problem with 12 volt lights flickering...

Milopez · March 2010

I have several sets (5 total) of 12 volt track lights in my office that each uses 3 x 20w MR-16 Halogen bulbs. The problem is whenever I turn on 3 or more of the light strands (or any combination of more than 7 to 8 of the 20 watt bulbs, the lights begin to flicker).

My system is comprised of 4 x 165 watt BP panels (24 volts) and 8- 100 AH batteries. In addition to my 120v AC inverter I also have a 50 amp DC 24 to 12 stepdown transformer. When I initially installed the lights, I did not use the 120 AC transformers that came with each light strand and instead connected them directly to 2 dedicated 12 volt lines that originate from the DC stepdown transformer (one line has 2 strands or 6 lights on it whereas the other dedicated line has 3 strands or 9 lights on it). Each of the dedicated 12 volt lines is solid 10 gauge wire, although the 2 switch wires are 12 gauge Romex.

The work perfectly fine as long as I don’t have more than any 7 lights on at a time (I tried various combinations of removing bulbs in different combinations from the 5 strands till I discovered that any combination of more than 7 lights on at a time causes the flickering). There is nothing else powered by the 2 dedicated 12 volt lines. I’ve checked and double checked all the connections and bulbs, but nothing seems to solve this problem.

I am tempted to try and switch some of the bulbs to lower wattage LED MR16 bulbs, but it doesn’t seem that there should be a problem of too high of a load of 300 watts of halogen lights with the 50 amp DC transformer. I am hoping that someone has some other suggestions for what might be causing this problem (other than the suggestion to connect the lights back up to the 120 v AC transformers, as that would defeat the purpose of having the solar set up in the first place!).

BB. · March 2010

Re: problem with 12 volt lights flickering...

I would start looking the input to the DC down converter... Check the input voltage right at the 24 VDC input of the converter.

Is the voltage > 21 VDC?
What are the input and output voltages when working and when failing.
What is the input voltage range of the down converter (does it have a cutoff voltage)?

-Bill

westbranch · March 2010

Re: problem with 12 volt lights flickering...

do you have any other loads on the bank at the same time? this could also lower your out voltage from the bank .

Eric

Milopez · March 2010

Re: problem with 12 volt lights flickering...

Regarding your questions:

* Is the voltage > 21 VDC?
* What are the input and output voltages when working and when failing.
* What is the input voltage range of the down converter (does it have a cutoff voltage)?

The input & output voltages for the 24-12V transformer were as follows:
*26.2 volts in and 12.0 volts out with no load
*26.2 volts in and 12.0 volts out with a set of 2 strands or 6 lights; and then
*26.1 volts in and 11.59 volts out when I turn on a 3rd strand with 3 lights and all 9 lights start to flicker.

I think the input voltage range of the converter is 16 - 32 volts.

BB. · March 2010

Re: problem with 12 volt lights flickering...

Sounds like the down converter is going into over-current limit on its output when around 20 amps. I don't see any installation/usage issues? Are you disxelict, dislectic, uh-mm dyslectic? "5" for a "2"?

Lights are a reasonably stable loads (interestingly, they are sort of a constant current load... As voltage goes down, filament cools down, resistance goes down, and current stays relatively steady at the lower input voltage).

-Bill

Brock · March 2010

Re: problem with 12 volt lights flickering...

Do you have a make and model for the 24 vdc -12 vdc converter? It certainly sounds like it is overloaded. You could either get a second converter or add a 12v battery on the output side large enough to handle the load.

Milopez · March 2010

Re: problem with 12 volt lights flickering...

BB. wrote: »

Sounds like the down converter is going into over-current limit on its output when around 20 amps. I don't see any installation/usage issues? Are you disxelict, dislectic, uh-mm dyslectic? "5" for a "2"?

Lights are a reasonably stable loads (interestingly, they are sort of a constant current load... As voltage goes down, filament cools down, resistance goes down, and current stays relatively steady at the lower input voltage).

