800va single 12v Battery 'Online UPS'

[Chitrawan]

I will appreciate if you experts can please suggest & advice.

Is it possible to get this ‘online-ups:
- fully on-line – always working on DC bus - giving pure & clean power to computers
- capacity of around 800va @ 220v, single-phase
- pure sine-wave output
- using single unit of external 12v lead-acid battery of 70ah to 200ah
- sufficient battery-charging capacity to face longer load-shedding hours and power-fluctuations (around 140v to 260v)
- (desired) option to add solar-panels for battery-charging
- (desired) having lcd dispay as well LEDs & alarms for various information of output & input power, charging, battery-condition, etc.

Is such system technically limited anyway? I could not find any similar system in (at least in Indian) market – is there any?
Thanks.

 

[iop95]

Most of online UPS are for power from 3-5kVA. For 800VA is too expensive and no chance on today IT market (maybe only for special applications). You can made yourself.

 

[Chitrawan]

Thanks iop95.
If you don't mind, can you please suggest exactly where this high cost involves? Is there anything special which is not used in already available home-UPS, Inverters or line-interactive ones.

My main concern is to limit the need of battery to single unit of 12v. The already available 1kva/2kva online UPSes need at least 3 or 4 batteries of 12v.
Although line-interactives and home UPS/inverters are already available in 800va range using 12v battery but they don't protect the connected devices from power fluctuations.
Any hope!

 

[iop95]

Online UPS need that inverter work all the time and transfer time (from line to battery) is zero; that mean no relay in involved and battery feed instantly inverter when line is down. Also, there are a DC converter that compensate line voltage variation (up or down). For online UPS all inverter components are rated to work at 230-240V output rms voltage and not 12 - 24 -48Vdc like in cheap UPS that use a transformer to boost voltage to 230-240vac. Using such transform, efficiency is low and need bulky transformer because it work at 50 or 60Hz. In same UPS there are a boost converter that work at high frequency (with small ferite trasnformers); this solution improve efficeincy and reduce weight but are not cheap because boost converter and inverter need components at high voltage.
Regarding battery number / configuration, you know that power=voltage x current, so to reduce current to acceptable values (to reduce loses and cable area) in DC UPS section, need to increase voltage by adding more batteries in series connection. Also, increasing battery number increase back-up time for same load.

 

[Chitrawan]

Thanks iop95.
I got your point but still hope someone manufactures the online ups which works with 12v single battery.
For me, the one-time high cost is acceptable but bulk of 3 or 4 external lead-acid batteries is being burden.
Thanks again.

 

[kam1787]

An UPS is not a voltage regulator. To handle the voltage fluctuations you can use an AVR. outlet===>AVR---->UPS

no UPS is designed for continuous operation as you seek.............it seems you are looking more for an inverter:

outlet----->battery charger----->battery---->inverter---->equipment


not sure what you mean by 'clean, pure' power. Cheap inverters usually output a square wave which is usually tolerated. Better inverters give a close approx to a sine wave.

 

[iop95]

All UPS include a simple or more complicate AVR. Most simple have a transformer with 2 taps, one for overvoltage and one for under-voltage. Online UPS is a voltage regulator; it keep constant output voltage for a wide line voltage and also for variable battery voltage (from 13.75V in charged state up to 10.5V minim allowed, when UPS is shut-down). All UPS include an inverter.