How much time do you need after main supply fails? Based on battery capacity you mentioned, it sounds like 10-20 hours. OTOH, a later statement implies that you might only need a couple of minutes. On Thu, Oct 18, 2018, 06:39 Neil wrote: > Diode (or MOSFET) and supercap? > > > > > On 10/18/2018 6:04 AM, David Duffy (AVD) wrote: > > Customer specification. Not my call. > > David... > > > > On 18/10/2018 7:39 PM, AB Pearce - UKRI STFC wrote: > >> Why don't you want Li cells? > >> > >> > >> -----Original Message----- > >> From: piclist-bounces@mit.edu On Behalf Of > David Duffy (AVD) > >> Sent: 18 October 2018 10:24 > >> To: Microcontroller discussion list - Public. > >> Subject: Re: [EE] 5V UPS > >> > >> Yeah, I've seen a few but so far they are all lithium cell based. > >> David... > >> > >> On 18/10/2018 6:45 PM, AB Pearce - UKRI STFC wrote: > >>> There are "UPS" devices around for use with raspberry Pi. The one I > recall seeing is done as a HAT board. Maybe something like this could be > adapted to your usage. > >>> > >>> > >>> > >>> -----Original Message----- > >>> From: piclist-bounces@mit.edu On Behalf Of > >>> David Duffy (AVD) > >>> Sent: 18 October 2018 05:08 > >>> To: PicList > >>> Subject: [EE] 5V UPS > >>> > >>> I have a need for a "5V UPS" for want of a better term. > >>> > >>> Input from the mains power source is 5V and limited to around 150mA . > Output to the system is 5V, 90mA at idle with short bursts of up to 500mA > required. > >>> > >>> Battery capacity required is somewhere in the 1AH - 2AH range. Batter= y > can not be Lithium based. Options are Ni-Mh or SLA or ??? > >>> > >>> Mains will normally be available 24/7, but if it fails I need to keep > running from battery until it reaches its safe low voltage point. > >>> > >>> Any pointers on the best battery chemistry to go with and what type o= f > charging will keep it healthy long term? > >>> David... > >>> > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 .