How to tell if your battery is dead: Difference between revisions

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:

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 condition of your battery, you'll need a [http://en.wikipedia.org/wiki/Multimeter multimeter].  Follow [[How to read a multimeter|these instructions]] if you don't already know how to use a multimeter, and check the following values:

'''Note''': Older bikes, and the occasional new battery, are not of the sealed variety.  They will periodically require electrolyte to be added.  Make sure the electrolyte level is full, and if it isn't, top it up with ''distilled'' water.  A battery with low electrolyte will mimic the symptoms of a dying battery, but can be fully revived by adding distilled water and charging.  You can tell if your battery is sealed by looking for a row of six caps (or some kind of removable strip) across the top of the battery casing.

If you'd like to know more about lead-acid batteries and their care and feeding, Yuasa produces a very comprehensive [http://www.yuasabatteries.com/pdfs/TechMan.pdf technical manual]  (PDF) that explains all this in detail.  Yuasa batteries have a deserved reputation for excellence, which is usually reflected in their price.