Searching for solar battery maintainer kit
I'm looking for a small, complete setup to maintain a deep cycle marine battery in my fishing boat. I usually keep a charger on it every so often to keep it charged but it would be nice to have a sola...
Forum Discussion
I have some solar marine info, was looking into this for our boats as well. I kept this below from D.C. I hope this info is helpful.
(Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and is one of the BoatUS Magazine's panel of experts.)
If you have a wet cell marine battery they self-discharge at about 1% of amp hour rating per day depending on outside temp. (less on hot days-more on cold days)
A watt panel has an output of approx .33 amps. But that's at peak power = noon . The rest of the time it's less. On average, we expect about 5 peak hours per day out of any solar panel.
The expected daily output of a five-watt panel about 1.65 amp-hours (5 x 0.33).
Allowing for recharging inefficiencies, this is still about 50% more than necessary to float a 100-amp-hour battery. A good rule of thumb is 3.5 watts per 100 amp-hours of battery capacity. But throw in an occasional sunless day, put blocking diodes in the circuit, and let the bilge pump run once in a while, and five watts will be about right. A small amount of extra capacity won't damage the batteries as long as you maintain the water level in them.
Whatever size panel you select, it should have at least 33 cells. Count them. Panels with fewer than 33 cells will have inadequate voltage to fully charge the battery. This assumes crystalline panels, which deliver the most output from the smallest package, but if you sail where overcast days outnumber sunny ones, you might consider a thin-film panel, as this type can have better low light output.
(Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and is one of the BoatUS Magazine's panel of experts.)
If you have a wet cell marine battery they self-discharge at about 1% of amp hour rating per day depending on outside temp. (less on hot days-more on cold days)
A watt panel has an output of approx .33 amps. But that's at peak power = noon . The rest of the time it's less. On average, we expect about 5 peak hours per day out of any solar panel.
The expected daily output of a five-watt panel about 1.65 amp-hours (5 x 0.33).
Allowing for recharging inefficiencies, this is still about 50% more than necessary to float a 100-amp-hour battery. A good rule of thumb is 3.5 watts per 100 amp-hours of battery capacity. But throw in an occasional sunless day, put blocking diodes in the circuit, and let the bilge pump run once in a while, and five watts will be about right. A small amount of extra capacity won't damage the batteries as long as you maintain the water level in them.
Whatever size panel you select, it should have at least 33 cells. Count them. Panels with fewer than 33 cells will have inadequate voltage to fully charge the battery. This assumes crystalline panels, which deliver the most output from the smallest package, but if you sail where overcast days outnumber sunny ones, you might consider a thin-film panel, as this type can have better low light output.
