NiMH Battery Not Holding Charge: 4 Ways to Fix It

NiMH Battery not Holding Charge
Reading Time: 5 minutes

Last Updated on October 11, 2021 by Mesbah Sakib

You might just have bought a NiMH battery for your RC Car. But after a week or two, you found out that your battery is draining charge. Or, it is not holding the charge for too long. You have tried charging your battery again and again but found no solution.

So, how to fix the NiMH battery not holding charge?

Well, there can be some reasons why your NiMH battery is not holding charge. Although, there are many ways to fix it. You can check the voltage of the battery using a Digital Voltmeter (DVM). If the value is less than 1 V/Cell, you can try reviving the cell. You can try storing the battery at a low temperature. This can slow down the energy drain. Sometimes you might have to rebuild the cell.

Got a few minutes? Jump on to the whole article to know entirely about the problems.

How Should You Know That Your Batteries Are Damaged

You might not be sure if your batteries are damaged or not. To know this, just check the cell voltage with a voltmeter. A fully charged NiMH battery should show a reading of 1.5 volts. If the reading is between 1.3 – 1.5 volts, your batteries are in good shape. But if the reading of the voltmeter is below 1.3, it means that your battery is damaged. And so it will either not take or fail to hold charge.

Things You Should Check Before Blaming Your Battery

Sometimes you think that your batteries are draining charge. But actually, the problem is with the charger. And so, charging the battery becomes the real problem

Check If The Charger Supports The Battery

La Crosse and its clones are known to reject cells under 0.5DC. Take a good read about your charger datasheet.

However, buying a quality NiMH battery can save you a lot of hassle. So don’t try to save money on buying a cheaper one.

Why NiMH Batteries Fail to Hold Charge: 4 Common Reasons

NiMH Batteries can malfunction or underperform for multiple reasons. To find out, have a look at the reasons one by one. You’ll surely know what problem you’re having.

Reason 1: Your Batteries Might be A Little Damaged

Unfortunately, your batteries might be a little damaged. But, they have some chance of recovery.

Solution: 

To counter a damaged battery, you can volt up the charger. This can cause the batteries to accept charge again. However, the process is different for single-cell NiMH batteries and a battery pack.

For Single Cell NiMH Battery:

Use DVM to check the voltage output of the cell. The calculation process is to divide the total output voltage by the number of cells in the pack. If the result is less than 1.0V, you can try to revive the cell.

Charge the cell with a 12V DC 0.5Amp AC adaptor for not more than 3 seconds. Make sure to keep the polarity correct. 

For A Battery Pack

Use DVM to check the voltage output of the battery pack. The Calculation Process is the same. Divide the total output voltage by the number of cells in the pack. If the Result is less than 1.0 V/Cell, you can revive the battery. 

Charge the battery with a 12V DC 0.5Amp AC adapter for not more than one minute. Make sure to correct the polarity.

Measure the voltage again, this should increase the voltage by 80%. If it is still below 50%, there is a dead cell in your pack. In that case, charging the batteries will be useless. And so, you will have no other way but to throw the battery away.

Reason 2: Keeping the Batteries at High Temperature

NiMH batteries lose charge fast if they are stored above 70 degrees Fahrenheit (20C). The batteries can lose up to 40% of their charge within just a month. The higher the temperature these batteries will be stored at, the higher the rate of draining will rise.

Solution:

By knowing the problem, it’s very easy to find out the solution. Store the battery comparatively at a lower temperature. The lower the temperature you will store them at, the slower will be the energy drain of the batteries.

Reason 3: NiMH Batteries Can Self Discharge.

Even though most batteries lose their charge at some point even if kept unused, self-discharge is a particular problem for NiMH batteries. Its high discharge rate makes it lose 20% of its capacity within 24 hours. For each month it loses 10% of its capacity.

Also, their low internal resistance results in a fast charge drain rate.

Solution:

This is a natural case for NiMH batteries. So, there is no particular solution to counter it. Although, you can follow the solution mentioned in [Reason 1]. This can somehow lower the self-discharge rate of the batteries. 

Reason 4: Some Cells Can Become Negatively Charged

In special cases, some of the cells in your battery pack can be negatively charged. This can cause your battery to drain charge.

Solution

To solve this, you can buy some cells and build them yourself. Otherwise, you can find people who can rebuild them for you.

You might be confused and troubled to find an ideal charger for NiMH batteries. Worry not, as we have picked up some best-performed NiMH battery chargers for you.

Panasonic Advanced Individual Cell Battery Charger
Energizer Rechargeable AA and AAA Battery Charger
Product Title
Product Title
Panasonic Advanced Individual Cell Battery Charger
Energizer Rechargeable AA and AAA Battery Charger

We hope this could help you to narrow down our choices.

If you are too annoyed with using NiMH batteries you can switch to Li-Po batteries. Comparison between NiMH batteries and Li-Po batteries shows that Li-Po batteries are better.

Do’s and Don’ts for Charging NiMH Batteries

There are some tips you can follow to maintain battery health. This enhances your battery’s longevity and performance. Take a quick peek at the points below.

  • Charge at room temperature. Charging NiMH batteries at high or low temperature is unsuitable.
  • Always check the temperature of the cell while it’s on charge.
  • Abort from charging the NiMH cell if the temperature rises too high.
  • Don’t charge NiMH batteries with Lithium-ion Battery chargers. Lithium-ion battery chargers run a different algorithm.
  • Fully charge your battery for about 14-16 hours at a streak immediately after buying them. If you don’t, your batteries can develop a charge memory and not accept full charge anymore.
  • Never overcharge NiMH batteries. Overcharging them will shorten their useful life.

Keeping these easy points in mind can benefit you with performance. What to say, sometimes it’s just the little things that matter.

FAQs

Question: How long do NiMH batteries last?

Answer: NiMH batteries can be recharged hundreds of times. Which saves you from buying hundreds of alkaline batteries. However, they have a lifetime of around 5 years.

Question: Should I fully discharge NiMH batteries?

Answer: Never discharging NiMH batteries can increase their durability. It’s better if you recharge it before discharging the last 10% of the battery or so.

Question: What happens if you overcharge NiMH batteries?

Answer: NiMH battery cells like NiCds require constant current for charging

Question: What is the ideal amp for charging NiMH batteries?

Answer: 4 amps is ideal for charging a high capacity (3000-5000 mAh) NiMH battery completely.

Question: Can NiMH batteries be fast-charged?

Answer: Yes, NiMh Batteries can be fast-charged. But, it is not appropriate for all. Check the datasheet if it’s appropriate for it.

Summing Up

Though NiMH batteries are widely used, they can have crucial charge-related problems. However, we have tried to mention all the possible problems that can cause your NiMH battery not holding charge. 

We understand if you’re having some other problem regarding NiMH Batteries. Then why hold back? Feel free to mention them in the comment section below.

Also, leave a comment if you found this article of any help.

Till then, best wishes.

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