My bike won't start - Is it my battery?

Battery Basics - My bike won't start, is it my battery?

Written by Alan Whealy of Whealy Motorcycle Repair // See his shop in our Shop Visits here on the blog.  


It’s that time of year again. You pull the cover off your slumbering motorcycle, turn the key, and…nothing. Maybe the lights come on, but it won’t crank, or maybe nothing comes on at all. What happened?

More often than not, the source of these early-spring issues is the battery. There are a range of reasons this can happen, and a few options to solve it, but first we have to make sure our problem really is the battery.


If your bike won’t turn on, won’t crank, or is cranking slowly, what do you do next? First let’s narrow down the common causes of these symptoms.

If your bike is cranking slowly, you might still have a shot! Connect your battery to a maintenance charger, wait for it to achieve a full charge, and try starting your motorcycle again. If the problem persists, it likely means that your battery is at the end of its life, and is no longer able to accept a proper charge or deliver the amperage you need.

If your lights turn on, but your motorcycle won’t crank, there’s a good chance that your battery is the culprit. The starter places more load on the battery than anything else on your bike. Before testing your battery, first make sure to cycle all of your safety switches (kill switch, neutral switch, and side-stand switch) to make sure that the problem isn’t a stuck switch interrupting the starter. If the symptom persists, it’s time to test the battery as discussed below.

If you turn your key, and absolutely nothing happens, you may have a failed battery, a blown main fuse or loose / disconnected battery wires. In most cases, checking any of these things requires getting to wherever your battery is located.

First make sure that both your power and ground wires are securely attached to your battery. You shouldn’t be able to move them. Visually inspect them at the same time to make sure they don’t look corroded or dirty. If the terminals are loose or corroded, this should be corrected before moving on.

Battery in motorcycle

Next, we need to check our main fuse. To locate the main fuse on your motorcycle, you may need to consult your owners manual. In general, the main fuse will be located close to wherever your battery is located. It is often located near the relays, or may be located in your fuse panel. The main fuse will be the highest rated fuse overall - usually rated between 20-40 Amps.

Motorcycle Fuses

Most modern motorcycles use plastic, automotive-style blade fuses, which can be inspected after removal by viewing them through the side. If you see an unbroken metal filament you can re-install your fuse and move on. Older style glass fuses also have a metal filament running through the centre. If the fuse has failed, it will need to be replaced, and may or may not indicate an additional underlying problem.

Blown motorcycle Fusesblade style motorcycle fusesglass motorcycle fuses

Lastly, you may have a battery which has completely failed. The best way to verify this is to use a voltmeter, or multimeter to test the battery’s resting voltage (with the key off), and voltage under load (with the key on). A healthy, standard battery should read 12.6V at rest, and should only drop slightly (0.1-0.4V) with the key on. If you see a resting voltage below 12V, or a significant drop with the key turned on - it is very likely that your battery has failed.

motorcycle battery with a multimeter


Batteries fail for a variety of reasons, which can be broken down into three categories: overcharging, sulfation, and undercharging.

Overcharging can happen if you have a defective voltage regulator on your motorcycle that allows the battery to experience a rate of charge outside of its operating range (12.6-15.5V) for a prolonged period of time. This can also occur if you use a defective maintenance charger, or an external charger with too high an amperage rate (under 2.0 Amps is generally safe).

Sulfation is a chemical reaction that happens naturally in traditional batteries, but happens rapidly when the battery doesn’t get used for a prolonged period, or if the battery is drained down and not recharged for a while. Some brands of maintenance charger have a built in test for sulfation and a charging cycle designed to desulfate the battery.

Undercharging is the most common cause of failure. Batteries lose charge whenever they are not in use, so over a period of months they can discharge completely if not kept on a maintenance charger. A defective charging system, or repeated short trips can also deplete your battery’s charge without giving it a chance to recharge.


Most importantly: keep your battery charged! If you go more than a week between rides, or most of your trips are shorter than 15 minutes, connect it to a maintenance charger regularly.

motorcycle battery tender

Once your battery fails, you’ll need to replace it. There are a few main types of powersports battery: traditional lead acid, maintenance free/AGM, and Lithium Ion.

Types of motorcycle batteries

Many older bikes came with traditional lead acid batteries, which are usually translucent white with black tops, and a vent tube on one side. These must be kept upright, and are filled with liquid electrolyte which must be checked and topped up periodically to ensure the level is high enough. It’s important when using a traditional battery to install the included vent hose, and route it down to the bottom of the motorcycle. These batteries are vented, which means they give off a small amount of acid vapor when in use, which you definitely don’t want on any part of your motorcycle! That being said, traditional batteries last just as well as other types of batteries if properly maintained, and are almost always the least expensive option.

Most modern motorcycles come with maintenance free batteries, which are sealed, generally black in colour, and can be mounted in any position. These are a great option for new and old bikes because they are available in all the standard sizes, don’t vent acid, and don’t require you to check or adjust the electrolyte levels. They tend to be 50-100% more expensive than traditional lead-acid batteries.

Lastly, lithium ion batteries have become increasingly popular in the past ten years, and even come as the original battery from some bike manufacturers now. They tend to be significantly more costly, but are lighter, smaller, more powerful, and don’t really discharge when not in use. The downside is that they are less able to tolerate overcharging or undercharging and tend to fail outright more frequently under these conditions. Since they’re more sensitive to over and under charging, they don’t work perfectly as a replacement option for older motorcycles which often have weaker charging systems. To ensure optimal performance and longevity when using a lithium ion battery in an older motorcycle, it is recommended that you upgrade your voltage regulator to one designed specifically for lithium ion batteries. This isn’t an especially difficult or expensive modification, and it will keep your motorcycle’s charging voltage in a range that is safe for your pricy lithium battery!

Regardless of which type of battery you choose, the usual life of a well maintained battery is between 2-5 years, although with careful maintenance and consistent use, they can certainly last longer. Charge your battery regularly, and it will keep you riding!

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