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Discussion Starter #1
Wondering what people are using the rear 12v for. Have some ideas but unclear about draining the car battery, if I can get a $20 inverter off amazon to use, etc.
 

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2007 Forester Sports XT 4EAT
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The rear cargo area 12V outlet is fused at 20A, so make sure what you plug into it doesn't exceed that. In addition, the 12V outlet has a thermal fuse attached to the back, that blows if the outlet overheats! :icon_eek:

The cargo area 12V outlet is switched... meaning no power unless the engine is running or the ignition switch is set to ACC.

Members have modified the cargo area 12V outlet to provide constant power. :wink:

The other option, for higher current needs, is to run a new cable from the engine compartment to the cargo area. This has been covered in other forum threads.

Also...
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Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2019 Forester Sport CVT
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10 Posts
I use mine to power a portable compressor when I need to adjust tire pressure, and for an electric food & beverage cooler when travelling.
 

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Discussion Starter #4
Nice, I like the air compressor idea. I have an electric inflatable air mattress pump which would be cool. How do you know if you are going to draw more than 20A? Any inverters anyone recommends? Is there a way to use a seperate car battery as auxillary power that gets charged through that port while driving?

Wondering if I could use some of these products on an auxillary battery and somehow have the battery charging while driving when hooked in? https://www.amazon.com/NOCO-GC017-Adapter-Socket-Battery/dp/B00G8WLX78
 

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Discussion Starter #6
So I couldn't just throw a battery in something like this https://minnkotamotors.johnsonoutdoors.com/accessories/battery-and-charger/battery-power-center then hook the 12v to the rear port and have the battery charged when the car is powered on? Sorry for my limited knowledge here. What is involved in wiring an alternator? Or, if I am looking to use the battery for 2-3 day excursions maybe it isn't entirely necessary to have it charging on the road and coukd be charged at home?
 

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2019 Limited
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I have a Bestek pure sine wave 300watt inverter (around 45.00) I use . Inverters are a whole subject unto themselves. Keep in mind many inverters need higher amps than a cig outlet circuit and should go directly to a battery. It depends on what your trying to power. The Bestek works fine in the back outlet for my 110v needs, but:

I just set up an aux battery for use in the 19 forester limited. It uses an agm battery in a minn kota battery box with an isolater and fused separate lines. (we camp off road and have an Engel fridge, and an air compressor that attaches, plus electronics.) The battery box goes in behind the driver seat and connects to the car via anderson powerpole connectors.

It can be easily unplugged and removed when not needed. Overkill if your you dont need power when the car is off.

This is my battery box. INPUT from car goes to a voltage regulated isolator I wired in the box with the agm battery that I had. The large 6gauge output cable attaches to the higher amp connectors. There are two cig outlets and a battery test light the box came with. All protected by breakers. The Big connectors are Anderson Powerpole

Both power sources (the start battery and the aux battery) must be fused.
My car battery has its cable running under the center console inside the cab (6 gauge). Its connector (75amp). The aux is placed behind the driver seat and plugged in when we need this.

I may do a DIY at some point if there is interest.


 

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The setup @turnkey describes seems pretty nice....
@Clef - The plug is designed for accessories... as in occasional use.
While you could use it on an ongoing basis, that was not the original intent.
While it can be wired to be enabled without the key, that would also mean an accessory left on by accident can kill your battery... especially one hiding in the back.
If you are out camping, the last thing you want to do is to hook up a high wattage appliance which can drain your battery leaving you stranded - thus the battery isolator comment, which is a good idea.

In my case, about the only time I've ever used the rear power port is when I need to add air to the tires on my trailer.
For some reason, it doesn't bother me that most of the time it isn't used.
 

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Discussion Starter #10
The minnkota battery boxes seem really cool. Newport Vessels make a similar one that also has a USB port and 12v which seems useful. Nit sure if minnkota has USB but not really a big deal.
 

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Discussion Starter #12
This seems like a cool isolator, I like how you could use the aux battery to jump the primary. Isolators could be too advanced for me at this time.

https://www.amazon.com/WirthCo-2009...0f-20&linkId=b318353b60ebc2ebc0f626729197bf30

I could also just use one of those battery tender trickle charges and the marine battery boxes and just have my battery charged when I head out. How many hours you think I could get out of a couple laptop charges, phone charges, a small radio and maybe some nighttime holiday lights or somethin?
 

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For your needs I think for most folks with your list you would be ok for a few days (using led lights etc). Batteries last longer if they are only drawn down 50% before recharging. So a 100amp battery gives you 50 amps of use... add up your requirements and do the math. If you use an inverter note they use their own power to do the conversion to 110volts (or whatever they are changing voltage to), so this loss of efficiency should be accounted for. I use a pure sine inverter in case electronics are sensitive to modified sine wave (most of the cheap inverters are modified sine.... or use 12volt appliances/tools.


If you dont need the battery recharged from the car, everything is simplified ... you can even mount the trickle charger in the box.
One person on this site uses a tool bag for his battery system. You can also charge your small electronics directly from the car while underway to lessen the loads at night , of course.

Hope this helps.
 

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Sahuarita, Arizona USA 2018 Forester Limited
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I use mine to power a portable compressor when I need to adjust tire pressure
I do, too, because if I plug my portable compressor into the dash or console box power port it blows the fuse.
 

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Discussion Starter #15
Thanks for the info! So would what this guy is doing in his element work? He doesn't seem to be using an isolator.
 

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That video shows a pretty funky setup, starting with the temp battery clamps on the aux battery... go over a bump, get a short , that sort of thing. You like to see a fuse installed near the battery. The system he set up appears to "slow" charge the aux battery with no way to shut off or control the charge if the battery is full (while the car is underway).

voltage sensing Isolators stop charging a battery when its full. Large occasional uses such as an air compressor might prevent the the battery from ever recovering although his power needs seem low.
 
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