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Jamce Build

Generic Li-Ion-Cell Battery Charger Kit

Rechargeable Battery Technology

By GUSTECH

Li-Ion-Cell Battery Charger Kit Description: A generic Li-Ion-Cell Charger Kit
Skill Level: Intermediate
Assembly Time: 1-2 hours (depending on experience)

This Lithium Ion Battery-Cell Charger (LiBaC) Kit enables the user to use and recharge a broad spectrum of the latest rechargeable battery technologies, that of Li-Ion and Polymer Li-Ion cells and battery packs. Unlike the older, ubiquitous battery technologies, Li-Ion technologies are gradually replacing Li-Ion cells and polymer packs that are currently only available from a few sources. They come in a very large range of ampere-hour capacities and have very few options for recharging them. If you have a cell phone, you are already using a Li-Ion battery, or more likely, a Polymer Li-Ion battery, where the cell phone includes an integrated battery recharger specifically configured for that battery's capacity.

A single cell, regardless of ampere-hour capacity, is typically referred to as a 3.7 volt Li-Ion battery or a Polymer Li-Ion battery with the maximum voltage of either 4.1 volts, or 4.2 volts, the latter being the most common. These Li-Ion batteries typically include either pigtail wires (no connectors) or two-position (JST) connectors, and usually an integrated safety circuit board protects the battery from over-currents and over-charge/discharge voltages conditions.

Chargers for Li-Ion batteries use a very specific, constant-current/constant-voltage charging algorithm, usually with thermal and timing limiters, sometimes with trickle-pre-chargers for severely discharged batteries, to prevent damage to the battery and maximize safety. Commercially available Li-Ion battery chargers are available with fixed constant-current capacities, which may or may not match the recharging requirements. If an experimenter or hobbyist happens to be using five different capacity cells, 170mAh, 400mAh, 750mAh, 1050mAh and 2000mAh for five different applications, then they may need to purchase and use five different battery chargers to maintain them safely.

Alternatively, they could buy and build the LiBaC Kit and perform safe charging for all five of these and many other capacities, including most future battery-capacities not listed in this example. The LiBaC Kit includes:
  • Switch selectable maximum (float) voltage selection for 4.1 volts or 4.2 volts, LiPo cell dependent.
  • Switch selectable maximum charging currents of 100mA, 333mA, 600mA, 1.0A, and 1.5A; something no other commercially available charger has.
  • Switch selectable ability to disable the safety timer for some charging operations can benefit from this ability.
  • Integrated automatic-resettable (PTC-thermal) fuses on both the input and the output circuits for maximum safety.
  • Switch selectable "SHUTDOWN" or "CHARGE" master-control.
  • "Obvious-correct" LiPo cell connection scheme using red-black 5-way binding posts with (added-safety) "Connection FAULT" Red LED.
  • Four different "HUGE" (10mm) on-board status-indicator LEDs, indicating "Input Power OK," "Charging", "FAULT" (condition during charging), and even an indicator the LiPo Cell has been connected to the LiBaC incorrectly (before attempting charging).
  • The GUSTECH-feature of front-end goof-proof wiring, where it is impossible to apply incorrectly a wrong polarity input voltage as a charging source.
  • The ability to use a bench power supply, or any one of many available, linear or switching, wall-wart power sources using the common 2.1mm x 5.5mm power plug, with either positive-or-negative-center polarities.
  • Many on-board silkscreen notes for easiest usage of the LiBaC.
  • Printed circuit board-based enhanced-copper-pour thermal heatsink for the charging integrated circuit.
The printed circuit board for the LiBaC Kit can be used outside the box with standoffs or within a plastic enclosure, even bolted to a board (as in a row of chargers gang-recharging many different LiPo cells), as desired.

WARNING: If you are unsure of the dangers involved with your particular project, consult with someone who is experienced. Always wear eye protection and gloves. FAILURE TO INITIATE AND FOLLOW YOUR OWN SAFETY PROCEDURES MAY RESULT IN BODILY INJURY OR DEATH!

