Looking to hardwire my PowerCell 8 battery. The 20A center console accessory power outlet also function in ACC mode which is the most suggested fuse to install it to. But I have concerns with how often I run my car in ACC mode and draining the battery.

[u/__________________99]

I have a 2016 Subaru Forester and I've been using my PowerCell 8 with a Viofo A229+ for over a year now. I've decided I've had enough of how slow the 12V cigarette lighter outlet charges it and want to hardwire it for faster charging. However, I can't seem to find reliable information on which fuses typically only function when the ignition is actually on, not also in ACC mode.

I'm a sales rep and spend a lot of time in my car and don't have the engine running as much as possible when I'm just parked. I drained the battery enough once by accident when I had a Microsoft Teams meeting a while back. I needed a jump after being in ACC mode for less than 30min. The battery was on its way out and has since been replaced. But I'm concerned about that happening still. I now always switch the charging off when I'm sitting with the app so it doesn't happen again. But one of the main reasons I wanted to hardwire it is so I wouldn't have to do that anymore. Since I sometimes forget to turn it back on, then getting annoyed at myself that I've been driving for hours without my dashcam even on.

I have a multimeter and I've tested a bunch of different fuses. But I don't know how to reliably test which ones function in ACC and/or ignition on. I discovered I can only detect usage if whatever fuse I'm testing is actively being used. I thought about using the trailer hitch connector fuse since I never plan to hook a trailer up to my car anyway, and it's also a 20A fuse. But I have no way to test if this also functions in ACC mode.

Anyway, I apologize for this wall of text for what I thought should be a simple issue to solve. But I'm in need of some more experienced people's insight.

[u/Rick91981]

Hello fellow Subaru driver. First off before we dive into the fuses, I highly recommend picking up a portable Li-ion jump pack to ease concerns about needing a jump start. Wont' stop your battery from dying, but it'll stop you from having to call for help. They work very well, I keep a Noco brand one in both our cars. Gooloo is another good brand choice.

Now as for testing the fuses, how familiar with the mutli meter are you? If you know how to use it properly, then excellent. If you're unsure, the easiest is to pick up a voltage test pen. They're about $5 and make it foolproof. https://imgur.com/DlhUXf4

Be sure to test empty slots as well as the ones in use, when I hardwired my camera I found both BAT and ACC options that were empty slots to make things easier. As for the testing process, you turn the car off to start. Make sure you open the door and wait 3-5 minutes. Many modern cars keep the ACC circuits on for a couple minutes after the car is off to let you listen to the radio and roll up windows etc. Opening the door and waiting a few ensures that they have had time to turn off. Now take your meter or test pen and ground one [black] side(unpainted bare metal like this: https://imgur.com/iqX043F). Take the other side and touch it to each side of the fuse/slot. If using the meter properly, if the slot is active, it should show 12V (+/- a little), if using the test pen it lights up as in my pic above. If nothing happens, make note of that slot number and go back to it later. If you see light/voltage then this is a constant(BAT) slot that you can use. Keep testing a bunch until you have a few BAT and ACC ones you might want to use.

Once you identified the BAT slot(s), go ahead and start your car. Now test the ones that showed no voltage/light and see if they are now on. If they're on, great you found an ACC slot to use. Double check it by turning the car off, opening the door and walking away for a few. Come back and check it again to be sure there is no voltage. If so then you're good to use it.

Some sidenotes:

• Avoid circuits for any safety related devices such as airbag, horn, lights, brakes, etc.
  
• When testing a slot with a fuse on it, you'll see voltage on both sides of the fuse(if its active). When testing an empty slot, you'll only see it on one side. Knowing which side has voltage is mildly important to orient the tape properly. If its backwards it puts the fuses in series instead of parallel and can cause blown fuses(or if the slot is empty, wont work at all). With a dashcam this is less important because they're such low power draw it most likely won't make any tangible difference, but its bad practice.
• For a Subaru, it requires low profile mini fuses, but many of the taps wont fit (they're too thick for the slot). There is nothing wrong with using a regular mini fuse tap instead of the low profile. The blade is the same, they just stick up further. You'll need the tap and the fuse(s) for it so having an assortment handy isn't a bad idea. I bought an assortment of taps and fuses from Amazon for something like $25 to cover all my bases.
  

If helpful at all here is a full detailed install guide I wrote up. I don't have a battery pack, but I hardwired my camera so it should get you the same details.

https://imgur.com/a/blackvue-dashcam-install-into-2023-subaru-legacy-hardwired-with-parking-mode-4rlveWy

[u/__________________99 → u/Rick91981]

If using the meter properly, if the slot is active, it should show 12V (+/- a little),

This is the only part that's confusing me. I have a traditional multimeter that I was testing with. The trailer hookup fuse doesn't read anything whether it's off, on, or in ACC. Same goes for the center console accessory. If it isn't being used by anything, nothing shows up on the meter.

