Aerostich Waterproof 12-Volt Digital Voltmeter | Gear Review

Aerostich Waterproof 12-Volt Digital Voltmeter

I’ve got a few bikes that don’t get the regular exercise they require to keep their batteries in a healthy condition. Without a judicious schedule of battery maintenance, parasitic voltage drains like immobilizers, clocks and alarm systems will eventually nibble a battery down to a critical level often unable to rally the starter system dependably.

Two of my bikes are well-known serial offenders. Both need a fully healthy battery to provide adequate confidence to roam far afield without carrying a rechargeable jump battery. They may start well at home but fail at a later inconvenient location.

Aerostich has an inexpensive way to measure that risk. Its trio of waterproof 12V digital voltmeters provides a visual check for real-time battery health. Simply wiring one into a switched circuit will give an instant key-on, three-digit reading of the battery with no load. Then hit the starter and watch the voltage drop. Whenever an electrical load — brake lights, high beam, horn — is triggered, voltage will also dip. However, a properly functioning charging system should return the voltage quickly. If the voltage doesn’t stabilize quickly or if voltage continues dropping, trouble may not be far away. If the initial key-on, no-load level is much less than 12.6V, you may need to carry that jumper.

Sadly, we know bikes never fail close to home. A flatbed tow in my area is a hundred bucks and a few hours. Ugh.

Wiring the voltmeter into a switched circuit is easy. The leads, as supplied, are short so some lengthening will be required. The voltmeter readout itself can be easily mounted somewhere visible with double-stick tape or installed in a sheet metal bracket made from hobby shop metal.

The voltmeter is a waterproof, dust-proof and vibration-proof unit that measures 1 x 0.6 x 0.7 inches, so it’s small and inconspicuous. Some may complain about the brightness of the three-digit readout at night but I never felt it to be an issue. It accurately measures voltages from 3.5 to 30 volts in increments of a tenth of a volt.

Newly installed, mine already shows that the “fully charged for 12 hours on the Tender” battery in my Ducati is really holding only 11.8V. It might be time to replace it. Until then, at least I can monitor it. And slide that jumper in my jacket. Dependable information is always good.

Three display colors, Red, Blue or Green, are available for $13. Pick your color. Way cheaper than a tow and you can keep that jump battery for your friends’ bikes.

For more information: call (800) 222-1994 or visit


Please enter your comment!
Please enter your name here