How long can a motorcycle sit before the battery dies?
A small bike battery has far less reserve than a car's, so it can go flat in a few weeks. Enter your battery's amp-hours and parasitic draw for a closer estimate.
Estimated time before it may not start
~35 days
In cold weather, expect closer to ~23 days - a battery delivers less when it is freezing, and an older battery even less.
How this is estimated
A starter needs a fairly full battery, so we assume the bike may fail to crank once about half the battery's capacity is gone. Days = (Ah × 0.5) ÷ draw in amps ÷ 24. It is a guide only - cold weather, an aging battery, and a higher-than-normal parasitic draw all shorten it, sometimes a lot.
Not sure of your battery's Ah? Convert CCA to Ah → or look up your machine's battery →
Frequently asked
How long can a motorcycle sit before the battery dies?
It depends on the battery size and the parasitic draw. A small bike battery holds far less reserve than a car battery, so a few weeks to a couple of months is typical, and much less in the cold, with an alarm fitted, or with an older battery. Use the calculator with your own amp-hours and draw for a closer number.
What is parasitic draw?
It is the small current the bike uses while parked and off - an alarm, immobiliser, clock, or ECU keep-alive. A simple bike may draw only a milliamp or two; one with an alarm or accessories can draw much more and flatten the battery in days.
How do I stop my battery dying while parked?
Put it on a smart battery maintainer if the bike sits more than a couple of weeks (use a lithium-mode charger for a lithium battery), disconnect the negative terminal for long storage, or ride it long enough to fully recharge every week or two.