3 way fridge

Submitted: Monday, Mar 08, 2010 at 22:17
ThreadID: 76692 Views:2393 Replies:4 FollowUps:4
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Hi,could the forum please tell me the latest thinking with regard to running 3-way fridge on 12v while travelling.
Is it 1.Run fridge from van battery which is being charged by car.
Or 2.Run fridge from car battery direct while also charging van battery on separate circuit.
I ask this question because I was of the view as in 2 however a reputable 12v shop has advised me to install as described in 1
look forward to any help
kman
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Reply By: Batt's - Monday, Mar 08, 2010 at 22:23

Monday, Mar 08, 2010 at 22:23
Hey kman I use to run mine straight of the 2nd batt with twin core 6mm no problems.
AnswerID: 407960

Reply By: Member - Graham H (QLD) - Monday, Mar 08, 2010 at 22:35

Monday, Mar 08, 2010 at 22:35
Mine runs off 2nd battery with 8 B & S

Batteries in van charge off car via 6 B& S Both through a pair of Anderson plugs.

Battery wire has 60 amp resettable fuses at BOTH ends

Fridge has 25amp fuses at both ends.

Pin 2 on van 7pin plug has 6mm charging the breaksafe unit only.


AnswerID: 407964

Reply By: Member - Bentaxle - Monday, Mar 08, 2010 at 23:51

Monday, Mar 08, 2010 at 23:51
I run my camper trailer fridge from the battery in the c/t while travelling. This battery is being charged from my second battery in the Patrol while travelling via an Anderson plug. I believe this is the normal way.
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AnswerID: 407978

Reply By: Member - John and Val - Tuesday, Mar 09, 2010 at 08:19

Tuesday, Mar 09, 2010 at 08:19
kman,

Either should work, but option 2 is far better than option 1, though obviously more expensive.

Why? - The fridge draws at least 12 amps continuously when running on 12V. If connected directly to the van battery, both fridge and battery will draw current from the alternator while the engine is running. That 12+ amps being drawn by the fridge will result in reduced voltage reaching the battery so that it can never be fully charged.

In either case there must be a controller up front to disconnect the line/s from the vehicle battery when the engine isn't delivering charging current. If you do decide to go with option 2, it will also be necessary to disconnect the 2 lines independently, otherwise with the engine not running, current will flow from the van battery forward to the engine bay through the battery charging line, then back to the fridge through the fridge line. (I use 30A headlamp relays to switch these lines independently.)

Hope that makes sense.

John
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Follow Up By: Ray - Tuesday, Mar 09, 2010 at 09:17

Tuesday, Mar 09, 2010 at 09:17
On 12v my 3way runs off 150 amphr battery in the caravan but only when the engine of the car is running. I have installed a circuit breaker between the caravan battery and the 3way which opens and is deactivated when the car ignition is turned off but don't be skimpy with the cable size or fuses. I am using 4aswg cable to charge the caravan battery and 8aswg for the rest.
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Follow Up By: Member - John and Val - Tuesday, Mar 09, 2010 at 09:44

Tuesday, Mar 09, 2010 at 09:44
That's another good option Ray, but relies on very heavy cabling to minimise voltage losses, plus a second cable to operate the breaker when the engine isn't running. I chose to seperate the two current paths and break both circuits in the engine bay. Same number of wires, but avoids having the fridge current dropping the battery charging voltage. Provided good heavy wiring is used, as you have done, the losses should be very low.

Cheers

John
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Follow Up By: Member - shane (SA) - Tuesday, Mar 09, 2010 at 20:59

Tuesday, Mar 09, 2010 at 20:59
I went another way, I used 4aswg from the 2nd battery to the caravan through 175 anderson plugs and also put a 2nd 110amp alt just for charging the 2nd battery and van batteries.

cheers
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Follow Up By: Member - John and Val - Wednesday, Mar 10, 2010 at 07:21

Wednesday, Mar 10, 2010 at 07:21
Good way to go Shane, and offers the advantage of conveniently carrying a spare alternator - good to have if you are going into remote areas which we often do. I've looked at fitting a second alternator myself, but the mechanicals look like the sort of thing that could be left for another time!

Cheers

John
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