too big a battery?

[Czechmate]

Japanese built Engels with the mechanical thermostat are way better than the newer "platinum" hahahahhahaa series fridges with digital controls
Seriously all us 4wd guys should get degrees in marketing we'd be rich
I remember when clipsal started putting
"new and improved!" on all their gear
Which is Australian for used to be made in oz now made in china

 

[happy john]

A 23 year old Engel in near new condition sold recently for $700. It was a 39 ltr model, it shows the older models are keenly sought and highly regarded.

 

[jonney]

yes and the Engel fridge is not made of plastic either.

 

[KevinE]

We have a 105ah AGM battery in the back seat area of the car, powering a 45L fridge. It works! The battery is a year old & the volt meter shows 13.3V when its charged. Over 4 days in central Aust last winter it dropped to 12.6V in mid 30'sC temps every time. During our summer here down south the worst we got was 12.7V in temps over 40C after 2days. This was traveling out in the boonies around Pine Valley when it was stinking hot over the Aust Day W/E. Good luck with it!

 

[happy john]

Kev 13.3 is the resting charge after the charge is put in. 14.4 is what charges it properly. Tony will give his thoughts but we should be on the money.

 

[Old.Tony]

It varies on battery type but that's pretty close. 13.2V-13.5V is considered the ideal 'float' voltage range for a lead acid battery - this is the voltage that you need to apply to keep the battery at full charge. 14.1V is the charging voltage for a lead acid gel battery, and up to about 14.7V is the charging voltage for flooded cell (eg starter) or AGM batteries.

The reason for the lower voltage for gel batteries - slightly higher voltages cause the battery to charge faster but also cause minor bubbling at the surface of the plates in each cell of the battery. Flooded and AGM batteries can tolerate this without consequence, but imagine a bubble in jelly ... once it forms, it lifts the gel off the surface of the plate and it's the beginning of the end for the gel battery. That's why I don't like them - a small mistake is lethal.

Another issue that needs to be clearer - once a battery is charged, it should settle (after a couple of hours) at about 12.8V at full charge. A fully charged battery will show about 11.0-11.5V when drawing large current from it (eg starting the car). Voltage drop is normal. Relying on the "surface" or apparent voltage as an indicator of the battery's state of charge is a little misleading, because if you're drawing anything from it, the apparent voltage will be lower than what it really is. The best way of measuring a battery's capacity is to use a coulomb meter that tracks amps in and out, or unload the battery and let it rest a little before measuring it.

Wikipedia has a good page on batteries, how they work, charge/discharge voltages etc. It's worth a read if you want to understand the technical side.

 

[Boogieboots]

Ahh that makes sense. When I put my camping battery on to the charger every few weeks it goes to maintain quite quickly and is at about 13.3 ish when I unplug. A few times I have checked it a day or so later to find it at 12.8 ish and wondered if it has had the dick. It has never been discharged below 70%.