Several things, apart from (as already noted) NiMH don't like float charge. You don't have any cut out mechanism when the battery reaches full charge. You don't have any temperature monitoring of the battery - rolls into the p= revious point. Check out the Linear technology devices at Analog Devices. The LTC4060 does NiMH up to 4 cells, which won't be enough, and you would n= eed to limit the input voltage as it doesn't go to 12V input. The LTC4079 looks like it will be right up your street though, 4 resistors,= 1 capacitor and 1 thermistor, 2.7V to 60V input range, 1.2V to 60V output = range, 10mA to 250mA charge current. https://www.analog.com/media/en/technical-documentation/data-sheets/4079f.p= df Biggest hassle is it is in a DFN package. Then in the switching battery chargers there are LT1512, LT1513 and LT1513-= 2 that would look hopeful. These use more components though. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of David = C Brown Sent: 30 October 2018 14:49 To: Microcontroller discussion list - Public. Subject: [EE} Am I carrying KISS too far? Power supply for a circuit with a handful of CD400 chips. 12vdc from wall-wort charges a 9volt NiMH through a series resistor. CMOS = runs of battery. Just the two components. What have I overlooked? __________________________________________ David C Brown 43 Bings Road Whaley Bridge High Peak Phone: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb *Sent from my etch-a-sketch* -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .