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2007 Forester Sports XT 4EAT
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@Marija1204 welcome to the forum from Oregon!

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Bobby...

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2015 Forester CVT
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766 Posts
@Marija1204 I have just completed an extensive search for an inverter to use my other car's (Nissan Leaf) battery as backup power for the infamous California blackouts and have the following advice:
1. Stick with pure sine wave units. They are more efficient and your electronics will thank you.
2. If you are going to do a permanent installation, such as 110VAC outlets in the back of the console, you will need a compact unit that can fit in a small, well ventilated space.
a. keep at or below 300W due to cooling requirements. Consider mimicking the Subaru option. You can probably do it cheaper and better anyway.
3. For occasional use as a direct battery hookup, go big, like up to 3,000W constant power. This will run tools and appliances that have heavy starting loads. No need to be too compact here. spend money on the guts, not a fancy case.
a. consider using a 50A quick disconnect (Anderson connector) permanently wired to the battery.

Happy inverting!

GD
 

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2016 XT Premium
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299 Posts
Fully depends on what you intend to power with the inverter, and how it will be plugged/wired into the car.

The DC plugs in the car (at least my 2016) share a 20A fuse, and are individually rated to 10A, which is somewhat confusing. A 150W inverter should work fine in either DC plug, if the device you want to power pulls more than that, hardwire it to the battery with big wires. Your mileage will vary with loads surging over 150W, but continuous shouldn't be a problem at that level.

I have wired my car to power a fridge when driving/parked, and charge a 2nd battery that powers the fridge when camping. Its pretty easy to run wires for larger loads if needed. I considered inverters for both of these purposes, but DC-DC power ended up being the easier way to do it.
 

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2018 Forester XT Limited CVT
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1,526 Posts
I have just completed an extensive search for an inverter to use my other car's (Nissan Leaf) battery as backup power for the infamous California blackouts and have the following advice:
1. Stick with pure sine wave units. They are more efficient and your electronics will thank you.
2. If you are going to do a permanent installation, such as 110VAC outlets in the back of the console, you will need a compact unit that can fit in a small, well ventilated space.
a. keep at or below 300W due to cooling requirements. Consider mimicking the Subaru option. You can probably do it cheaper and better anyway.
3. For occasional use as a direct battery hookup, go big, like up to 3,000W constant power. This will run tools and appliances that have heavy starting loads. No need to be too compact here. spend money on the guts, not a fancy case.
a. consider using a 50A quick disconnect (Anderson connector) permanently wired to the battery.

Happy inverting!

GD
1. Pure sinewave is preferable, however they are not more efficient. The pure sinewave will cause fewer problems with your electrical loads though.
2. The most important installation issue is the voltage drop along the dc cables between the battery and the inverter. Voltage drop along these cables will cause the inverter to enter low-voltage shutdown during non-insignificant current draw. As an example, if you are going to run a 300 W ac load, you're going to draw approx 30 A from the battery.
3. You're not going to put a 3,000 W inverter in a Forester (3,000 W = 300 A dc draw). A 50 A switch is not going to cut it for more than a 500 W inverter.

For a Forester or similar vehicle, you won't be doing more than charging your phone or running a laptop or similar load, and I'd recommend you have the engine running since the vehicle battery is a starting battery and not a deep-cycle battery.

Find the power draw of the loads you want to run, and then see if the dc socket in the car can supply the current (at a decent voltage). If the socket can't supply the power, you're looking at direct connection to the battery. Remember to size the wire appropriately -- calculate the dc current required, calculate the voltage drop through copper, look up the wire gauge needed to provide the needed (or less) voltage drop, and as close to the battery as possible, install your overcurrent protection, sized for the gauge of wire installed.
 

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2018 Forester XT Limited CVT
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The DC plugs in the car (at least my 2016) share a 20A fuse, and are individually rated to 10A, which is somewhat confusing. A 150W inverter should work fine in either DC plug, if the device you want to power pulls more than that, hardwire it to the battery with big wires. Your mileage will vary with loads surging over 150W, but continuous shouldn't be a problem at that level.
Without breaking out the calculator, you can just divide by 10. A 150 W inverter will draw approx 15 A from a 12 V vehicle system. There is a bit of fudge in this approximation to account for efficiency and voltage drop. Using the sockets will incur additional voltage drop at the contact resistance (between socket and plug).

Also look at the inverter ratings. Some ratings are "surge" ratings, power that the inverter can supply for a short time, limited by the physical electronics and connections, and some are "continuous" ratings, power that the inverter can supply indefinitely given appropriate input, at a given ambient temperature.
 

