WK2 Dual Battery Set Up

[Jasman]

Hey Scarps, thanks for sharing your install. I was wondering if you've run any test on the charging capacity of the alternator as I've read in some other forums that the WK2 has a smart alternator that shuts down when the main battery comes upto voltage and the only option is a dc-dc charger? Any comments would be appreciated.
Jasman

[Savvas]

Nice work Scarps and JnK.

Jasman ... All alternators stop charging once the battery gets up to its correct charge, by way of a regulator. So the WK2 is really no different in this regard other than its just a more design modern.

The problem with an alternator though is that it cant charge a deep cycle battery fully or at the correct rate, as they are only made to get a starting battery to a voltage that can start the engine.

A good DC-DC charger is used to charge an auxiliary battery at the correct rate and to get it to the correct voltage. Which in turn gives you the maximum charge and maximum battery life too.

[scarps]

Originally Posted by Jasman

Hey Scarps, thanks for sharing your install. I was wondering if you've run any test on the charging capacity of the alternator as I've read in some other forums that the WK2 has a smart alternator that shuts down when the main battery comes upto voltage and the only option is a dc-dc charger? Any comments would be appreciated.
Jasman

Hey Jasman, I've been running the Piranha unit now for a couple of weeks and without fail so far, prior to starting the ignition, the 2nd battery guage reads about 13v, then approx 30 seconds after I start the motor, I can hear the Piranha unit switch in and the 2nd battery guage kicks up to approx 14v and sits there until around 15seconds after I shut the motor off and I hear the Piranha switch off. It's winter here at the moment and I'm not using the Waeco that is connected to the 2nd battery, so no power draw. So I can only assume from this that the 2nd battery is fully charged, the Piranha is working and at no time is the alternator shutting down. If it did, the guage would drop back while driving to the 13v mark.
Hope this reads right, but if you need more info, let me know.

[scarps]

Originally Posted by Savvas

Nice work Scarps and JnK.

Jasman ... All alternators stop charging once the battery gets up to its correct charge, by way of a regulator. So the WK2 is really no different in this regard other than its just a more design modern.

The problem with an alternator though is that it cant charge a deep cycle battery fully or at the correct rate, as they are only made to get a starting battery to a voltage that can start the engine.

A good DC-DC charger is used to charge an auxiliary battery at the correct rate and to get it to the correct voltage. Which in turn gives you the maximum charge and maximum battery life too.

Thnx Savvas. I will also be adding a Redarc DC to DC unit to my system in a couple of years (when I add the caravan to the back of my rig) to charge the van batteries, but like John, it will be wired between the Piranha unit and the caravan battery.
From what I also understand, the Redarc unit also allows me to use smaller cable over the distance to the caravan battery without significant power drop.

[scarps]

Originally Posted by scarps

Hey Jasman, I've been running the Piranha unit now for a couple of weeks and without fail so far, prior to starting the ignition, the 2nd battery guage reads about 13v, then approx 30 seconds after I start the motor, I can hear the Piranha unit switch in and the 2nd battery guage kicks up to approx 14v and sits there until around 15seconds after I shut the motor off and I hear the Piranha switch off. It's winter here at the moment and I'm not using the Waeco that is connected to the 2nd battery, so no power draw. So I can only assume from this that the 2nd battery is fully charged, the Piranha is working and at no time is the alternator shutting down. If it did, the guage would drop back while driving to the 13v mark.
Hope this reads right, but if you need more info, let me know.

Thought more about this today while driving, and at some stage the alternator would shut off, but suspect that would be programmed to occur when the battery is at an optimum charge. Potentially because of the dual battery set up, the alternator is trying to charge up the 2 batteries atm.
I'm driving to Sydney today from Melbourne, so will watch to see what happens.
Would also suggest that the battery guage would be reading the power rate from the 2 batteries when the Piranha solenoid is open.

[Jasman]

Thanks Scarps and Savvas for the feedback, I've been making plans for a camp trailer and want to make sure I do it right.

[Savvas]

Scarps,

Can you post a photo that shows where you put the battery? You mention it's strapped to the rear seat mounts, but I'm having trouble visualising it.