what size batterys/solar panel do i need ?

Phew!, what size? How long is a piece of string?

The bigger the battery capacity, the longer you can draw on it before needing a recharge.

One of the biggest problems is the "footprint" size of the battery that will fit in a second cradle, mounted in the engine bay.
Unless you have "heaps" of room, I would suggest an 80Ah deep cycle battery in AGM construction would be about the limit. This would be suitable for for the 29 litre Engel and should get you at least a couple of nights running before recharging the auxiliary battery via the vehicles alternator. An AGM battery, although more expensive to purchase, will charge quicker and more fully than a conventional "wet cell" battery. To control this dual battery system, you will need a dual battery controller which will give priority to charging the starting battery, then once it has reached a certain capacity of charge, the controller will swap over to the auxiliary battery. This will happen within a couple of minutes if the starting battery is in sound condition. The Dual Battery Controller, providing it is a "smart" one, will also keep the starting and auxiliary batteries electrically isolated from each other.

Now for the camper battery. The best way to charge this one is via an Arrid twin charge controller which limits the need for heavy duty cable all the way through the vehicle and on to the camper via Anderson connectors. The twin charge controller takes a lower input voltage and boosts it as output to the camper battery therefore restricting any impact from voltage drop.

Mate there are other options, some cheaper perhaps, but the above configuration is the most common for multiple battery charging as you have defined and will give you trouble free operation.

Brad

What do you drive ?

Have you got any of the mentioned items already ?

Regards

Derek.

Try and get the biggest AGM batteries you can fit and afford. 100-120 amphr - Fullrivers or Lifeline are good brands. around $300
If you're camped without driving for a week you'll need at least 2 x 90-120watt panels. There huge so a lot mount permanently on the roof rack.

To give you some perspective we have 3 x 120amp AGM's and 3 x 120watt panels and we still come up short and we're economial with our usage.
John

Brad
You post-> ""i have the 2 fridges, & led lights and a 75amp hr n70z wet cell from a previous 4wd, but dont mind buying a new agm .
after reading the thread re: solar panels , i think i should rephrase the question, here goes, how much power will the 2 fridges use (MAXIMUM) in a 24 hr period ?

Buy 2 x new AGM's - give the wetcell to a family member lol

-> {Assumption: the fridge draws 2.5ah} 2 x 2.5ah each = 5ah x 24 hours = 120 Amps per 24 Hour day.
-> the lights after dark 5 Amps

two fans running at sleepytime another 20ah -> at least ???
the odd dvd on the laptop ->???

if i have 2 x 100ah batterys in parralel is it ok to discharge them to 50% daily and what wattage solar panels will i need to charge these back up to full capacity each day
-> when we know the Amps used we can answer the question, unless you will accept a realistic guess.

As MOST of you power consumption is used at night and no solar power supplied during that time you have to be sure of the numbers relevant to the "fans" and "dvd on the laptop"

You will need at least a 85 Watt panel to replace the 5 Amps the 2 x fridge's will use during the day and maintain the voltage left in the battery at dawn.
Depending on the *QUALITY* of the AGM batteries, you will probably have close to 12.5 Volts in the battery at dawn, (My agm system is 12.8v each morning, running only 1 x 2.8ah F/F & lights etc) however a cheaper battery system will be lesser voltage.

If you have 2 x 100ah agm's you should have no major problem with power consumption, UNLESS the fan or dvd uses excessive power.
Solar panels should be able to replace whatever is used by fan and computer on inverter, my guess would be 2 x 100 or 2 x 120 Watt *quality* panels will suffice.

Mainey . . .