Motorcycle Voltage Monitor

Revised 12-10-2011

Motorcycle electrical charging system failures are not uncommon. I've personally experienced stator failures with a Honda Silverwing, and recently a friend with a Kawasaki Vulcan 1500 experienced a regulator/rectifier failure.

Once the charging system fails, only a limited amount of riding time is available before the bike quits running due to insufficient voltage to power the ignition system. Fortunately, there is usually an hour or so of riding time left before the bike completely stops. This time may be further extended if steps are taken to reduce the electrical load, such as removing fuses for the lights and other nonessential loads. So it's important to have a timely indication if a charging system failure occurs, especially when traveling in a remote area.

An easy way to assess the charging system operation is to measure the battery voltage. With the bike running normally above 2000 rpm or so, the battery voltage should be around 13 Volts or greater. This indicates that charging is taking place.

At idle, it is not uncommon for the voltage to drop somewhat as the rpm's may not be sufficient for charging to take place. This is not a problem as long as charging occurs during normal non-idle running conditions.

The voltage should also never rise above approximately 15.3 Volts, or the battery may be overcharged. This type of charging system failure is rather rare but it does happen on occasion.

Some voltage monitors I've tried are described below.

Lascar EMV 1200 Voltmeter
Lascar Voltmeter
Initially, the Lascar unit appeared to be a very nice voltmeter. But I found it was terribly inaccurate in damp weather and its readings could not be trusted then. Too bad. It seemed about perfect in other regards.

Five Function Voltmeter
Five Function
This "5 Function Volt Meter" is fairly popular. I've seen the same basic unit marketed by several vendors, including Radio Shack and Aerostich. Unfortunately, this unit was also found to be inaccurate in damp weather conditions.

Signal Dynamics Heads Up Voltage Monitor
The Signal Dynamics Model 1050 Heads Up Voltage Monitor is what I finally used. It seems to be perfect for this application and its accuracy is not affected by the weather.

Note this device is not a voltmeter, as the display is simply a multi-color LED. Its sole purpose is to monitor the bike's charging system performance and provide a simple "heads-up" warning in the event of a problem. It is not intended to replace a regular multimeter during troubleshooting.

The unit is well made. Its case appears to be black anodized aluminum and it is sealed with a pliable potting compound. It feels solid and appears to be waterproof, although it may be a good idea to mount it in a sheltered location such as inside a fairing or under the seat if possible.

The voltage monitor does not have its own battery. It obtains its power directly from the circuit it is monitoring, and draws tens of milliamperes of current. This is a negligible amount when the engine is running, but it is a bit much to leave on the battery at all times when the engine is switched off. It could drain the battery over a period of days so it is best to have a switch inline to the device. The bike's ignition switch can be used for this.

Installation of Heads Up Voltage Monitor in GL500I Fairing

The unit was mounted inside the bike's fairing using the double-sided adhesive pads provided with the unit.
Voltage Monitor Mounting

A 3/4 inch diameter plastic plug was purchased from the local hardware store to mount the LED.
Plug and LED

The LED was installed in the factory provided hole located just above the left fairing pocket.
Installed LED

Electrical connections were made to the wire harness located within the fairing.
The green fairing wire, denoted as - in the photo, was connected to the black voltage monitor wire.
The black fairing wire, denoted as + in the photo, was connected to the red voltage monitor wire.


The heads up voltage monitor has been installed for over a year now and seems to be working well. Occasionally I'll notice a flashing red indication if stopped at a light with the brakes on, but this clears as soon as the rpm's increase again. To me, this is a good thing as it shows the unit is doing its job.

I've been very pleased with it. I especially appreciate the peace of mind that comes with knowing the charging system is being monitored so if a failure occurs there will be some advance warning prior to the bike ceasing to run.

Sparkbright Products LED Battery Monitor

More recently, a single multicolor LED battery monitor has become available from Sparkbright Products in the UK. It is advertised as being waterproof, shockproof, and accurate to better than 0.03 Volts. In addition, the voltage thresholds can be set to custom levels at the time of order placement.

Although I have not yet personally evaluated this unit, it has been getting rave reviews on several motorcycle forums and seems perfect in all respects. I intend to purchase one the next time the occasion arises to install a voltage monitor. It is shown in the following two photos.

Return to Home Page