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 lea...