Required tools and parts:

Flux, solder and soldering iron
Enclosure
Wire cutters
Needle nose pliers
Surface mount equipment
Goggles, tweezers, and magnification equipment

Bill of Materials:

(1) Battery Charger Li-Ion 1500ma 4.1 Volt 4.2 Volt 10-Pin MSOP Ep
(1) Connector Terminal Blocks 2 Position 5mm Solder Straight Thru-Hole 16A
(1) Connector Power Male 3 Position Solder Lug Right Angle Panel Mount 3 Terminal 1 Port
(1) Binding Post Dual with Base 3/4" Spacing 30A Current Rating
(4) Switch Slide Min Single Pole Double Throw On-On PCB Mount 50 VDC @ 0.5 Amps Lead 4mm
(1) 600 Volt 2 AMP KBP Bridge Rectifier Diode
(1) 10mm Jumbo Diffused LED Green
(1) 10mm Jumbo Diffused LED Orange
(3) 10mm Jumbo Diffused LED High Efficiency Red
(1) DIP Switch 10 Cross Slot 0.025 Amp 24 Volt PC Pins 2000 Cycle 2.54mm Through Hole
(1) Capacitor Ceramic Disc 0.1µF 50 Volt 20%
(1) Epoxy Dipped Capacitor 1µF 50 Volt Z5u 20% Radial 5.08mm
(1) Capacitor Axial 10µF 450 Volt 20% 85c 1mm3 x 25mm
(1) Resistor Carbon Film 10kΩ 1/4 Watt 5% (In Bags of 10)
(8) Resistor Carbon Film 1kΩ 1/4 Watt 5% (In Bags of 10)
(4) Resistor Carbon Film 1.5kΩ 1/4 Watt 5% (In Bags of 10)
(1) Resistor Carbon Film 1.0Ω 1/2 Watt 5% (In Bags of 10)
(2) Resettable Fuse 1.60A-H 3.20A-T 40A-M 60VDC

Step 1 - Assembly IC1 part 1

It is probably a good time to break-out your optical magnification equipment for this tiny-work. May as well warm up your soldering iron.

Per this step's picture, locate the LTC1733 IC and place it near the position where it will be needed in the center of the PC board (in the next two steps), making sure the IC is rotated properly to ensure Pin1 will be soldered to its proper SMD pad.

IC1 Location on PCB

Step 2 - Assembly IC1 part 2

Under magnification the kit-builder will notice a large solder-covered metal area passing through the middle of the IC pins like a large silver bow-tie. This large solderable metal area is for connecting the bottom of the IC to the top surface of the PC board in order to establish a good metal path between the IC's die and the large copper areas on the PC board below the IC designed to act as a large heatsink for pulling away heat as it is generated within the IC during heavy-current charging operations.

The data sheet for the LTC1733 indicates the 'air-gap' between the 'exposed pad' on the underside of the package and the top surface of the PC board is between 0.005" and 0.007", nominally. The next step will fill some of that air-gap with a thin layer of solder prior to installing the IC to ensure a good solder flow will occur as the last operation after all of the IC pins are soldered (in the next step).

Study the picture with this step, comparing it to what you see on the PC board, ensuring a thorough understanding of the layout and attachment goals before proceeding with soldering. Once IC1 is fully soldered, it will be almost impossible to remove it for correcting improper orientation without destroying it in the process.

IC1 Pre-solder

Step 3 - Assembly IC1 part 3

*** IMPORTANT NOTE *** READ ALL OF THIS STEP'S TEXT BEFORE DOING THE ASSEMBLY WORK

Under magnification the kit-builder should first 'pool' a thin layer of solder over the entire 'bow-tie' metal area between the IC pin-pads. With the hot iron pull the solder from the center regions that will be under the IC to areas beyond where the package boundaries will be.

Before applying a little bit of solder to the pad for pin 1, first place the IC in position using your tweezers to ensure there is not too much solder under the IC, to prevent all ten leads from making solid connections with their respective pads (no leads hanging in the air).

