Thread: 12V power in the rear boot.

Originally Posted by Bohica

The fridge draws 0.7 to 1.0 Ah
....

What fridge?
Proper fridge or a chiller (peltier) type?
I'd say max draw on the fridge will be more like 5A or so .. due to startup. once running yeah, they can settle down to 1A or so.
But I guess all that is dependent on the fridge.

If your cable run would do 15A without issue, I'd try to find an auto resetting circuit breaker type.
I fitted a 20A breaker to my D1 but can't think of ever running more than about 10A myself(but you never know).
The 12v plugs are capable of 10A or so, and most devices will be fused themselves anyhow.

I don't have a fridge(compressor type) but have an old chiller(peltier) from about 25 years ago. Draws about 4A constantly.
Stupid plug shyte itself and fused internally in the 12v plug(didn't know this at the time tho as the fridge was plugged in)

Anyhow, auto reset breaker did it's thing perfectly and just wouldn't allow any power down the line. Once I noticed all power ports and the volt readout all zilched .. penny dropped.
Had a peek in the 12v port where the fridge plug went into and noted the fitting ring on the end of its plug had got jammed in there.
The 12v plug I fitted to the fridge cord was one of those split types that uses a chrome ring at the tip to lock it all down, as it had a fuse in the plug head. Stupid things .. but that was almost 20 years ago too.
Pulled it out, power restored

From experience, I wouldn't use cigarette plugs for powering fridges. Much too unreliable.
All our fridge plugs are now 50amp Anderson plugs with cable sized to match, and fuses. The camper also has a separate master circuit breaker.
If both the fridge and freezer are running flat out trying to stay cold on a stinking hot day, that is a heavy power drain.

That also means I can plug solar panels with Andersons in and directly charge the batteries. I have metered up to 12 amps from solar going through 15 amp controllers into the batteries.
Its better to oversize and be safe.

Originally Posted by Tombie

USB and current require a bit more thinking

A USB port is nominally 5v @ 2a, that’s 0.84a at 12v (assuming no losses so let’s say 1a)

And the other thing to note with that is that it's unlikely that they'll even output 2A too.

I have many of them(4 in mine) 3 in brothers, and about 5 in my top drawer, none have even outputed more than about 1.1 -1.3 amps.
Maybe a higher quality 2A unit from a half decent manufacturer may achieve that, but not these generic Chinesium things.

measured using one of those USB power meters.
My Galaxy S8+ only draws 1 amp and my Lenovo M10 running Ozi and backlight full on draws a max of 1.3 amps on their respective USB-C cables(so it's not the cable).

so more like 5-7w at 12v is more like 0.5A max x 2 of them .. 1amp at 12v.

So don't assume that because the device is capable of drawing x amount of power that the USB port is going to give it that.

In saying that, I've yet to have any issues maintaining battery on the M10 tablet for hours on end, with the backlight on full during the day.

It is a compressor fridge freezer, 60L Adventure Kings.

Most plugs are maximum 1 amp. Some are rated 2 amp. Neither is likely to be enough for a fridge-freezer trying to stay cold in hot weather, in my experience. I suggest you fit a separate heavier power lead for the fridge-freezer.

Originally Posted by AK83

And the other thing to note with that is that it's unlikely that they'll even output 2A too.

I have many of them(4 in mine) 3 in brothers, and about 5 in my top drawer, none have even outputed more than about 1.1 -1.3 amps.
Maybe a higher quality 2A unit from a half decent manufacturer may achieve that, but not these generic Chinesium things.

measured using one of those USB power meters.
My Galaxy S8+ only draws 1 amp and my Lenovo M10 running Ozi and backlight full on draws a max of 1.3 amps on their respective USB-C cables(so it's not the cable).

so more like 5-7w at 12v is more like 0.5A max x 2 of them .. 1amp at 12v.

So don't assume that because the device is capable of drawing x amount of power that the USB port is going to give it that.

In saying that, I've yet to have any issues maintaining battery on the M10 tablet for hours on end, with the backlight on full during the day.

Our experience is that normally a tablet is okay, unless the charge gets really low, when it might only respond to 230 volts.

Originally Posted by DiscoMick

Our experience is that normally a tablet is okay, unless the charge gets really low, when it might only respond to 230 volts.

Huh? That makes absolutely no sense.

A tablet only responds to current / voltage in the correct range. If you have a suitable USB charger, putting out the correct current then it’s the same as a mains unit which is doing exactly the same thing.

Cables can and do have an impact on charging also. Cheap cables can be underrated and fail to provide sufficient current flow.

No idea why, cables are fine, only happened a couple of times when the tablet was really flat.