Intelligent Lead Acid Battery Charger

Product Image

A photograph shows an assembled electronic circuit board with a large black heatsink mounted on top. The circuit board is populated with various electronic components, including resistors, capacitors, integrated circuits, and connectors. The heatsink is designed with multiple fins to dissipate heat.

The charger is suitable for 6V and 12V sealed and open lead-acid batteries.

Features & Specifications

Features:

• ✔️ Suitable for 6V and 12V sealed and open lead-acid batteries.
• ✔️ Fully automatic charge and maintenance cycle.
• ✔️ Status indicators for charge, float, and end-of-charge.
• ✔️ Protected against polarity reversal.

Specifications:

• Power Supply: 2 x 9V/25VA
• Charge current: 0.3A or 1A selectable
• Dimensions (wxdxh): 97 x 140 x 41mm (3.8 x 5.5 x 1.6 inches)

Note: Not suitable for non-rechargeable or NiCd/NiMH batteries!

Options:

• Transformer prim. 230V - sec. 2x9V/25VA: 2090250MST
• Enclosure: TKAUS22G
• Power cord: NETSNOER

Assembly Instructions

1. Assembly (Skipping this can lead to troubles!)

These hints will help you to make this project successful. Read them carefully.

1.1 Make sure you have the right tools:

• A good quality soldering iron (25-40W) with a small tip.
• A wet sponge or cloth for cleaning the soldering iron tip. Applying solder to the tip after cleaning, known as 'thinning', protects the tip and aids in making good connections.
• Thin raisin-core solder. Do not use any flux or grease.
• A diagonal cutter to trim excess wires. Hold the lead when cutting to prevent it from flying towards the eyes.
• Needle nose pliers for bending leads or holding components.
• Small blade and Phillips screwdrivers.

For some projects, a basic multi-meter is required or might be handy.

A diagram shows a soldering iron, a spool of solder, a pair of wire cutters, and a pair of needle-nose pliers.

1.2 Assembly Hints:

• Ensure the skill level matches your experience to avoid disappointment.
• Follow instructions carefully and understand each step before performing it.
• Perform assembly in the correct order as stated in this manual.
• Position all parts on the PCB (Printed Circuit Board) as shown on the drawings.
• Values on the circuit diagram are subject to changes.
• Values in this assembly guide are correct (typographical inaccuracies excluded).
• Use check-boxes to mark your progress.
• Read the included information on safety and customer service.

1.3 Soldering Hints:

1. Mount the component against the PCB surface and carefully solder the leads.
2. Ensure the solder joints are cone-shaped and shiny.
3. Trim excess leads as close as possible to the solder joint.

Diagrams illustrate correct and incorrect soldering techniques, showing cone-shaped joints and trimmed leads.

Important: Remove axial components from the tape one at a time. Axial components are taped in the correct mounting sequence.

An illustration shows a strip of axial components (resistors) on tape, ready to be fed into a PCB.

Component List

1. Jumper wires

• J1
• J2
• J3

2. Diodes (150mA). Watch the polarity!

Diagrams show a diode with cathode and anode marked, and a surface-mount diode.

• D1: 1N4148
• D2: 1N4148
• D3: 1N4148

3. Metal film resistors (1%)

Diagrams show a resistor with color bands and a schematic representation.

• R1: 47K (4-7-0-2-1)
• R2: 27K (2-7-0-2-1)
• R3: 120K (1-2-0-3-1)
• R4: 180K (1-8-0-3-1)
• R6: 270K (2-7-0-3-1)

4. 1/4W resistors

Diagrams show a resistor with color bands and a schematic representation.

• R13: 10K (1-0-3-B)
• R14: 10K (1-0-3-B)
• R15: 33K (3-3-3-B)
• R16: 10K (1-0-3-B)
• R17: 1M (1-0-5-B)
• R18: 680 (6-8-1-B)
• R19: 15K (1-5-3-B)
• R20: 10K (1-0-3-B)
• R21: 10K (1-0-3-B)
• R22: 220K (2-2-4-B)
• R23: 2K2 (2-2-2-B)
• R24: 2K2 (2-2-2-B)
• R25: 12K (1-2-3-B)
• R26: 1M (1-0-5-B)
• R27: 1K (1-0-2-B)
• R28: 2K2 (2-2-2-B)

5. Metal film resistors (5%)

Diagrams show a resistor with color bands and a schematic representation.