If the leads are NOT all sitting on their pads, then repeat last half of the previous paragraph's instructions again (pulling the solder from the center region outwards) then rechecking the pins touch their pads. When all the leads touch their pads OK, then proceed... Apply a small amount of solder to the pad for just pin #1.

Using your tweezers, hold IC1 in its proper position, touching pad and pin #1 until its solder reflows, removing the iron while holding the IC in place until the solder solidifies.

If all of the other nine pins are not lined up over their respective pads, then repeat the above paragraph until all the other nine pins are lined up over their respective pads. Be careful not to push too hard on the IC pin while soldering this next location to ensure the IC remains in place. Rotate the assembly 180° and solder pin #6 to its pad (diagonally across from Pin #1). With two corners locking down the IC. Next, solder all eight pins that have not yet been soldered. Then, go back and reflow pins #1 and #6 if they need additional heat and/or solder for good filets.

*** IMPORTANT NOTE *** BEFORE PROCEEDING, CAREFULLY INSPECT ALL CONNECTIONS ENSURING THERE ARE NO SOLDER BRIDGES BETWEEN PINS AND PADS.

The last step involves reflowing the solder on the large metal bow-tie-heatsink that passes under the IC, applying enough heat and more solder to ensure solder connects the bottom of the IC's exposed metal pad to the top of the circuit board. Do this for both ends of IC1. Last Task: Inspect (on edge) the air-gap to make sure the solder has successfully bridged the air gap between the bottom of the IC and the top of the PC board.

IC1 Soldering Details

Step 4 - Assembly RESISTORS part 1

*** IMPORTANT OPTION NOTE BEFORE STARTING ***

If the kit-builder wishes to have higher accuracy for the various constant-current charging levels than those that can be obtained by using the 5% tolerance resistors supplied in your kit:
  1. Skip steps 10 and 11 at this time (don't forget to do them later)
  2. Purchase (from some other Distributor):
  3.       a) at least eight 3/4 Watt 1.0kΩ resistors with better tolerance
          b) at least one 3/4 watt 10.0kΩ resistor with better tolerance
  4. Perform step 10 installing the tighter tolerance 1.0kΩ resistors
  5. Perform step 11 installing the tighter tolerance 10.0kΩ resistor
»» see the notes in the bottom left corner of the schematics for more details

In the envelope with Jameco #659577 you will find the larger-body-size resistors. These are 1/2 watt resistors color-coded with Brown-Black-Gold with the value of 1Ω. You will need just one of these from the set of ten. In the envelope with Jameco #690742 you will find the smaller body-size resistors than the 1/2 watt found in the above paragraph. These are 3/4 watt resistors color-coded with Orange-Orange-Brown with the value of 330Ω. You will need five of these from the set of ten.

In the envelope with Jameco #690865 you will find 3/4 watt resistors color-coded with Brown-Black-Red with the value of 1kΩ. You will need eight of these from the set of ten.

In the envelope with Jameco #691104 you will find 3/4 watt resistors color-coded with Brown-Black-Orange with the value of 10kΩ. You will need just one of these from the set of ten.

Resistor Identifications

Step 5 - Assembly RESISTORS part 2

In the envelope with Jameco #659577 you will find the larger-body-size resistors. These are 1/2 watt resistors color-coded with Brown-Black-Gold with the value of 1 ohm. You will need just one of these from the set of ten. Remove one of these resistors and place the remaining nine in your own bench stock for other projects. Bend the leads as depicted in the picture for this step and insert them into the two holes (either direction) as shown. Bend the leads on the back side of the board to retain the resistor in place. Solder both leads in place, and trim the excess lead length using your side or flush cutters.

Resistor Installation Location

Step 6 - Assembly RESISTORS part 3

In the envelope with Jameco #690742 you will find the smaller-body-size 3/4 watt resistors color-coded with Orange-Orange-Brown with the value of 330 Ohms. You will need five of these from the set of ten. Remove five of these resistors and place the remaining five in your own bench stock for other projects. These five resistors are the current limiters for the JUMBO LEDs, with the (far right) Connection Fault Red LED having a pair of these resistors (R14 // R15) in parallel so the equivalent resistance of 165Ω permits higher current and a much brighter Red LED as a WARNING of a misconnected LiPo Cell should that accidentally occur. For each of the five resistors, bend the leads as depicted in the top left corner of the picture for this step, and insert them into the two holes (either direction) as shown in the top right corner of the picture for this step, in the five locations noted with red ovals. Bend the leads on the back side of the board to retain the resistors in place. Solder both leads in place for each of the five resistors, and trim the excess lead length using your side or flush cutters.

