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 NiCads   NiMHs   SLAs   LiIONs   Bike batteries   Car batteries. . . IT'S THE ONLY BATTERY CHARGER YOU WILL EVER NEED, EVER AGAIN! Fast   Universal Power Charger . Part 2 By JOHN CLARKE For power tools, camcorders, R/C equipment and car batteries Last month we introduced our new, improved Universal Fast Charger for a huge range of batteries. Here’s the nitty gritty: how to build it! 66  S ilicon hip 66  S iliconCC hip I t’s arguably the only “high capacity” fast battery charger you’ll ever need – ever again! It will easily handle all the batteries you have in your power tools – it will even charge your car or motor bike battery! And while it won’t handle low capacity “AA” cells it can charge their big brothers – 1200mAh and above – along with “C” and “D” types of 1200mAh or more. For a more detailed list, see the panel at right or refer to the full description of operation in last month’s SILICON CHIP. Construction The SILICON CHIP Universal Fast Battery Charger is housed in a plastic instrument case measuring 257 x 190 x 85mm while the components are mounted on a PC board coded Main Features  Fast charges Nicad, NiMH, LiION, SLA and Lea d-Acid batteries  Suitable for 1.2V, 2.4 V, 3.6V, 4.8V, 6V, 7.2V, 8.4 V, 9.6V, 12V & 14.4V bat from 1.2Ah to 4.2Ah plus teries LiION 3.6V, 7.2V & 14.4V  Charges either 6V or 12V SLA batteries from 1.2 Ah to 4Ah  Charges 6V or 12V Lead-Acid batteries of any cap acity above 1.2Ah  Includes a discharge r for Nicad batteries  Top-off charging at end of fast charge plus pul sed trickle charge for Nic  Voltage limited charge ad & NiMH for SLA & Lead-Acid bat teries  Voltage drop & tem perature rise (dT/dt) full charge detection for Nicad  Under and over-temp & NiMH erature cutout for battery  Over temperature cut out for charger  Short circuit battery protection  Time-out protection  Fuse protection  Multi-LED charge ind icators This photo shows the completed project, giving a good idea of where the various components are located. Probably the most difficult part is winding the inductor (bottom right) but even this is a snack! July 2001  67 Figs 1&2 show both sides of the PC board, with the relevant section of the under-side shown below. LEGEND: = PC BOARD PIN NP = NON-POLARISED (BIPOLAR) CAPACITOR K A K A 56k K K 12k LED4 2.2k Q2 BC337 K 10mF 100V 2.2k 0.5W D1 MUR1550 68W ZD1 4.7k 14106011 and measuring 121 x 173mm. If IC1 is the surface mount or “ T” version, a small satellite PC board, coded 14302982 and measuring 29 x 16mm is also required . Transformer T1 is mounted sideways onto the rear metal panel as shown in the photographs. Underneath its mounting position on the case are several integral ribs and bushes (mounting pillars). These must be removed to allow the transformer to sit flat. The easiest way to remove the ribs is with a sharp chisel (careful!!) while the bushes are easily cut out with a large, sharp drill bit. The main PC board fits over four integral bushes in the base of the case, secured with self-tapping screws. Other bushes (under the board) may get in the way of the PC board or components – again, these can be easily removed with a large drill. Begin construction by checking the PC board against the published pattern. There should not be any shorts between, or breaks in, the tracks. If there are, repair these as necessary. 68  Silicon Chip 10mF 100V 0.1W 5W 0.1W 5W 1000mF IC3 4020 Q5 BC337 D5 1N914 1N 4148 0.1mF 10mF 16V 1 220k Q1 TIP147 22k IC2 4093 NP 10W 3.3mF 1N 4148 D4 680W 1 VR1 250k A BC548 LED5 D6 1N914 15k Q4 A 33k 1k D3 1N 4148 10k ZD2 D2 MUR1550 1M L1 1k 1W 33k 1mF 18k 25V A 18k 1k 1W 33k 100mF 20k LED3 100k 10mF 35V 27k 0.18mF 10k 100k LED2 820pF IC1 TEA1102 100k Q2 TIP142 27k 12k TPGND 100mF 16V 1 33k LED1 3.3k 30k PC stakes are used wherever connections need to be made to the PC board. These are soldered in first, in the positions indicated. Doing these first also acts as a guide to the positions of the links and resistors, which can be soldered in next. Use the accompanying table as a guide to working out which resistor goes where – or measure them with a digital multi-meter. Note that some resistors are mounted as a parallel