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Unread 15th February 2009, 06:55 PM
Eastie Eastie is offline
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I have an inherent dislike for “bling” in circuits that is installed for supposedly useful purposes (but ultimately does little to understand the condition and time left in batteries). Typically it just adds more connections, more resistance, more heat and voltage drop, so that’s where’d start looking also.
It sounds like you’re working it through in a pretty logical fashion, so given the fridge is working some next steps you might want to look at are voltage drop and a bit further assessment of the wiring size and circuit connections.
From my experiences a lot of fridges can be finicky in not starting up straight away once they have been flicked off or cut-out due to low voltage – as you’ve experienced they do eventually rest and go again if they are getting enough volts and amps. I’m not sure why this is, but keep it in mind.
I’m wondering if the circuit’s got enough capacity for the juice the fridge needs, which is likely >12.4v and somewhere between 5-10 amps (probably at the higher end of this, and possibly even a higher spike upon startup) for the compressor to even think about firing up. A lot of fridges are spec'd to only cope with a 3% voltage drop = 0.37 volts.... not very much at all. I’ve never heard of a problem with a redarc isolator, so I suggest you leave that in place for now and bypass the jewellery in the battery box - if that doesnt work then diconnect the redarc and re-connect the battery box to see if it works. Hopefully it's just a case of a dead deep cycle due to excessive discharge. Here’s some other questions and areas to eliminate:
  • What size cable did you run from the battery to the redarc, from the redarc to Anderson plug and negative from the Anderson plug to earth? (hopefully no smaller than 8 B&S / 7.91mm2 copper conductor)
  • What sort of terminals have you used for the wiring? Did you crimp them or solder them?
  • Where did you earth the redarc? (did you earth it to an earth point or scratch paint off to ensure a good earth?)
  • Where is the Anderson plug earthed? (again, did you earth it to a chasis earth point or grind the paintwork off, not just put it under a bolt?)
  • Have you got a fuse/breaker in the cable to the second battery, if so is it auto re-setting? What sort of connection is it, crimped/soldered?
  • You are using the Anderson plug to connect the second battery right, not a cig plug?
  • Are you using a hella plug/socket for the fridge, or a normal cig lighter socket/plug? (normal ones can have problems with making a good connection)
  • You said it's possible that you’ve over-drained the deep cycle - how bad? to a point where it’s failed or not fully charging or holding charge?
  • How new/good is the car’s primary battery – is the red light on the redarc coming on within a minute of the car starting?
  • Have you got a smart battery charger (ctek or the like?) to keep your batteries fully charged?
  • Do you have a multi meter? If so, have you tested voltage drop in the circuits?
If you need help with testing voltage drop, follow this as it’s fairly simple with a multimeter: Turn the car engine and fridge on and make sure you have access to the power terminals of the fridge, either as they come of your second battery or more ideally at the fridge itself (which may mean opening it up). With the multimeter set to volts DC, connect the positive (red) test lead to the primary car battery positive (+) terminal, and the negative (black) test lead to the + terminal of the fridge (or fridge lead), this will give you a direct reading of the + voltage drop, make a note of it. Now connect the positive (red) test lead to the ground terminal of the fridge/fridge cord, and the negative test lead to the negative (-) terminal of the primary car battery. Your multimeter will again give a direct reading of the voltage drop, make a note of it. Add the two voltage drop figures obtained, and this is the total circuit voltage drop. If you are losing more than 1 volt (e.g. >7% given 12.4-13 volts) this may affect the fridge starting up, especially if the alternator is not giving 100% performance.
Another way to spec voltage drop in a design before install is = length of conducttor (m) x current (amps) x 0.017 divided by the cross section mm square of the conductor (sq mm of copper, not the plastic).

If you can get to a point where you know it's not the wiring or the batteries then check out the alternator. If this all comes up fine you know it's almost certainly the fridge and you will have some evidence to go back to ABR with to see what they recon.

As a work around you could attach the fridge directly to the andersons plug (make a short connection lead) and see if the problem goes away.

Last edited by Eastie; 15th February 2009 at 10:42 PM.
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