After cooking my lawnmower batteries because I forgot to disconnect after their full charge, I thought; why not make / buy an outlet timer that automatically turns off after a few hours. What does that... aha.. a coffee maker does...and there is a broken d'longhi sitting in the broken bin in the garage.. aha I thought... how to do it..
Easy peezy! I connected a yellow wire to the spot where I removed a blown thermister and reconnected that circuit. I connected a black wire to the black wire on the thermocouple, removing the thermocouple and replacing with a switch. I ran those out the input hole and hooked a female socket; I cut a rectangular hole for the switch in the lower housing. Now I push 'make coffee' and hear 3 beeps indicating that the keep warm circuit is on; 2 hours later the outlet timer goes off, and the batteries are full at 40 volts! The switch seems to be needed to be on before the 'make coffee' function is available, so I switch it on momentarily. And if'n I need a longer time: there is a big brown object on my circuit board that is likely a capacitor for the RC time constant; soldering another capacitor onto the back of the circuit board attaching to that one will double the time constant of that circuit.
Step 1: Get Inside
Slide the white sleeve off of the heating element circuit to reveal the thermister. Remove the thermister coz' it is burnt, using a sharp chisel to open the clasps holding the thermister connections. Using those clasps, reconnect the circuit and include a wire(yellow, in my case) long enough to reach out the bottom of the housing.; slide the white sleeve over the new connections.
The disk thermocouple is removed and the black wire is connected to a manual switch and to another black wire long enough to reach outside the bottom of the housing. The white wire from the other end of the thermocouple is connected to the other terminal of the manual switch, thus replacing the automatic temperature shutoff during the warming circuit activation, by a manual switch, eliminating the heating elements since the switch will remain off the whole time.
Step 2: Make Square Hole in Bottom Left of Housing
Depending on the switch chosen, make a hole in the bottom left of housing using a hack saw blade and a drill to initiate the cuts.
Connect the 2 wires to a female 110 V AC outlet plug. Plugin the Switching Power supply 100-240 VAC, 800 ma, 44VDC output.
Step 4: Operation:
1. Connect charger to battery plug; set white switch to off; I marked the top with a felt tip as that was the On position for my switch.
2. Push the "On/Auto/Off" button on the coffee maker; 3 beeps sound immediately when first used. However, re-use within a day or so, requires a reset using the white switch be momentarily pushed to On position. Always run the outlet timer with this switch in the Off position; 3 beeps indicate that the "keep warm" circuit is in use.
3. After 2 hours, the outlet timer switches off.