In short
- Signs: slow starting or a ‘click’, a flickering dashboard, a swollen case or a battery that keeps going flat.
- Charge it fully and let it rest before measuring; otherwise, the reading can be misleading.
- At rest, a healthy AGM battery reads 12.8 V or more; below 12.4 V, it needs charging.
- Starting test: if the voltage drops below 9.5 V when starting, the battery needs replacing.
- At 3000–4000 rpm, the reading should be 13.0–14.5 V: if not, the charging system—not the battery—is at fault.
A discharged battery and a dead battery cause the same symptom: the motorcycle won’t start. The difference is that the first can be brought back with a charge, while the second cannot. There’s also a third, trickier possibility: the battery is fine, but a faulty regulator or alternator isn’t charging it. A basic multimeter can help you tell these three cases apart.
Signs of a failing battery
- The starter motor turns slowly, or you just hear a ‘click’.
- The dashboard flickers or resets when you press the starter.
- You have to charge the battery frequently, even when the motorcycle is being used.
- The case is swollen, deformed or leaking.
- It gets very hot while charging.
- There is sulphation or corrosion on the terminals.
A swollen or leaking case is reason enough to replace the battery. In other cases, test it before deciding.
Before you measure
- Check the terminals: they should be clean and tight. A loose or sulphated terminal can cause the same symptoms as a failing battery. Clean it and protect it with dielectric grease.
- Charge it fully with a motorcycle battery charger.
- Remove the surface charge: after charging, let the battery rest for an hour, or switch on the ignition for 3 minutes and wait 10. A freshly charged battery shows a higher reading than its actual charge level.
Resting voltage
Set the multimeter to DC volts (V⎓, 20 V range), place the red probe on the positive terminal and the black probe on the negative terminal:
| State of charge | AGM (YTX, YTZ) | Conventional (YB, 12N) |
|---|---|---|
| 100% | 12.8–13.0 V | 12.6 V |
| 75% | 12.5–12.8 V | 12.4 V |
| 50% | — | 12.1 V |
| 25% | — | 11.9 V |
| Discharged | Less than 11.8 V | Less than 11.8 V |
- Below 12.4 V: the battery is discharged; charge it now.
- Below 11.5 V: this is a deep discharge. It needs a charger with a recovery mode; if the voltage hasn’t risen after 30 minutes of charging, replace the battery.
- If it reads less than 75% just after charging: charge it again; if the reading stays the same, the battery is worn out.
This table doesn’t apply to a lithium battery: when healthy and at rest, it should read 13.0 V or more.
Starting test
This is the test that really shows whether the battery is up to the job, because it measures how it performs when asked to supply current:
- With the battery charged and the multimeter connected to the terminals, operate the starter motor for a few seconds.
- Check the lowest voltage reading.
- If it drops below 9.5 V (at around 20 °C), the battery can’t supply the current needed and should be replaced.
If you have a load tester (a tester with a resistor), apply a load of three times the Ah rating for 10 seconds. If the voltage drops below 9.5 V for a 12 V battery, or below 5.25 V for a 6 V battery, replace it.
Check the charging system too
A new battery in a motorcycle with a faulty regulator will end up just like the old one. Start the motorcycle and measure across the terminals with the engine running at 3000–4000 rpm:
- Between 13.0 and 14.5 V: the charging system is working.
- The same as at rest (12.x V) or lower: the battery isn’t being charged; check the regulator, alternator and connections.
- Well over 14.5 V: the regulator is overcharging the battery and will eventually damage it.
If you need to replace it
Look for the battery part number on the old battery’s label and check the dimensions, polarity and cold cranking amps, as explained in our guide to choosing a motorcycle battery. If you can’t read the label, measure it: how to test your motorcycle battery. Take the old battery to a shop, garage or recycling centre—never put it in the bin.
Frequently asked questions
How many volts should a motorcycle battery have?
A fully charged AGM battery at rest should read between 12.8 and 13.0 V; a conventional battery should read around 12.6 V. With the engine running at 3000–4000 rpm, it should read between 13.0 and 14.5 V.
Can you recover a very deeply discharged battery?
Sometimes. If you use a charger with a recovery mode and the voltage starts to rise after 30 minutes, the battery may still be usable; check it afterwards with the starting test. If the voltage doesn’t rise, the battery is worn out.
My battery is new but keeps going flat. What’s wrong?
The most likely causes are the charging system (check the voltage with the engine running at 3000–4000 rpm), parasitic drain from something like an alarm, or trips that are too short to recharge it.
How long does a motorcycle battery last?
It depends mainly on how well it’s looked after. Deep discharges and leaving it unused for months without charging it shorten its life the most.
Satkit battery
OUTDO UTX12-BS
12 V, 10 Ah battery with 180 A cold cranking amps, a replacement for the YTX12-BS. Factory-activated and charged, ready to fit. Positive terminal on the left.
Where to buyfrom €27.40
Prices incl. VAT checked on 7 October 2026; they may change.
OUTDO HCZ10S-MF
12 V, 9 Ah battery with 170 A cold cranking amps, replacing the YTZ10S. Factory-activated and charged, ready to fit. Positive terminal on the left.
Where to buyfrom €32.48
Prices incl. VAT checked on 7 October 2026; they may change.
