On Jul 31, 3:34*am, wrote:
Another one for your welcome input.... an intro to the backup power
options

OK, version 2... and hopefully the last version.

And a brief note - there seems to have been a lot of confusion around
UPSes, and since theres a fair bit to write about them I decided to
move the ratings info to a prospective UPS article rather than within
this one - it doesnt seem to belong here after all.

Oh, iron carbon batteries are he
http://www.wiki.diyfaq.org.uk/index....carbon_battery


Thanks, NT




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
* the Cult of the Listeroid
* connecting to mains wiring

===Torch===
[[Battery]] torches tend to turn out to have flat batteries. [[Nicad
battery|Rechargeable batteries]] are worse in this respect, with quite
high self discharge rates.

Wind-up and shake torches don't need batteries, so are more likely to
work when they haven't been used in ages. They don't run long on a
charge, but can be useful to see to get another power source running.

[[LED Lighting|LED]] torches give out less light and light of lower
CRI, but run longer, are much less prone to bulb failure and are far
more robust.


===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

A small camping lantern will produce more light than a 60W incandesent
light bulb for several hours at maximum brightness. If longer run time
or less light is required they can be turned down and give really long
run times, 10 hours or more depending on cartridge size.

The quality of the light is quite good, and much better than the low
CRI and high CCT types of electric lighting, such as LEDs and
[[Fluorescent Lighting|cool white fluorescent tubes]].

Gas lights produce a lot of heat due to low efficiency, 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 can't be
knocked over in use. Hanging from the ceiling 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. Small cheap units may only manage minutes
of backup time.

To avoid disappointment, the required capacity of UPS should be
calculated before purchase, otherwise its likely to fail to deliver
the run time wanted.


===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 acid battery|lead
acids]] with higher capacity and lower cost per hour, or an [[iron
carbon battery]]. Manufacturer's instructions should be followed in
such cases.


===[[Lead acid battery]], 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 happens, and the battery must of course be charged and
ready.


===Candles===
Though basic, candles are a workable way to provide occasional
lighting. £1 buys a lot of tea lights, but not a lot of light level.

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. Finding them in a new location can be a
hopeless task in the dark.


===[[Emergency Lighting|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 Lighting|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 Lighting|fluorescent tube]] is much more energy
efficient than the [[Filament Lamps|filament bulb]].

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


===[[Iron carbon battery]]===
The home made iron carbon 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. Very large
batteries are quite constructable.


===Luminaire backup pack===
Mains [[Fluorescent Lighting|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 aren't generally styled for domestic use, but
this issue is easily sidestepped with [[Fluorescent Lighting|trough
installation]].


===12v battery & 12v lights===
[[Fluorescent Lighting|Fluorescent lights]] give several times the run
time per light output than [[filament Lamps]]. A practical option
where mains voltage 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. See [[Low Voltage Wiring]].

A [[Lead acid battery]] requires a few minutes of maintenance every
couple of years to last well.


===Glowsticks===
Low light output and high price, but long shelf life, completely safe
to give to kids and keeps them amused.

Glow in the dark tabs can be added to door handles to help small
children navigate the dark.


===Paraffin lamp===
Old fashioned pressurised paraffin lamps (Coleman, Petromax etc) are
much cheaper to run than gas canister lamps, but a little knowledge &
time is needed to get them started. They're also not the safest
lighting option.


===Nothing===
Most 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
* freezer
* cooking
* etc

What will that cost, and is it worth it? Now, more realistically, what
will do?


==Services==
===Cooking==
If power for cooking is needed, as well as the above options it can be
provided by any of:
* disposable charcoal BBQ tray
* wood/coal fire
* gas stove, either mains, bottled gas or camping canister type
* paraffin stove
* and maybe self heating instant meals

If considering these options, bear in mind that old fuel cookers such
as paraffin types can sometimes produce significant CO, and will
require proper ventilation or use outdoors.

===Phone===
Wired phones connected direct to the line should continue to work in a
power cut. Not all companies keep as much reserve run time at the
exchange as BT.

Mobile phones may stop working as most nearby cell towers have no
backup power source. A mobile with a flat battery will of course be
dead - obvious, but sometimes overlooked.

Cordless phones stop working if the base unit doesn't have a built in
[[Nicad battery|rechargeable battery]]. Those that do should continue
to work for a fair time if the battery is serviceable.

===Internet===
Dialuppers using a land line should have no problem for a while.
Wireless mobile net access will suffer the same fate as mobile phones,
and usually stop working.

Broadband services require power to the modem to work, otherwise net
access stops. Any routers will also need power if you want them to
work.

===TV===
[[TV aerial]] systems that include an [[Aerial amplifier|amplifier]]
will play dead during a power cut.

Set top boxes and anything else the aerial signal runs through will
also want power providing, or won't co-operate. However its not hard
to connect the [[Cable for TV aerials|aerial lead]] direct to the TV
to just get the 5 main channels.

===Computers===
Desktop systems and CRT monitors are both power hungry. Cheap plug-in
power backups won't run these for long, and in some cases won't run
them at all. Laptops are more practical.

Desktop systems with a CRT monitor on a UPS suffer a particular issue:
if the monitor is off when power is lost, switching it on tends to
glitch the backup power, which often resets the computer or shuts down
the UPS. This is due to the high initial current consumption of the
degauss circuit in nearly all CRT sets. Even a 1kVA UPS can be caught
out by this in some cases.

CRT monitors can be modded to sidestep this problem by putting the
degauss circuit on a switch, and normally leaving it off, but few
would bother for domestic use.


==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. A
quick calculation shows that UPSes are a no-brainer for many
businesses.

Bear in mind that power cuts are in practice due to [[Circuit faults|
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 the right safeguards aren't in place. 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 source to appliance is a simpler option.


==Wiring Design==
Its possible to choose what appliances you want to work in a power
cut, and provide a separate circuit to run them, possibly with a UPS
to keep the circuit alive for a while. Very few of us go that far, but
some will wish to at design time.


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



[[Category:Electrical]]