Generic Li-Ion Battery-Cell Charger [ LiBaC ] Kit Brief:
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 are currently only available from a few sources, 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 3.7volt Li-Ion battery or a Polymer Li-Ion battery, with the maximum voltage of either 4.1volts, 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 that 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 to 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 4.1volts or 4.2volts, 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 that 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 that 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 2.1mmx5.5mm 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 (available from JameCo), or within a plastic enclosure (also available from JameCo), or even bolted to a board (as in a row of chargers gang-recharging many different LiPo cells), as desired.
Not including the cost of the printed circuit board, all the components for the LiBaC are available from Jameco for about the same total cost as just one of the commercially available single-rate battery chargers, without all of the extended features the LiBaC provides. All of the parts for the LiBaC Kit are thru-hole components, except for one component that is a 10-pin surface mount device (hence the “intermediate” assembly rating). The instructions and the BOM include a short list of available “wall-warts” that will work with the LiBaC Kit, if desired. The Instructions also include a list of some LiPo cells and their sources, as well as test results for a few of them used with the LiBaC kit. The Performance Test Results of the 'instructions' even include a preview of (working breadboard) circuitry used to test the discharge characteristics of various LiPo cells, the "LiPo-cell Electronic Load Tester" [LELT], another (future) JameCo kit from GUSTECH.