Hi, On 2020-09-27 09:02, Poul-Henning Kamp wrote: > -------- > Bill Notfaded writes: > >> Are you saying if the load is small it'll still run out pretty quickly? > Yes. > > The constant loss of the inverter-stage will be nothing compared > to the full design load, but will totally swamp your light load. > > This is why UPS vendors only publish hold-up times for full load. > Which is why it is a good idea to run the load directly off the batteries. In telecom, that is -48 VDC (check out the ETSI EN 300 132-2 spec) but there is also one for modern switch-mode supplies for more IT-infrastructure which is feeding the 230 VAC side the DC it achieves after rectifier (ETSI EN 300 132-3 spec), but that has not taken off as far as I know. Both avoids the inverter part. Running straight of the batteries for 24 VDC matches many of our devices. For instance, all the atomic clocks and many OCXOs I have essentially run off 24 VDC, so that will be my focus.
The voltage range for the -48 VDC is really -40 VDC to -60,5 VDC to match the out of charge to charging voltages of normal lead-acid batteries. Sure, the 24 V or 48 V may not fit the needs of applications, but you can usually find DC/DC converters that can be decent enough loss-wise as they do switched mode drop-regulation. Choosing wisely amongst those, you can get better losses than a large supply which runs in a non-optimal mode. Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.