solar system

[reefrunner7]

Looking to add a solar system to my boat, anyone know of a good system to use and what the recommended number of battery's to be used should be. currently have 1 gen, 2 eng start's on board. I would like to be able to run lights and such at night without using gen all the time

 

[Bondo]

Re: solar system

Ayuh,.... How many square feet ya got to cover with photo-voltic cells,..??

It takes a Huge area to be effective...

 

[reefrunner7]

Re: solar system

Have 2 hardtops both at least 120 sq ft

 

[CaptainKickback]

Re: solar system

I looked at three different ones at the last Ft. lauderdale boat show. One was made so you could walk on it, one was rigid (but no walking on it), and the other was flexible and couls be sewn to canvas. All were expensive. I think I calculated I could run my fridge most of the day with one 45 watt panel (about $400). I decided just to beef up my battery capacity instead. My goal was to not have to run the generator during the day (only at night for a/c and to charge the batteries).

What you should do is research the formulas for calculating how many watts it will take to run the load you would like to cover. Most 45W panels are about 8 sf. But remember, the optimum output is when they are aimed directly at the sun. Lying flat on the T-top and swinging at anchor will not yield maximum output. Also, you can only count on 5 decent charging hours per day, at best.

I decided letting my generator charge a bigger battery was the way to go.

Good luck...

 

[Don S]

Re: solar system

First of all, you say you want to run lights and such at night. Whats an "and such"? Lights shouldn't be a problem, and if you have a generator, what size? What size is the boat? What size is your house battery bank?
You say you have 1 gen and 2 starts on board. Does that mean you have one generator start battery, and 2 starting batteries for everything else?
I lived on board and using 4 size 27 dual purpose batteries and one starting battery, could go a couple days with the refer running, using lights at night and watching tv in the evening and running a diesel heater for about an hour to heat up the water heater.
I had a small, fairly quiet running generator that I plugged into the shore power outlet on the boat with an adapter cord with the generator, I had setting on the back of the boat and using the boats battery charger, it would recharge the batteries in about 2 hours of running during the day.

 

[reefrunner7]

Re: solar system

42 ocean yachts 1 fridge, 1 freezer, 2 raritan heads take juice per flush, if I were to add house batt bank how many 3 or 4? and use solar panels to charge them back up during the sun periods? otherwise we are plugged in at the dock but want to be indep to a point on the hook, I'm changing most all lighting to led so will cut that usage by 90%, and what's the best type of batt's?

 

[CaptainKickback]

Re: solar system

In your last post, you mentioned "independent to a point". It seems you already are that since you have a generator. But given you stated goal in the original post, I take it you, like me, prefer to not run the generator until you have to. However, there are a lot of variaes here that only you can answer. Like all the devices you want to run, for how long, their individual amp draws, etc.

The basic formula is Watts = Volts * Current (W = VI)

I is the symbol for current measured in amps. Each device you have should state its current draw in amps or its rating in watts. If watts, use the formula to convert to amps (to meet your stated goal, you will be using only your DC devices, so V = 12).

Batteries are rated in amp hours. A 250 amp hour battery can deliver that number amps for an hour. Or, say, 25 amps for 10 hours, etc. However, you only want to draw your batteries down to 50%, so plan that in your calculations.

Once you add up your amp draws per device and the amount of time for each, you will know how long you can run on your house battery.

I know that all seems a bit overwhelming, but in my case, I'm just going to change from 1 Group 27 deep cycle house battery to 2, in parallel. From experience with my last boat, I would shut the generator off after breakfast (about 10 am) and could run on batteries (fridge, part time steroe, occasional head flush) until about 4 pm. So, doubling my battery capacity will take me up to the time to start the generator for night (a/c).

Sorry for the long answer. Hope this helps.

 

[reefrunner7]

Re: solar system

thanks so much I will do the calc's and try to work it out, one thing we are going to is the new bose portable speaker that connects via bluetooth to the iphone and ipods therefore I can take the stereo power out of the mix, which in my case with teenage girls was huge with it running morning till night, that speaker runs for 8 hours on its own. The rest is fridge,freezer,icemaker and i'm spending the $ on going LED with all the lighting just the energy savings on these is tremendous 75watt bulb down to 2watt led's. I'm thinking of 2 to 4 batt's and two solar panels on hardtop to keep them charged and or run other stuff on sunny days. I would like to find someone who knows these systems though.

 

[Silvertip]

Re: solar system

In my view even two 45 watt panels is not enough power to keep up with the load you have. But until you do those calcuations you simply won't know. Solar has it's appplications but as a replacement for a generator they are simply not capable -- at least for what one might consider reasonable cost. 90 watts is a bit over 7 amps. Since a 1.5 - 2 amp on-board charger is considered a "maintenance" charger or "battery tender" that's all that panel would qualify as with four batteries. Maintenance chargers are intended to keep a "slightly" discharged or fully charged battery topped off during periods of non-use, I don't see the value in or the expense of a solar system of that size on any boat except perhaps a sail boat where the prime power consumer might be lights and communications equipment. Remember -- this is about power consumed vs available power for replenishing the batteries. Less power consumed than being input means the batteries are charging. More power being consumed than being replensihed means the batteries are discharging.