NiMH Charge Rate Calculator: Best Charge Rate, Calculating and Charging Hour

May 28, 2020   Pageview:196

Have you ever had a battery that can be reused by recharging it? If you do, you probably have NiMH batteries, which is short for nickel-metal hydride batteries. If your NiMH battery still looks good, excellent! We can try to recharge it and use it for your electronic devices. Before we charge the batteries, we need to understand some of the terms used for charging batteries. Without further ado, let’s talk about the NiMH charge rate calculator and facts about NiMH batteries.

What is the best charge rate for NiMH batteries?

Before we talk about the NiMH charge rate calculator, let’s talk about NiMH batteries first. Basically, NiMH is an improved version of NiCD (nickel-cadmium) batteries.

Being an upgrade of NiCD, NiMH batteries have several advantages. It is more potent than NiCD since it has a higher capacity by at least 30%. Moreover, it has less risk of suffering from the memory effect. It means that we can easily reuse the battery as long as it is charged.

You can also store NiMH batteries easily. It has a dull appearance and does not require any specific requirements for the location. It means that temperature does not affect the quality of the battery. To make it even better, it has little dangerous chemicals, meaning that it is safer to use NiMH batteries for the environment compared to NiCD batteries.

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Of course, there are several disadvantages to NiMH batteries as well. For example, NiMH batteries cannot last for a long time. It would be best if you also were careful not to overcharge, as NiMH batteries tend to be sensitive to overcharge. It is also vulnerable in regards to heat, as it tends to heat up during fast charging. NiMH batteries also have sophisticated algorithms that cannot be understood easily.

There is no specific way of knowing the charge rate for NiMH batteries. However, the voltage for charging is usually around 1.4–1.6 V per cell.

How do you calculate the NiMH battery charge rate?

The best way to calculate the NiMH battery charge rate is by knowing the mAh of the battery. So the more significant the mAh is, the larger the charge rate the battery will have. This means more energy and more capacity. However, there is no universal standard for the amount of time where NiMH batteries will finish its power. It depends on the device that uses the battery.

There are, however, some ways where we can ensure that the battery can retain its quality during charging. First, you must check whether the battery is available for a fast charge (the method is below). If it can fast charge within 1.5, then you’re good to go. If the quick charge does not work, you can opt for a slow charge after 25 hours.


You also need to check the volt during charging regularly. Make sure that it does not climb over 1.78 V/cell. Usually, the battery would terminate the process if it rose until that much. If it doesn’t end by itself, you have to terminate the process manually.

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How long does a NiMH battery take to charge?

The amount of time for a NiMH battery takes to charge itself depends on, again, the mAh of the battery. There are, however, some ways on charging NiMH batteries that can shorten or extend the time to load. It can also tell you at times whether the battery is overcharging or not. Here are some of the ways to charge NiMH batteries:

1. Timer charging

This is probably the easiest way to charge NiMH batteries. What you need to do is find a timer and time the charging. So, if the person has two hours to be able to charge NiMH batteries, give them around fifty minutes or so for the charging.

2. Slow charging NiMH batteries

Slow charge usually happens when we use slow rates, such as 0.1 and 0.25 C, for the batteries. You will barely be able to see the increase of energy though once you use slow charging. The same goes for the rest, such as charging progress and the amount of time used for the charging. So if you want something that can be easily measured or seen, slow charging is not your guy.

3. Trickle Charging

Many believe that trickle charging is probably the safest option for slow charging, where you literally do not have to watch over the charging process. You do trickle charging by charging below 0.1 C.

4. Negative delta voltage detection

This method is probably the most liked method to charge NiMH batteries. The process is based on the negative delta voltage method, where the voltage drops once the battery is full. However, it would be best if you made sure that the drop in the voltage is at least 5mV per cell. Sometimes you should also install noise filter during the charge so that there’s nothing that can trigger the charge by itself.

5. Thermal detection

Thermal detection is the easiest but riskiest way to charge a NiMH battery. You figure out that the battery is done charging by measuring the temperature of the battery. If the battery is heated enough, then yes, it has finished charging.

Unfortunately, not all NiMH have the same kind of temperature. Each battery differs, so relying on heat is not something we can rely on.

6. Fast charging

Fast charging is the most preferable way to charge NiMH batteries. You can check whether your battery can do fast charging by its temperature. If the battery remains cool even when it is charged beyond 70%, then you’re good for fast charging. If not, then it is best to use other methods for charging.

Don’t be discouraged, as there are plenty of ways to charge NiMH batteries. As long as you can predict the charge rate and decide which method you will use, we are sure you will be able to charge your NiMH batteries properly.

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