Hi all we're looking for opinions on what to do with running power to 3 way dometic fridge whilst driving, I'd like to have our auto electrician run decent size cable through with anderson plugs but not sure to run through setec or go straight to fridge??? BTW my car has a smart alternator not sure if that matters...
17' Series DC power to fridge
- Thread starter MickyG83
- Start date
Go straight to fridge. Consider a fridge switch in the van or some sort of ignition controlled relay in the engine bay to isolate the fridge when parked up. Sorry don’t know much about smart alternators but I believe you connect the negative to the chassis before the battery and not the battery itself. I have the fridge switch and it does the job but next time will look at the relay because if you won’t be connecting/disconnecting in stop/start traffic or the like.
I agree with @MDS69 . A separate heavy cable from tug battery to Anderson plug at rear, connected to van and fridge terminals with another Anderson plug. No need to go through Setec. To isolate tug from van to prevent fridge draining tug battery when tug engine not going, you definitely need some sort of switch in ignition line if you can remember to switch it OFF when engine not running AND switch it ON again when engine is running. You can also have a relay connected to your ignition line so that when ignition is on, so is power to fridge. Remember, if cranking tug engine with switch on, you are putting extra load on starting battery, probably at least 15 to 20 amps.
Myself, I don't depend on my memory. I would go for a fridge switch or better still a voltage sensitive relay (VSR). I have the latter and although it may cost more, it is ALWAYS supplying power to fridge whilst tug engine going. Fridge switches depend on movement, so if tug and van not moving, fridge switch cuts power after a short delay. Not good if stopped for a while at traffic lights or road construction or any hold up causing you to stop for a time. VSR only cuts power if battery voltage drops below 12.8 volts and cuts in again (automatically) when voltage above 13.2 volts. Your choice there but be careful if "smart" alternator drops voltage too low!!
If your car has a "smart" alternator, you are unlikely to get any useable voltage/current to charge van battery if that was necessary. To overcome that, you need to have a DC to DC unit fitted. See attached. By having a cable connection direct from Tug battery to fridge terminals (through ignition switch, fridge switch or VSR), you do not have to worry about alternator type as it will always provide sufficient current (regardless of voltage fluctuations).
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Direct cable run via andersons to fridge as stated above, regarding smart alternators it really depends on the vehicle, not all are the same and even model year can be different set ups, some supposedly smart ones aren't really, so best to get the correct information on yours, usually not from a dealer ....... Ford Rangers of a few years ago direct POS to the actual POS terminal on battery and NEG to chassis/battery ground point not on battery but later models need something different...... then Jeep Grand Cherokees have a jump start points under bonnet, AGM under the seat, no smart alternator so hook up is simple, straight onto jumper points so you know the wiring is certainly HD.
I prefer the Fridge Switch located in van, stopping in traffic really isn't an issue, maybe if you were stuck for an hour or so and in that case you wouldn't be idling the engine that long anyway, besides I have forgotten to turn my fridge on to 12v and went for 5 hours in 35 deg back of Winton and it had an increase of 2 deg, so a fridge switch set up in the van isn't going to make any more difference than opening the door ................ In all my travels accidents have held me up for hours but then we sat in van with fridge on gas having a cuppa.............. Ideal fridge temp is fridge 4 deg, freezer -12 ....
I prefer the Fridge Switch located in van, stopping in traffic really isn't an issue, maybe if you were stuck for an hour or so and in that case you wouldn't be idling the engine that long anyway, besides I have forgotten to turn my fridge on to 12v and went for 5 hours in 35 deg back of Winton and it had an increase of 2 deg, so a fridge switch set up in the van isn't going to make any more difference than opening the door ................ In all my travels accidents have held me up for hours but then we sat in van with fridge on gas having a cuppa.............. Ideal fridge temp is fridge 4 deg, freezer -12 ....
Fair comment @Drover , especially regarding length of time when stopped. I certainly would not keep the tug engine idling for long periods either just to keep fridge going. Switch over to gas in that case - if level enough!!
Hi,
an absorption fridge, when stationary, needs to be level to work properly and avoid damage regardless of whether it is running on 12V, 240V or Gas.
This requirement to be level is NOT needed whilst the van is in transit. The rocking motion during travel is enough to ensure the fridge works correctly and is not damaged. Obviously, this is only practical if the fridge is being powered by 12V.
This is explained in the Dometic User's manual.
take care
Mike
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I just upgraded the 12v wiring directly from battery and ran it through a relay. Works perfectly, see this video. It was VERY easy, once I bought the right parts required. See video. If you are charging your batteries whilst towing and use gas once setup. This is a very good solution as the video explains the standard wiring is poor quality and this mod will assist the fridge working better on 12v.