"CAUTION" ** SHOCK HAZARD ** This Circuit is "Live"as it Operates directly from the line voltage. Use this circuit ONLY when it is Completely Isolated from any persons coming in contact with it, or the battery it is charging and All associated connecting circuits.
"I Assume No Liability from the Construction or Use of this circuit"
So USE IT AT YOUR OWN RISK!
Using this circuit will give Good Charging results to a Sealed Lead Acid Battery, like I use in the Metal Detector.
This Circuit is Extremely Small in size and has a low parts count, making it ideal in some situations. It can also be adapted for Charging Nicads.
This charger is both Current and Voltage Regulated and the Output is short circuit protected.
The 1 Ohm resistor is a Fusing Resistor, Protecting the battery in case a short occurs.
With the 2.2 ufd capacitor it will produce an output of about 100 Ma. A capacitor of 1 ufd will produce an output of about 50 Ma.
The Zener used here, is rated at: 14 Volt and 5 Watts. Do Not use a lower wattage Zener.
For Charging a 12 Volt Nicad or NiMh Battery, use a capacitor to produce a current of 1/10 battery Capacity. (for a 1000 MA/H Battery, the 2.2 uf is suitable.) But use a 1N5352B Zener, as this zener has a 15 Volt Rating. Normal Charge Time at 1/10 capacity is 16 hours. But it Won't over charge or Over Heat your batteries.
The Fuse on this board is a "European" type, as they are smaller and fit the board better. Fuse is a 1 Amp rating or Smaller.
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Charger Schematic and PCB
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