How Do NIMH Chargers Detect End of Charge?

[borisgazza]

i am intersted in the end of charge detection(-deltaV) on some NIMH chargers, i would like to test that effect on some chargers.
I got some chargers(like GP Smart power bank, GP H500,etc...),all the chargers i have use the drop of voltage as end of charge detection, so what i did is, I connected in serie to a battery a low ohmic resistance, i initiate the charge and after i while a short the resistor ,so drop of voltage but none of the charger did react to that drop,i manage to get a drop of 0.1V but still none of the charger i worked with reacted to that drop, so i would like to know if there are more criteria that i have to take in consideration to generate that drop?

 

[vk6kro]

You would have to know how the charger worked.

Microprocessors are so cheap now that the charger may well have one in it.
If it did, the programmer may have got it to do a series of voltage readings over several minutes and tried to detect a gradual decline in voltage which would indicate that the battery was charged.

An instantaneous voltage drop like you produced would not fool it. If it was only taking readings every minute or so, it would not even know you did anything unless you happened to do it when it was taking a reading. Even if it did register, it would look for a further decline in the next minute and so on over several minutes.

I have two chargers that work by detecting a rise in temperature of the battery when it is charged. Each battery sits in a metallic frame that gets hot if the battery gets hot. There would be a thermistor on each one that detects if the temperature varies above ambient.

 

[oswaler]

Thank you for sharing your interest in end of charge detection on NIMH battery chargers. It is important to thoroughly test the performance of these chargers, as proper end of charge detection is crucial for the safe and efficient charging of batteries.

In regards to your specific testing method, it is possible that there may be other factors at play that are affecting the detection of the voltage drop. It would be helpful to provide more details about your setup and methodology, such as the specific batteries being used and the exact process for initiating and stopping the charge.

Additionally, there are other criteria that may need to be considered when testing end of charge detection, such as temperature, charging current, and battery age. It may be beneficial to consult the manufacturer's specifications and guidelines for their recommended testing procedures.

Overall, it is important to continue exploring and testing different methods to ensure accurate end of charge detection in NIMH battery chargers. Your efforts in this area can help improve the safety and efficiency of battery charging.