Another one for your welcome input.... an intro to the backup power
options



There are lots of ways of providing '''Backup power'''. This article
introduces the various options, with their main features. Some of
these have their own articles that go into the option in more detail.


==Power options==
===Generator===
* how to detemine power needed
* noise
* maintenance
* cost
* service life (often very short)
* 2 strokes and starting reliability
* listeroids
* connecting to mains wiring

===Torch===

===Gas lighting===
Despite being historic technology, gas lighting has some advantages
over electrical power. The main one is its long term reliability,
which is hard to match using elecrical kit. Gas lights can be expected
to work for decades without attention or failure.

Gas cylinders don't discharge in storage, so power is always there
ready to go. This contrasts noticeably with rechargeable batteries,
which are prone to either
* being flat when wanted if not left on trickle charge
* having limited life if left on trickle

Gas lights produce a lot of heat due to low efficieny, and with
suitable care this can be used to cook or heat water. Even a small
camping gas light will put out around 400w of heat, which is enough to
cook on.

The high heat output means it should be put somewhere it cant be
knocked over in use. Hanging from the ceilng is often practical.

Putting foil round half the globe produces nearly twice the level of
forward light.

Cost per volume of gas varies widely for different cartridge types.
High gas cost lights can be uneconomic purchases, even if cheaper
initially.


===UPS===
'''U'''ninterruptible '''P'''ower '''S'''upplies provide a mains feed
that's not interrupted in the event of a power cut. The switchover to
internal battery is instant.

Large whole building units are available, but nearly all UPSes sold
are plug-in items intended to run one or a few low power appliances,
typically a computer system.

To avoid disappointment, the required capacity of UPS should be
calculated before purchase, otherwise its likely to fail to deliver
the run time wanted. UPS capacity is rated in kWh (kilowatts x hours),
so for example a 0.2kWh UPS could run a 100w (0.1kW) load for 2 hours.

UPSes are also rated by their max continuous power output. The load
appliance(s) should not exceed this rating. Note its the load's VA
that matters rather than watts. For some loads VA = watts, and for
some their VA rating is greater than watt rating.

Finally UPSes are also rated by peak power output. Some appliances
draw well above running power for a brief period at startup. It would
be wrong to assume that if the UPS meets an appliance's run current it
would also meet the startup current requirement.


===Laptop===
A laptop is often a practical way to get computer time during power
loss.

Where TV is wanted to sedate the kids, a laptop with a USB TV card can
be cheaper than a UPS to run the main TV, and of rather more use.

Extra batteries can give more run time. As well as expensive Li-ion
laptop batteries, laptops can be run off lead acids with higher
capacity and lower cost per hour, or carbon iron batteries.
Manufacturer's instructions should be followed in such cases.


===Lead acid, charger, invertor===
A good option for people that already have most or all of the parts.
However the necessary bits and leads need to all be to hand when the
power cut bhappens, and te battery must of course be charged and ready
to go.

===Candles===
Although basic, candles are a workable way to provide occasional
lighting. £1 buys a lot of tea lights.

Candles are associated with significant fire risk, so its only
sensible to use some means to keep the candle safe in use. Wall
sconces are effective, placing the candle high up out of reach,
especially of young kids.

Always keeping candles and matches in the same place makes finding
them in the dark easy.


===Emergency escape lights===
Non-maintained lights will light up automatically when mains power
fails. (Maintained units are designed for a slightly different job.)

Run time typically 1-3 hours, typical cost £15-20.

Fluorescent units generally give more run time due to the much higher
efficiency of fluorescent tubes.


===Rechargeable torch===
These are left permanently on trickle charge. Some can be set to come
on automatically when power goes off. Available light output and run
time vary.

Fluorescent torches generally give better run time, since the
fluorescent tube is much more energy efficient than the filament bulb.

All share one defect, limited battery life, and will require re-
celling after so many years. Cells with higher capacity can give
longer run time if required.


===Carbon iron battery===
The home made carbon iron battery can provide plenty of power at any
chosen voltage during a power cut. These are stored dry, and water is
added to activate them. Because of this, shelf life is indefinate.

Construction cost is trivial, they're easily replenished after use,
and can be built to any size for any load requirement.


===Luminaire backup pack===
Mains fluorescent lights are available with a battery backup pack
built in which will light the tube when mains fails. Be aware that
battery operation is usually at much reduced power. While popular in
commercial premises, this is not one of the cheaper options for
domestic use, expect to pay anywhere in the region of £80 or so. They
also arent generally styled for domestic use, but this issue is easily
sidestepped with trough installation.

===12v battery & 12v lights===
Fluorescent lights give several times the run time per light output
than filament lamps. A practical option where mains power isn't
needed.

Its possible to feed 12v wiring to every room, and add a relay that
switches a 12v lighting system on when mains fails. This may be an
attractive option when carrying out work that permits running new low
voltage wires, such as major redecoration, rewiring, installing a
wired network, etc.

Lead acid batteries require a few minutes of occasional maintenance to
last well.


===Nothing===
A lot of people choose no back up power, and are quite happy to sit in
quiet for once. It can be a nice break in a hectic life, and quite
refreshing.


==Choice==
The usual question that's posed when choosing is:

What do you want power for?
* lighting
* ch/hw
* tv
* computer
* etc

What will that cost, and is it worth it?

Now, more realistically, what will do?


==Business use==
When using backup power for commercial premises, its helpful to
estimate how much business is lost in one power cut, and roughly what
this value adds to over say a 10 year life of a power backup system.
This quick calculation shows that UPSes are a no-brainer for many
businesses.

Bear in mind that power cuts are in practice due to on-premises faults
as well as supply outages, and that getting an electrician generally
takes many hours.


==Connecting to house electrical circuits==
Care should be used in doing this, as its quite possible to kill or
injure a linesman if its not done right. Integrating the backup power
source with the whole house wiring is more involved than most DIYers
are willing to do. Running an extension lead from power to appliance
is a simpler option.


==See Also==
* [[Special:Allpages|Wiki Contents]]
* [[Special:Categories|Wiki Subject Categories]]



[[Category:Electrical]]


NT