Size of solar maintainer for car battery?
Had a 2.4W panel for $30 or so, on my truck while in storage. Seemed to be adequate at latitude 27 with plenty of sun and almost no clouds. Flat on the roof. Didn't worry much because the battery was...
Forum Discussion
Zero parasitic loads in truck. No LED/LCD display when off, no nothing. No engine computer - this is 1993 truck.
Was watching it for a week. 2.4W panel keeps battery at 12.6 at dawn, can't raise voltage any higher, but battery is almost dead. Borrowed another used battery for a week, in a better shape - panel brought it up from 12.67 to 12.71 at dawn after 2 days, and was keeping it at 12.71.
2.4W/18Voc = 0.13A Isc. 0.13A*6hrs = 0.8 AH a day. This is what I'm getting most of the days. Clear desert skies, Lat 27, plenty of sun. Hot weather in summer should cause high self-discharge, and this is what I was trying to find out. Ballpark figure for self-discharge of NEW battery of this size is 0.4 AH a day at 77F. So... say, 0.8-1.0 AH at 100F.
From experiments it looks like 2.4W was doing its job. Or almost doing. Will give it a try with new battery - regular wet. $200 AGM is too much to swallow.
MEXICOWANDERER wrote:
... connect the panel you have now, then two weeks later check the voltage at the battery terminals. Do this before the sun has a chance to recharge...
Was watching it for a week. 2.4W panel keeps battery at 12.6 at dawn, can't raise voltage any higher, but battery is almost dead. Borrowed another used battery for a week, in a better shape - panel brought it up from 12.67 to 12.71 at dawn after 2 days, and was keeping it at 12.71.
2.4W/18Voc = 0.13A Isc. 0.13A*6hrs = 0.8 AH a day. This is what I'm getting most of the days. Clear desert skies, Lat 27, plenty of sun. Hot weather in summer should cause high self-discharge, and this is what I was trying to find out. Ballpark figure for self-discharge of NEW battery of this size is 0.4 AH a day at 77F. So... say, 0.8-1.0 AH at 100F.
From experiments it looks like 2.4W was doing its job. Or almost doing. Will give it a try with new battery - regular wet. $200 AGM is too much to swallow.
