Beat Auto Start/Stop with your own Brown-Out Buster

THE CHALLENGE: In an attempt to meet increasingly stringent emission standards, many new vehicles incorporate a feature called “Auto Start/Stop” that under specific conditions will turn off the engine, for instance while motionless at a stop light with the brake pedal depressed, and then turn the engine back on immediately when the brake pedal is released.  The feature is often indicated with an icon of a capital letter “A”, partially encircled by a curved arrow.

Unfortunately, while many components of the vehicle are upgraded to handle this new demand, it’s not uncommon for the voltage to drop momentarily as the engine is rapidly restarted.  If the voltage drops below the minimum threshold of your radar detector, it will reboot.

You can imagine the frustration as a radar detector beeps and whistles through its boot-up routine at every stoplight, and you might cringe at the wear-and-tear on the internal components as the voltage is repeatedly dropped and reinstated.

The makers of Valentine One created a solution to the problem called the Brown-Out-Booster (BOB), basically a miniature 12V booster in a plastic shell, with IN and OUT phone cable connection ports (technically known as RJ-11's).  It even comes with a convenient short “pigtail” cable.  Positioning the BOB between the original power cord and the radar detector provides just enough of a voltage boost to keep the radar detector running through the Auto Start/Stop cycle, so long as the voltage doesn’t drop out completely, or below a much lower threshold, usually 3-5V.

The problem?  The makers of Valentine One only sell peripherals to certified owners of their radar detectors, and even if you place an order on their web site and receive a confirmation, you’ll eventually receive an email from their Customer Service department demanding proof of ownership.

THE SOLUTION: So what to do if you own a different brand of radar detector, but still want the benefits of the BOB?  Roll your own, and call it your “Brown-Out Buster”!

With only four readily-available parts and a few simple tools, you can make your own voltage booster that will support your radar detector through the Auto Start/Stop process.  Bear in mind, this is NOT an “uninterruptible power supply”, and it does not have a battery or capacitor that will keep your radar detector running in the event power is removed entirely.  But it will continue to put out 12V of power even if the input power drops down to 3V, which is more than enough cushion for most modern vehicles.

This is where I put the disclaimer that you follow these instructions and use the components at your own risk, and I’m not responsible for any damage you may cause to anything or yourself as a result of this concept.

The voltage booster is a relatively simple circuit that will take a varying input voltage and attempt to output a steady (usually higher) voltage, in my case I set it at 14V to be safe.  NOTE: A “buck booster” does the opposite, and outputs a lower voltage than the input – be careful when buying components online that you don’t end up with a “buck booster”.

Using a simple potentiometer in the circuit, it’s possible (and critical) to “tune” the booster so you get a steady 12-14V output to feed your radar detector.  There is *no* way of knowing how a new booster is configured without testing it with a multi-meter, so don’t just plug one in and fry your radar detector with 30 volts.

INSTRUCTIONS: The following four components are available as of Dec. 1, 2017 on Amazon.com, along with dozens of other suitable versions on Amazon and eBay.  Bear in mind that you can order multi-packs of everything and make 4-5 boosters for not much more than the cost of a single Valentine One BOB.  Just think of how many new friends you’ll have!

Name	URL	Price
DC-DC Boost Converter, 3-32V to 5-35V, Adjustable XL6009	https://www.amazon.com/Converter-Voltage-Adjustable-Module-XL6009/dp/B01KUYERYA	$4.59
RJ-11 Female Telephone Cable Connector, 20 cm Wire	https://www.amazon.com/gp/product/B00N41BM0O/	$5.32
(4 Pack) Cable RJ-11 Male to Male 4”, Black	https://www.amazon.com/gp/product/B01MSRGB54	$9.99
(5 Pack) Plastic Project Box 60x36x25mm	https://www.amazon.com/gp/product/B00O9Y633G	$7.06

STEP 1:  Take the lid off your project box, and using a Dremel, small saw, or utility knife, carefully cut a 7/16” x 11/16” hole in each end (or sized to fit your particular female RJ-11 connectors).  Cut a similar-width piece out of the lid’s apron, and trim away any mount points that are in the way.  Test-fit an RJ-11 connector into each end of the box.

STEP 2:  Unpackage a voltage booster, and using a 12V battery or similar 12V power source clipped to the IN+/- terminals, connect an electrical multi-tester to the OUT+/- terminals. Turn the screw on the potentiometer until you get the desired output voltage.  I chose 14V to be safe.

STEP 3:  Paying careful attention to polarity, strip the wire ends on two RJ-11 female connectors, and solder them to the voltage booster.  For my unit, the Beltronics RX65, I opted to mount the connectors upside-down (like on the detector), and that meant the green wire was IN+, and the red wire was IN-.  NOTE: They swap on the other end of the board, green is OUT-, and red is OUT+.  Refer to the picture of the finished board below.

STEP 4:  Place the circuit board into the project box (line the bottom with a thin piece of non-flammable material to cushion the board if you’re so inclined), paying attention to which end is IN and which end is OUT.  Mark the outside of the project box somehow to clearly denote the IN and OUT ends. I chose a silver permanent marker. Pro tip: Don't mark the lid, which is reversible.

STEP 5:  Insert each RJ-11 connector into the hole you cut in the end of the box.  If the holes are too big and they are not friction-fit, you can use a dab of glue and tape them while it cures.  Place the glue on the inside of the box to preserve the looks on the outside. Once the glue is dry, you can safely replace the lid.  

STEP 6:  In your vehicle, plug your radar detector’s original power cord into the IN side of your new Brown-Out Buster.  Plug one of the RJ-11 "pigtail" cords into the OUT side of your Brown-Out Buster, and then plug the other end into the power port of your radar detector.  Test the performance of your Brown-Out Buster by starting and operating your car through several Auto Start/Stop cycles.

STEP 7:  If your Brown-Out Buster performs as expected, mount it near your radar detector with your method of choice.  I chose 3M Command Strips on the back side of the rearview mirror, which makes for a semi-permanent solution that is practically invisible.  If you use this method, consider sticking the lid to the mirror, then you can remove the unit for adjustment and reattach it to the still-adhered lid. Zip-ties to the mirror stalk are also a possibility. If your Brown-Out-Buster does not keep your radar detector from rebooting during Auto Start/Stop cycles, you may need to turn the potentiometer to increase the output voltage slightly until you get the proper level, but do so at your own discretion.

Pro Tip: Many radar detectors have a mode that will display the input voltage on the screen - if present, that mode can help you monitor the voltage for a while through various conditions (AC on, cooling fans on, high beams on) to ensure enough voltage is still available for Auto Stop Start.