Some NIMH will "Tolerate" low current overcharge. This requires more catal= yst to recombine the hydrogen and oxygen, and these cells usually aren't th= e highest capacity. Most NIMH cells specify ZERO float current.=20 Nicad is better in this regard, as well as working over a wider temperature= range. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of David = C Brown Sent: Tuesday, October 30, 2018 12:00 PM To: Microcontroller discussion list - Public. Subject: Re: [EE} Am I carrying KISS too far? Thank y'all for your comments First to Art: My etch-a-sketch has been customised by a man in the back of= Glossop market. It has 802.11.ac wi-fi,, 4G connectivity and satellite connectivity. It is powered by a small water turbine so can be used anywhere a faucet is available. One bug, that answers Dave's comment, is that it cannot sustain runs zeros longer than two. For that reason I have = had to negotiate a cut in pay of a penny to avoid a run of six zeros in my = salary advice. :-) Seriously. I should have specified a NiCad battery since this is part of my retro 1978 clock and NiMH were not around back them. And it is my recollection that NiCads can be safely trickled at C/20 albeit with some de= gradation. And on further reflection it might be simpler to use a non rechargeable bat= tery. A good PP9 will supply about 400mAH which will cover a lot of short = outages. __________________________________________ 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* On Tue, 30 Oct 2018 at 16:52, AB Pearce - UKRI STFC < alan.b.pearce@stfc.ac= ..uk> wrote: > Several things, apart from (as already noted) NiMH don't like float charg= e. > > 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=20 > the previous 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=20 > would need 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=20 > resistors, 1 capacitor and 1 thermistor, 2.7V to 60V input range, 1.2V=20 > to 60V output range, 10mA to 250mA charge current. > > https://www.analog.com/media/en/technical-documentation/data-sheets/40 > 79f.pdf 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=20 > 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. =20 > 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=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > -- 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 .