• R5: 10K (1-0-3-B)
• R7: 10K (1-0-3-B)
• R8: 1K5 (1-5-2-B)
• R9: 1K (1-0-2-B)
• R10: 10K (1-0-3-B)
• R11: 4K7 (4-7-2-B)
• R12: 1K (1-0-2-B)
• R29: 1.5 (1-5-B-B-9)
• R30: 1.8 (1-8-B-B-9)
• R31: 2.2 (2-2-B-B-9)

6. IC socket. Watch the position of the notch!

Diagrams show an IC socket with a notch indicator and an IC chip being inserted.

• IC1: 14P

7. Diodes (3A). Watch the polarity!

Diagrams show a diode with cathode and anode marked, and a surface-mount diode.

• D4: 1N5400 ... 1N5408
• D5: 1N5400 ... 1N5408
• D6: 1N5400 ... 1N5408
• D7: 1N5400 ... 1N5408
• D8: 1N5400 ... 1N5408

8. Transistors

Diagrams show a standard NPN transistor (e.g., BC547) with base, collector, and emitter pins labeled, and a TO-92 package illustration.

• T1: BC547
• T2: BC547
• T3: BC547
• T4: BC547
• T5: BC547
• T6: BC557

9. Reference diode

Diagrams show a Zener diode with anode and cathode marked, and a schematic symbol.

• VR1: LM385Z-2.5

10. Screw connectors

Diagrams show two types of screw terminal connectors.

• SK1: 2p (AC)
• SK2: 2p (Accu)

11. Electrolytic capacitor. Watch the polarity!

Diagrams show an electrolytic capacitor with polarity marking (+/-) and a schematic symbol.

• C1: 2µ2

12. Switches

Diagrams show a slide switch and its schematic symbol.

• SW1: ON - ON
• SW2: ON - ON

13. Electrolytic capacitor. Watch the polarity!

Diagrams show an electrolytic capacitor with polarity marking (+/-) and a schematic symbol.

• C2: 4700µF/35V

14. Power transistor

Diagrams show a power transistor (e.g., MJ3001) in a TO-220 package, with mounting hardware (M4 nut, lock washer, M4 bolt) and a heatsink.

• T1: MJ3001

15. LEDs. Watch the polarity!

Diagrams show an LED with anode and cathode marked, and its schematic symbol. Dimensions for lead length (7mm) and body (3mm) are indicated.

• LD1: RED
• LD2: RED
• LD3: YELLOW
• LD4: GREEN

16. IC. Check the position of the notch!

Diagrams show an IC chip (e.g., LM324) and its socket, highlighting the orientation notch (Pin 1 indicator).

• IC1: LM324 or eq.

Testing

17. Testing

Perform all tests as shown below before the first use of the unit to check every function of your charger kit. Use the supplied 5W dummy load resistors and a reliable multimeter.

Test 1: 12V Output Voltage

Put SW2 in the 12V position. Measure the voltage across the output terminals. Output voltage should be 13.6V +/- 0.2V.

A circuit diagram shows the K8012 charger connected to a multimeter set to measure 13.6V DC, with SW2 set to 12V.

Test 2: 6V Output Voltage

Put SW2 in the 6V position. Measure the voltage across the output terminals. Output voltage should be 6.8V +/- 0.2V.

A circuit diagram shows the K8012 charger connected to a multimeter set to measure 6.8V DC, with SW2 set to 6V.

Test 3: 12V Load Voltage (>4Ah)

Put SW2 in the 12V position, and SW1 in the >4Ah position. Connect the supplied 33Ω resistor to the output terminals. Measure the voltage across the resistor. It should read 14.7V +/- 0.1V.

A circuit diagram shows the K8012 charger connected to a 33Ω resistor and a multimeter measuring voltage, with SW2 set to 12V and SW1 set to >4Ah.

Test 4: 6V Load Voltage (>4Ah)

Put SW2 in the 6V position, and SW1 in the >4Ah position. Connect the supplied 33Ω resistor to the output terminals. Measure the voltage across the resistor. It should read 7.3V +/- 0.1V.

A circuit diagram shows the K8012 charger connected to a 33Ω resistor and a multimeter measuring voltage, with SW2 set to 6V and SW1 set to >4Ah.

Test 5: 12V Current Limit (1A)

Put SW2 in the 12V position, and SW1 in the >4Ah position. Connect the supplied 8.2Ω resistor in series with the multimeter. Switch the multimeter to the ‘10A DC' position. It should read 1A +/- 0.1A.

A circuit diagram shows the K8012 charger connected in series with an 8.2Ω resistor and a multimeter set to measure 10A DC, with SW2 set to 12V and SW1 set to >4Ah.

