Hello NY,

>> On the down side, I've heard it said that some won't supply power while
>> they're charging themselves. I have no idea if that's true or not, but it
>> has rather put me off the idea :-{ Can anyone confirm/refute this?

> I've got an Anker 79AN7925 13,000 mAhr battery. I'd occasionally wondered
> about using it as a UPS for my Pi, but I've just tested it and it does what
> you feared: the output power is turned off whenever the battery is
> receiving power from a mains source. Grrr.

> I wonder if there are any batteries which maintain output power when
> input power is connected and turned on?

Yes, you could do that with domestic Lead Acid traction accumulators and
a good charger combined with a 12 or 24 Vdc= to 5.1 Vdc= converter.
Do not use car starter batteries for this.

> It would be a useful backup in case of power cuts. I use my Pi for logging
> data from a weather station and for recording TV programmes (using TVheadend
> and DVB-T or DVB-S adaptors) so some resilience would be useful. Mind you,
> when recording from satellite (DVB-S) I'd still need to find a way to
> provide 12V for the dish LNB, and from terrestrial aerial (DVB-T) I'd need
> to provide mains to the distribution amplifier in the loft. Maybe I just
> need a UPS for the whole house ;-)

That's doable with a bigger traction lead acid accumulator and chager/inverter
combination, even better when sunpanels and/or a windmills are available.
Inland ships use the same technics. Some also have a water generator ;-).
At the river they produce their own electricity.

> I have used my 12V-to-240V inverter that I keep in the car, to supply
> emergency power at work to essentials like routers and telephone VOIP
> switchboards during a lengthy power cut (JCB through high-voltage cable -
> nasty), so they could continue to make/receive phone calls, even if they
> couldn't use desktop PCs.
> I earned a few brownie points for coming up with that solution ;-)

We do the same here with inland ships and a 230/400 Vac~ three phase generator
and accumulator chargers and 3 inverters of 3000 VA.

> They left the engine of the company van ticking over (to
> avoid flattening its battery) and had an extension mains cable snaking
> from the van in through the door to the office -
> probably contravening loads of health and safety rules, but what the hell.

You only need first the Zero line earthed,
a 30 mA RCD switch in the inverter output of the Phase and Zero and
a 16 Amps current breaker in the phase line for the correct safety of lives.
Lower that currect breaker value if the inverter has less capacity.

Henri.

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