Most cost effective / Min requirements to keep 1 POS PC and modem alive

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southafricanrob

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Hi,
I know there are many threads with varying info - am trying to establish the minimum and best solution to keep 1 PC (running a POS) and 1 ADSL modem/route going over loadshedding. I have a coffeeshop / cafe and am struggling to keep track of the table bills and people are exiting like the boss as soon as the wifi drops.

Some info: its a small form factor PC, I cant see the wattage as the power supply is all covered in glue but it a small external power supply, a 15" touch monitor, Linksys WRT54 Router.

As I understand so far my options are:
- medium sized UPS that also allows batteries to be added
- deep cycle batteries
- battery charger

OR

- approx 300W inverter
- deep cycle batteries
- battery charger

OR
- Generator
- small UPS to clean up the electricity

If I am correct so far then what I am trying to figure out is what sized batteries and what rated charger I need - I'm still struggling to get my head around amps and amp hours etc...I know something is wrong here in my calculations - can someone explain better? ie a 105Ah 12V battery has 1260 watts. Assuming only want to use 50% to not damage the battery that gives 600W approx. My PC and modem draw approx 150W so I sould be okay for 4 hours?? Something seems to good to be true here...?

Anyway any suggestions for my requirements with budget in mind from ppl running similar setups would be very welcome....
Thanks
 
If you want a seamless switchover to backup power a UPS is your best bet. The ADSL modem you can easily run for 4 hours on a normal cheap UPS (600 - 1000 VA). Running the PC is going to take a lot more though. Remember that a UPS is inefficient at converting power from the batteries. Also your use time decreases exponentially as you use more of the rated power.

A good place to start is the APC website, there is a calculator that will show you your required UPS size. It will cost you quite a bit though. With your details it looks like a 1000VA UPS with 1 or 2 extra battery packs will work, giving you between 500 and 800 minutes of power. Wootware sells these APC UPS's and one of the battery packs as well.

UPS
Battery

The recommended UPS is the SMART-UPS XL 1000VA, I don't see that sepcific one at Wootware, so I am not sure if that battery will work with that UPS, its just an example.
 
If you are not afraid of some wiring I would just buy a good quality sine wave inverter, good charger, 105Ah deep cycle battery.

You can then leave the pc and modem permanently connected to the setup and the charger will just charge the battery when the power is on.

If you discharge the battery to 50% you have 105x12/2 = 630Wh thats useable so at the full 300watt of the invertor you have just over 2 hours or 4 at 150watt.
 
Last edited:
Thanks guys,
Is there no issue with overcharging a battery if left charging permanently?
 
southafricanrob said:
Thanks guys,
Is there no issue with overcharging a battery if left charging permanently?
Click to expand...

Haven't looked at only chargers yet, but if it's a smart charger it should be ok. Normal charger that keeps pushing current will kill the battery. Don't know if the continuous power draw from the equipment will fool the charger into thinking the battery is still flat and thus keep a high charging current? Or will it just bypass the battery if it is in parallel to the load? That's how a UPS is wired.
 
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