Advanced Guide: How to Charge a Motorcycle Battery

How to Charge a Lithium Motorcycle Battery

For the task, knowing the battery type is crucial, as lithium batteries require a special motorcycle battery charger. They differ in chemical composition from lead-acid energy blocks, and using a standard trickle or even floating charging device might lead to battery damage.

Thus, how to charge a motorcycle battery of the lithium type? Here are the steps:

• Take the battery out of its place. Disconnect the terminals starting with the negative one, the positive one following.
• Make sure you have enough space and ventilation, as well as electricity access.
• Hook up the charger to the power block terminals (first the positive wire (usually red), then the negative one), set the voltage and amperage if applicable, and plug in the charger to the outlet. Turn on the charger.
• Upon the time, see if the battery is full. The smart charger will display the rate of charge. Otherwise, you’ll need a voltmeter to test it.

Charging a lithium battery, you should take precautions, as these blocks have a different chemistry from the regular lead-acid ones. Wonder how to charge a motorcycle battery for the first time or after some discharge safely? The first piece of advice is to follow the manufacturer’s manual and take the charger that fits it the most. However, at the moment, you may not have a specific device along. Each type (lithium-ion, lithium phosphate, and lithium-iron) ideally requires its own charger. The good news you could use some of them on the different types of lithium power blocks.

Notions to know before charging the lithium battery:

• The nominal voltage of the battery and the charger. For example, the lithium titanate power blocks have 2.4V, while the lithium-ion ones produce a much bigger one, 3.7V. The trick is to have them matching each other or at least not going far apart. The charger’s voltage shouldn’t exceed the voltage of the battery.
• Battery capacity. Again, depending on the actual type, lithium batteries can take more or fewer Amperes per hour. For instance, lithium-ion power blocks should be powered with the current of no more than half of their capacity (interpolated in the Ah). It means that the battery of 9Ah can be charged with the 2A charger, but not the 5A one.
• The BMS regulator. It’s installed in the majority of the modern lithium batteries and serves as the fuse against excessive voltage or amperage. The devices without these controllers should be charged with special caution.

How to Charge a Motorcycle Battery with a Car

The motorcycle batteries usually have a much smaller capacity than the car ones. This means that charging a motorcycle battery with a car charger might lead to the overcharge and consequent changes in the battery chemistry. The latter might be non-repairable, so it’s preferable to use a specific device for charging. However, sometimes all you have along is a car charger. It’s not the safest way to get your bike going. Still, if you’re sure to go, the steps are the same as with the motorcycle charger (read above). Here are some tips to make it safer.

How to charge a motorcycle battery with a car charger:

• Do the math. The safety rule in case of the car trickle charging devices is using the current of no more than a tenth of the battery capacity. It means that for the 9Ah power block, the charger should send a current of no more than 1A. Consider the voltage as well. Excessive voltage might ruin the inner structure of the power bank leaving it non-usable.
• You might need to decrease the charger capacity by hooking up other devices. For instance, if your available charger sends the 5A current, connecting two 100W light bulbs into the circuit will decrease the number almost to 4A. Remember that the resulting current shouldn’t exceed one-tenth of the motorcycle power block amperage, for safety reasons. With some chargers, it’s easier to do (if they have two charging wire sets or a USB port, for example). With others, you might need to use some appliances to create a two-step charging circuit. This will require fiddling with the wiring and is not recommended for a non-techie.
• Keep an eye on the charger and the battery and make sure you can disconnect them quickly once there’s a need. It’s better not to top off the bike battery longer than the time your calculations have proven to be enough. If it doesn’t seem to be full upon that time, there might be internal damage, and further charging could be harmful.
• Turn off the charger and disconnect it from the battery in a reverse way (first removing the negative wire, then the positive). Connect the battery to the motorcycle and try to crank the engine. If the starter doesn’t whizz, and you still wonder how to charge a dead motorcycle battery, then, probably, the battery hasn’t taken a charge. Try testing it with a multimeter, replacing it with another battery, or if the battery isn’t a culprit, test the other parts of your bike for malfunction.

How to Charge a Motorcycle Battery without a Charger

It might happen that your bike doesn’t turn on, the battery is flat, and there’s no charger at hand. The good news is that it still can be replenished in different ways.

Here are the ways to power up your motorcycle battery without using a charger. If you deal with a recently bought unit and wish to know how to charge a new motorcycle battery, some of these ways are also applicable.

• Jump starting / push starting. If there’s another bike or a small car available with the running engine, you can jump-start your bike and get the alternator running replenishing the battery. Still, this method should be used with caution, especially with cars. Consider the capacity and voltage and make sure to disconnect the clamps as soon as the motorcycle engine gets running. Upon using this method, it’s better to check your battery for discharge rate / charge level.
• Push starting is considered less harmful. If the starter works well, ask the help or direct the bike down the hill. Put it into the 2nd or 3rd gear and push ahead turning on the starter.
• Using another electric appliance. To implement this method, you should have basic knowledge of electricity (voltage, amperage, resistance, capacitors, diodes, etc.) and access to the outlet. If you have a diode and a light bulb, and the wire with clamps with the electric plug (this can be assembled manually out of the laptop power cord, for example), you can create the circuit by connecting the diode to the positive terminal of the battery, with the light bulb connected after it (farther from the battery). This scheme, upon being assembled, should be connected to the electricity. This will supply a slow charge, the actual amount of which depends on the number of diodes used and the light bulb capacity. If you build a diode bridge out of four diodes and use the 200W bulb, the current will be about 0,9A, which is enough to power up the motorcycle battery in a few hours.
• Using a regular AA battery. This method can be used if you’re stranded on the road. However, it involves cutting wires so that it should be used only if there’s no other alternative. You should have sturdy gum gloves as well. It also will work only if the bike’s alternator / starter is in a good condition. Search for the cable connecting the alternator and the battery which sends the signal at the turning of the key in the lock. Cut the wire with caution and insert the AA battery in the place of cut. Then push the bike either with the help of other people or down the hill and crank the engine. Upon the start, remove the AA battery with caution. If possible, connect the wire with the isolation tape. The working engine will start the alternator, which, in turn, will be charging the battery. Still, to get a charge enough for the next motor start, you’ll have to keep the bike’s motor running at least for an hour.