330 ohms Resistor Installation Location

Step 7 - Assembly RESISTORS part 4

In the envelope with Jameco #690865 you will find 1/4 watt resistors color-coded with Brown-Black-Red with the value of 1kΩ. You will need eight of these from the set of ten. Remove eight of these resistors and place the remaining two in your own bench stock for other projects. These eight resistors are part of the resistor string used two set the charging current for the LiBaC LiPo Cell charger, as short-circuited by S1 for the required range. For each of the eight resistors, bend the leads as depicted in the top right corner of the picture for this step, and insert them into the two holes (either direction) as shown in the top left corner of the picture for this step, in the eight locations noted with red ovals. Make sure you don't accidentally install a resistor in the location at the very bottom edge (no red oval) near the white silkscreen text of "LiBaC by GUSTECH June2015", as this location is reserved for the resistor in the next step. Bend the leads on the back side of the board to retain the resistors in place. Solder both leads in place for each of the eight resistors, and trim the excess lead length using your side or flush cutters.

1 kohms Resistor Installation Location

Step 8 - Assembly RESISTORS part 5

In the envelope with Jameco #691104 you will find 1/4 watt resistors color-coded with Brown-Black-Orange with the value of 10kΩ. You will need just one of these from the set of ten. Remove one of these resistors and place the remaining nine in your own bench stock for other projects. This resistor is also part of the resistor string used two set the charging current for the LiBaC LiPo Cell charger, as short-circuited by S1 for the required range. For this last resistor, bend the leads as depicted in the top left corner of the picture for this step, and insert them into the two holes (either direction) as shown in the top right corner of the picture for this step, in the one location noted with the red oval. Bend the leads on the back side of the board to retain the resistors in place. Solder both leads in place for this resistor, and trim the excess lead length using your side or flush cutters.

10k ohms Resistor Installation Location

Step 9 - Assembly SWITCHES

Various features and functions performed by the LiBaC are user-selected via one rotary switch (for choosing the maximum charging current during the constant-current phase) and three different Single-Pole-Double-Throw (SPDT) Slide switches selecting the maximum charging voltage, the use, or not, of the safety timing circuitry, and whether the charger is enabled or disabled. More details are provided in notes on the schematics later in this manual. Find the parts: The 10-position rotary (DIP) Switch, Jameco #139636, is most likely packaged in a short plastic tube with rubber stoppers for part retention. The three SPDT Slide switches, Jameco #109171, should be in a bag of their own. All four of these switches will be installed in this step.

*** STUDY THE PICTURE FOR THIS STEP ***

Rotary Switch Installation:
The 10-position rotary switch is polarized; it MUST be installed correctly (as shown) to ensure proper functioning of the LiBaC after assembly. The pin 1 dot is in the upper left corner; the number "0" (zero) position is upwards. Insert the six leads of the rotary switch into their holes, and solder them into place. No lead trimming is really needed for this device.

Slide Switches Installation:
The three SPDT Slide Switches are not polarized; they can each be installed in any direction and still function just fine. The holes for these switches were designed extra-large to enable these switches to be flush-mounted. For each switch, insert the three leads into their holes. While holding the switch in place, solder-tack (use just a little bit of solder) just the center lead enough to hold the switch in place. Inspect the top side of the board to ensure the switch is mounted flush against the board and is square in its location. If it is not, reflow the solder on the center lead while readjusting the switch's position to suit your preferences. Once the switch is positioned properly, solder the two outer leads in place, and add more solder to the center lead (if needed) to complete the switch's installation. Repeat these same operations for the two remaining slide switches. These switch leads do not need trimming.

