February 10, 2010
about 3 years ago
I have seen two problems with this. First, if you leave it connected to the battery while the power supply is disconnected current flows through the body diode of the pass transistor and lights the power LED. This drains the battery and makes the power LED useless. I solved this by removing the power LED, but a shottky diode in front of the current sense resistor would be a better solution. This would also keep the battery from discharging if the input is shorted.
The second problem is the timer. There is a 1.5 hour fast charge safety timer controlled by C1, a 100 nF capacitor. This means you can’t use it on a large pack like the 6 Ah. You just have to replace that capacitor with the value you like – the timer is proportional to the capacitance. The ideal situation would be to add a footprint to the board so the user can add a second capacitor in parallel to set the charge time. There is plenty of empty space on the PCB, so it should be no problem to add both a through-hole and a SMT capacitor slot.
about 4 years ago
Mine displays garbage characters when the input is floating. I am using it with an Arduino (using softserial so it doesn’t conflict with the USB->serial) that configures all pins as high impedance inputs on reset, which immediately overwrites whatever is on the display. Perhaps the next rev could include a pull-up resistor on board?
No public wish lists :(
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