Question about battery chargers

Thread Starter

Sasuke Uchiha

Joined Jan 15, 2022
21
Hi.

When picking chargers for batteries, how do we know if the output voltage/amperage is not too low or too high for the battery? What do we need to look at?

For instance, here I have a battery, the only thing I know about the battery, is that it is a Ni-MH type and has 2000mAh and 7.2v

The charger has an output of 12V and 2A.

How can I know if this charger is safe or dangerous for the battery?

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AlbertHall

Joined Jun 4, 2014
11,952
Welcome to AAC, @Sasuke Uchiha.

Does the battery get charged in the equipment through an external power connector or do you need to remove the battery to charge it?

If through an external connector there should be an indication of what should be connected, printed on the case or the instruction manual.
 

DC_Kid

Joined Feb 25, 2008
924
Battery chemistries typically need a charging profile, this allows the chemistry to charge the right way so it can be used many times, and, to not overcharge it.

I have charged small "non rechargeable" button batteries by placing a voltage on them from my bench supply, let the mA flow for a few min, and voila, battery is back in business. 100% wrong way to charge it though. Pros & Cons as they say.
 

Thread Starter

Sasuke Uchiha

Joined Jan 15, 2022
21
Welcome to AAC, @Sasuke Uchiha.

Does the battery get charged in the equipment through an external power connector or do you need to remove the battery to charge it?

If through an external connector there should be an indication of what should be connected, printed on the case or the instruction manual.
Thank you.

The battery can be charged without removing it. The manual says that the operating Voltage Range for the controller is 6~15V. And the operating Current is 260mA.

Take another battery for instance. A 12V battery. Would using a 100V charger destroy the battery? Many devices use 5V/2A for charging. Does that mean that a 20V/10A charger would destroy the battery?
 

AlbertHall

Joined Jun 4, 2014
11,952
Batteries need a proper charging scheme - correct voltage, current, and time - to avoid damage.
If the battery is charged inside some equipment then, commonly, the chatger is built into the equipment (think mobile phone). In this case connecting the wrong voltage might damage the charger.
 

Thread Starter

Sasuke Uchiha

Joined Jan 15, 2022
21
Batteries need a proper charging scheme - correct voltage, current, and time - to avoid damage.
If the battery is charged inside some equipment then, commonly, the chatger is built into the equipment (think mobile phone). In this case connecting the wrong voltage might damage the charger.
What about connecting the correct voltage but higher amperage?
 

Thread Starter

Sasuke Uchiha

Joined Jan 15, 2022
21
In general this will not cause a problem as the circuit will draw the current it needs. Consider a car headlamp bulb. The battery supplies the correct voltage but is capable of many times the current that the bulb needs but the bulb is OK.
I see. Thanks. I found a picture of the original charger. Its 18V/0.5A. So the charger I have should at least not be too much for the battery.
 

MisterBill2

Joined Jan 23, 2018
11,556
Charging for an excessive time may do some damage. And with any charger it is wise to check the temperature of the battery after a few minutes of charging. I have seen batteries explode when charged with the wrong charger. A 7.2 volts, I think, battery connected to a 12 volt automotive charger exploded after about 10 miutes, totally split open lengthwise. Some things just don't work.
 

Tonyr1084

Joined Sep 24, 2015
6,861
Different types of batteries have different charging profiles. Too much current on certain types can overheat the battery and destroy it. It can also erupt in flames and potentially burn the house down. I wouldn't recommend charging batteries with just any kind of charger - you need the right charger for the right job.

12 volt chargers (for things like car batteries) are not so tightly controlled because car batteries are pretty robust and it's not easy to harm them. And for a 12 volt car battery the correct float charge is 13.6 to 13.8 volts. Holding a car battery at that voltage won't harm the battery. And as the battery is charging it will draw as much current as is needed. As the charge tops off the current drops because the difference in voltage between the battery and the charger drop closer to zero volts difference. When the battery is fully charged the charger is no longer delivering current to the battery. But with Lithium Ion type batteries it's critical to control the amount of current being delivered. The battery would LIKE to draw as much current as possible, but like a child in an ice cream store - too much is never a good thing. Also, the profile of charging Li-Ion batteries isn't so straight forward. I'm no expert on charging Li-Ion's but I believe as they charge for a certain period of time the charge current is one thing but as the battery approaches full charge the current is automatically dropped down by electronic circuitry. The battery won't do that on its own. I know even less about Nickel Metal Hydride batteries. But I'm sure they have a charge profile that needs to be considered as well.

So don't just experiment with voltages and batteries. You could end up with (not egg - but) acid on your face.
 

Audioguru again

Joined Oct 21, 2019
4,523
You are confusing the word "charger" which is inside the device that is powered by the battery, with the words "AC Adapter" that powers the charger circuit.
If you wrongly try to charge a battery from an AC Adapter then the battery will probably explode.
 

MisterBill2

Joined Jan 23, 2018
11,556
The requirements for a battery charging device depend on the type of battery to be charged. Flooded lead acid is the simplest, lithium batteries are the most critical and have the tightest charging specifications and the least forgiving conditions if done wrong. So it is not possible to describe a charger and how it works without knowing what type of battery is to be charged with it.
 
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