combination: one is inserted as normal from the component side of the PC board while the second (shown in red in Fig. 2 at right) is soldered between the pigtails of the first resistor on the underside of the PC board. When inserting the smaller diodes and zeners, take care with their orientation and be sure to place each type in its correct place. Solder in the ICs and transistors, also taking care to orient them as shown. As mentioned before, IC1 may be supplied as a surface-mount type. If so, it must first be soldered onto the small carrier PC board, which in turn is connected to the main PC board with wire links or pin headers. Parts List – Universal Fast Battery Charger II 1 PC board coded 14106011, 121 x 173mm 1 PC board coded 14302982, 29 x 16mm (required for T version of IC1) 1 front panel label 244 x 75mm 1 plastic instrument case 250 x 190 x 80mm 1 aluminium rear panel to suit above case 1 heatsink 109 x 75 x 33mm (DSE H-3460 or equivalent) 1 18V 6A mains transformer (T1) (DSE M-2000 or equivalent) 1 ETD29/16/10 transformer assembly with 3C85 cores (L1) (Philips 2 x 4312 020 37502 cores, 1 x 4322 021 34381 bobbin, 2 x 4322 021 34371 clips) 1 NTC thermistor (DSE R-1797) (NTC1) 2 3AG panel-mount safety fuse holders (F1,F2) 1 630mA slow-blow 3AG fuse 1 7A fast-blow 3AG fuse 1 SPST Neon illuminated mains rocker switch (S1) 1 SPDT centre-off toggle switch (S2) 1 2-pole, 4-position rotary switch (S3) 1 4-pole, 3-position rotary switch (S4) 1 single pole, 10-position (1P10W) rotary switch (S5) 1 80°C thermal cutout (TH1) 1 momentary normally off push button switch (S6) 1 black 4mm heavy duty banana panel socket 1 red 4mm heavy duty banana panel socket 1 black 2mm micro banana panel socket 1 red 2mm micro banana panel socket 1 black 4mm heavy duty banana plug 1 red 4mm heavy duty banana plug 1 black 2mm micro banana plug 1 red 2mm micro banana plug 5 M4 screws x 10mm 6 M4 nuts and star washers 4 M3 screws x 10mm and nuts 1 M3 screw x 25mm and nut 4 self-tapping screws to mount PC board 4 insulating bushes for TO-220 and TO-218 packages 2 TO-218 insulating washers 2 TO-220 insulating washers 31 PC stakes 1 7.5A mains cord with plug 1 mains cord grip grommet 2 1mm spacers 10 x 5mm to gap L1 1 600mm length of red hookup wire 1 600mm length of green hookup wire 1 600mm length of blue hookup wire 1 600mm length of yellow hookup wire 1 600mm length of black hookup wire 1 300mm length of red heavy-duty hookup wire 1 300mm length of black heavy-duty hookup wire 1 150mm length of 0.8mm tinned copper wire 1 2m length of 1mm enamelled copper wire 1 55mm length of 15mm diameter heatshrink tubing 1 50mm length of 25mm diameter heatshrink tubing 10 small cable ties 2 solder lugs for earth terminals 2 10-way single in-line pin headers (if IC1 is surface mount “T” version) 5 5mm LED bezels Semiconductors 1 TEA1102 or TEA1102T fast charge IC (IC1) 1 4093 quad Schmitt NAND gate (IC2) 1 4020 binary divider (IC3) 1 TIP147 PNP power Darlington transistor (Q1) 1 TIP142 NPN power Darlington transistor (Q2) 2 BC337 NPN transistors (Q3,Q5) 1 BC548 NPN transistor (Q4) 2 MUR1550, BYW81P/200 fast recovery diodes (D1, D2) 1 1N4004 1A diode (D3) 3 1N914 or 1N4148 diodes (D4-D6) 1 35A 400V bridge rectifier (BR1) 1 12V 1W zener diode (ZD1) 1 11V 400mW zener diode (ZD2) 5 5mm red LEDs (LED1-LED5) Capacitors 1 1000µF 63VW PC electrolytic 1 100µF 25VW PC electrolytic 1 100µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 2 10µF 100VW MKT polyester (Philips 373 series) 1 3.3µF bipolar electrolytic 1 1µF 16VW PC electrolytic 1 0.18µF MKT polyester 1 0.1µF MKT polyester 1 820pF MKT polyester or ceramic Resistors (0.25W 1%) 1 1MΩ 1 330kΩ 1 150kΩ 5 100kΩ 1 68kΩ 4 33kΩ 2 27kΩ 1 22kΩ 2 18kΩ 1 15kΩ 1 10kΩ 1 4.7kΩ 1 2.2kΩ 0.5W 2 1kΩ 1W 1 680Ω 1 68Ω 2 0.1Ω 5W 3 220kΩ 2 82kΩ 1 30kΩ 1 20kΩ 2 12kΩ 1 3.3kΩ 1 1kΩ 1 10Ω Miscellaneous Heatsink compound, solder, etc. July 2001  69 should be written on each component. The electrolytic capacitors must be oriented with the correct polarity (with the exception of the 3.3µF bipolar type which can be mounted either way). Now install the trimpot. In similar fashion to the power transistors, the LEDs solder to the PC board and also emerge