Updating Battery

Steve,
How much physical space do you have available ??

Maîneÿ . . .

Steve,

Not too sure of your question. The energy budget works like this :

The demand

The fridge is the big consumer. It will take about 4 amps when running, and if running as a freezer will run for much of the time. You are talking of a remote area trip - if that means in a desert in January, the fridge will probably run continuously and will probably not maintain freezer temperatures. If it draws 4 amps for 24 hours each day, that's 96 amphours per day. Add in some LED lights and call it 100 amphours per day.

That amount is the total capacity of your 100 amphour battery. In practice the battery will not be able to supply that much - it's good practice never to run a deep cycle battery down more than 2/3 of its capacity. Repeated deep discharge will seriously shorten the life of the battery.

The supply

Solar - An 80 watt solar panel will deliver up to about 5 amps if aimed directly at strong sunlight. If you are stationary and can harvest strong sunlight for say 8 hours, that's 40 amphours per day. If you're travelling, the vehicle should supply some charge to the battery and power the fridge too. Just how much charge will depend on the current carrying capacity of the wiring and connectors.

On the face of it - your demand is much larger than your supply, and within 1 or 2 days the fridge won't be freezing.

I think your question was - what is the biggest amphour battery I can run with the 80W solar panel? The simple answer is - as big as you like. The battery is there to provide storage, the panel is to provide electricity to the battery. The panel isn't concerned with the size of the battery. The battery however is very concerned that daily input should be big enough to at least match daily output. That is where your problem lies - demand far exceeds supply.

Sorry to disappoint, but those the facts.

HTH

John

steve
It seems your problem stems from wanting to use the Waeco on Freeze. There are alternatives to frozen food which would allow you to reduce the running time on the Waeco. Meat can be cryovac'ed, vegetables dehydrated. We have had numerous stays in the outback and never felt the need to take frozen food. I would suggest that your solar setup would probably run the whole system if you run the Waeco only as a fridge.

teege

"What is the highest A/h I can run on my C/T with 80 watt solar panel."

You can run any size battery with an 80 watt panel.

What you should be asking is "what loads can I run from an 80 watt panel ?"

A battery doesn't supply any power, it just stores it between charges from panel, alternator or generator.

"what size battery" depends on how long you want to power loads before recharging is needed.

Steve,

Good to see you got home OK from St George.
That Tvan is impressive.

I am going through the same calcs too.

We have the 30 litre old green engel, and some lights, running off a 50ah battery.
Up to now we could only stay stationary for about 2 to 3 days in colder climes, and about a day in hotter areas like FNQ and NT.

We don't freeze but cryovac our food, and run the fridge on about 2 to 5 deg.
Reckon that cuts our fridge power consumption by 25% to 50%, over freezing.
Depends on how many beers and wine goes in the morning for camp that night too :o)

Just bought a 80w solar panel, and I reckon we will be OK in cooler climates, and on the margin in warmer weather. Limit it to one or two beers a day, and wine at room temp and we will be OK for a good few days, such as 5 to 10. If we got an overcast or wet day (solar panel output low), or a heat wave (fridge use high), we might have to go for a drive for an hour or three every couple days until the weather changes.

Those are the variables I see. So your current 100ah battery might be OK.
Bigger battery, and rain, might mean the solar cell won't catch up on the previous night(s). :o) The solar cell really just delays the flat battery that could happen sooner or later.