My new multitester came by FedEx. I was immediately disappointed that it was encased by a putrid green shell instead of bright yellow as advertised. Also the documentation revealed a DC volts accuracy of 0.8% error instead of 0.5%. My camper battery read 12.5 volts indicating 90% of full charge. With .5% error, it could be anything between 82% and 98% charged. With .8% error, it could be anything between 78% and 102% charged. Or it could be right on, and good enough for a $25 voltmeter.
I burned two ceiling lights (6 amps/hr.) for eight hours (48 amps) and the charge on the batteries dropped from 13.1 volts (slightly overcharged) to 12.1 volts (50% charge). That corresponds well with the rating of the batteries at 105 amp-hours (50% of 105 amps = 52.5 amps). I thought I had damaged my batteries by draining them down to zip a couple times in camp but I guess not. Even though they are "deep-cycle", it is said they begin to suffer damage if discharged to less than 40% (12 volts). The fact that I had recharged them using a generator may have saved them because a hard fast charge is a method for refurbishing sulfated batteries.
Today I tested to see how long my 80-watt solar panel takes to restore 48 amps to the batteries. 80 watts divided by a rated peak output at 17 volts would produce 4.7 amps so I figured it should do it in 10 hours of direct sunlight (48/4.7). We only had 5 hours of sunlight and the batteries were restored to 12.5 volts (80% charge). It would appear there is not enough hours of daylight on a Wyoming winter day for a single 80-watt 12-volt solar panel to completely restore all the charge that can be safely drained overnight from a 105 amp-hour battery. And that's no global-warming fabrication.
I burned two ceiling lights (6 amps/hr.) for eight hours (48 amps) and the charge on the batteries dropped from 13.1 volts (slightly overcharged) to 12.1 volts (50% charge). That corresponds well with the rating of the batteries at 105 amp-hours (50% of 105 amps = 52.5 amps). I thought I had damaged my batteries by draining them down to zip a couple times in camp but I guess not. Even though they are "deep-cycle", it is said they begin to suffer damage if discharged to less than 40% (12 volts). The fact that I had recharged them using a generator may have saved them because a hard fast charge is a method for refurbishing sulfated batteries.
Today I tested to see how long my 80-watt solar panel takes to restore 48 amps to the batteries. 80 watts divided by a rated peak output at 17 volts would produce 4.7 amps so I figured it should do it in 10 hours of direct sunlight (48/4.7). We only had 5 hours of sunlight and the batteries were restored to 12.5 volts (80% charge). It would appear there is not enough hours of daylight on a Wyoming winter day for a single 80-watt 12-volt solar panel to completely restore all the charge that can be safely drained overnight from a 105 amp-hour battery. And that's no global-warming fabrication.
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