-Bill

I'm not sure I'm following your dyslexia joke re: "5" for a "2"???? Were you suggesting that perhaps the transformer I have is a 20 amp and not 50 amp transformer? That's a somewhat interesting hypothesis, but it seems to start having trouble right around 12 - 15 amps (when I have 7-8 20 watt bulbs going).

However, just to be sure, I did double check both the original receipt, as well as the actual board on the transformer and they both say "EQ 12/24-50 R12", so if you were correct, the would have had to had to have really screwed up by mislabeling the board during manufacturing. I'm not sure how I'd test it.....

After I put back up all but one of the 15 lights, I retested the voltage at the transformer and here's what I got:

*25.5 volts in and 12.0 volts out with no load

*25.5 volts in and 12.0 volts out with a single strand of 3 lights (no flicker);

*25.4 volts in and 12.0 volts out with just the furthest 2 strands or 6 lights (no flicker);

*25.4 volts in and 12.0 volts out with just the nearest 2 strands or 5 lights (no flicker);

now the flickering starts....

*25.3 volts in and 11.9 volts out when I turn on the single strand of 3 lights + the furthest set of 2 strands or 6 lights for a total of 9 lights (flickering);

*25.3 volts in and 12.0 volts out when I turn on the single strand of 3 lights + the nearest set of 2 strands of 5 lights for a total of 8 lights (flickering most of the time, but not always); and last, but not least;

* 25.1 volts in and 10.3 to 10.6 volts out when I turn on all 14 lights (still flickering).

I forgot to mention that I was wondering whether the batteries might be going bad and possibly might have something to do with this problem? They are 5 or 6 years old, but haven't seemed to have any problems that I've noticed. I don't often use my office much at night so after the sun goes down, there's typically only very minimal 120 AC loads from the inverter (e.g., my phone charger and occasionally I may leave my computer docking station on which has a few 12 volt transformers for some of my computer devices).

The problem still exists even when my panels are getting full sun and producing 17 amps, but I didn't know if that would still be a problem if my batteries were starting to fail. Of course, I'm not sure how I'd test the batteries. However, the other night I did turn on all 15 flickering halogen lights, a 120 v fan, and a 24 v fan and didn't see much of a drop in the battery voltage. Anyway, I thought I'd mention my question about whether the batteries could be playing a role, since I can't otherwise figure out what else could be going on....

Milopez · March 2010

Re: problem with 12 volt lights flickering...

The transformer is made by Solar Converters (in Canada) and the model number is EQ 12/24-50 R12.

If I can't figure out what the main problem is, then I'm kind of intrigued by Brock's suggestion to add a 12v battery on the output side large enough to handle the load.

I guess I'd have to add it after the transformer, but before the circuit breaker box where it splits into the 2 dedicated lines (each with a 30 amp Square D QO series breaker which is supposed to be rated for DC voltage). Just in case nobody else comes up with another alternative, does this sound right?

mike95490 · March 2010

Re: problem with 12 volt lights flickering...

I would bet that you have discovered an instabiality in the circuit, and that a low ESR capacitor at the input or output (trial & error) would solve it. Or write the Mfg, and describe your loads exactly, so they can duplicate it, they should have either a work-around or a new box for you.

BB. · March 2010

Re: problem with 12 volt lights flickering...

Sorry--was intended as a joke--I am mildly dyslectic and I have seen mistakes like that in the past...

I don't think you are doing anything wrong. I would contact the retailer of Solar Converter Inc. directly and ask. Their data sheet shows your exact configuration (24 volt battery and 50 amp maximum 12 volt load).

www.solarconverters.com
EQ 12/24-50

Connecting to a 12 volt battery--interesting... It appears (from above link) that this is a supported configuration. Charging one battery will automatically charge the other battery (I wonder how close the voltages track and what the I/V curve looks like).

If you don't need a 12 volt battery for any other reason--I would try to avoid it... Extra cost and maintenance.

-Bill

Brock · March 2010

Re: problem with 12 volt lights flickering...

I agree with Bill, if you can avoid the extra battery, you’re better off. Knowing it's that converter it should be able to handle the load you have so something’s not right. Maybe it needs a cap across the output side, but a resistive load like lights should really be fine.

