Thanks for your reply. That’s a great tip. BUT it won’t help me for this situation.
The supplies I’m starting to use more and more are float-charged Ultracaps. This is where you have a power supply at the target voltage connected to Ultracaps to keep them topped up while they are used.
For a 3.3V or 5V input to a DAC or endpoint or similar, I’ll use 2 350F Ultracaps (that’s farad, NOT microfarads!) in series with a balancing resistor network. I charge them to the working voltage with a current-limited regulator (as they have a very low impedance and will take every milliamp or amp that a supply can provide until they are near or at the working voltage, which can easily overheat a regulator and send it into thermal or current shutdown). The charging process takes awhile… with the typical 250mA-limited regulator I use, they’ll reach 3.3V after about 1/2 hour. I only connect them to the devices after they are all charged.
In some cases I leave the Ultracaps connected to the original charging supply and regulator, in other cases I’ll jumper out the regulator and connect them to a supply at the same voltage level. I will do the latter where the current usage of the target device is above the 250mA level, such as powering an RPi-like player endpoint.
Given the time and effort to ‘start-up’ the setup, I generally leave these setups running all the time (and bring my BHK-250’s out of standby to play music). The problem I have with a power-outage is that even though the input float-charging voltages will be off, the Ultracaps will continue to supply the target equipment as they run down. First this means that the gear shutdowns will be random based on the current draw of each particular portion of the setup or circuit (a typical setup will have 3-5 of these Ultracap supplies powering different parts of the setup). Second, when the power comes on, where the original current-limited charger in in place, they’ll start recharging, but will get to their target voltages at various random times and likely not in the sequence needed for proper startup. Third, where I’ve jumpered out the current-limited chargers, the Ultracaps will try to charge at a much faster rate. The supplies I use here SHOULD be ok, they also have current-limiting (though at a higher current level) and are well heatsinked, but I’d rather not find out.
I know I can add relays to connect the supplies, but that’s a performance hit over a low-impedance direct connection and a bit more complexity to manage.
So at this point I’ll continue to monitor the weather predictions daily and shut down / disconnect my setups when adverse weather is predicted. AND hope for no random power outages (while they are rare, they do happen in this area) before this feature is available.
AND before anyone asks, these setups are solidly the best sounding supplies for the DIY builds I do. I have and continue to use LiFePO4 battery supplies in some cases where appropriate and have a number of very high-quality AC connected supplies that remain in use. BUT where I can use these Ultracap setups, only the LiFePO4 supplies come relatively close and are still in 2nd place.
AND SQ is everything to me!
Greg in Mississippi
P.S. There are some commercially-available supplies becoming available that use similar configurations. Three that I am aware of are:
https://www.ciunas.biz/product-page/iso-ps-ultracapacitor-power-supply
https://faradpowersupplies.com/shop/en/
https://allo.com/sparky/shanti.html
Search for them and you’ll find comments on them at Audiophile Style, DIYAudio, TirNaHiFi.org, pinkfishmedia.net, and Audio Asylum.