Battery Voltage
Diagnostics

The whole test takes about sixty seconds, and it answers three questions: is the battery charged, does it hold up under the starter, and does the charging system keep up.

Start with everything off. That is the resting reading. Twelve point six volts is a fully charged battery. Twelve point four is about three-quarters. Twelve point two is half, and it wants a charger before it sulfates. Under twelve, it is effectively flat and may not crank at all. Whatever it says, that is your baseline, and the rest of the test builds on it.

Now hit the starter and watch the gauge, not the engine. A healthy battery dips to about ten volts while the starter pulls, then snaps back the moment the engine catches. If it sags below nine and a half under the starter's load, the battery is weak no matter what its resting number claimed. Resting voltage can flatter a battery; the crank cannot be fooled.

Engine running at idle, expect something modest, around twelve point eight to thirteen point two. The stator is barely turning at idle; that is normal, not a fault. Now bring the revs up to about three thousand. This is the number that proves the charging system: thirteen point eight to fourteen point four volts is a healthy system keeping up. Under thirteen at speed means the bike is draining its battery as you ride, and the suspects are the stator, the regulator, and bad connections, in the order you can reach them.

Finish with the load check. At three thousand revs, switch on the headlight, the grips, everything the bike carries. The voltage should hold above thirteen and a half. And one reading ends the test early whenever it appears: over fifteen volts at any rev means the regulator has failed and is boiling the battery. Stop, and fix that first. Rest, crank, cruise revs, loads: four numbers, and you know the whole electrical story of the bike.

A motorcycle's electrical system tells its whole story in one number, as long as you read that number at the right moments. At rest, voltage tells you the battery's charge. Under the starter, it tells you whether the battery is strong or just pretending. At cruising revs, it tells you whether the stator and regulator are keeping up with the bike or quietly losing to it. Three readings, one gauge, and every charging mystery on an older bike is one of those three gone wrong.

The top of the page is the live gauge. The big number is system voltage, and the colored band under it reads the verdict: under eleven point eight, discharged; up to twelve point four, low; from there to fifteen, healthy; over fifteen, overcharging, which is its own emergency. Beside the gauge, the page tracks the engine's revs, because stator output climbs with revs, and a tile keeps the battery's state of charge as a percentage, so you can watch a session spend it or restore it.

Under the gauge, three tiles sum up the fight: the electrical loads currently switched on, the net current, and whether the battery is holding, charging, or draining. Below that is the voltage history, the last thirty seconds drawn as a line, with the healthy charging band marked on it and the fifteen-volt overcharge line above. A sag or a spike you would miss on a number stays visible on that line.

Further down is the Battery and Loads section, where your hands go. The state-of-charge control sets where the battery starts, from fully charged down to flat. The load switches are the bike's real electrical appetite: the headlight, auxiliary lights, heated grips, turn signals, and the phone charger, each with its draw in amps, plus the ignition's draw, which the page counts for you because the engine pays it whenever it runs. In this demonstration those switches drive the gauge exactly the way the real loads will when the dongle is fitted; your switch settings are saved on this device.

Beside them sit the fault scenarios: a failing regulator, which sends voltage climbing past fifteen as revs rise, and a weak stator, whose output caps out low so the bike discharges at cruise. Run them here and you will recognize them forever out there.

Keep scrolling and the page teaches its own numbers: a reading table, from twelve point six at rest meaning fully charged, down the crank dip of about ten volts, up to the thirteen point eight to fourteen point four that proves a charging system, and the two failures on either side of it. Then the sixty-second test, the same four steps in order: rest, crank, idle, cruise revs, with the load check to finish. On the real bike, with the dongle fitted, this page is that test, live, in a minute.