I'm considering the purchase of a solar battery charging system for the H26. I want something to charge the single 12volt system for my weekend trips so I don't have to haul the battery home each time it fails. What's the best, most economical solution?
About recharging the battery
- Thread starter Pete17840
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VW Solar Charger
This is what I use to keep the battery up on my H23. I got it off Ebay for about $10.00 but if you know a Volkswagon dealer you might be able to get a couple for free. This is the info I copied off a listing on Ebay: "These are factory OEM VW solar panel battery chargers. They are used by Volkswagen when transporting their A Class vehicles. This will keep your battery charged when the vehicle will not be in use. Four (4) Suction cups allow it to adhere to any glass or pexiglass surface. These can be used with ANY 12 volt vehicle (boat, car, rv, motorcycle, snowmobile or whatever) that is not going to be in use for a period of time. Plugs into ANY 12V power outlet and trickle charges the battery. Cigarette lighter in your car must work when the key is off to charge the battery." • VW part number is 1C0 915 687V • Measures 9.25" x 12.75" x 1" thick • Max. Power: 3.2w • Voltage @ Max Power: 18.8v • Current @ Max Power: 170mA
This is what I use to keep the battery up on my H23. I got it off Ebay for about $10.00 but if you know a Volkswagon dealer you might be able to get a couple for free. This is the info I copied off a listing on Ebay: "These are factory OEM VW solar panel battery chargers. They are used by Volkswagen when transporting their A Class vehicles. This will keep your battery charged when the vehicle will not be in use. Four (4) Suction cups allow it to adhere to any glass or pexiglass surface. These can be used with ANY 12 volt vehicle (boat, car, rv, motorcycle, snowmobile or whatever) that is not going to be in use for a period of time. Plugs into ANY 12V power outlet and trickle charges the battery. Cigarette lighter in your car must work when the key is off to charge the battery." • VW part number is 1C0 915 687V • Measures 9.25" x 12.75" x 1" thick • Max. Power: 3.2w • Voltage @ Max Power: 18.8v • Current @ Max Power: 170mA
How deep do you cycle your battery
on the weekends? You need to know this to size the solar panel properly. a 10 watt panel will produce about .75 amps when charging a 12 volt battery. figure 4-5 hours of usable sunlight per day (assuming no clouds), thats about 4 amp hours per day or 20 amp hours for five days. Reality will be less than that considering clouds, shading of panels, placement, etc.
on the weekends? You need to know this to size the solar panel properly. a 10 watt panel will produce about .75 amps when charging a 12 volt battery. figure 4-5 hours of usable sunlight per day (assuming no clouds), thats about 4 amp hours per day or 20 amp hours for five days. Reality will be less than that considering clouds, shading of panels, placement, etc.
You need to do some homework
As Reudi mentioned, you need to know how much you discharge the battery each time you use it. As a general rule, lead-acid batteries shouldn't be discharged past 50% of their rated capacity for very long. If left undercharged for too long, the battery will be irreversibly altered and cannot be recharged. Battery storage capacity is rated in ampere-hours (Ah). In theory, a 60 Ah battery should produce 1A of current for 60 hours, or 20 A for 3 hours. Actual performance is usually not as good. To calculate current draw for any electrical device, divide its rated wattage by 12 volts, e.g. a 12W device like a single light bulb draws about 1A when lit. The worst offendor is probably the anchor lighy, which draws up to 2A and stays on from dusk till well past dawn. To figure the total draw on the battery over a weekend, figure the current draw for every electrical device you intend to use, note how long each device runs, calculate each device's draw in Ah for the entire weekend and add them up, The sum is how much energy (in Ah) you withdrew from the battery and now have to restore with the solar panel. To figure charge time, divide the solar panel wattage by 12V to get the charging current, Then divide the energy in Ah by the charging current and you have the total charging time in hours. Divide by 4 to 8 to get days. The panel gives max. rated current when the sun is perpendicular to it, there are no clouds and the panel is clean. Panel efficiency also goes down the farther away you are from the equator. Select a panel that can restore full charge in two to three days. Otherwise, you run the risk of ruining the battery. A 10 to 15W panel should be fine for casual weekend use, but if you routinely use a tillerpilot and a bunch of other electronics, you need at least 30W. Bigger panels need a charge regulator because they can cook the battery if left unmonitored (please don't ask me how I know this). Water levels in the battery cells should be checked at least once a month. The other alternative is to be frugal with your electrical use so that a 10W panel is all you need. On the odd weekend when you do get power-hungry and draw the battery past 50%, take it home ASAP afterwards and put it on a conventional charger. Sorry this was so long. Peter H23 "Raven"
As Reudi mentioned, you need to know how much you discharge the battery each time you use it. As a general rule, lead-acid batteries shouldn't be discharged past 50% of their rated capacity for very long. If left undercharged for too long, the battery will be irreversibly altered and cannot be recharged. Battery storage capacity is rated in ampere-hours (Ah). In theory, a 60 Ah battery should produce 1A of current for 60 hours, or 20 A for 3 hours. Actual performance is usually not as good. To calculate current draw for any electrical device, divide its rated wattage by 12 volts, e.g. a 12W device like a single light bulb draws about 1A when lit. The worst offendor is probably the anchor lighy, which draws up to 2A and stays on from dusk till well past dawn. To figure the total draw on the battery over a weekend, figure the current draw for every electrical device you intend to use, note how long each device runs, calculate each device's draw in Ah for the entire weekend and add them up, The sum is how much energy (in Ah) you withdrew from the battery and now have to restore with the solar panel. To figure charge time, divide the solar panel wattage by 12V to get the