Rotary and Slide Switches Installation Location

Step 10 - Assembly CAPACITORS part 1

0.1µF CAPACITOR at C2:
Find the 0.1µF axial ceramic multilayer capacitor, Jameco #536542. It is depicted in the top left corner of the picture for this step. Note the invoice you receive from Jameco may not mention the value of 0.1µF in the description for this part. This capacitor is non-polarized; it can be installed in either direction. Bend the leads as shown in the picture and insert the leads into the two holes (just left of the slide switch S3 installed in the previous step). Bend the leads (on the bottom side of the board) to hold the capacitor in place. Solder both leads and trim the excess leads with your side or flush cutters.

1.0µF CAPACITOR at C3:
Find the 1.0µF radial ceramic multilayer capacitor, Jameco #544956. It is depicted in the top right corner of the picture for this step. Note the invoice you receive from Jameco may call the value of this capacitor 1,000,000pF (which is 1.0µF) in the description for this part. The part may have a value inked onto it of #105 (as shown in the picture), which is a one, followed by a zero, and followed by five more zeroes (in Pico farads) = 1-0-00000 pf = 1µF. This capacitor is non-polarized; it can be installed in either direction. Insert the leads and bend them (on the bottom side of the board) to hold the capacitor in place. Solder both leads and trim the excess leads with your side or flush cutters.

Step 11 - Assembly CAPACITORS part 2

Find the (largest component, mostly) Black-body Electrolytic 10µF 450v axial-lead capacitor, Jameco #331425.

*** LOOK AT THE CAPACITOR CAREFULLY *** LOOK AT THE PICTURE FOR THIS STEP ***

Notice the capacitor's black insulation has a silver-arrow band with a minus sign pointing towards the one end of the capacitor that is all silver-color where its lead attaches. This end is the MINUS end of the polarized capacitor MUST be installed in the right-end hole, as depicted. Notice the other cap-end of the capacitor is black (insulator). This end is the POSITIVE end of the polarized capacitor that MUST be installed in the left-end hole, as depicted. FAILURE to install this capacitor properly could result in its over-heating, possible smoke, and even flames given the right conditions. INSTALL IT CORRECTLY. Bend the leads of this 10uF capacitor straight down and insert them into their proper holes. Bend the leads on the bottom of the board to hold the capacitor in place. Before soldering, recheck one more time to make sure the black end is to the left and the silver end is to the right. If okay, then solder the leads and trim the excess using your side or flush cutters.

Polarized Capacitor Installation Location

Step 12 - Assembly Photo-Check 1

The purpose of this step is to provide the kit builder with an assembly view as it appears following step 14 for comparison purposes. This particular photograph shows the LiBaC board in the (optional, recommended) box, Jameco's #141832 (without mounting screws installed or the clear lid in place).

LiBac Assembly

Step 13 - Assembly FUSES

*** STUDY THE PICTURE FOR THIS STEP ***

Important points (annotated on the picture) include:
  • These fuses are non-polarized; they can be installed in either position
  • The PC board silkscreen does NOT include the outline for these parts
  • The picture includes part of the assembly drawing (in the lower left corner) with reference designators and FUSE outlines to aid the kit-builder in finding the proper holes for the installation of both fuses.
Locate the bag with both fuses in it, Jameco #199938. Install one of the fuses at F1 (left of the large capacitor C1) and bend the leads to hold it in place. Install the other fuse at F2 (right of the large capacitor C1) and bend the leads to hold it in place. Solder both leads of both fuses and trim the excess with you side or flush cutters.

Fuse Location on the PCB

Step 14 - Assembly DIODES

*** STUDY THE PICTURE FOR THIS STEP ***

Important points (annotated on the picture) include:

The POSITIVE (output) Lead of this four lead module is marked three different ways to ensure the kit-builder has no doubts about the proper orientation for assembly:
  1. The longest lead is the positive terminal - goes in the square pad hole.
  2. There is a slant edge on the top of the package body on the end that has the (longest) lead that goes in the square pad hole.
  3. There is a (white) PLUS SIGN "+" on the side of the package body on the end with the positive lead - goes in the square pad hole.
THE POSITIVE LEAD GOES IN THE SQUARE PAD HOLE (nearest the white silkscreen text that reads "PWR in OK". Locate the bag with the diode bridge, Jameco #253260. Install all four leads, bending two of them to hold the diode bridge in place. Solder all four leads of DB1, and trim the excess with your cutters.

