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Measuring the capacity of your e-bike battery

Difficulty level : average

Reading time: 5 minutes

While you’re out cycling, or even when charging your e-bike battery, you might realise your battery no longer has the capacity it was originally supposed to. Before buying a new one or having your old e-bike battery reconditioned, it should be looked over carefully.

The first step is to check the voltage and power of the battery with a measuring device. Read on to find out more.

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Preparing to measure the capacity of your e-bike battery

Want to check the total capacity of your e-bike battery? You can always visit a dealer, where you’ll find someone happy to help. But you can also test your battery by yourself at home.

To do so, you’ll need a digital multimeter, which is a measuring device with several measuring ranges. The device should also have a capacity monitor, which makes it quicker and easier to read the battery’s total capacity.

First, remove the battery from the e-bike. When the energy-dense Li-ion (lithium-ion) batteries came onto the market, they were mostly attached to the downtube of the e-bike to ensure good balance. Nowadays, though, there are more and more solutions that integrate the battery almost invisibly into the downtube.

After removing the battery, place it on a table. This makes it easier to see the negative (−) and positive (+) terminals on the battery connectors. In order to measure the voltage and other electrical values accurately, the digital meter must be correctly set up and connected. There are different controls and connections available for this purpose.

The so-called measuring leads are used to connect the measuring device to the object to be tested. The sockets of the measuring device are usually clearly labelled to prevent incorrect connection of the measuring leads. If you’re in any doubt, read the enclosed operating instructions in detail.

Note that in order to measure its capacity accurately, the battery has to be fully charged.

How to measure the capacity of an e-bike battery?

Many multimeters are equipped with fuses that blow if used incorrectly or with too high a current. You don’t have to throw away the whole measuring device if this happens – you just need to change the fuse. Sometimes manufacturers even supply spare fuses when you buy a digital multimeter, just in case.

Many multimeters have an on/off switch that can be used to start the device. To prolong the life of the multimeter battery, many models switch off automatically after a certain length of time.

As soon as you have made all the necessary preparations, connected the measurement leads correctly and set the measurement ranges, the measurement process can begin.

You can now read the voltage value of the battery on the digital display. Voltage measurement is one of the simplest measurements available in electrical engineering, because the multimeter is simply connected to the voltage source or the object to be measured in parallel.

Excessive current flowing through the measuring device could lead to inaccurate results. To prevent this, the multimeter has particularly high internal resistance during voltage measurement.

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What do the results of the measurement tell you about the battery?

What do the results of the measurement tell you about the battery?

The exact voltage value of the battery can be read off the display. A battery that is in good condition should show a minimum reading of 36 volts.

The total capacity of an e-bike battery is determined by the electrical voltage (V), the amount of charge (Ah) and the resulting stored electrical energy (Wh). In other words, the more watt-hours (Wh) a battery has, the more powerful it is.

When choosing a bicycle battery, you should therefore pay attention to the Wh rather than the Ah. For example, an e-bike battery power pack 500 is calculated as follows: 36 (V) x 13.4 (Ah) ≈ 500 (Wh).

A reading of less than 36 V indicates that your battery is already pretty much worn out. Measuring your battery capacity with a digital multimeter in your garage is not as precise as having it professionally measured by your dealer. A specialist can also measure what a battery is capable of while in operation. A reading of 36 V or more doesn’t automatically mean the e-bike can deliver optimum performance.

If your e-bike battery no longer works, or if it seems significantly less powerful than before, have it tested by a specialist dealer to be on the safe side. A professional measurement is always a better option than a quick test at home.

Calculate the status of your battery yourself

A closer look at the time it takes to charge your bicycle battery will tell you a lot about its condition.

Let’s assume that you have a battery charger that delivers a charging current of 2A. Your charger will need 6 hours to fully charge your battery. This gives your battery a capacity of 12 ampere hours (Ah). Now compare this capacity with the original capacity of your battery. If your battery had a maximum of 14 Ah in its original state, you can assume that your bicycle battery is already somewhat worn out.

Charging an e-bike battery that has become old and no longer functions properly due to years of wear and tear can take a very long time. That makes it difficult to measure the total capacity of an old battery accurately.

A small, handheld digital multimeter for measuring the capacity of an e-bike battery is definitely a handy thing to have at home. But if you’re in any doubt, always contact a professional.

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Having your e-bike battery capacity measured by a professional

You realise that your e-bike battery is not charging well and that your battery loses its charge much too quickly. What now? Maybe you’ve thought about measuring your total battery capacity yourself, but you’re not sure what kind of multimeter to use.

Are you unsure about the possibilities, or do you feel you don’t have sufficient knowledge or equipment to measure the capacity of your bicycle battery yourself? Don’t worry! Just get in touch with a Velosophy dealer, who will gladly take professional measurements for you.

One of our dealers will be able to provide you with a customer report, along with the battery parameters obtained from the measurement. They can also discuss in detail whether you need to buy a replacement battery. Another possibility might be to recondition your bicycle battery, which involves replacing the old cell block with a new one, which is installed within the old battery housing.

Before spending a lot of money on spare parts, you should first make sure you’re thoroughly informed, whether by your own measurements or by consulting with a dealer. There are often more options available to you than might be obvious at first.

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