You can try that but you may have a problem. Brother printers pull much more than HP printers. So you need to check the specs for your printer on how much wattage it uses. So for instance, my HP Laserjet Pro MFPM426FDW uses 600 watts. However, peak power is 1200 watts. That is why I have no problem using the 1500 watt sine wave inverter. But the Brothers usually use 1000 or more to run them and their peak power is closer to 3000 watts!
Our favorite printer is Brother. But, we cannot use them in the car because of the wattage they pull. They just won't work. Maybe that is why MMHOUGH was told by an electrician to use various batteries. However, if you use the correct inverter, the correct size and the correct battery, you don't need all of that.
Also, don't you have (google it) specific radio / burglar alarm systems installation shops in your town? They only install those types of items in vehicles and I find them knowledgeable regarding cables and they have them already available for the install. I wouldn't take mine to Best Buy.
Lastly, when you go to install it in your car, pay special attention to where it will actually be installed. You want to have access to it, regardless of the weather. I originally installed mine in the very back of my SUV. Then, when it was raining, I'd have to jump out to turn it on (although some do come with remotes that you can install in your dash which means you can them place the inverter anywhere in the vehicle). My sister installed hers in her trunk because it was a bulkier model than mine. But she has an opening into her backseat so she could get back to it through that opening, if it was raining or whatever. You never just leave the inverter on. Only turn it on, then back off, whenever you will be using it. So, I paid an additional $80 to have them move the inverter from the back of my SUV to under the passenger seat. So, when I need to turn it on (i feel it is safer to leave the car running while using the inverter) I reach over and flip the switch on the inverter. Since I leave the printer in the on position, once the inverter comes on, so does the printer. With my laptop sitting in the front seat, and of course, my phone is turned on as a "Hotspot", I am able to set the document to print and I can head to the next appointment while it is printing. When I get to a light, I grab the printed pkg off the printer and hit the "print" on the computer to print the borrower's package. So, by the time I reach my appointment, the packages are ready.
That is why I am able to accept more appointments than I usually would have so I make more money! But, I never charge for this service. This is a built in service that allows me to accept additional closings, but the title company or signing service doesn't care where or how you print, so it is not on them to pay you more.
Also, FYI, I have an all in one in my vehicle. However, I also have an Epson es-300w scanner which is so much faster than the scanner on the all in one. And, since it is small and compact, I can take it into nursing homes when I do power of attorney forms, and closings too....specially when I am closing with a small package since it is so fast. But I will also use this in my car instead of the big one. I just connect it to the same inverter and use the scanner in the passenger seat.
Good luck to you!