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2015 Forester CVT
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766 Posts
1. Pure sinewave is preferable, however they are not more efficient. The pure sinewave will cause fewer problems with your electrical loads though.
2. The most important installation issue is the voltage drop along the dc cables between the battery and the inverter. Voltage drop along these cables will cause the inverter to enter low-voltage shutdown during non-insignificant current draw. As an example, if you are going to run a 300 W ac load, you're going to draw approx 30 A from the battery.
3. You're not going to put a 3,000 W inverter in a Forester (3,000 W = 300 A dc draw). A 50 A switch is not going to cut it for more than a 500 W inverter.

For a Forester or similar vehicle, you won't be doing more than charging your phone or running a laptop or similar load, and I'd recommend you have the engine running since the vehicle battery is a starting battery and not a deep-cycle battery.

Find the power draw of the loads you want to run, and then see if the dc socket in the car can supply the current (at a decent voltage). If the socket can't supply the power, you're looking at direct connection to the battery. Remember to size the wire appropriately -- calculate the dc current required, calculate the voltage drop through copper, look up the wire gauge needed to provide the needed (or less) voltage drop, and as close to the battery as possible, install your overcurrent protection, sized for the gauge of wire installed.
Allow me to clarify: Pure sine wave inverters are not more efficient than modified sine wave inverters. Most of the items power by inverters run more efficiently on a pure sine wave current. Efficiency counts on both ends.

GD
 

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3 Posts
Discussion Starter · #9 ·
@Green Darter
I am very grateful to you for sharing your best practices and experience! 😉🙂I will try to listen as much as possible😌

@asphaltaddict33
Thank you for reply! I want to connect a marching refrigerator, a pump for inflating a mattress and a boat, and some little things...

@Botnik
Thank you so much!🙌🙌🙌 I would be very grateful if you could suggest a variant from this list (automotivecraze.com/best-power-inverters-for-cars-and-trucks/) if it is possible, cos I'm not experienced in this and don't understand how to follow your recommendations in the last paragraph😅🙂
 

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connect a marching refrigerator
I'm not familiar with the term "marching refrigerator" - what is it?

It is much more efficient to connect your devices directly to 12V rather than going through an inverter. You can buy 12V charging adapters for all sorts of mobile products be it phones, laptops, iPads (maybe?) etc.. All my devices use 12V except for an inductive cooktop, toaster and kettle that I use on extended trips in the ute.

In the Foz I run a 50 litre 12V fridge and a 300W inverter off an aux 100 amp hour battery.

In my ute I run a 110 litre fridge/freezer and a 3000W inverter off 2 x 110 amp hour batteries.
 

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2020 Forester
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I just spoke to the Subaru dealer in West Hartford and was disappointed to hear that they do not recommend any inverter for the newer Forester (if not all the models) because they have seen problems with it disrupting the complex electrical system of these, specifically, my model year, 2020. They mentioned the sensors in the doors, the automatic ignition system and other aspects, and said if the inverter caused a problem, which they have seen, it would invalidate my warranty. Does anyone know of a work-around so that I have another way to power my laptop without risking disrupting the electrical system and having my warranty invalidated?
 

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2019 Forester Touring
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2,299 Posts
I, too, would like to know more specifics of the actual problems seen.

Still, depending on how the inverter is connected to the electrical system as well as the load, it’s entirely possible that an inverter could impact the electrics/electronics on the vehicle.

Modern vehicles of just about any make share this issue, since so many things are electrically controlled on late-model vehicles these days.
 

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2018 Forester XT Limited CVT
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Power inverters are very good noisemakers, but then so is a gasoline engine's ignition system. The charging system might not be that quiet either.
 

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Does anyone know of a work-around so that I have another way to power my laptop
Sure; you do not need an inverter. I have 12V chargers for all my gear, cameras, laptop, torches etc. Just look at the output specs of the laptop charger, plug type and polarity and search for a supplier. Maybe start with a google search "12V charger for xxxx laptop"
 

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2021 Forester Limited
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Years back, an inverter would not run a 110V refrigerator, the specs specifically said they would not power anything with a compressor. Things might have changed since then.

I have used my old inverter to run a crock pot when traveling a long distance to family gatherings so the food was hot on arrival. The crock pot was put in the trunk. I would not recommend doing this in a vehicle that does not have a closed trunk from the passengers. It would be bad if you got in an accident, and the scalding contents went flying.

But it's been quite a while since I have used it at all. It's been sitting out in my garage on a shelf for probably over 6 years, as I bought a generator for power outages.
 

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2018 Forester XT Limited CVT
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Years back, an inverter would not run a 110V refrigerator, the specs specifically said they would not power anything with a compressor. Things might have changed since then.
Inverters come in different sizes and capabilities. A passenger car may struggle with or be incapable of running an inverter of the required size.
 

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I have a 3000 watt invertor in my ute running off 2 x 110 amp hour aux deep cycle batteries from which I powered my house fridge / freezer during a recent power outage. (240VAC down here of course)
 
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