I have an Oday 25 on an offshore mooring, which I purchased with a dying wet-cell 27 series battery. I don't run the motor enough to charge the battery. I'm buying a new battery, and would like to pair it with a solar charger so that I don't have to motor over to the courtesy dock once a week or so to charge with an AC charger. The boat doesn't draw much juice, powering only a depth finder, vhf, and occasionally cabin and running lights. I have seen several boats on offshore moorings with fairly small solar panels that are apparently "trickle charging" the battery. They seem to leave the panels charging any time they are not on the boat. So, the questions I have for this forum are: 1. Is this a sound practice for maintaining battery charge? 2. Is a charger in the 4-6 watt range adequate for this type of trickle charging, or do I need something larger with a controler to prevent overcharging? 3. And finally, I've looked at the Brunton flexible panels, which come in 4.5, 9, and 14 watt configurations. I think a flexible panel would be an advantage, but they are fairly expensive ($360 or so for the 14 watt) compared to rigid panels. Does anyone have experience with these to offer some advice? thanks for the help
Trickle charging with solar?
- Thread starter Lang Smith
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Solar
1) Yes, I kept the battery up on my old 24 footer for 6 years or so with one of the 5 watt square panels. 2) Yes, 5 watt panel will do the job as long as it gets enough sun. 3) No experience with the flexible units. If your budget allows and it helps you with installation, go for it.
1) Yes, I kept the battery up on my old 24 footer for 6 years or so with one of the 5 watt square panels. 2) Yes, 5 watt panel will do the job as long as it gets enough sun. 3) No experience with the flexible units. If your budget allows and it helps you with installation, go for it.
I’ve had good success
with this 5 watt last year. I don’t know how it will be this year as I moved to another cove that is well shaded from noon on. Although I checked it today around 5PM and it was still putting out 19.5 volts. We’ll see. The unit comes complete with battery clips AND an anti draining diode. Bob SV Miss Lisa
with this 5 watt last year. I don’t know how it will be this year as I moved to another cove that is well shaded from noon on. Although I checked it today around 5PM and it was still putting out 19.5 volts. We’ll see. The unit comes complete with battery clips AND an anti draining diode. Bob SV Miss Lisa
Sizing Solar cells
Wet cell batteries loose about 1% of their charge per day. Solar cells up to 5 Watts are usually considered "Battery Maintainers" as they will probably not be able to provide much charge above the replacement of charge being lost. West Marine as well as several solar sites on web recommend that cells which provide less than 1% or so of battery ampere hours per hour do not need a charger. Don't forget your occasional bilge pump cycle and or any other power draw that might be inadvertently left on when sizing your solar cell. Ebay has may sweet deals on solar cells. I got a 35 Watt Kyocera (Cadilac of units) for about $150. Search on Kyocera, Siemens, Shell, etc. Flexibles are very nice for portablility but besides being expensive are also less effecient so you need one that covers a larger area of your deck.
Wet cell batteries loose about 1% of their charge per day. Solar cells up to 5 Watts are usually considered "Battery Maintainers" as they will probably not be able to provide much charge above the replacement of charge being lost. West Marine as well as several solar sites on web recommend that cells which provide less than 1% or so of battery ampere hours per hour do not need a charger. Don't forget your occasional bilge pump cycle and or any other power draw that might be inadvertently left on when sizing your solar cell. Ebay has may sweet deals on solar cells. I got a 35 Watt Kyocera (Cadilac of units) for about $150. Search on Kyocera, Siemens, Shell, etc. Flexibles are very nice for portablility but besides being expensive are also less effecient so you need one that covers a larger area of your deck.
<1% = un-regulated
John Meyers was right when he indicated “...West Marine as well as several solar sites on web recommend that cells which provide less than 1% or so of battery ampere hours per hour do not need a charger ...” Except he meant to say they don’t require a REGULATOR. Hence, a Photo-Voltaic of under 15 Watts should not require a regulator, if maintaining a 105 A/H battery (or larger bank). Hope I’m not flogging the obvious.
John Meyers was right when he indicated “...West Marine as well as several solar sites on web recommend that cells which provide less than 1% or so of battery ampere hours per hour do not need a charger ...” Except he meant to say they don’t require a REGULATOR. Hence, a Photo-Voltaic of under 15 Watts should not require a regulator, if maintaining a 105 A/H battery (or larger bank). Hope I’m not flogging the obvious.
Solar trickle charging
HI Lanf - Using the recommened standard lead acid battery I'd look online for as large a panel as you can afford; I would focus on rigid multi-crystaline panels and look for used panels (i.e. eBay). The math here is that a 14watt panel will produce about 1 amp of current per hour at 14 volts. This is barely enough to maintain a fully charged battery and will not recharge the battery. Any single panel should not require a charge controller as the higher voltage at low amperage will do no harm. This will provide maintaince charge but you will still need to find a way to periodically fully charge the battery. Best, Trevor
HI Lanf - Using the recommened standard lead acid battery I'd look online for as large a panel as you can afford; I would focus on rigid multi-crystaline panels and look for used panels (i.e. eBay). The math here is that a 14watt panel will produce about 1 amp of current per hour at 14 volts. This is barely enough to maintain a fully charged battery and will not recharge the battery. Any single panel should not require a charge controller as the higher voltage at low amperage will do no harm. This will provide maintaince charge but you will still need to find a way to periodically fully charge the battery. Best, Trevor
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