DemonicSandwich
Member
Long story short, I don't have a good enough charger for my several 8 cell NiCd battery packs and as the result the batteries (and plane I used them for) went mostly unused for a couple years.
But with a renewed interest (and better knowledge of electronics) I decided built a battery charger for those NiCd packs(circuit attached) using only the components I have on hand and would rather to keep it as such.
From what I've read on NiCds, when charging they peak at a voltage of 1.6V per cell when they reach full charge then start to fall slightly so for an 8-cell pack that peak voltage would be 12.8V.
Another thing that I found was that NiCds respond to charging better if it's pulsed.
The circuit I built uses a constant current circuit found here but uses a power BJT rather than a FET.
I added extra transistors (Q3, Q4) so I can pulse it on and off.
R1 being 1Ω sets the current to about 500-600mA. The power supply is regulated supply rated at 16V, 4A.
The IC is a LM555 with a rated max supply of 16V so I added D3 and D4 to drop it into a safe area. I plan on replacing them with a 6V regulator.
The circuit works and the batteries respond very well to the pulsed charge and peak at ~12.8V as expected.
But my problem is is that it has to be watched. I need a circuit that shuts down the charging circuit(or oscillator) when the battery reaches 12.8V. I was thinking of using an LM1458N OpAmp I have from another project but I am not very familiar with opamps.
I just need something to change states when the battery reaches a set voltage using either that opamp or simple components.
(Image above is attachment)
But with a renewed interest (and better knowledge of electronics) I decided built a battery charger for those NiCd packs(circuit attached) using only the components I have on hand and would rather to keep it as such.
From what I've read on NiCds, when charging they peak at a voltage of 1.6V per cell when they reach full charge then start to fall slightly so for an 8-cell pack that peak voltage would be 12.8V.
Another thing that I found was that NiCds respond to charging better if it's pulsed.
The circuit I built uses a constant current circuit found here but uses a power BJT rather than a FET.
I added extra transistors (Q3, Q4) so I can pulse it on and off.
R1 being 1Ω sets the current to about 500-600mA. The power supply is regulated supply rated at 16V, 4A.
The IC is a LM555 with a rated max supply of 16V so I added D3 and D4 to drop it into a safe area. I plan on replacing them with a 6V regulator.
The circuit works and the batteries respond very well to the pulsed charge and peak at ~12.8V as expected.
But my problem is is that it has to be watched. I need a circuit that shuts down the charging circuit(or oscillator) when the battery reaches 12.8V. I was thinking of using an LM1458N OpAmp I have from another project but I am not very familiar with opamps.
I just need something to change states when the battery reaches a set voltage using either that opamp or simple components.
(Image above is attachment)
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