through the front panel. To allow this, the LEDs are inserted through the board with just enough length poking through to allow soldering. The LEDs are then bent over over Fig.3: the detail of the inductor winding. It so that they can protrude through has two windings but both go on as one. the holes in the panel. We don’t have to remind you to make sure The power transistors and power they’re the right way around, do diodes solder to the PC board but are we? No, we didn’t think so. . . also secured to the rear panel and The inductor (L1) is wound with heatsink. They are oriented with the two lengths of 1mm enamelled copper metal flange towards the edge of the wire, wound in “bifilar” mode – the PC board and are positioned above two lengths are wound as one with the board with sufficient lead length each turn of the winding actually being to allow them to reach their mounting two turns side-by-side, one from each holes on the rear of the case. length of wire. Capacitors can be soldered in next. Fig.3 explains this method of windThe accompanying capacitor table ing. First, if the wire is supplied as a shows the various codes, one of which two-metre length (as specified in the parts list) cut it exactly in half. Now let’s see . . . each length will be, uhh, um, too hard . . . Next remove the insulation from one end of each of the two lengths of wire and terminate (solder) the two ends onto two pins on the underside of the transformer bobbin. The actual pins used doesn’t matter since they are connected together on the PC board anyway. Now wind on the two windings of 20 turns by holding both lengths of wire between your thumb and forefinger and winding them on as one (ie, side-by-side). Once wound, cut the excess wires off, strip the insulation from their ends and terminate the wires onto the pins on the opposite side of the former. Again, the actual pins used are not important. Insert one core in place and secure with a clip. Now place the 1mm spacers on the two faces of the inserted core and place the second core in position, securing it with the clips supplied. Insert this inductor assembly into the appropriate place on the PC board and solder in place. An angled view of the rear of the case, particularly showing the method of mounting the power transistors and diode, the thermistor (with the red wires), bridge rectifier (block in the middle), transformer and mains wiring. Note that all mains wiring must be insulated with heatshrink tubing, as shown on the fuseholder at right of picture. 70  Silicon Chip That pretty much completes the PC board assembly – all that's left now is to mount the board (and everything else) inside the case. Assembly Place the PC board into the case (on its four bushes) and mark out the positions for the power transistor and diode mounting holes on the metal rear panel (a fine-tipped felt pen is ideal). Remove the rear panel from the case (it slides out) and drill out these holes plus two holes for the cord grip grommet and fuseholder in the position shown on the wiring diagram. 4mm holes are required for the transformer mounting and the earth termination plus the bridge rectifier mounting position above D1, along with the holes to mount the thermal switch TH1. All holes should be deburred with a larger drill, especially for the semiconductors to prevent punch- Capacitor Codes          Value 0.18uF 0.1uF 820pF IEC 180n 100n 820p EIA 184 104 821 Resistor Colour Codes – Universal Fast Charger    No. Value 4-Band Code (1%) 5-Band Code (1%)  1 1MΩ brown black green brown brown black black yellow brown  1 330kΩ orange orange yellow brown orange orange black orange brown  3 220kΩ red red yellow brown red red black orange brown  1 150kΩ brown green yellow brown brown green black orange brown  5 100kΩ brown black yellow brown brown black black orange brown  2 82kΩ grey red orange brown grey red black red brown  1 68kΩ blue grey orange brown blue grey black red brown  4 33kΩ orange orange orange brown orange orange black red brown  1 30kΩ orange black orange brown orange black black red brown  2 27kΩ red violet orange brown red violet black red brown  1 22kΩ red red orange brown red red black red brown  1 20kΩ red black orange