Test 6: 12V Current Limit (0.3A)

Put SW2 in the 12V position, and SW1 in the <4Ah position. Connect the supplied 8.2Ω resistor in series with the multimeter. Switch the multimeter to the '10A DC' position. It should read 0.3A +/- 0.03A.

A circuit diagram shows the K8012 charger connected in series with an 8.2Ω resistor and a multimeter set to measure 10A DC, with SW2 set to 12V and SW1 set to <4Ah.

Troubleshooting Note: If any measurements show a considerable difference from the reference values, recheck the entire assembly, paying special attention to resistor values.

Building into an Optional Enclosure

18. Building into an optional enclosure

Figures 7 & 8 provide a drill pattern for the optional enclosure (ref. TKAUS22G). The included adhesive front panel label can be used to mark hole positions.

Steps:

• Position the label on the front panel and fix it temporarily with tape.
• Mark the center of the holes with a center punch.
• Remove the label and drill the holes.

Pay attention to the correct diameter and ensure all holes are free of burrs. Degrease the front panel before sticking the label. The label edges may need trimming with a sharp cutter.

Drill Patterns (Figure 7.0)

A diagram shows drill hole patterns for the REAR PANEL and FRONT PANEL of an enclosure, with dimensions indicated for hole diameters (e.g., Ø12.5, Ø3.5) and positions.

Drill Pattern (Figure 8.0)

A diagram shows a top-down view of an enclosure's internal layout with various hole positions marked for mounting components and ventilation, including dimensions.

Internal View

Figure 9.0 provides an internal view of the finished unit, showing the placement of the transformer, PCB, switches, connectors, and wiring inside the enclosure. It also illustrates the connection of the battery terminals (RED and BLACK wires) to the ACCU (battery).

Note: Make sure the unit is well ventilated, as the heatsink might run hot during charging.

Connection & Use

19. Connection & Use

Connection:

The unit can be connected as shown in Figure 10. This diagram illustrates the AC power input (L and N), a fuse (0.25A Slow), a resistor (R1823A/B), a 25VA transformer (9V outputs), and the K8012 charger unit with connections to the ACCU (battery).

Ensure your assembly complies with local safety regulations. For improved safety, use a non-conductive enclosure.

Use:

Perform the necessary settings before hooking up the battery:

• Select the appropriate charge current and voltage according to the battery capacity:
• Batteries < 4Ah: 0.3A charge current
• Batteries > 4Ah: 1A charge current
• You can estimate the charging time with the formula: Approx. charging time (hours) = (battery capacity (Ah) / charging current (A)) x 1.2

Note: Pay attention to the polarity when hooking up a battery to the charger. ?

• Switch on the unit to start the charging cycle.

Note: Batteries should be charged in a well-ventilated area due to the possible emission of gases. ?

Operation & Troubleshooting

20. Operation & Troubleshooting

Operation:

When a discharged battery is connected, the unit starts charging with the maximum current (0.3A for batteries <4Ah, 1A for batteries >4Ah) until the battery voltage reaches 14.7V (7.35V for a 6V battery). Once this voltage is established, the charger adjusts the charge current to maintain this voltage. At the end of the charging cycle, when the charge current drops significantly, the output voltage reduces to 13.6V (6.85V for a 6V battery). This allows the battery to remain connected indefinitely without risk. If the battery discharges, the charge cycle restarts automatically.

Troubleshooting:

If you have successfully completed the tests, there is not much that can go wrong. If the unit never leaves the 'charge' cycle, it could indicate a defective battery, a too low charge current setting, or a battery with too large a capacity.

PCB Layout

21. PCB

A diagram shows the top-down layout of the Velleman P8012'1 Lead Acid Battery Charger PCB, with component designators (R1, C1, IC1, etc.) and connection points labeled.

Schematic Diagram

22. Schematic diagram.

A detailed electronic schematic diagram illustrates the circuit of the K8012 battery charger. It shows the AC input, transformer, rectifier diodes (D4-D8), voltage regulator (IC1), transistors (T1-T7), reference diode (VR1), resistors, capacitors, switches (SW1, SW2), and LEDs (LD1-LD4). Component values and connections are specified, along with indicators for charging status, polarity, and voltage selection.

Manufacturer Information

VELLEMAN Components NV

Legen Heirweg 33

9890 Gavere

Belgium Europe

Website: www.velleman.be

Website: www.velleman-kit.com

Modifications and typographical errors reserved.

© Velleman Components nv.

Product Code: H8012IP - 2005 - ED1

Barcode reference: 5410329290719