be a good idea too.

The Garbone · Jul 10, 2016

sesmith said:
And just a data point for you. We used to own a Hunter 23.5. It had one group 24 battery in it. We only had lighting, fishfinder, charging of our tablets and phones to worry about. Motor was manual start. We used a 15 watt solar panel to keep the battery up when at our slip. We just put it out on deck when needed and could move it around...no permanent mounting. This worked fine at our marina. When we traveled with the boat, it wasn't quite enough for daily use. The boat also had shore power, so we just planned on doing a full charge at a slip, every few days. Current boat has refrigeration, and no shore power, diesel motor, so our battery and solar installation is much larger and more involved.

FWIW, you can get a big bang for the buck by changing out all your interior lighting to led (likely, you can just swap incandescent bulbs for led replacements). Swapping the mast light for led would be a good idea too.

We had a C27 that was the exact same setup, 15 watt, our C30 we have a 50watt panel also loose, once we go full time it will be 200+watts on the bimini.

Batteries should be matched in size and age, in general they should be replaced as a set much like tires. Reminds me of passwords on my work computer, have 3 passwords I need each expires at a different interval. I just change them all together at the interval of the shortest password, otherwise you get out of sync and seem to always be changing the damn things out and it drives you nuts.

Stu Jackson · Jul 10, 2016

sesmith said:
Browse Mainesail's forum and his website (compass marine).

You can get here from this link

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

Ron20324 · Jul 10, 2016

Chief said:
Ron: He has a small boat like mine. Huge batteries are not practical due to weight plus he needs to select a battery the same basic battery type /size he has installed now. ...

That is why I quantified my answer with "can fit in". He can always install a bigger battery box if he wants to.

SFS · Jul 10, 2016

Fred, it works ok for me, takes me directly to a thread. If you are clicking on it, and it doesn't work, try cutting and pasting it into the browser URL line. Good luck.

Just as another option, I've cut and pasted from my browser to here:
http://c34.org/bbs/index.php/topic,5977.0.html

Stu Jackson · Jul 10, 2016

fred1diver said:
It takes me to a general forum menu

Fred, the do what SFS suggests, or use the General Forum and scroll down to the 101 topics and then the Electrical 101. Good luck.

Chief RA · Jul 10, 2016

Garbone: 200 watts of solar coupled with about 200ah battery bank sounds like a good basic self sustaining system. With my 2 ea. 24's and a pair of 80w panels my boat is completely self sustaining indefinitely. This encompasses use of a 2.7cu ft DC , .7a,reefer as well as rest of DC system. Chief

Charlie Jones s/v Tehani · Jul 10, 2016

Cruised full time for 2 1/2 years on my 25 footer, using one group 27 battery and a 32 watt solar panel. Had to pull in and connect the battery charger twice during that time. If I were buying new now, I'd get a 50 watt panel.

Agree big time on the charge controller. I've used a Morningstar Sunsaver 20 for years now with excellent service

Meriachee · Jul 10, 2016

Sunsaver seems like a decent unit.

Howdy Chief - Where ya been?

JCall · Jul 10, 2016

fred1diver said:
why 2 matching batteries?

Batteries have an internal resistance that is best if matched. If you divide the current draw on the battery by the batteries voltage at that load, you will find the internal resistance of the battery. The battery with the least internal resistance will take most of the load. The high(er) internal resistance or "lazy" battery will not take its share of the load. Batteries in parallel should be put into service in pairs.

Bad Obsession · Jul 10, 2016

I have a 23 foot trailer sailor.

My set-up, because I do extended cruises, is to have 2 GC2 batteries wired in series to get 12 Volts. I have an outboard that has a small alternator but that is way too small to replace the power I draw since I tend to use a lot of electronics. My main charging system is a 100watt flexible solar panel that sits on my bimini. It runs to a Genasun GV-10 Charge controller.

Overkill? Maybe...but...
I run an autopilot (tiller pilot) a lot. I also run a GPS that is hooked up to my VHF and I get AIS targets. I also use lights in the cabin at night, mostly LED, and my anchor light is LED. My stereo spends a lot of time on and once in a while I use a small inverter to charge my laptop. I also spend a few weeks out without ever going into a dock to charge. I have pressurized water, cold only, and even have a cockpit shower in the boat.

To better answer your question consider what your intentions are. How long do you plan to cruise? How remote are you cruising? How much power do you THINK that you will use? How much will you actually use.