FollowupID: 715568 Submitted:
Sunday, Jan 30, 2011 at 09:03
Being no expert I was always under the impression the solar
panel voltage of 18 t0 21v was only achieved under OCV and as soon as you connected it to a battery it would drop to the voltage of the battery.
AGM batteries do have to have a different charging limit to lead acid but that upper limit would not be achieved from 1 x 80 W panel being used to power a car fridge and the requirements of the van as well ie you would only get about 30 amps on a good day out of a 80 watt panel, IF it was a good day, and the fridge would draw if the temp was only about 30 degrees a minumum of 48 amps plus the other requirements so the chances of overcharging of the battery or even getting it up to float is highly unlikely.
All things being equal I would say fit a regulator if the application is permanent but for a trip away I would certainly not bother, I would just ensure that I monitored the battery .
I will insert here a post which virtually agrees with my theory
"PV panels are "current (amp) devices", so if you connect a 30V panel to a 12V battery, the voltage instantly (and harmlessly) falls to the battery voltage, and you are just pumping amps into the battery. Since 12v is way below the peak power curve of a 30V panel, you will not get full power, but more like the short circuit amps listed on the nameplate.
With an 80W panel, 120AH battery, heavy nighttime loads, and 1 week camping connected only, no controller needed."