Hello everyone, I have purchased an emergency ballast for my two bulb t8 shop light in my shed. It is a cooper FBP-140XLP emergency ballast. I have it wired up to an un switched line so the light is on constantly. When I hooked everything up yesterday I wanted to test it just for a few seconds to make sure everything was working.  I disconnected power and it operated one lamp as it should, so I just turned on ac power again to let it charge for 24 hours before I did a full 90 min test. I started the 90 minute test and about 2 mins in the tube started to flicker. One side of the tube does not flicker but the other side does. I tried switching the bulb around to see if it was the bulb but it’s not. I tired tightening the socket connections on the side that it flickers on but Doesn't seem to help. Any help would be very much appreciated!!!

Some of those inverters have stability problems, that may show up under specific set of conditions. Some possible reasons include :

Degrading battery - When its voltage is still in spec but source impedance isn't, or other effects of battery degradation - Possibly enhanced by tendency of some of those ballasts to overcharge batteries

Dried up battery bypass electrolytic capacitor

Being rated for the wrong battery (i.e. values of base drive resistors etc. have been chosen for one battery voltage, but then it was labeled with another battery voltage rating on the ballast outside). I have seen this way too often, from manufacturers who dont really have a clue what they are doing. Within the voltage range the battery goes through when charging/discharging, it might be stable through some of the range but not in the ends (fully charged and maybe a little overcharged battery, or low battery conditions)

Some unintended interaction with the line voltage ballast (it is supposed to be disconnected by an internal relay, but it might be miswired), or the one side of the HF source that stays connected + parasitic capacitances may close unintended current paths, affecting how the HF source (oscillator and its feedback) runs. To eliminate the latter, try to run it on the bench with just the tube connected, and see what happens

Thanks Ash! Turns out it was too cold in the shed that night when I tested it. It got to a low of 57° F. I put a heater by the bulb just for a few seconds and the flickering Stopped. The emergency ballast lasted for 3 hrs and 30 mins exact as well.

Good observation. The ambient temperature may have effect on either the tube or the battery

Yea I know electronic ballast can work in extreme temps so when it has ac power and is using the electronic the bulbs don’t flicker a single bit but yea when in emergency mode the bulb will flicker.

The electronic can run at lower temperatures, but only if the supply power is not compromised.

But the battery impedance and capacity severely deteriorate at cold...

Yea I’m still working on the shed. Trying to make it so it’s insulated. Everything is still working fine tho. Switched to new Phillips alto 2 technology bulbs yesterday since they last forever apparently.

I’m going to do another test this Saturday. The temp will reach a high of 75° that day so it will be perfect. The reason why I did it at night was so I could see how dim the lamp was. I think it can beat 3 hours and 30 mins since it will be warmer it it has been charging for almost a week now. I’ll let you guys know how it goes. Thanks.

By the way what battery chemistry is used there?