It was a long time ago – back in the last millennium. In 1999 we published material about various interrupters (switches) of the “mass”. And already at that time it was noted that microelectronics had come to the automotive industry, and therefore the installation of additional mechanical switches may seem strange.
However, for many car owners they are of interest even today.
Advantages? There are at least three
On vehicles that are idling more than driven, these switches shift stop current leakage in external circuits, preventing premature battery discharge.
At the same time they prevent possible ignition of a parked car due to wiring errors.
Finally, these are the simplest anti-theft devices that disable all circuits, including starting. They are not afraid of code grabbers and other modern features. And in fact there is nothing to break into. And the prices are not exorbitant.
What are the disadvantages?
The disadvantages of the “mass” switches are also enough.
Many modern cars painfully notice even a momentary disconnection of the battery – the RAM is reset, a certain error is fixed, sometimes the engine starting is blocked – they say, welcome to the service. And changing the clock on the front panel every time is an activity for the patient.
For everyday use, the “mass” switches are also generally not suitable: not everyone wants to climb under the hood every time.
However, there are products with remote control. But the main drawback of many of these switches is related to their contact resistance. During engine starting, the current in the regular circuit reaches several hundred amps, and any additional resistance can greatly reduce it. In this case, all the energy will be spent on heating this contact, and the starter will not even flinch. Therefore, the main electrical indicator of such devices is the magnitude of the voltage drop across the switching element.
Experiment with “Drive”
We decided to evaluate the magnitude of the voltage drop across the switching element first, having purchased five “mass” switches of various types for testing.
In our previous work, NIIAE experts pointed out that this voltage should not exceed 200 mV at a current of 50 A. We decided to make the tests more difficult by briefly passing currents of 500 A through the tested products: for the Russian winter and a powerful engine with thickened engine oil, this is quite a normal value.
Members
A23–9B, PRC
| estimated price 1800 ₽ 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 creeps onto the fixed contacts from the side. This ensures self-cleaning of the contact surfaces from oxides and deposits. In the event of poor contact, there is hope of restoring this by repeatedly switching on and off. The device mounts in a large diameter hole that you don’t want to drill in the back of the car. Such a holder is more suitable for an SUV, pickup, boat or yacht. |
| estimated price 1100 ₽ Indicated switching current unspecified The overseas switch looks good. The control flag is removable, which, at least a little, but increases the “anti-theft” of the product. The body is mounted on four brass rivets. A thick copper plate closes in the head of two copper contact bolts. The principle of operation is the same as with the starter relay. To mount the switch, you need to shield a homemade bracket. |
| estimated price 350₽ Indicated switching current 50A This switch took part in the test in 1999, but it has still not disappeared from the scene. Using an ugly product is easy: switching it on and off is done by turning the plastic handle 90 degrees. It is not clear why manufacturers frankly declare a low switching current, when the actual currents can be much higher. Among the shortcomings, we note that the design of the switch is designed to be attached to the stripped metal of the body, so it is difficult to connect it to the opening of the starting wire without interrupting the rest of the circuit. |
| estimated price 5000 ₽ Indicated switching current 250 (400) A The device resembles a junction box for industrial buildings. A rather complicated electronic circuit, controlled by a latch button, ultimately determines the position of a two-position mechanical relay. But, despite the mechanical contact device, the circuit breaker at rest consumes a small current – about 1 mA. It can be difficult to fit such a bulky device in a cramped car engine compartment. But the remote control makes it much easier to use. |
| estimated price 4800 ₽ Indicated switching current 520A The device is designed to protect the battery from being discharged when consumers are left powered on, for a long period of parking or a “gluttonous” alarm. Flexible settings allow it to be an easy one, no intervention requiring a massive switch. For example, you can set it to lift off shortly after a ride, targeting a battery voltage of 12.6V. Or you can set a low threshold near 11.7V, but then the power will always be on, except in the case of a very long vehicle standstill. There are no mechanical contacts in the device, but a solid state semiconductor relay is used. That’s why we didn’t open it. It is like sawing a microcircuit to study the principle of operation. The voltage drop is small. The disadvantages are a current consumption of about 1.5 mA, even with the car circuits turned off. The installation is simple – the device is installed directly on the negative terminal of the battery. |
Sum up
The results were pleasing: not a single switch felt like a heating element and did not put unnecessary stress on itself. As for the recommendations, they are ambiguous.
- Those who don’t care about anti-theft features will SD‑004EU “Stop discharge” – this device shuts down the battery in time if the discharge becomes critical for the subsequent start of the engine.
- For those who do not have the desire to climb under the hood again, Kaluga is suitable DVM1: This is the only switch in our example that can be operated from the passenger compartment.
The remaining three products are united by their maximum usefulness: you can choose according to their appearance.
Test results of mass switches
| Name | Voltage drop at a current of 500 A, mV |
| A23–9B | 300 |
| Ak Sa | 260 |
| VK-318B | 160 |
| DVM1 | 200 |
| SD-004EU Stop discharge | 210 |
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The role of the “mass” switch in modern conditions was studied by the experts of “Behind the wheel”.
