Adding second battery for fridge, wiring?

BroncoAZ

Veteran Member
Joined
Apr 25, 2009
Location
Flagstaff, AZ
TDI
2015 Touareg Lux, 2015 Passat 6MT, 2009 Jetta (long gone), 2011 Touareg (bought back 02/18)
I will be adding a second battery to my Passat to run my ARB 37 QT fridge. Can anyone tell me if I can run 1/0 gauge power cable through the firewall and where it could go? I could go with 4 gauge power cable, but with the potential for full alternator power to charge the rear battery I’d just assume go larger. I will be using a Blue Sea charge isolation relay and likely an Optima Yellow Top deep cycle battery. I was also considering running a smaller power sports AGM battery and mounting it somewhere further forward in the car but I need to calculate what the fridge will consume.

For those wondering why, I commute to Phoenix for a few days each week, the fridge allows me to bring all my food and save $$$. I’ve been running the 50 QT fridge in my Touareg for the past year, but the 50 would only fit on the back seat of my Passat so I ordered the 37 for the trunk.
 

BKmetz

Administrator, Member #10
Staff member
Joined
Sep 25, 1997
Location
Illinois
TDI
2015 Passat, titanium beige, 6MT
The VR6 equipped NMS Passats have the battery located in the trunk. The battery tray is along the left side of the trunk behind a side panel. You should be able to look up the parts and see what is involved if you want to go that route.

Installing the trunk battery tray, battery, and side panel would be easy. Fishing cables back there and tying it into the front battery would take some doing.

I found a link over at Vortex that shows the battery location.
http://forums.vwvortex.com/showthread.php?6035965-Trunk-Battery-on-the-V6

:)
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
The VR6 equipped NMS Passats have the battery located in the trunk. The battery tray is along the left side of the trunk behind a side panel. You should be able to look up the parts and see what is involved if you want to go that route.

Installing the trunk battery tray, battery, and side panel would be easy. Fishing cables back there and tying it into the front battery would take some doing.

I found a link over at Vortex that shows the battery location.
http://forums.vwvortex.com/showthread.php?6035965-Trunk-Battery-on-the-V6

:)
This is the best option for adding a second battery, in my opinion. You can even add isolation relays from an RV (or a V10 Touareg if you want to use stock VW parts) so that the fridge can't kill your primary battery.
 

Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont.
TDI
2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
Just for. What it's worth. Do you know how thick # 1 cables are. That's electric welding able size!
When I had a sailboat with 3 batteries, one for starting and two house batteries I had # 4 stranded cables connecting them all. For your purpose I would think # 8 at most or # 10 should suffice.
 

BroncoAZ

Veteran Member
Joined
Apr 25, 2009
Location
Flagstaff, AZ
TDI
2015 Touareg Lux, 2015 Passat 6MT, 2009 Jetta (long gone), 2011 Touareg (bought back 02/18)
The VR6 equipped NMS Passats have the battery located in the trunk. The battery tray is along the left side of the trunk behind a side panel. You should be able to look up the parts and see what is involved if you want to go that route.

Installing the trunk battery tray, battery, and side panel would be easy. Fishing cables back there and tying it into the front battery would take some doing.

I found a link over at Vortex that shows the battery location.
http://forums.vwvortex.com/showthread.php?6035965-Trunk-Battery-on-the-V6

:)
Awesome, thanks for the link. I was thinking of bolting an Optima battery specific tray there. It’s the only spot that won’t interfere with the trunk liner. I would prefer to have the battery on the passenger side to offset my weight on the drivers side, but it probably doesn’t matter. Here is the tray I was looking at:

https://www.amazon.com/Optima-Bille...1&ref_=ox_sc_saved_image_5&smid=A1TNMI4LHV0ZX

This is the best option for adding a second battery, in my opinion. You can even add isolation relays from an RV (or a V10 Touareg if you want to use stock VW parts) so that the fridge can't kill your primary battery.
I have purchased a boat isolator relay to keep the main battery from getting discharged:

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

Just for. What it's worth. Do you know how thick # 1 cables are. That's electric welding able size!
When I had a sailboat with 3 batteries, one for starting and two house batteries I had # 4 stranded cables connecting them all. For your purpose I would think # 8 at most or # 10 should suffice.
I wired my truck with 1/0 cable for the rear winch, I agree it seems overkill for this application but it is what’s recommended according to Blue Sea for the charge amperage. I think 4 gauge is plenty for the realistic load in this setup, I wouldn’t be comfortable with 8 gauge.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
1/0 would be overkill for a fridge. A winch draws some major amperage compared to a fridge. I would size the wiring based on the loads that you intend to pull. I think 4 gauge would be the way to go, but some wire size and load calculations would be a good idea.
 

jjblbi

Veteran Member
Joined
Sep 27, 2000
Location
lbi, nj
TDI
2014 Passat SEL TDI
Throwing out another option that may work for you: Yeti Cooler. Super insulated and portable may cost less although you'll need ice.

Good luck, John
 

BroncoAZ

Veteran Member
Joined
Apr 25, 2009
Location
Flagstaff, AZ
TDI
2015 Touareg Lux, 2015 Passat 6MT, 2009 Jetta (long gone), 2011 Touareg (bought back 02/18)
After already having the fridge on my Touareg for a year I don't think I could go back to ice and a cooler.
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
or move further north, for 4 months a year no fridge or ice cooler needed, constant temps bellow 30!
 
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