Will A Motorcycle Charger Charge A Car Battery?

Car Battery Charging

You want to charge your car battery but you do not have the required charger. But you do have a motorcycle charger with you right now.

And you are wondering if you can use the motorcycle charger to charge your car battery.

Usually, you can use a motorcycle charger to charge a car battery since both the charger and the car battery’s voltage specification will be around 12V. Exceptions are when you are using an old motorcycle or a low volt battery of 6V.

However, it is better to check whether your car battery amp-hour rating falls within the specified capacity range of the charger before you start charging.

Here are the steps you need to take.

Check The Specifications

You need to check the specifications of both the car battery and the motorcycle charger.

Look for the Voltage and Capacity or the Amp-hour rating in your car battery. For example, the voltage of a battery could be 12V and the capacity is 70Ah (amp-hours).

For the motorcycle battery charger, you need to check the Voltage and the recommended battery amp-hours range. A typical charger could read 12V – 2amp, suitable for 6-45Ah.

Does the battery’s capacity fall within charger’s suitable range?

Next up, you need to verify whether the battery’s amp-hour capacity is indeed within the recommended range of your motorcycle battery charger.

Say, the capacity of your car battery is 40Ah, and the recommended range for the motorcycle battery charger is 6-45Ah. Since 40Ah falls within the suitable range for the charger, it is okay for you to use.

On the other hand, if the capacity is 70Ah for your car battery, it does not fall within the recommended range of the charger, which is 6-45Ah, for example. Then, it might not be the best alternative to use this charger to charge your car battery.

Compare The Voltage Specification

Another parameter to look at is the voltage specification for both the car battery and the motorcycle battery charger. Ideally, both the voltage parameters should be same.

Even if the specification is around the same number, that should work fine as well. However, if the voltage difference is too large, say 12V for car battery and 6V motorcycle charger, you should not use this charger to charge your car battery.

Typically, both the charger and the car battery voltage specification will be around 12V. Exceptions are when you are using an old motorcycle or a low volt battery which usually has a voltage of 6V.

How Long Does It Take To Charge?

If you were using a car battery charger for your car battery, the average time taken to charge will be around 10 hours.

However, since we are using a motorcycle battery charger to charge the car battery here, the time taken will be entirely dependent on the amperage of the charger.

So, if the motorcycle charger is charging at 10 amps, it will take less time to charge when compared to 2 amps charging. Higher the amperage of charging current, lower will be the time taken.

Charging Time vs Charging Current

The relationship between the charging time and amperage specification of the charger is detailed below.

Relationship Between Charging Time And Charging Current

The charging time of the battery is dependent on two factors – i) Battery Capacity; and ii) Charging Current.

The relationship is best defined as:

Charging time of the battery = Battery Capacity / Charging Current

The units corresponding to each unit are:

  • Charging time in Hours (Hrs)
  • Battery Capacity in Ampere-hour rating of the battery (Ah)
  • Charging Current expressed in Amperes (A)

Ideal Scenario

Let us take an example to calculate the time taken for charging the battery.

Suppose the battery capacity has an ampere-hour rating of 40 Ah. And let the charging be happening at 2 amps.

Then,

Charging Time = 40 Ah / 2 A = 20 Hrs.

It will take the charger 2 Hrs to completely charge the battery. However, this is an ideal scenario where we are assuming there will be no losses occurring.

Usually, it will take much more time to completely charge when accounted for the losses.

Actual Scenario

If we factor in the losses while charging the battery, the hours will be higher than the ideal case for completely charging.

Suppose, if the losses occur at the rate of 40% while charging the battery, the time taken for charging is calculated as below.

Charging Time = 40 * 1.4 / 2 = 28 Hrs

As you can observe, losses in charging results in a higher time required to completely charge your battery.

Can You Charge A Motorcycle Battery With A Car Charger?

Now that we know the things to check before using a motorcycle charger to charge a car battery, what about the converse situation? Can we use a car charger to charge a motorcycle battery?

Motorcycle Battery

The same steps mentioned above are applicable here as well. Look up the specifications of both the battery and the charger. Compare the Voltages. Check whether the battery amp-hour rating falls within the specified capacity range of the charger, then charge.

Typically, you should be able to charge your motorcycle battery with a car charger. However, if you have an old make motorcycle or a low volt battery of 6V, you cannot be able to charge with a car charger.

One thing to note here is that most motorcycle batteries nowadays are maintenance-free, which means they are sealed and you don’t have to check the battery acid.

The complication with maintenance-free batteries is you can’t overcharge the battery since they are sealed. So you need to keep this in mind to not overcharge if you are using a car battery charger.

How To Charge A Car Battery Using Motorcycle Battery Charger?

The steps to charge are same as what you do with a normal charger. The instructions include:

  • Put on appropriate safety gears.
  • Remove the battery if you have to.
  • Remove the ground cable from the battery and clean the terminal.
  • If the battery is not maintenance-free, check the water levels. If low, pour distilled water.
  • Now, take the charger out and make sure it is off.
  • Connect the negative cable of the charger with negative terminal of the battery and the same for positive cable and positive terminal.
  • Set the charger to the appropriate charging rate.
  • Switch on the charger and set the timer.
  • Once charged, turn off the charger first before disconnecting the cables.

Summing Up

  • In order to check whether you can use motorcycle battery charger to charge your car battery, here are the things you need to do –
    • Note down the specifications of both the battery and the charger;
    • compare the voltages, they should be around the same number;
    • check whether your car battery amp-hour rating falls within the specified capacity range of the charger
    • If the above conditions are satisfied, you can go ahead and charge your car battery.
  • The same steps apply for the converse case as well, i.e. when you want to charge your motorcycle battery with a car charger.
  • Typically, both the charger and the car battery voltage specification will be around 12V and will not create problems in charging. Exceptions are when you are using an old motorcycle or a low volt battery of 6V.
  • The time taken for the battery to completely charge is calculated as: Charging time of the battery = Battery Capacity / Charging Current.
  • When accounted for losses in charging, the actual time taken will be slightly higher than the calculated one as above.
  • The time taken to charge will be entirely dependent on the amperage of the charger. If the motorcycle charger is charging at 10 amps, it will take less time to charge when compared to 2 amps charging. Higher the amperage of charging current, lower will be the time taken.