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How to charge my 9V battery with a no load 5V output?

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sr13579

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I am pretty much new with this adapter thing. I bought an adapter today with a 9 V rechargable battery. I tried my multimeter between the output and found something interesting. The output voltage is 5 volts on the 9V port. But when I am connecting the battery and turning the adapter on the voltage between them is 9V. What is wrong with my charger? I am using a DD Shager charger. Can anyone help?
 

audioguru

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You bought an adapter for it to do what? Is the DD Shager charger actually the "adapter"? Maybe its output pulses with an average voltage of 5V but its pulses have a higher voltage, then the battery is charging at 9V.

The very cheap DD Shager charger sold on ebay has no detailed spec's like its maximum charged voltage and its charging current. It does not say if it detects a full charge then shuts off. Its cover says it charges old fashioned 9V Ni-Cad batteries.

Is your 9V rechargeable battery old fashioned Ni-Cad or modern Ni-MH? Is it half charged at 7.2V (6 cells) or at 8.4V (7 cells)? What is its mAh rating?
 

sr13579

Member
You bought an adapter for it to do what? Is the DD Shager charger actually the "adapter"? Maybe its output pulses with an average voltage of 5V but its pulses have a higher voltage, then the battery is charging at 9V.

The very cheap DD Shager charger sold on ebay has no detailed spec's like its maximum charged voltage and its charging current. It does not say if it detects a full charge then shuts off. Its cover says it charges old fashioned 9V Ni-Cad batteries.

Is your 9V rechargeable battery old fashioned Ni-Cad or modern Ni-MH? Is it half charged at 7.2V (6 cells) or at 8.4V (7 cells)? What is its mAh rating?
I missunderstood the concept of charger and adapter. Sorry! Here is a picture.
 

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audioguru

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The charger says it will charge a Ni-MH battery. Good, your Chung Chang battery is Ni-MH (I wonder where it was made?).
The charger has two red lights with no labels. Do its instructions say it will detect a full charge then shut off or instead does it only have a simple timer (then a battery that already has a charge will be over-charged)?

Since the battery is Chinese then it probably has 6 cells and is fully charged at 8.4V but the charger might over-charge it to 9.0V.
 

audioguru

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Maybe the charger is extremely cheap and uses half-wave rectification with no filter capacitor. Then for 9V peak pulses its average DC measurement is about 5V with no load.

My 9V charger measures 5.98VDC with no load and it charges to at least 8.4V with no problem.
Yes, my 'scope shows 22V half-wave pulses with no load. With a 330 ohm load then the pulses drop to about 10V peak. Then the peak current is about 30mA which averages to 15mA which might be correct.
 
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