Thoughts about Emergency Ballast AC/DC

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ben sorenson

Joined Feb 28, 2022
106
Hello, I have these emergency ballasts. They have a built in 6 volt NiCad Battery. How they work is they are connected to 120/240 AC, when the AC power is removed, it goes into "emergency mode" and supplies power to the output for a minimum of 90 Min.

The question that I have is... I cannot find any data stating what the output is, and if it is AC or DC.

Can florescent bulbs work on a Pulsed DC? To me it would inefficient to go from AC to DC back to AC again.

I wanted to try to use these on a project I'm working on ONLY if they had a DC output. I don't really feel like messing with high voltage AC...

Also, if they did have an AC output, and and I rectified it to DC, would it be better to use a transformer circuit? Or could I do a full wave rectification with high voltage diodes? Again, there is no connection to the AC Mains when there is power to the output, the only advantage I see to use a transformer circuit would be to step the voltage down, and then the "stepped down" voltage would be isolated.
 

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Ian0

Joined Aug 7, 2020
6,681
Are they maintained or non-maintained? Do they have four wires to the fluorescent tube? Are they heavy? (as heavy as a transformer of that size would be) Do they still employ the fluorescent tube glow starter?
 

Audioguru again

Joined Oct 21, 2019
5,413
I bet the ancient battery does not work, I used Ni-Cads 40 years ago and they did not last long. Ni-MH batteries replaced them and today most rechargeable batteries are Lithium.

The charger/battery/AC inverter product's label says its input is 120/277VAC at 3.3W, that is probably used only to charge the battery, not to power anything.
 

schmitt trigger

Joined Jul 12, 2010
510
Fluorescent tubes, once that they strike, present a negative resistance load. Unless you use a ballasting impedance, they would almost immediately burn out.
For DC, you could use a resistor, but the losses would be so large that it would negate the fluorescent’s efficiency advantages.
That is the reason AC is employed on the output of all ballasts, and then reactive ballasting is employed. Reactive impedances (inductors, capacitors) ideally dissipate no power, but even real world components with their losses, are far more efficient than a resistor.
 
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