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Solar Trickle Charger

700 Views 6 Replies 4 Participants Last post by  TimSBLI
I just installed a 25 watt solar panel on my boat to keep the batteries fresh. I also installed a controller to make sure the batteries don't overcharge. The panel output was 21 volts before the controller according to my multimeter, after the controller it is also 21 volts. I would expect the output from the controller to be more like 14.5 volts. When connected to the batteries it drops to 11.8 ( the batteries are discharged) and the controller reads "charging". Is this normal?
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Thanks that's what i suspected but I just wanted confirmation. I did't want to overcharge the batteries. The boat is in a boat yard so I can't leave it plugged in to a charger unattended. For some reason they get all funny about leaving extension cords plugged int to tightly packed unattended fiberglass boats. The panel is rated for 25 watts, so if it shows 21 volts that are dropped down to 12, it's putting out 3-4 amps? I'll check on it tomorrow and see if the voltage improved. I hooked it up to the house bank, after the isolator. I am hoping that once they exceed 13 or so they will also charge the start battery.
yeah, thats right. the 25 watts is rated at 12 volts but the days are getting longer now, we will be at equinox in 3 weeks so I think I'll get a bit more sun.
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