Charging time ?

Two to three days for each battery would be something to work on using say 6 amps for 5 hours as a conservative estimate.
Taking the batteries down to 11.5 would do them no favours at all.
The best way to have used the panels would have been to connect both batteries in parallel and charge them together from the panel, they would have run the fridge for a few days before needing additional charging and probably wouldn't have been dragged down so low either.

Bucky,

A 120W panel should deliver about 7 amps, or up to about 9 amps if using an MPPT controller. If you keep the panel roughly facing the sun for 6 hours, you will collect about 40 - 50 amphours a day.

How long to charge a battery that's been run down to 11.5V? That's not a good way to measure the state of charge of the battery. The measured voltage depends on recent battery history - at the same state of charge the voltage might be 11.5 while running the fridge, or 14.4 if the panel's pushing charge in, or anywhere in between. It takes hours for a battery voltage to stabilise.

I'd expect a 120W panel to keep up with the fridge demand unless the fridge is in the sun or running as a freezer.

HTH

John

Bucky,

To roughly work out how much current is being output by the panels I divide 75% of the rated power of the panel(=90w) by the battery voltage (=12v). Therefore the current output is 7.5 Amps. If you multiply this by 6 hours you get 45 Amps going into the battery in a day. If the battery is 11.5 volts to start with then it is flat so you need to put close to 80 amps back into the battery to fully charge it.

They would have to have the fridge on freeze and be sitting in the sun and be opening it all the time to use that many amps. I have used over 60 Amps a day with my fridge but not very often. Normally if it is set to 0 deg C it would use about 30 to 40 Amps on a warm day. Your panels should handle that if kept pointed at the sun all day.

Maybe the batteries weren't fully charged to start with or were old and not able to be fully charged.

Regards,
Bob

You need to ask -

- were the panels FULLY in sunlight i.e no shadow on even a part of them.
- were they placed so that the sun was reasonably close to a right angle to the surface.

I'm amazed how often I see people with their panels in the shade, e. leaning conveniently on the side of the van or tent - people seem to think that as long as there's daylight on them, they're charging fully.

Also people seem to think that if 5% of the panel is shaded, it will still put out 95% of its rated current !

Maybe Mythbusters need to work on peoples' misconceptions about Solar Panels.

"How long would it take me to charge an 80 amp deep cycle battery, that has been run down to 11.5 volts....?"

Is it a wetcell or AGM Deepcycle ?? Their ability to accept charge is very different.

Is that 11.5 volts measured while the fridge compressor is running, or after the batteries have had no discharge for several hours. A battery that's 90% full could indicate 11.5 volts under a heavy load.

12 volts DC "wasn't meant to be easy" !!!

" 2 * 80 watt deep cycle battery's,"

I assume you mean 80 AMPHOUR batteries

120W solar panel is not going to power a 60L fridge in March. If you were at a latitude comparable with Griffith the maximum you would get in a day is 36.82A further south less and further north more. Check out GD's solar hours web page.

A generator would have kept them charged.