Can You Charge a Motorcycle Battery With a Car? (Explained)
Motorcycle batteries can often surprise us rather unpleasantly.
If you happen to find out that your motorcycle battery is dead, you already know what you have to do. You have to recharge it.
But what do you do if you don’t have anything to charge it with except your car? Can you, and more to the point, should you use your car?
Can you charge a motorcycle battery with a car? You can charge a motorcycle battery with a car, however, the car can supply amperage that is too high, which can damage and destroy the motorcycle battery. You should not try to charge your motorcycle battery with a car for more than a few minutes, however, you can jump-start a motorcycle using a car.
There are some caveats when doing something like that and some considerations that we need to take into account. After all, you don’t want to make matters worse, so let’s take a more in-depth look.
The problem with charging a motorcycle with a car
There are some differences between car batteries and motorcycle batteries that you should be aware of if you want to ensure your motorcycle battery will remain in the best health possible.
Most cars today are equipped with a 12.6 Volt battery. This means a fully charged car battery should supply 12.6 Volts or higher. While the engine is running, the readings can go up between 13.7 and 14.7 Volts.
In addition to that, car batteries also have a capacity between 48 to 70 amp hours on average.
Motorcycle batteries are usually 12.6 Volts. Much like car batteries, they are comprised of 6 cells, each being 2.1 Volts. That being said, older motorcycles used to have 6 Volt batteries.
So far, so good.
However, motorcycle batteries usually should not be charged at a current exceeding 3 amps. The motorcycle battery can draw too many amps from the car battery, leading to overheating and overcharging the motorcycle battery and damaging it in the process.
That being said, the general rule of thumb is to never charge a motorcycle battery at more than one-tenth of its amp hours. So if you have a 14 amper-hour (AH) battery, it should be charged at 1.4 amps (14 ÷ 10 = 1.4 amps)
Because of this, usually, most motorcycle batteries are charged at 1.5 to 2 amps.
Some people have been charging their motorcycle batteries at 3 to 4 amps as well and have not seen any difference in its performance. However, it is hard to tell if the battery’s life has been affected or not.
Doing this is a gamble, and at the very least, you should not leave your battery unattended while charging it.
That being said, charging a motorcycle battery at 10 amps can result in frying it.
Can you charge a motorcycle battery with a car charger?
The other thing you may be considering is using your car’s battery charger. However, since the batteries found on motorcycles and cars have different specs, this also means the chargers will be made differently as well.
Both motorcycle and car batteries have the same voltage, but they have different amperage.
Car battery chargers can pump out between 13 and 50 amps in certain cases.
Although it is possible to charge your motorcycle battery with a car charger, the car charger can supply too higher amperage, which could overcharge and overheat the motorcycle battery. This can cause irreparable damage to the motorcycle battery and completely fry it.
Conversely, some car chargers may have the option to be switched to lower amperage, but even then, it is recommended not to leave your motorcycle battery unattended. You will have to constantly monitor your motorcycle battery and be extremely careful how long you leave it charging with the car battery charger.
Is charging a motorcycle battery with a car bad?
Although possible, it is usually not recommended to charge your motorcycle battery with a car or a car battery charger.
Although both newer motorcycles and most cars use 12.6-volt batteries, their amper ratings are different.
A car battery—especially if the car is turned on—will supply too many amps, which is bad for the motorcycle battery as it will overcharge and fry it.
Batteries have charging rates, which should not be exceeded. Going beyond these rates can result in different problems.
For example, the battery can overheat, causing its electrolytes to start boiling. Due to the excess heat, the plates can ever bend and warp. It is also possible for the battery to catch fire or even explode.
In addition to that, 24 Volt batteries, although very rare, can also be found in heavy trucks and specialized heavy vehicles. And older motorcycles can also use and have a 6 Volt battery. This means that it is possible to have a situation where the voltage is mismatched, which should be avoided as the batteries can explode.
You want to charge a 6-volt battery with a 6-volt charger and a 12-volt battery with a 12-volt charger.
Can you jump start a motorcycle battery with a car?
Although leaving your motorcycle battery to charge for a longer period with a car may be a bad idea, you can jump-start your motorcycle using a car.
Here’s the thing.
Generally, it is not recommended to jump start a motorcycle battery with a car—the car battery can supply too high amperage, which can damage the motorcycle battery.
Nonetheless, you can use a car to jump start your motorcycle’s battery, as long as the car is turned off.
Turning on the car can potentially overcharge and fry the motorcycle battery because cars can supply more current than what motorcycle batteries need.
All you need to do is connect the motorcycle battery to the car battery.
Both vehicles should be completely turned off.
The red clamp goes to the positive terminal on the motorcycle battery and the black clamp to a metal part on the motorcycle frame. The other red clamp then goes to the positive terminal on the car battery and the black clamp to the negative terminal on the car’s battery.
After you have connected the two vehicles, start the motorcycle.
The motorcycle should start easily. Let it run for no more than a few minutes, and then disconnect the leads in reverse order.
The car should be kept turned off to prevent damage to the motorcycle’s battery. However, if you are jump-starting two motorcycles using this method, the motorcycle with the good battery can be turned on before the motorcycle that will be jump-started.
This can be a good idea if you are caught in a pinch. However, jump-starting a motorcycle with a dead battery and then taking it for a ride in order to charge its battery usually does not work. Doing so can be very hard on the charging system and, for example, cause some of the wiring to melt.
The motorcycle charging system is designed for maintaining the battery and not charging it. (Especially when the battery is dead, to begin with.)
Let’s take a look at the Cold Cranking Amps (CCA) or Cranking Amps (CA) of the battery.
The CCA rating refers to how much amps can a 12.6 Volt battery deliver for 30 seconds at 0°F while not dropping below 7.2 Volts.
Generally, the CCA for most passenger cars is between 350 to 600A, and some larger motor vehicles may need up to 1,000A. In comparison, the typical CCA rating on most motorcycles is between 100 to 400A. However, owners may often choose to switch their original battery to another with higher CCA—sometimes going as high as 600A.
The starter will use as many amps as it needs to start. So if your motorcycle battery has a CAA of 500A, it needs a jumper that can supply 500 amps or more. However, if the jumper is rated at 350 amps, it may not be able to jump-start the 500A battery.
What you should use to charge a motorcycle battery
Accidents can always happen, and that is okay. However, it is worth considering investing in a trickle charger that you can use to keep your motorcycle battery charged and in good health.
Trickel chargers do not cost a lot—typically between $25 to $45—but make the whole process of charging your battery super easy, and you will not have to worry again.
Trickle or smart chargers are designed to monitor the condition of the battery and supply just enough current to keep the battery from overcharging or undercharging.
That being said, the trickle or smart charger should be designed for motorcycles and not cars. Car maintenance chargers (trickle or smart chargers) can supply too many amps even at trickle, damaging the motorcycle battery if used for long periods of time.
Some car trickle charges may be suitable for use on a motorcycle, though, if they have the option to be switched to a lower amp trickle.