Long ago, in the late 1990s, material about various mass interrupters or switches appeared. It was noted at the time that microelectronics had entered the automotive world, and adding extra mechanical switches could seem odd amid modern electronics.
Yet these devices still attract interest from many car owners today.
Advantages? There are at least three
On vehicles that idle more than they are driven, these switches reduce stop current leakage in external circuits, helping to prevent premature battery discharge.
They also help prevent possible ignition of a parked car due to wiring mistakes.
Finally, they function as simple anti theft devices by disabling all circuits, including starting. They resist code grabbers and other modern bypass methods and offer cost effective protection without easy means of tampering.
What are the disadvantages?
There are significant drawbacks to these mass switches as well.
Many modern cars notice even a brief battery disconnect. RAM may reset, errors can appear, and engine starting may be blocked, leading to service visits. Updating the clock on the instrument panel can become a frequent task.
For everyday use, mass switches are often impractical since not everyone wants to crawl under the hood each time.
Remote controlled models exist, but many switches suffer from contact resistance. During engine start up, currents can reach several hundred amps, and any added resistance can cause voltage drop. The energy is then wasted as heat, and the starter may not respond. The main electrical signal of these devices is the voltage drop across the switching element.
Experiment with the Drive
The decision was made to measure the voltage drop across the switching element first, so five mass switches of different types were tested.
In earlier work, experts noted that the voltage should stay under 200 mV at 50 A. The tests were made more challenging by briefly passing currents of 500 A through the devices, which is a common scenario in cold weather with a powerful engine and heavy oil.
Participants
A23–9B, PRC
| estimated price 1800 rubles Indicated switching current 300 (450) A There are not two operating positions of the switch, but three: in the latter case the handle can be removed. The contacts are closed by a rotating plate, which slides onto the fixed contacts from the side. This arrangement helps keep the contacts clean from oxides and deposits. If contact quality degrades, one can sometimes restore it through repeated switching. The unit mounts in a relatively large hole that may require a back panel modification. This holder suits larger vehicles such as SUVs, pickups, boats, or yachts. |
Ak Sa Battery Isolation Switch 06–013, Turkey
| estimated price 1100 rubles Indicated switching current unspecified The overseas switch presents a neat appearance. The control flag is removable, adding a layer of anti theft protection. The body is mounted with four brass rivets. A thick copper plate closes in the head of two copper contact bolts. Mounting the switch requires a custom bracket to shield wiring. |
VK-318B, Russia
| estimated price 350 rubles Indicated switching current 50A This switch appeared in the 1999 test but remains common. Activation is simple via a 90 degree turn of the plastic handle. It is unclear why the declared current rating is so low given real currents can exceed it. A noted weakness is its design to attach to stripped metal of the body, making a clean connection to the starting wire challenging without interrupting other circuits. |
External mass switch DVM1, Russia
| estimated price 5000 rubles Indicated switching current 250 (400) A The device resembles a junction box for industrial use. It features a fairly intricate electronic circuit controlled by a latch button, directing a two position mechanical relay. Even in rest, the circuit breaker draws only about 1 mA. The unit is bulky for a typical engine bay, but remote control improves usability. |
SD-004EU Stop discharge
| estimated price 4800 rubles Indicated switching current 520A The unit protects the battery from deep discharge during long parking or when a heavy load is left active. Its settings allow it to be a simple one device without manual intervention. For example you can set it to disengage shortly after a ride, at a battery voltage of 12.6V, or set a threshold near 11.7V for extended standstill. There are no mechanical contacts; a solid state semiconductor relay is used. The voltage drop remains small. A drawback is roughly 1.5 mA current draw even when all car circuits are off. Installation is straightforward, mounted directly on the negative terminal of the battery. |
Sum up
The tests produced satisfactory findings: none of the switches behaved like a heating element, and none imposed undue stress. The recommendations varied.
- For those unconcerned with anti theft features, the SD-004EU Stop discharge device is a good choice because it disengages the battery before starting becomes impossible.
- For drivers who want to avoid crawling under the hood, the DVM1 offers a convenient option that can be controlled from inside the vehicle.
The remaining options offer varying levels of practicality and aesthetic appeal; the choice largely depends on user needs and preferences.
Test results for mass switches
| Name | Voltage drop at 500 A, mV |
| A23–9B | 300 |
| Ak Sa | 260 |
| VK-318B | 160 |
| DVM1 | 200 |
| SD-004EU Stop discharge | 210 |
Vote and win a Lada
Readers were invited to participate in the Behind the Wheel Grand Prix vote to help identify the best car novelties of the year. As a thank you for participating, three prizes were offered to survey respondents who completed the questionnaire before the stated date in 2023.
COMPLETE THE 2023 DRIVING GRAND PRIX QUESTIONNAIRE