Krumlink

I just cannot figure out how to charge these
These little stinkers
Ive tried a 5V regulator with the output limited to 60ma (resistor) and it diddnt charge it at all google spammed me with 4.8V batteries, so I am stuck here. Any schemmehs or tips?

specs:
4.8V
60ma
NICad

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MechTronics

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blueroomelectronics

C/20 will work, but you might need a little more voltage.
Therefore if the batteries are 60ma then you can safely charge them at 60ma / 20 so 3ma won't hurt them.

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mvs sarma

Most of Cell chargers should work. Else, you have to create a constant current source. Simple way is to use a 7805 with a 2 diodes in the common path to ground. this will lift the supply to 6.4V approx. on the output put a diode for preventing reverse discharge and add a small resistor to limit the current to say 5mA.
you will find the battery charged in about 5 to 6 hours, as it was not charged earlier.discharge with an LED at say 25 mA until the voltage falls to just 4*0.8=3.2v and repeat the process.

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audioguru

The 4.8V battery needs a charging voltage of about 6V, not 4.8V.
It will overheat and POP if you charge it at 60mA. Charge it at 6mA and turn off the charger when it is fully charged.

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Uncle $crooge

k7elp60

I used to work for a electronic distributor that had a value added department.
In that department they built and rebuilt all kinds of rechargeable battery packs. And they also built lots of custom battery chargers for ni-cad
batteries.
They were very sucessful building Ni-cad chargers that charged at C X .095. constant current. They found that charging them at this slightly reduced rate a room temperature the batteries never overcharged and as a result the chargers could be left connected for extended periods of time.
Using this concept on Nickle metal hydride has worked well also.
A large number of the chargers used the LM317T in the constant current mode with the controlling resistor chosen so that the charge current was at the .095 or slightly lower rate. They also ensured that the charge voltage was at a minimum of 1.5 volts per cell or slightly higher.
As a side note:
As the Ni-Cad cells reach full charge three things happen, 1 the temperature of the cells rise slightly. 2. The internal gas pressure increases. 3. The voltage on the cell rises to a peak and then drops slightly.

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audioguru

On their website, Energizer shows that Ni-Cad cells that are continuously overcharged at 0.1C for two years are still good. But Ni-MH cells have 5 times the capacity of old Ni-Cad cells so their 0.1C charge rate is also 5 times higher. So Energizer recommends switching to a trickle charge rate of only 0.04 when the calls are fully charged.

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Uncle $crooge

on1aag

Hi Krumlink,

Try this one, I know it's a rather expensive and complicated
circuit but it's better than nothing.

on1aag.

Attached Images

Krumlink schematic.PNG (14.1 KB, 12 views)

Hero999

That 4.8V battery needs at leat 6.4V to charge.

Just use a resistor, rectifier and mains tranformer - simple easy and cheap.

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