Hi All,
Just a quick that's not of utmost importance but would love to know.

I have a dual battery system in my camper. The 2nd battery is 75AH. I was wondering how quickly it would recharge with the engine running?

Basically I do a fair bit of camping and run a fairly efficient waeco fridge. And am trying to work out how often I would need to drive to keep it charged when on a trip and if it's worth getting a solar panel?..

Any feedback would be great and much appreiated.

Cheers,
Dustin

Try overlander.com.au.. lots of dual battery info there, but I reckon the tiny genny on a VW will need to be run for about 2hrs a day to keep up

Hi
You really need two batteries the same... amp hours..

what I did years ago in a mitsubishi L300..
two batteries... one connected normally... for the starter motor only... [and ignition]

the other battery was wired thru a heavy duty relay and was connected in parallel to the other battery when the ignition was turned ON...

so the 2nd battery was used with the ignition off...
for anything... can be flattened...

turn the key and the Main battery starts the engine and the 2nd battery is connected via the heavy duty relay...
and will be charged...

Buy a cheap digital multimeter - Dick Smiths etc..

and measure the battery voltage [2nd battery - Ignition - OFF - ] then drive around - turn engine off and measure again...

the BEST part is...
the Main battery will always be charged...
[unless you have the ignition ON]

cheers

LEE


I hope You can understand that OK... took a bit of thinking.. lol

Reality sucks on this issue. I have a 80 liter Waco fridge, and I have lived on boats with only solar charging for quite a few years, I'm trained as an electrical fitter and mechanic, and I have been playing with 12 volts for most of my life. The waco fridge in my present transporter (80l) can only sit on the spare battery for a day or two before it will need charging, I run it on a 75 W solar panel and it will run almost indifinately like this only when good sunlight is on the panel ALL day. With only the engine charging the batteries, to replace say 24 hrs of use by the fridge, you'll probably need to run your engine oooo about 6 - 12 hours depending on if your driving or not, how good condition the battery is in, what the ambient temp is and how full do you need to charge it. This last point is dependant on how many days you intend to be 'out there'. Sounds like a rediculous amount of time but unless you understand the charging characteristics of a standard alternator and regulator you probably wont believe this. Most dual battery change over relays designed for isolating the battery but connecting to the car when the engine is started and the alternator charging, are of a design that inherently reduces the charging voltage by .4- .7 v, which is enough to also limit the amount of charge this aux battery receives. I have wired my own car system with a manual relay that the driver turns on or off to maintain a full charging voltage to both batteries, this system works well,as long as you remember to 'flip the switch'. There's heaps more on this subject, many books even, so that will do for starters. Hope it helps.

Thanks for the feedback, it all helps paint the picture. The system I have installed is the automatic charging and isolated with ignition off.
It's good to get a bit better idea about it all. The Waeco I have is around 50 litres so presumably a bit less drain than 80. By the sounds of it the charge time is going to be quite variable.

The sysytem is just a basic solenoid by the looks of it, I'll have to check with the multimeter what it's actually charging at with the car running. Is there a particular level that's optimum?

Thanks for all the help and tips, guess I'll have to do a few more trips to get a better sense of the capacity and whether a bit of solar might be worth it... A 75w panel would be good, but pretty expensive and rather large... I'll suss it all out a bit more

Better on your alternator if there is at least some solar charge help.