battery backup for a friends workshop surveilance kit

[adomakin]

my mates workshop has been busted into so we have fitted some infra red ccd stuff to catch the c--nts the next time they try it on. the problem with the system is that the 240v supply is really tempremental and has a habit of cutting out every couple of weeks. it will be out from anywhere between 1 min to 12 hours. when it comes back on the system needs to be setup again. there are five pieces to the system- a black and white CCD cam with motion detection and infra red, a secondary infra red light source, a video switcher, a VCR activator and a VCR. the switcher, activator and cam all run off one 12v transformer. the secondary IR light has its own 12v transformer and the VCR runs on 240v. I was thinking that perhaps i could use a pair of 12v car batterys wired in sequence hooked up to a car battery charger. then, to power the equipment, i thought that i could use a step-up transformer (like the ones you get to turn 12v into 240v for camping etc) hooked up to the charging batterys. what do people think of the setup in theory? i realise that a lot of it will depend on power demand of the equipment but how about the rest of the setup?

Andy, UK

[pwd72s]

20 12V batteries hooked together?

[adomakin]

that many?

[SteveStromberg]

Try a 12 Gauge with OO buck.

[Hugh R]

Hey Andy, its Hugh from Disney.

Try a Doberman with AIDS

Seriously, though the VCR probably steps down to 12 V look to tap in on the stepdowned side of that transformer. Or go to a computer store and get a 240 V UPS (Uninteruptable Power Supply) for a computer.

[304065]

Man, don't do anything to hurt anyone, you will be liable, even in the UK.

Famous case here called "Katko v. Briney," homeowner rigged up spring-gun, blew leg off intruder.

http://www.law.mq.edu.au/Units/law405/Study_Guide/Katko_v_Briney/katko_v_briney.htm

Anyway, add up the amperage draw of all of your stuff. If you don't have a clamp-on ammeter, look at the amperage draw on the power supply for each thing. I would think the IR illuminator would be the biggest draw, unless it's LED. That should help you size the battery capacity in amp-hours. Remember that you don't want to fully discharge a regular (non deep-cycle) battery, that will kill it. Check the hawker battery site for some good information about how far down you can pull the batteries.

[Fuzzbeaner]

Doing my electric car thing I've sponged up some battery info...

I'm not sure how to wire this up exactly, but I'll tell you this. For batteries to be float charged and then counted on for backup, you want deep cycle AGM batteries. No gassing, no spilling, and can handle high amp draws without...melting...:-D

Also, assuming that your 240v figure is from an AC wall outlet, you could just buy a 240 V AC/DC inverter that runs on your desired input voltage rather then matching the voltage with a battery pack. If anything that would make your job more difficult.

-Jeff

[adomakin]

thanks for the replys blokes. this place is great!
how you doing Hugh?