brown red black black red brown  2 18kΩ brown grey orange brown brown grey black red brown  1 15kΩ brown green orange brown brown green black red brown  2 12kΩ brown red orange brown brown red black red brown  1 10kΩ brown black orange brown brown black black red brown  1 4.7kΩ yellow violet red brown yellow violet black brown brown  1 3.3kΩ orange orange red brown orange orange black brown brown  1 2.2kΩ red red red brown red red black brown brown  3 1kΩ brown black red brown brown black black brown brown  1 680Ω blue grey brown brown blue grey black black brown  1 68Ω blue grey black brown blue grey black gold brown  1 10Ω brown black black brown brown black black gold brown Here’s a similar view to the facing page, this time looking from rear to front and showing the switch wiring. Follow the wiring diagram and photos and you should have no difficulties. Note that the front panel is plastic, providing insulation from the mains. If a metal panel is used, it must be securely earthed back to the main earth point on the rear panel. July 2001  71 USAGE NOTES: (1) This charger is not suitable for charging cells and batteries with capacities below 1.2AH and voltages below 6V. AA and AAA Nicad and NiMH cells should not be connected to this charger as the "No Batt" LED will light due to the cell voltage rising above 2V with initial charging. However, the charger will charge a 6V AA Nicad battery pack successfully. (2) When charging older cells either singly or in series it is important to ensure that their contacts are clean to prevent voltage drops across these connections. High resistance connections will prevent the charger from operating correctly as it will detect a high voltage per cell and simply indicate "no Battery". In addition the connecting leads from the charger to the cell or cells must be rated at 7.5A or more and be no longer than necessary to prevent voltage drops. Fig.4: the complete wiring diagram of the charger, shown with the two panels laid out and flat. The earth lug (top of drawing) should ideally be a crimped type, not a solder type. The front panel should be the plastic one supplied with the case. If a metal panel is used it must be earthed back to the main earth point on the rear panel. The thermistor mounted on its flying leads. Connection to the front panel is via miniature banana plugs. through of the insulating washers and to ensure a flat contact to the heatsink. Place the heatsink against the rear panel and mark out the hole positions for drilling into the heatsink. Note that you must line up the heatsink so that the screws for Q1, Q2 D1, D2, bridge rectifier and thermistor will pass through the heatsink between the heatsink fins. Drill out and deburr these holes. Attach the PC board to the case with self-tapping screws. Apply a smear of heatsink compound to the flat face of the heatsink and secure the transistors and diodes to the rear panel and heatsink with a screw, nut, insulating washer and insulating bush. If you use a mica washer apply a smear of heatsink compound to the Fig.5: Cross-section through the heatsink, panel, semiconductor and its mounting hardware. It’s vital that the power transistors and diode are insulated from the rear panel. mating surfaces before assembly. (Silicone-impregnated glass fibre washers, much more common these days, do not require heatsink compound.) Check that the metal tabs of the devices are indeed isolated from the case by measuring the resistance to the case with a multimeter – it should show open circuit. Apply a smear of heatsink compound on the face of the rectifier (BR1) before securing it to the rear panel. It is not necessary to insulate the rectifier case from the rear panel. Pass the mains cord through its cord-grip grommet and secure the grommet into its rear panel hole. Also attach the fuseholder and secure the transformer with 4mm screws, star washers and nuts. Attach the earth wire (green/yellow stripe) to the solder lug (or preferably a crimp lug) and secure to the rear panel with a screw, star washer and nut. The front panel can now be drilled out to accept the switches, terminals and fuseholder. We used bezels to mount the LEDs – they hide a multitude of