Diode Bridge Location on the PCB

Step 15 - Assembly LEDs part 1

*** STUDY THE PICTURE FOR THIS STEP ***

Normally thru-hole LEDs have a flat-spot on their body at the base to indicate which lead is the Cathode Lead. The dimensional diagram portion of the picture for this step, from the Data Sheet for these LEDs, shows this 'normal' method of indicating which lead is the cathode. HOWEVER, the actual LEDs in your kit do NOT have this flat-surface indicator. Implied in the technical information is the fact the longer lead is the Anode lead of the LED, and it is this fact we are going to use for installing these four LEDs on the LiBaC PC board. THEREFORE: THE SHORTER-CATHODE LEAD GOES IN THE SQUARE PAD HOLE [short-square]. The LONGER-ANODE LEAD GOES IN THE ROUND PAD HOLE [long-round].

LEDs Assembly

Step 16 - Assembly LEDS part 2

*** STUDY THE PICTURE FOR THIS STEP ***

THE SHORTER-CATHODE LEAD GOES IN THE SQUARE PAD HOLE [short-square]. The LONGER-ANODE LEAD GOES IN THE ROUND PAD HOLE [long-round]. Locate the Green 10mm LED, Jameco #2152104. With the longer lead to the left (at the round pad) insert the Green LED at the LED2 location, as shown in the picture for this step and bend the leads to hold it in place. Locate the Orange 10mm LED, Jameco #2152139. With the longer lead to the left (at the round pad) insert the Orange LED at the LED1 location, as shown in the picture for this step and bend the leads to hold it in place.

Locate one of the two Red 10mm LEDs, Jameco #2152112. With the longer lead to the left (at the round pad) insert this first Red LED at the LED3 location, as shown in the picture for this step and bend the leads to hold it in place. Locate the other Red 10mm LED, Jameco #2152112. With the longer lead to the left (at the round pad) insert this last Red LED at the LED4 location and bend the leads to hold it in place.

Solder both leads of all four LEDs, and trim the excess using your side or flush cutters.

LEDs Assembly Diagram

Step 17 - Assembly CONNECTORS part 1

This step assists the kit-builder in properly identifying and installing the two input power connectors on the LiBaC PC board.

*** STUDY THE PICTURE FOR THIS STEP ***

Input power to the LiBaC can be supplied via either a standard 2.1mm x 5.5mm DC Male Power Jack or a 2-position terminal block. Polarity is not an issue with the input connections due to the "goof-proof" wiring scheme made possible by the DB1 device installed in step 17. It is important to install both J1 (the power jack) and CONN1 (the terminal block) so their access to power (cable, or wires) is from the left side towards the board, as shown in the two detail views in the picture with this step. Locate the Power Jack, Jameco #101178. There are two oversized pads and a hole to accept this power jack, which uses solder tabs instead of pins for their wiring connections. The SQUARE Pad (at J1) connects to the center pin of the jack, and the OFFSET Pad connects to the sleeve. There is no connection to the BREAK circuitry within the jack (where the simple hole is located on the side of the Power Jack. Insert the Jack into the holes at J1 and, while holding it in place, solder the two tabs to hold the jack in place. Locate the 2-position (blue) Terminal Block, Jameco #2094485. Making sure the wire cages are facing outward, install the terminal block at the CONN1 location and, while holding it in place, solder both pins to hold the terminal block in place. You are finished soldering, if you want to turn off the iron now.

IMPORTANT NOTE: There is one more component to install on this board; it does NOT involve soldering. See the USER's Manual for more details.

END OF THE ASSEMBLY INSTRUCTIONS.

Input Connectors Location on the PCB