Electronic Ballast for Fluorescent Light [Hack] ?

I have two identical electronic ballasts that will each power a 20 Watt tubular fluorescent light bulb.

Will the two 20W ballasts drive a single 40W tubular fluorescent light bulb if the two ballasts are connected (parallel) to the 40 Watt fluorescent bulb?


(The 20W bulbs are removed from the two circuits before connecting the ballast circuits to the 40W bulb.)

Reply to
C. Nick Kruzer
Loading thread data ...

"C. Nick Kruzer" schreef in bericht news: snipped-for-privacy@storefull-3256.bay.webtv.net...

No. These ballasts produce a (relative) high frequency AC voltage. As they are not synchronized, they will blow each other.

petrus bitbyter

Reply to
petrus bitbyter

I wouldn't do that. The THD ( total harmonic distortion) would increase and could present a dangerous situation. Without knowing the specs on your device I could only guess this. The unit may even power the 40 Watt lamp alone. I just wouldn't do it considering the cost of the proper unit.


Reply to
Tom Biasi


Check what the electronic ballast says for its power ratings (of tubes it can drive). Anyway the correct ballast will be peanuts in cost, a whole new fitting would be cheap as well.

Leaving alone the synchronisation of the outputs of the ballasts, you have fundamental problems.

Electronic Ballasts (normally with integral starters) provide a means of getting the correct voltage for the LENGTH of the tube -the 40W tube will be almost double the LENGTH of a 20W tube. Tube wattage is proportional to the LENGTH of the tube. Compact fluorescent tubes get higher wattage in smaller space by compacting the length using bends and spirals.

Two 20W in parallel will give INCORRECT operating voltage.

Electronic Ballast/starters apply a lower voltage but higher current through the slectrodes to HEAT the electrodes for 1 - 2 seconds to enable the START of the plasma discharge with the HIGH strike volatge. Typical start voltages are around 20-30V, strike voltages are 100V and greater (says he having had voltage frequency burns from 600V 40KHz strike voltages).

TWO 20W ballasts in parallel WILL shorten the life of the tube electrodes by applying too much heating current, hence releasing mercury inside the tube from the electrodes.

Similar voltages and issues are seen for LCD backlights (except LED backlights).

Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
 Click to see the full signature
Reply to
Paul Carpenter

C. Nick Kruzer (me) asked:

Petrus answered:

Tom agrees and responds:

I'm trying to save money on a set-up for growing plants indoors under artificial light. I'm growing vegetables which requires a good amount electricity (wattage) for light. Lights made for growing plants are expensive, I think because farmers of illicit indoor marijuana gardens use them. I'm looking for ways to cut costs. I'm sick and tired of paying three dollars a pound for tomatoes at the supermarket. I live in a city apartment and can't grow anything outdoors. No direct sunlight from windows...have to use lamplight. I get a discount on electric power. Even if I break even in costs with tomato prices in supermarket I figure I'm ahead..I will also get the pleasure of watching plants grow, will eat organic grown, will have fun putting the fixtures together and will have a conversation piece for guests to admire...

The two 20 watt ballasts I have are from screw-in compact fluorescent lights with the bulbs removed. I can get these for about a buck apiece. I have already tried one to power a small, linear, tubular fluorescent light bulb, and it works. I matched the wattage ratings of the fluorescent grow bulb with the compact fixture wattage from label on fixture package. I attached wires from ballast to pins on the fluorescent light tube with molex type connectors salvaged from old junk computer parts. They fit perfectly. I'm looking for ways to power larger tubes, that's why I asked about the two 20W ballasts for a 40 Watt tube.

Looks like that's what I'll be doing.

I'm glad I asked. I knew the electronics involved high frequency, but didn't know much about the technology and applications..

That's good to know. It makes sense to me knowing what I know about high voltage.

That certainly would be the incorrect start voltage for the larger tube.

Mercury!!...I don't want to become the "Mad Hatter"! :-)

Such great answers to my question from everyone... You have my gratitude.

Here is something I found when reading about using plant grow lights. It is what initiated my inquiry, starting this thread. It involves rewiring a two bulb fixture to run only one bulb, resulting in a greater intensity of light. The author (Zink) advises that the "overdrive" process shortens the life of the fluorescent tube. I found the information while reading a Gardening forum.

formatting link

formatting link


Reply to
C. Nick Kruzer

In , C. Nick Kruzer wrote in part:

That was talking about evaporating mercury from the electrodes to the inside of the tubing.

This is somewhat incorrect - in normal operation, the electrodes are too hot to have any mercury at all on them.

Overheating the electrodes will merely shorten their life by accelerating evaporation of the thermionically emissive material that the electrodes are coated with.

In any case, the mercury stays inside the tube.

Combining ballasts is merely a *Big Bad Idea* for the other reasons (edited out for space). You are unlikely to match the proper wattage and, voltage, the electrodes have a fair chance of shortened life, and the ballasts are independent high frequency AC generators that are unlikely to synchronize with each other.

One more good reason - UL listing of electrical equipment (including fluorescent lamp ballasts) is invalid when they are used other than as directed. Your fire insurance company and your landlord may cause you major grief if you burn up your apartment (and any other apartments) from abused ballasts going KABLOOEY, as opposed to having a fire starting from them despite using them as directed (which is presumably much more unlikely).

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

Yes, the worst case scenario would be human injury/death in addition to the events proposed in your wise admonition. The chance of danger and failure has been unanimous with all those responding this thread.

I respect the scientific knowledge and advice of those who post this forum. And to those who take the time to respond to my inquiry with their expert knowledge I give a special "thank you".


Reply to
C. Nick Kruzer

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.