sins, especially holes that don’t quite line up! A photocopy of the front panel artwork (Fig. 6) can be used as a template for drilling. Attach the rear label in place after drilling and cut out the holes with a sharp hobby knife. The shafts of the rotary switches need to be cut down with a hacksaw. Many rotary switches supplied these days are universal – the number of positions required need to be set. If this is the case, you will need to set S5 as a 10-position, S3 as a 4-position, and S4 as 3-position type. Repeated from last month, this photo shows the mounting of the heatsink, transformer, mains lead and fuseholder. The screws in the heatsink go right through the panel to hold the power transistors and diode in place. 74  Silicon Chip July 2001  75 Fig.7: same-size drilling template for the rear panel. Fig 6: same-size artwork for the front panel. Use a photocopy as a drilling template. This label must be paper or plastic, not metal, to ensure insulation integrity is maintained between the wiring and the user. If a metal panel is substituted for the plastic panel ensure it is properly earthed. This is done by removing the locking collar from beneath the star washer and nut and rotating the switch fully anticlockwise. Then reinsert the locking washer into position 10 for S5, position 3 for S4 and position 4 for S3. Now assemble all the front panel components. Follow the wiring diagram, using coloured hookup wire. The mains wiring must be done using mains-rated wire, with the terminals for the fuse and power switch sheathed (insulated) with heatshrink tubing. Use heavy duty wiring for the connections between the rectifier and PC board, the thermal switch and to the output terminals and fuse F2. Tidy up the wiring with cable ties and insert the front panel into it slots in the case with the LEDs protruding through their bezels. You will need to make up some heavy-duty leads to connect from the output terminals to a battery, using heavy-duty banana plugs and large alligator clips. The thermistor, too, requires a connecting lead. This can be light-duty figure-8 or twisted hookup wire, terminated in miniature banana plugs. The thermistor leads themselves should be sheathed in heatshrink tubing where they solder to the connection lead. Testing Check your work carefully to ensure correctly placed components, orientation of the polarised parts and wiring. Test that the earth termination connects to the rear panel case by measuring the resistance between the earth pin on the mains plug and the case. It should be zero ohms (or very close). Now apply power and measure the voltage between the TP GND PC stake and pin 12 on IC1. You should measure about 12VDC. Check that pin 14 and pin 16 of IC2 and IC3 are at 12V. Switch S3 to the NiCd & NiMH position and check that the “no battery” LED lights. Connect the NTC thermistor and check that the voltage at pin 8 of IC1 is at about 2V when the temperature is around 25°C. Adjust VR1 for this voltage. If you heat up the thermistor slightly by gripping tightly between your finger and thumb the voltage should drop. If the temperature rises then it 76  Silicon Chip Figs.8 & 9: full-size artwork for the main PC board and the optional daughter board, required only for a surface-mount IC1. is either a very hot day and your body temperature is lower than that of the air (unlikely during winter!) or you have the wrong type of thermistor (eg, a PTC instead of NTC). When charging a battery make sure you select the correct battery type and voltage on the front panel switches. Also set the timer for the closest timeout period for the particular battery capacity. If you are charging a lead-acid battery then the timeout setting does not matter. You may wish to check the charge current using an RMS meter or a dig- ital oscilloscope which reads RMS. If a standard multimeter (ie, not a true RMS type) is used, you can expect the reading across the two 0.1Ω resistors in parallel to be about 200mV. An RMS reading should show about 300mV which is equivalent to 6A. Note that the heatsink and Q1 will run hot on fast charge and so the charger should be provided with sufficient ventilation to prevent the thermal SC cutout operating.