Advice needed on surge protectors and UPS

[CaptLimey]

IT buffs - advice please?
Power outages and lightening surges are not unusual in our neck of the woods so I'd like to install an interruptible power supply/surge protector. However I know naff all about them or what to go for. I need to run a 24" iMac and a Mac Book Pro laptop, as well as a WiFi router. I don't need to run the systems for a long period, just enough to save a file and close down. Ebay has a daunting array of options from sixty quid to over three grand!! Can anybody suggest what might be the most appropriate, reasonably priced bit of kit?
Rgds CL

 

[rayf3262]

A small 500VA UPS will protect you from brown outs and give you a minimum of about 10~15mins shutdown time.

 

[edgerton19]

Having worked for both APC and Dale Power Solutions in my past life I can offer the following advice.
The dual conversion UPS are considered to be the better option as far as power quality goes as the mains energy is converted to DC and then converted back to AC but ensure you get one with a sine wave output. They are not quite as efficient as line interactive units but there is no break between loss of AC and battery power supporting the load. Most dual conversion units can be put in ECO mode if you want improved efficiency and can tollerate a short break in power say 10-20ms as loss of mains is detected and the static switch goes onto the inverter.
Most if not all UPS have built in surge supression for mains trainsients caused by lightnig induced surges, direct lightning strikes onto adjacent power lines are another matter and even the best UPS will not be guaranteed to survive.
Sadly most of the lower cost UPS come out of China, India and othe Asian countries with China having around 2500 UPS manufactures.
You will need a UPS with at a minimum of 500 watts so I would get one rated at 1kVA (700 or 800 watts).
If you have the space choose a UPS with external batteries so you can define how much hold-up time you need and are not limited by the internal battery compartment.
I left Dale Power Solutions a year ago so I no longer have any involvement with the company but the UPS they sell are from one of the better Chinese UPS manufactures who have a good R & D team and manufacturing facilities and have proved to be reliable.

 

[solarman216]

You simply need a small inverter and a sealed lead acid battery with a charger that equals plus your current draw, you are then immune from external power problems, Rick

 

[(RIP) PLANK]

You simply need a small inverter and a sealed lead acid battery with a charger that equals plus your current draw, you are then immune from external power problems, Rick

That is an excellent plan!

 

[CaptLimey]

Thanks to all for the info. Particularly edgerton and solarman. I like your simplicity Rick!
Edgerton can I ask an update? A lot of the units on ebay say "Has the USB connection allowing communication to modern operating systems for auto shutdown and information gathering." What is the advantage of having/not having a USB to modem socket? And how do I tell if a unit is dual conversion and sine wave output? (Told you I knew naff all!)
Would a refurbished unit like item 400218096566 by UPS Trader fit the bill?
Rgds CL

 

[rustic]

You simply need a small inverter and a sealed lead acid battery with a charger that equals plus your current draw, you are then immune from external power problems, Rick

I agree with plank agreeing with Rick's suggestion, as it gives you greater flexibility as you can use the inverter for other tasks, the battery could also be used as a back up too.
This is the cheapest option. You will also be able to use the printer, scanner too.
Just buy an inverter that can handle twice what you need to save overloading it and allow ventilation for the battery as hydrogen gas will be given off, outside would be best.

Best regards, Rustic

 

[edgerton19]

Some interesting ideas from Solarman but it may not be quite such a good solution for the following reasons.
1) Low cost inverters when used 24/7 are not very reliable as they are not designed to run continuously day after day and will probably fail due to their capacitors drying out in 6-12months. Inverters can be purchased that will last but they are not cheap.
2) Low cost inverters have very little internal energy storage and therefore draw large 100Hz haversine ripple currents, now one of the things that shorten lead acid battery life is ripple current and as Corporal Jones remarked "they don't like it up um".
3) To keep the charging ripple current low and well regulated a simple low cost battery charger will not do the job it will require a well regulated output and as this will also see a proportion of the ripple current into the inverter some decent output capacitors are required so you need a decent regulated power supply again not cheap.
4) In the event of the inverter failing there is no backup, in a dual conversion UPS if the inverter fails for any reason the output is connected within a few ms to the incoming mains so the load is supported and an alarm is raised allowing the failed UPS to be sorted out. The lack of a static switch which can select inverter output or live mains is critical for system reliability.

There are three main types of UPS:
1) Simple: Mains powers the load via static switch and in the event of the mains failing the load is powered from the batteries via an inverter, in the cheap models the output from the inverter is a square wave. A small battery charger keeps the batteries topped up when mains is available.
2) Line interactive: Similar to the above but the UPS has a tapped transformer and a means (relays usually) of selecting the appropriate tap so the output of the transformer is kept within limits.
3) Dual conversion: Mains is converted to high voltage DC and an inverter converts this back to AC, In the small models the DC rail is usually around 350-420V and sufficient energy is stored in capacitors to allow time for the low voltage to high voltage DC-DC converter to run up without a break in mains output.

For the static switch to do it job the inverter output and the mains need to be synchronised.

Next question, Ebay item 400218096566 should do your job OK. As stated in the advert it is Sine Wave output, from memory these are Line Interactive units (see above) and although not quite as good as a Dual Conversion UPS it will power the devices you listed as all the devices should have 20ms of holdup within their power supplies.

Dual conversion and Sine Wave UPS will generally state such in their specifications.

If you want to ensure your computer shuts down properly even when you are not present then using the USB or serial output from the UPS along with the software provided should ensure you keep your data intact.

 

[CaptLimey]

Edgerton many thanks for the very full, useful and informative reply. I now know a little more than 'naff all' (dangerous!) but at least I can make a better decision than by just reading the advertising blurbs.
Rgds CL