Parts
| R1, R3 | 2 | 330 Ohm 1/4W Resistor | |
| R2 | 1 | 100 Ohm 1/4W Pot | |
| R4, R5, R7, R8 | 4 | 82 Ohm 2W Resistor | |
| R6 | 1 | 100 Ohm 1/4W Resistor | |
| R9 | 1 | 1K 1/4W Resistor | |
| C1 | 1 | 220uF 25V Electrolytic Capacitor | |
| D1 | 1 | P600 Diode | Any 50V 5A or greater rectifier diode |
| D2 | 1 | 1N4004 Diode | 1N4002, 1N4007 |
| D3 | 1 | 5.6V Zener Diode | |
| D4 | 1 | LED (Red, Green or Yellow) | |
| Q1 | 1 | BT136 TRIAC | |
| Q2 | 1 | BRX49 SCR | |
| T1 | 1 | 12V 4A Transformer | See Notes |
| F1 | 1 | 3A Fuse | |
| S1 | 1 | SPST Switch, 120VAC 5A | |
| MISC | 1 | Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output, Fuse Holder |
Notes
- R2 will have to be adjusted to set the proper finish charge voltage. Flooded and gel batteries are generally charged to 13.8V. If you are cycling the battery (AGM or gel) then 14.5V to 14.9V is generally recommended by battery manufacturers. To set up the charger, set the pot to midway, turn on the charger and then connect a battery to it's output. Monitor the charge with a voltmeter until the battery reaches the proper end voltage and then adjust the pot until the LED glows steadily. The charger has now been set. To charge multiple battery types you can mount the pot on the front of the case and have each position marked for the appropriate voltage.
- Q1 will need a heatsink. If the circuit is mounted in a case then a small fan might be necessary and can generally be powered right off the output of D1.
- T1 is a transformer with a primary voltage appropriate to your location (120V, 220V, etc.) and a secondary around 12V. Using a higher voltage secondary (16V-18V) will allow you to charge 16V batteries sometimes used in racing applications.
- If the circuit is powered off, the battery should be disconnected from it's output otherwise the circuit will drain the battery slowly.
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