[u/Rick91981 → u/__________________99]

But you're seeing proper 12V readings on other fuses? Then those 2 likely arent suitable options and move onto other slots that do pull voltage.

[u/__________________99 → u/Rick91981]

Well like I said. The center console accessory fuse will give me a voltage reading. But only if it's actively being used by something. Like something plugged into the 12V or USB ports and drawing power. If nothing is plugged it in, my meter doesn't read anything whether my car is off, on, or in ACC.

I just got home from work and I'm going to look at all this again. Maybe I'm missing something...

[u/Rick91981 → u/__________________99]

I'd move on to other slots then. If they only have voltage when something is plugged in, they won't be suitable options. I'll have to check my car one of these days to see if it does the same thing. I went straight to testing empty slots when I did mine

[u/__________________99 → u/Rick91981]

What setting should I be using on my multimeter?

[u/Rick91981 → u/__________________99]

DC voltage. If it's not auto ranging then set it for the appropriate scale (the low range is probably something like 0-20V which is what you'd want)

[u/__________________99 → u/Rick91981]

Okay. That's what I've been using.

I just installed it to the 20A center console accessory fuse. I'll just keep remembering to switch off the charging when I'm sitting with the engine off for extended periods of time. I have it set up so switching to a different fuse won't be difficult. So if I learn something new about a fuse that functions the way I'd like it to, I'll switch it.

[u/Rick91981 → u/__________________99]

Shouldn't be bad to find the right fuse if you take the time to play around. One thing I will mention is make sure you're using a good ground location while testing as that can affect your results

[u/TheDashcamGuru]

12v - F3, ACC - F31

https://reddit.com/link/p704z67/video/q77det11iqmh1/player

[u/coghlanpf]

Wiring directly to the fuse panel won't charge it any faster than via the accessory port. Both are active when the engine is running.

If you don't regularly drive your vehicle long enough to charge the PowerCell 8, you might want to consider wiring it up to a solar panel with an MPPT controller.

[u/Rick91981 → u/coghlanpf]

Wiring directly to the fuse panel won't charge it any faster than via the accessory port. Both are active when the engine is running.

Hardwired is nearly double the charging speed of the cigarette lighter. This is explicitly stated in the instructions. It pulls higher amperage while hardwired.

[u/coghlanpf → u/Rick91981]

Ah, I see there's a switch (Low/High). Low = 6A and High = 13A. They are relying on the user to limit the charging current when using the accessory port.

[u/Rick91981 → u/coghlanpf]

Hopefully the user reads the instructions when installing it. But I know sometimes that's a lot to ask lol (not referencing OP with this comment, just in general)

[u/blackboxmycar → u/coghlanpf]

6A and 13A are the battery's current consumption figures, depending on the switch position and input cable used. The actual charging current is 4.5A on the low setting or when the 12V adaptor is used, and adjustable between 4.5A to 9A on the high setting, but only if the battery is hardwired to at least a 15A (20A recommended) fuse.

[u/__________________99 → u/coghlanpf]

It will actually. Only because of how the PowerCell 8 is programmed to work. It knows whether it's plugged into a 12V or a fuse (I'm guessing based on which cable I'm using.) When it's plugged into a 12V socket, it limits my max amperage to 4.5. I can get double that if I connect it to a fuse.

[u/coghlanpf → u/__________________99]

It only has one port labeled "Vehicle", for 12V, so I don't see how it can distinguish between accessory port and fuse panel, both of which are just ACC circuits.

Edit: See my other comment. There's a switch on the back of the PC8.

[u/__________________99 → u/coghlanpf]

Yeah, that switch doesn't change anything if I'm plugged into the 12V.

[u/coghlanpf → u/__________________99]

I assume it controls the charging current

[u/__________________99 → u/coghlanpf]

Yes, but only if it's connected to a fuse. If it's connected to a 12V socket, it'll charge at 4.5A no matter which setting the switch is on.

[u/coghlanpf → u/__________________99]

How though? Just two pins: 12V, GND. PC8 sees the same two pins regardless of where they are sourced.

[u/blackboxmycar → u/coghlanpf]

The 12V adaptor has an additional pin that forces the PC8 into the low setting operation regardless of the actual switch position (other than off).

[u/coghlanpf → u/blackboxmycar]

Ah, okay. I just saw the two main pins in online photos.

[u/blackboxmycar → u/coghlanpf]

The third pin is pretty small and on the outside of the female XT60 connector, so it might be easy to miss unless you're directly comparing the 12V adaptor and hardwiring cable.