UPS for FTTP voip

[David Wade]

Folks,

Can anyone recommend a UPS that will run an ONT, Router and DECT base
station during a power cut? DECT base is a pain as manual says it needs
5.5 volt so not sure types which supply 12, 9 and 5v will work.

Any suggestions as you how long will it power these for?

Dave

[Theo]

David Wade <g4...@dave.invalid> wrote:
> Folks,
>
> Can anyone recommend a UPS that will run an ONT, Router and DECT base
> station during a power cut? DECT base is a pain as manual says it needs
> 5.5 volt so not sure types which supply 12, 9 and 5v will work.

Is that 5.5v DC or AC? Does it have a transformer wallwart (heavy lump
mains plug) or a switching supply (lightweight mains plug)?

If it's 5.5V DC, I'd try powering it from 5V - I'd guess it might be OK. If
it has a transformer DC supply it may be unregulated, in which there can be
significant variation in voltage due to load.

> Any suggestions as you how long will it power these for?

I'd guess the load would be about 10-20W.

The trouble with 'big' UPSes with lead acid batteries and mains sockets is
they're inefficient at very small loads like that, being more designed to
run a desktop PC for a few minutes until shutdown. I'd be looking at ones
with a DC output rather than going up to mains and down again. I think
there are lithium 'mini UPS' units that are worth looking at, or there may
be some 12V UPS units without mains outputs.

If it turns out you do need an exact 5.5V supply, a regulator down from 12V
or 9V is an option. They are available in basic modules that you adjust
with a voltmeter and screwdriver:
https://www.ebay.co.uk/itm/231914360614

through to full units with a display and controls:
https://www.ebay.co.uk/itm/115811933758

- search 'adjustable buck regulator' to find them.

Theo

[Angus Robertson - Magenta Systems Ltd]

> Can anyone recommend a UPS that will run an ONT, Router and DECT
> base station during a power cut?

I use an APC BX500CI UPS, 500VA, should run 12-24 hours with several devices
plugged in, about £70 from Amazon. I also bought two IEC to 4x13A mains leads
for all the power supplies. Beware battery life is 3 to 5 years, so they need
replacing regularly.

Forget about using DC low volts, trying to get the correct leads and voltages
will be a nightmare, unless they all powered by USB leads when you just need a
powerpack.

Angus

[Woody]

5.5V suggests it has a series diode to prevent damage if the 'wrong' PSU
is connected?

[Chris Green]

A UPS will usually provide 230v mains power so the voltages of the
individual devices don't matter. You just plug theiw wall-warts into
the 230v output provided by the UPS.

--
Chris Green
·

[Theo]

Woody <harro...@ntlworld.com> wrote:
> 5.5V suggests it has a series diode to prevent damage if the 'wrong' PSU
> is connected?

Could be, or to provide headroom for a regulator to take it to exactly 5V.
In the latter case it would cope with being fed with 6V or more, although if
it's a linear regulator the higher the voltage the higher the heat
dissipation.

(I hope it's not a linear regulator, but we don't know the age of the unit.
I'm guessing it's not that old? What's the model number?)

Theo

[Woody]

A linear regulator such as a 7805 or LM317 usually needs about 2.3V
headroom, so I'll stick with my earlier suggestion.

[Nick Finnigan]

On 08/06/2023 10:07, Angus Robertson - Magenta Systems Ltd wrote:
>> Can anyone recommend a UPS that will run an ONT, Router and DECT
>> base station during a power cut?
>
> I use an APC BX500CI UPS, 500VA, should run 12-24 hours with several devices

The run time graph for that suggests 55 minutes at 30w, and I get similar
performance from my mini-UPS supporting Router + DECT. It is enough to
avoid a disaster, and often the power is back quickly.

> plugged in, about Ł70 from Amazon. I also bought two IEC to 4x13A mains leads

I attached a redundant IEC plug to a standard 4-way

[Andy Burns]

Woody wrote:

> 5.5V suggests it has a series diode to prevent damage if the 'wrong' PSU
> is connected?

or so that it provides the maximum USB 2.0 voltage, which is 5.5V (up
from previous 5.25V)

[notya...@gmail.com]

Woody is almost certainly correct.

[Theo]

A modern low dropout (LDO) linear regulator, not one from 1970s, has a
dropout (headroom) voltage less than a volt. For example, the first one on
Farnell's list has a dropout of 0.45V:
https://www.farnell.com/datasheets/1902868.pdf

But I doubt it's using a linear regulator, however a buck switching
converter will have a similar dropout requirement, depending on choice of
part, load current and circuit design. It's possible to cover that with a
buck-boost configuration, but there would have been no need for that in the
original design.

Theo

[Rupert Moss-Eccardt]

On Thu, 8 Jun 2023 10:07 +0100 (BST), an...@magsys.co.uk (Angus
Robertson - Magenta Systems Ltd) wrote:
>> Can anyone recommend a UPS that will run an ONT, Router and DECT
>> base station during a power cut?
>
> I use an APC BX500CI UPS, 500VA, should run 12-24 hours with several devices
> plugged in, about £70 from Amazon. I also bought two IEC to 4x13A mains leads
> for all the power supplies. Beware battery life is 3 to 5 years, so they need
> replacing regularly.

I'm not sure you'll get the endurance you expect.
The only way to extend endurance is more batteries not more VA