Intermittently dimming 12V ceiling lights

[PhaetonPlace]

The 12 fluorescent lights in my 2008 Tiffin Phaeton intermittently dim about 10% for a duration of several seconds then return to their full brightness. I'm connected to shore power through a Surge Guard, so I think the AC power is OK. Batteries seemed to be fully charged as the voltage and specific gravity in the cells is OK. I'm suspecting a failing convertor. Any thoughts?

[Kirk W]

I would start by monitoring the voltage supplied with an accurate digital meter to know what it is doing. 

[I'mdonewiththis forum]

The 12 volt lights in one trailer I had did that. I put a new battery in and they worked normal again.

[oldjohnt]

  The dimming of more then just one light sounds to me like temporary lowered source voltage. Since all the bulk stored energy in a battery and its buffering ability (if left alone) is less prone to suddenly drop then suddenly recover voltage, my first suspect is the converter/charger subject to its design and configuration. My lights temporarily brighten now n then but return to normal level, but that's when my smart charger is performing its Equalize function. I guess an intermittent short like between battery cells or an excess accumulation in the bottom of lead acid batteries could be popping up then burning through and curing itself but that's NOT my prime suspect and I doubt it, just saying its "possible".  

 Other suspects may be a loose resistive connection in the supply circuit that's sort of appearing then heating up then healing to some degree (again I doubt it, just saying its "possible"). To test for that you would have to place a fairly high current load on your DC light feed circuit and measure voltage with the load on and off. A good load test can provide info as far as your batteries are concerned, but absent that I'm thinking more a charger problem or a supply circuit intermittent problem (loose burned resistive connection)       

 John T 

[Ray,IN]

Some low-end converter/chargers require a good battery to filter 12V electricity. If the battery is failing it cannot perform its job well. That's about as technical as I get.

[PhaetonPlace]

Thanks for all the help. Several good ideas to explore. Time to get to work.

 

[mrfrank]

A 2008 Phaeton came from the factory with a 2000 Zantrex MSW Inverter/charger. It is definitely not low end. That said, the things do fail. Surge Guards fail also. I replaced the Zantrex with a 2800 PSW Magnum inverter (along with a Residential Ref) in my previous 2008 Phaeton. Also had several Surge Guards fail. Installed a Progressive Industries Surge Protector/energy manager and no more trouble.

[Kirk W]

23 hours ago, PhaetonPlace said:

Time to get to work.

 

The key to correcting this is to first know what is causing it. I do not believe in random part replacement.  It may solve a problem and if you get really lucky, it might not cost you an outrageous amount.  If you get out your meter and chase voltages first you can probably determine what is happening and where. 

[Ray,IN]

On 5/23/2017 at 6:32 PM, mrfrank said:

A 2008 Phaeton came from the factory with a 2000 Zantrex MSW Inverter/charger. It is definitely not low end. That said, the things do fail. Surge Guards fail also. I replaced the Zantrex with a 2800 PSW Magnum inverter (along with a Residential Ref) in my previous 2008 Phaeton. Also had several Surge Guards fail. Installed a Progressive Industries Surge Protector/energy manager and no more trouble.

I reallly like my Xantrex RS2000 PSW unit. It is very dependable, I've only had one problem with it, while dry camping at Sigsbee Island, Key West, it locked in float mode for battery charging. I did a hard reset, which corrected the problem. It immediately went to bulk charge mode  when I turned it on again, and has operated normally ever since.

[BrianT]

Won't there be small voltage changes between equalize mode, float mode and absorption modes during normal operation of a converter charger? That's what I always blamed for the lights getting brighter or dimmer all of a sudden for no other apparent reason. It's never obnoxious but it can be noticeable in our RV.

[oldjohnt]

12 hours ago, BrianT said:

Won't there be small voltage changes between equalize mode, float mode and absorption modes during normal operation of a converter charger?

 Yes indeed Brian. A modern so called "Smart" 3 or 4 Stage Charger might BULK at 14+ volts,,,,,,,,ABSORB at around say 13.6 Volts,,,,,FLOAT at maybe around 13.2 Volts SUBJECT TO its charging algorithm and not all are the same. Due to such bulk energy storage and buffering a battery bank affords and SUBJECT TO the Amp Hours of Battery Storage and Charging Amps of the charger, the time required for the batteries (under a charger) to change voltage can vary. While sure a voltmeter can detect small voltage differences, it may take greater voltage differences before your eyes can detect light level change, subject to design. FWIW when my charger switches between Absorb and Float and the volt meter shows it I DONT NOTICE ANY CHANGE IN MY LIGHTS,,,,,,,,,,,HOWEVER when it switches to the higher Equalize 14 + Volts THE LIGHT INCREASE IS APPARENT TO MY EYES. 

 A battery alone (no charger connected) absent a large load swing doesn't instantaneously change voltage, its more a voltage drop over time, unless there's say internal shorting going on, so I'm thinking the OP above (if his batteries are okay) noticeable light changes may be due to his charger or there's a loose/burned/resistive connection in his wiring.

 

 John T  

 

[Kirk W]

27 minutes ago, oldjohnt said:

HOWEVER when it switches to the higher Equalize 14 + Volts THE LIGHT INCREASE IS APPARENT TO MY EYES. 

Is that true for all types of lights? I used to notice when we had incandescent lights but since changing all of ours to LED's I can't recall ever noticing the change. I'm not sure if that is the difference or just old eyes.....

[BrianT]

2 hours ago, oldjohnt said:

 ,,,HOWEVER when it switches to the higher Equalize 14 + Volts THE LIGHT INCREASE IS APPARENT TO MY EYES. 

 

 

That's the one I think I've seen on occasion, too. It seemed to happen fairly often when sitting in my chair watching TV in the evening, after it has gotten towards night time outside and the blinds are closed and inside lights turned on. It would just be the standard automotive incandescent bulbs in the light fixtures we'd have on as we don't typically have the fluorescent bulbs lit then.

The change wasn't obnoxious, but the lights got brighter enough that we would actually notice the change.

I honestly don't know if fluorescent or LED lights would give any reaction at all. (?)

[oldjohnt]

    Brian, I can say with certainty YES even with my LED's if my Smart Charger switches from probably 13.2 Volts FLOAT to 14+ EQUALIZE the lights get noticeably brighter and even our guests noticed and commented on it, so it's indeed REAL. The fact I have an 80 Amp Charger has something to do with it and again the ratio of battery storage capacity to charger amperage can make a significant difference. FWIW I would expect incandescent more likely to change in brightness then LED, but my LED's sure do. Still I cant say from here the cause of the original posters occurrence.

 John T