charging current, Then divide the energy in Ah by the charging current and you have the total charging time in hours. Divide by 4 to 8 to get days. The panel gives max. rated current when the sun is perpendicular to it, there are no clouds and the panel is clean. Panel efficiency also goes down the farther away you are from the equator. Select a panel that can restore full charge in two to three days. Otherwise, you run the risk of ruining the battery. A 10 to 15W panel should be fine for casual weekend use, but if you routinely use a tillerpilot and a bunch of other electronics, you need at least 30W. Bigger panels need a charge regulator because they can cook the battery if left unmonitored (please don't ask me how I know this). Water levels in the battery cells should be checked at least once a month. The other alternative is to be frugal with your electrical use so that a 10W panel is all you need. On the odd weekend when you do get power-hungry and draw the battery past 50%, take it home ASAP afterwards and put it on a conventional charger. Sorry this was so long. Peter H23 "Raven"
H26 Solar Panel
Pete, I just did the very project you are discussing on my own '94 H26. Everyone is correct about energy usage, Amp hours, etc... However, I got frustrated with the whole calculation thing and so just went with my own gut feelings to what I now consider a very good choice (for me). I have several pictures of the project which I will be happy to email you showing the adjustable fixture I built to hold the panel in the place normally used for the mast crutch pole. I purchased an 18W panel from West Marine with a regulator meant for it. Total cost was @ $200.00 and my group 31 deep cycle is topped off every weekend I use the boat (it charges the other 4-5 days). Now, lets also state that I have consciously reduced my power consumption by replacing all voltage drawing devices with the lowest amp draws I could find. My cabin is filled with close to 300 LEDs which lights the cabin like the sun at night, but only draw 1.6 Ah when ALL on at the same time. My VHF is handheld, my fishfinders draws barely nothing, etc... So, for me this was a great choice. Perhaps it could work for you. Send me an email and I can give you further details. (psaluv2sail@comcast.net). Happy sailing! PAT
Pete, I just did the very project you are discussing on my own '94 H26. Everyone is correct about energy usage, Amp hours, etc... However, I got frustrated with the whole calculation thing and so just went with my own gut feelings to what I now consider a very good choice (for me). I have several pictures of the project which I will be happy to email you showing the adjustable fixture I built to hold the panel in the place normally used for the mast crutch pole. I purchased an 18W panel from West Marine with a regulator meant for it. Total cost was @ $200.00 and my group 31 deep cycle is topped off every weekend I use the boat (it charges the other 4-5 days). Now, lets also state that I have consciously reduced my power consumption by replacing all voltage drawing devices with the lowest amp draws I could find. My cabin is filled with close to 300 LEDs which lights the cabin like the sun at night, but only draw 1.6 Ah when ALL on at the same time. My VHF is handheld, my fishfinders draws barely nothing, etc... So, for me this was a great choice. Perhaps it could work for you. Send me an email and I can give you further details. (psaluv2sail@comcast.net). Happy sailing! PAT
Measuring 50%
Peter - you mentioned taking the battery out to charge when it's drawn past 50%. Is there some way to measure this, or are you going by estimated consumption? I saw on an auto/RV show that batteries should be charged when the voltage falls to 12.4, but it wasn't clear if they were referring to deep cycle batteries. 12.4 doesn't sound very deep to me. Mine reads 12.7 or more _after_ charging. I just recently got the multimeter so I have no idea what the battery reads during sailing season (which starts this weekend here). ...RickM...
Peter - you mentioned taking the battery out to charge when it's drawn past 50%. Is there some way to measure this, or are you going by estimated consumption? I saw on an auto/RV show that batteries should be charged when the voltage falls to 12.4, but it wasn't clear if they were referring to deep cycle batteries. 12.4 doesn't sound very deep to me. Mine reads 12.7 or more _after_ charging. I just recently got the multimeter so I have no idea what the battery reads during sailing season (which starts this weekend here). ...RickM...
Measuring
I should have googled first. I found a few charts on the web. They vary a bit. State of Charge Voltage 100% 12.7 90% 12.5 80% 12.42 70% 12.32 60% 12.20 50% 12.06 40% 11.9 30% 11.75 20% 11.58 10% 11.31 0 10.5 State of Charge Voltage 100% 12.7 75% 12.4 50% 12.2 25% 12.0 Discharged 11.9 Battery Voltage State of Charge 100% 12.75 75% 12.40 50% 12.20 25% 12.03 Discharged 11.80 ...RickM...
I should have googled first. I found a few charts on the web. They vary a bit. State of Charge Voltage 100% 12.7 90% 12.5 80% 12.42 70% 12.32 60% 12.20 50% 12.06 40% 11.9 30% 11.75 20% 11.58 10% 11.31 0 10.5 State of Charge Voltage 100% 12.7 75% 12.4 50% 12.2 25% 12.0 Discharged 11.9 Battery Voltage State of Charge 100% 12.75 75% 12.40 50% 12.20 25% 12.03 Discharged 11.80 ...RickM...
battery voltage
Be aware, to use battery voltage to determine state of charge the battery needs to sit about 2 to 3 hours with no draw or charging current applied to it for the readings to be valid. Another way to estimate SOC, when the battery is being charged with a relatively small charger like a solar panel, say 1-3 amps after a period of time, and the voltage is above 14 the battery is close to fully charged. If the voltage is below 12.8 volts the battery is below 70%. This applies to a relatively small battery bank, about 100 amp hours or so.
Be aware, to use battery voltage to determine state of charge the battery needs to sit about 2 to 3 hours with no draw or charging current applied to it for the readings to be valid. Another way to estimate SOC, when the battery is being charged with a relatively small charger like a solar panel, say 1-3 amps after a period of time, and the voltage is above 14 the battery is close to fully charged. If the voltage is below 12.8 volts the battery is below 70%. This applies to a relatively small battery bank, about 100 amp hours or so.
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