How to tell if your battery is dead

The following is important information for the DIY rider. Quite often a seemingly impenetrable electrical problem can be traced to a battery that is no longer serviceable. This should be the first thing you look at.

Here are the classic symptoms of battery failure:

• Gauges on (neutral, oil and temp) but the starter won't catch
• Tach starts bouncing, and then the engine starts to act like it's out of gas.
• Engine keeps coughing, but tach is much higher than it should be, or it is bouncing wildly from low to high.
• Bike surges with turn signal on.

Sometimes a battery just dies. Not necessarily from neglect, age, or use. It just dies. Car batteries can give some advance warning when they start to go, but tiny bike batteries are more likely to be fine one moment and dead the next. This normally comes from sulfates building up along the bottom and shorting out a couple of the lead plates. It's difficult for many people to trouble-shoot because they'll just toss a voltmeter on the battery, see that it shows 12v DC and right away say it's fine. The truth is, if the resting voltage (after sitting, not on a charger) is below 12.2, that battery needs to be replaced. Below 12v and it's dead, for all practical purposes.

To confirm the death, do a little more investigating. Here's a bad battery (this one died WHILE the bike was running!). It's being tested with a multimeter to find the voltage drop.

Fresh off the battery tender. 13v is good.

Ignition on. 12v. Only a slight drop.

...and starter thumbed. This is the "drop" part of the equation. You shouldn't see lower than
about 10v DC.

6 volts isn't good. Time to head to the battery store.