Battery Doctor Install on Second Battery-Solenoid/Relay Needed?

[Wmcatl]

I recently bought the GoWesty Auxilary battery bundle with the solenoid, etc.

I since read the suggestion on vanagonhacks to use a thicker gauge wire to create a more direct route from the starter battery to the auxilary, and to install a Battery Doctor isolator. I bought the supplies for this, as well.

https://www.vanagonhacks.com/2019/03/auxiliary-battery-kit-improvements/

Getting ready to install the GW kit, I realized that my relay was no good (barely showing any resistance with multimeter). I then started questioning if the relay and solenoid were even necessary if I was using the Battery Doctor relay? Is it? My understanding of the Battery Doctor is that it will switch to charge my auxiliary when the starter battery is fully charged (but avoid any drain on the starter battery once it gets below 12.7 v).

Per the Battery Doctor instructions (below), I would just connect this between the starter and the auxilary batteries (with a fuse between the isolator and aux batteries, I think), and then connect all the accessories (refrigerator, pump, etc.) off the auxilary battery terminals, right?

https://www.wirthco.com/documents/products/WirthCo%20Isolator%2020090%20and%2020092%20manual.pdf

Any concerns doing it this way?

(and I apologize if this was covered in another thread, but I really looked and did not see an answer there).

[MarkWard]

Looks like it takes the place of any relay that combines/isolated batteries. If you have the stock fridge, you may want to use a relay and wire it so the fridge runs on 12 volts only when the engine is running. This will keep you from accidentally running down the battery it is connected to because you forgot to switch the fridge off of 12 volt. If you have a compressor type fridge adding a relay is probably not necessary because you will be monitoring battery voltage. That type fridge won’t drain the battery as quick as an original dometic model.
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[crazyvwvanman]

If you still have the stock fridge then you should still use a small fridge relay to protect your battery.

The"Battery Doctor relay" eliminates the need for the big solenoid relay.

Mark

[svig]

I also have a WirthCo isolator. It works great and I can confirm that I ripped out the old GW solenoid.

But... can someone smarter than me tell me why they don't recommend putting a trickle charger on the primary battery and letting it charge both batteries during prolonged times of not using the van? Here's what they say in the manual:

[Wmcatl]

[MarkWard]

That would be a good question for Battery Tender. I did the same thing long ago. I later installed a real battery charger to take the place of the Tender. The Tender has some circuitry for "float" charging, that might not be happy with a second battery. I really don't know. Report back what they say.
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[Chestercopperpot]

I used a wirthco battery dr a couple years ago. Their unit will have some parasitic draw. You either need to have batteries charging or put a toggle on the chassis ground wire, for extended periods without charging. I have since replaced it with an Eaton 1315a. After a couple days trouble shooting with their support staff they offered me a wirthco kill switch as a solution...