solar battery charger

[jlscjs]

Need some input on using a solar battery charger for my trolling motor. Talked to a couple of people and they feel a solar charger is worthless. Just now ask a man about his and he tells me that is all he uses, he says he has kept 2 batteries charged for the past year on nothing but his solar charger. All he could tell me was it was a GTO model but nothing else. So what size would one need to put on a 12 volt battery? I see they sell from 10watts to 100 watts, sometimes I have electric at my slip but more than not the breaker keeps kicking off, the park mgr says they are going to fix it but it's been like this for a year. So if I wanted to depend on my solar charger only what size would I need to keep my batteries charged? Thanks

 

[joeanna]

that is gonna be my next project the solar panel must be sized for your battery, and are not a quick charger. I was aiming for the 100 watt or more as I have a large battery and I would use it for a fast-trickle charge, there are many solar battery charger calculators on line and also solar battery charger circuits on line also.
there is also marine windmills out there that are nice also, they work at night too, combined solar-wind is even better.

 

[alldodge]

Never seen a solar charger that can recharge a trolling motor battery unless you have good sun shine and only use the motor maybe once a week, and that is a maybe. A 100W panel ($150) may do better, but it is still dependent on the amount of sun is available and for how many hours

 

[bruceb58]

100W panel is going to supply 5.5A max with a PWM controller. Going to take a long time to charge a battery.

 

[jlscjs]

Never seen a solar charger that can recharge a trolling motor battery unless you have good sun shine and only use the motor maybe once a week, and that is a maybe. A 100W panel ($150) may do better, but it is still dependent on the amount of sun is available and for how many hours

On the north shore of a lake in Florida, no shade of any kind, sun from morning till night.

 

[jlscjs]

100W panel is going to supply 5.5A max with a PWM controller. Going to take a long time to charge a battery.

So if the battery is charged from the start will a solar maintain the full charge?

 

[alldodge]

5.5A x 10 hours = 55 A per day

What is the capacity of the bat?

 

[Scott Danforth]

On the north shore of a lake in Florida, no shade of any kind, sun from morning till night.

florida has too much humidity for solar to be effective. its not as good as arizona or new mexico for solar. too much haze and the efficiency drops. this is a direct quote from the owner of S-Power, one of the largest solar plant builders in the world

solar panels need to be perpendicular to the sun's rays to be 100% efficient. the efficiency drops off quickly as the angle of the panel to the rays drops off from perpendicular, so unless you have an active array, and only a stationary mount, the efficiency of the panel will realistically be only about 20%, especially on a boat that is bouncing up and down on the waves.

So if the battery is charged from the start will a solar maintain the full charge?

yes, a solar panel would maintain a battery. it will maintain 2-3 batteries. it will just take a really long time to charge a discharged battery (trolling motor, etc.) as in a few weeks.

for reference it takes 6 250 watt panels with adjustable mounts and a wind generator to keep up with 4 batteries on a 37' sailboat that uses LED lighting and a small LED TV in addition to the refrigerator here in florida. add that is with daily washing of the seagull and pelican poop

 

[bruceb58]

5.5A x 10 hours = 55 A per day

What is the capacity of the bat?

Depending on where you are, even in the summer, the equivalent solar hours may only be 6 hours.

 

[bruceb58]

So if the battery is charged from the start will a solar maintain the full charge?

Yes

 

[bruceb58]

You can go to this site to see what the solar equivalent hours is for your location. For my home in Lake Tahoe, the peak is around 7 hours in the summer and 3.7 in the winter.

 

[bruceb58]

I am installing 4 175W panels on a 25' travel trailer I just purchased. My batteries will be 2 lithium batteries that can be discharged 90% for a total discharge of 180AH. My 700W system with an MPPT solar controller will have the batteries charged in less than 4 hours.

 

[dennis461]

I have a 15 watt solar panel on my boat to maintain my single battery while fishing at anchor. More than enough to keep a VHF radio on, fish finder on, and keep the battery from dropping voltage.
Mine is aimed straight up (almost) since the bright sky is a good source of light. (aimed directly at the sun is better, but that is difficult to do on the water.)

Harbor freight sells a 100 watt kit, but the panels are bigger and will not fit easily on my boat, (Google 100 watt solar panel kit, many stores sell them)
Would you have room for 3'x4' solar panel?

If your boat sits for a week or more, 100 watts (rated) may recharge your battery.
Figure only two hours of good light per day, sun not aimed directly at panels, clouds, etc approx, 200 watt hours @12 volts give you 17 ampere hours should recharge a 100 amp-hour battery in a week.

 

[bruceb58]

200 watt hours @12 volts give you 17 ampere hours should recharge a 100 amp-hour battery in a week.

Solar panels are rated at their 18V output. You have to divide by 18...not 12.

Use this site to calculate the number of solar hours:
http://pvwatts.nrel.gov/

 

[dennis461]

Be sure to get a kit with a MPPT controller versus the PWM controller, The MPPT controller is more expensive, but yields more power from the solar panel.