Running Stuff on Solar Via UPS/Inverter

[bhvm]

Dear all,

I am trying to work out a small Solar backup unit. I got the solar part right,I can now charge 2x12v 150AH tall tubular batteries at about 10~11A (In Series) Using a state of the art MPPT solar charge controllers. Now what remains is the UPS/Inverter part. Please provide guidance on the following questions-


1> I have 2 UPS options to use. Both are rated at 800VA. Made by Same manufacturer- Microtek (reputed manufacturer in our area). The Only difference is , One unit runs on 24v (2 batteries in series) and other is 12v Unit.
Surprisingly, the 12v unit is beefier & heavier. Does it mean that 24v units can use smaller transformer for the similar VA ratings? What is the underlying reason. I have modified Both units with fans for added cooling.


2> For this application, I am leaning towards the 24v Unit. As Charging batteries with 24v config appears more efficient. Is that correct?

I have connected the 24v 800va UPS for the moment.


3> There is a slight shock/ Stray current at battery terminals when UPS is ON. Is this normal?
The shocking is not present in 12v Unit.


4> The Lights connected to 24v UPS (On battery mode) Flicker a bit when there is hardly any other load on the UPS. I am using Seoul LED modules with appropriate Drivers & Heatsinks. The Flickering Vanishes when some additional load (Eg a Fan) is started on UPS. What is causing this behavior?

 

[Ken g6]

Using a UPS to power devices continuously in this way makes me nervous. I wouldn't expect most UPSes to be designed for such continuous use.

I'd prefer to look for an inverter for a car. But I'm not sure they have 24V units for that.

Do you have to use AC-powered LED lights? They have to re-convert the power to DC, anyway. I'm quite sure there are LED lights that could be powered directly from your batteries.

 

[bruceb]

You can get 24VDC to 110VAC inverters here --- various models and wattages / prices
I am sure you could also find 24VDC to 220VAC if you should need that type

http://www.voltageconverters.com/inverters_110v.html

 

[bhvm]

1> I pardon for using the term "UPS". In India, UPS means an inverter than has less than 10ms transfer time. So in summation, UPS is nothing but a better of Inverter.

My UPS has AVR, added cooling fans etc. I don't see any problem running it round the clock, and it has been running so successfully.

2> I do have DC LED Lightbars since 5 years. They are on my Solar unit. I have made lightbars in my Hall, Bed & Outdoors. Which means all high use areas already use DC LED. The problem after conversion is, the LEDs are designed for 12v system. After going to 24v, i've disconnected them until i plan to modify them for 24v system.


Bruce, I am not looking to buy new inverters, I am asking guidance on the questions asked above, with respect to my existing inverters.

 

[lakedude]

Does it mean that 24v units can use smaller transformer for the similar VA ratings?

If I understand the question correctly, yes. VA is basically Volts multiplied by Amps.

The current in a 24V 800VA inverter would be roughly 800/24=33.3

The current in a 12V 800VA inverter would be twice as much 800/12=66.6 or there about.

Wires are sized for current carrying so the lower voltage inverter would need bigger wires, yes.