Thread: 2001 TD5 110 Alternator

I’m thinking of upgrading my alternator and was wondering if anyone has done it and what they upgraded to.
The reason I’m considering the upgrade is that I’ve just purchased a Jayco swan (swan) so I’m looking as to how everything can be charged up while driving.
The swan has a 12v battery and a 12v fridge. In addition I have dual batteries and a 40L car fridge in the defender. (When camping the fridge will got to gas.)


As I see it I have a couple of options.

1. When driving I can wire the Swan so the fridge is run off the car battery system so two batteries and two fridges running at once.
2. Alternatively have the swan fridge run off the swan battery and have the swan battery charging off the car while driving. I understand that the swan fridge is a fairly high drain unit. Off battery power you’ll only get a “few” hours.

I'm thing more option 1

An interesting exercise.

The 'worst case scenario' I see here from a design point of view is that if the 3 way fridge (which suck power like there's no tomorrow, but great on gas) in the Jayco is inadvertently left on 12V power, say overnight, it could completely flatten the Jayco battery. Depending how it was wired to the Dico it could flatten the Disco's aux. battery as well (assuming the Disco has a main/aux setup with isolation between batterys).
When you started the Disco (in this scenario) the current draw by the Disco aux battery, Jayco battery AND the fridge would be large and the cost of dimensioning the cabling/connectors able to support this current would prohibitive.

So the go is to avoid this problem (with smart design) in the first place.
What I'd do is this.

1/. From the +ve of the Disco aux battery I'd connect a 30 amp auto resettable circuit breaker to a length of 7 core trailer cable with all wires commoned and run this to an Anderson plug at the rear of the Disco. The negative wire from the Anderson connector I'd connect the same way to a good chassis earth.

2/. Make sure the trailer plug on the disco has the Auxiliary power pin connected (to +ve from the Disco aux circuit, not aux battery).

3/. In the Jayco I'd connect +ve from its Anderson plug via a set of 30 A relay contacts to the Jayco battery. The relay coil I'd power from the aux +ve from the trailer plug.

What this does is ensure that the Jayco battery is charged when the disco is running and that the electrical load of the Jayco is disconnected from the Disco when the engine is off.

4/. From the Jayco battery I'd run power to the fridge via another relay also wired to operate from the aux +ve.

This ensures that the Jayco fridge can only run from the Jayco battery when the Discos engine is running or it's key is in the aux position.

What this means is that it's practically impossible to leave the Jayco fridge on electrical power inadvertently thus avoiding my worst case scenario.

A simpler, though more expensive solution (to using relays) would be to put a low voltage battery cutout device between the fridge and the Jayco battery.


Deano