Can I charge a 12v U1 sized battery via my 4x4's 12v accessory plug?

[off-roader]

I know it can be slow charged this way, but I'm worried it could possibly be overcharged since there's no overcharge protection.

Intent is to use the battery (deep cycle agm battery) to power my ARB fridge in camp at night and recharge them when driving on the trail during the day.

TIA.

 

[4x4junkie]

As long as it's a normal 12V lead-acid type battery (AGM or otherwise), no chance at all you'll overcharge it (your vehicle's electrical is already regulated so as not to overcharge it's own battery). What is more likely is it'll never reach full charge (or will take hours & hours of driving) due to the resistance of the wiring to your accessory socket (and that of the socket & plug itself).

Guessing it's a portable setup?
What I would suggest is run a separate power connection with say, #4 or #6 wire minimum to where it is you need it, then have something right there to plug your fridge battery setup into (I would suggest connectors having low contact resistance such as Anderson PowerPoles). This will give you a good high-current charging circuit that should be able to top off your aux battery at almost the same rate as your vehicle's own battery.

 

[off-roader]

In actual use it would be a days worth of driving off road. Another guy I know already has this setup & it charges the battery fine but I was just worried about the potential of overcharging the battery. I realize now that since it's a regulated 12.x VDC at that port there's no possibility it would overcome the full charge voltage of the battery.

Oh, and yes it is a portable setup. I think for now, using the stock rear power port is sufficient to maintain the battery's charge daily. For days where I'd be stationary, I realize I'd need a different plan for the fridge/charge port.

 

[4x4junkie]

Yea you'll probably be fine with driving that much then. Just use the biggest gauge cord you can that's practical for it.

Just a FYI, full-charging voltage should be around 14.4 VDC, but does vary slightly with temperature (higher when colder). An hour or so after engine-off you should see 12.6-12.7 VDC on a fully-charged battery.

 

[off-roader]

Thanks!