I would second or third contacting the manufacture and get their take on it, just make sure they know the load is 12v halogen lamps, and whatever the max load is.

In thinking about this, you’re sure each one is 30w? I mean are they really pulling 30w or 12v at 2.5 amps each? Maybe they are knockoffs and pulling more amperage than they should or maybe they are really mislabeled 50w lamps? That would explain it as well. Is there any way you can measure the amperage on even three of them?

Milopez · March 2010

Re: problem with 12 volt lights flickering...

I've put a call into the manufacturer to see what they have to say, as it is somewhat reassuring that based on the feedback here, it doesn't appear that I've done anything obviously wrong. However, I'll leave open that possibility as even though I had help from my electrician father-in-law, there's still a chance that it could be something I've done.

I even double checked the halogen MR16 bulbs and they clearly say 20 Watts. I don't have a way to measure the amps, so I'll have to assume that they are not mislabled. We'll see what the Solar Converters people say......

niel · March 2010

Re: problem with 12 volt lights flickering...

this might sound stupid and i skimmed so i don't know for sure if this was suggested or not, but try to turn on the 2nd light string and then the 3rd (the one it when crazy on before) to see if it does anything.

Milopez · March 2010

Re: problem with 12 volt lights flickering...

I did hear back from the manufacturer and even sent them a photo of the board. They had me increase the output voltage to 13 or 14 volts to see if that helped, but it didn't.

They also said that it looks like this particular model has built in current limit resistors that they don't always use on all their transformers. Thus, as someone here suggested, it's possible that the unit is hitting it's current limit and oscillating.

Their solution was also similar to what at least 1 person here suggested, installing an electrolytic capacitor that is rated for around 30V and as many micro farads (uF) as possible (what’s the typical range that I should look for??) and then add it parallel with the output of the unit.

However, I now need to figure out the best place to get an electrolytic capacitor and what;s the typical range of micro farads (uF) to shoot for. Any suggestions would be greatly appreciated. I also need to figure out if it can be wired in to the output lugs that go to the circuit breaker box for the 2 separate lines (since it would then still be contained within the box that holds the transformer....).

Hopefully, this means that I'm getting closer to a viable solution....

(oh, and it didn't matter which combination of sets of lights I tried or in what order as anytime I go over the magic number of 8 bulbs it starts to flicker).

mike95490 · March 2010

Re: problem with 12 volt lights flickering...

I had a client call me in a panic - all the lights were blinking off and on, 2nd day of a 5 day show. turned out the charger died, and the DC-Dc converters were starved at 35V in a 48V system. As some shut off, the drain was relived and the battery recovered a bit ... ... ...

niel · March 2010

Re: problem with 12 volt lights flickering...

the electrolytics will be in the thousands of mfd and if you can get them in the 10s of thousands at the proper voltage it will be all the better. you can parallel them to add more, btw, but keep in mind they have a polarity and must not be reversed. keep the + on the cap to the + voltages from your converter output.
where you are is considered like a silicon valley and i'm sure there are lots of places if you start inquiring via your phone book. if you must you can send for them by mail.
example place to buy,
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=131081&k=electrolytic%20capacitor

BB. · March 2010

Re: problem with 12 volt lights flickering...

I would make them tell you what size capacitor... The "right size" depends on their output stage and switching frequency (i.e., the capacitor has to supply power between the switching cycles).

Too small, won't help or may over heat the cap. Too large, a waste of money (big caps are not cheap).

-Bill

niel · March 2010

Re: problem with 12 volt lights flickering...

here is another possibility,
http://www.tecategroup.com/capacitors/products/aluminum_electrolytic.php
and they show it can get to $5-6.
i have gotten many of mine free at a hamfest even though one has to pay to get into it. they aren't rare big ticket items.

peterako · March 2010

Re: problem with 12 volt lights flickering...

Hi there sorry for kicking in late.

The internal electronics from This type of LEDs are switched powersupplys.
Switching fast to bring the current for the led on a avg. level. This requires high current spikes more than 2x.
So yes the dc/dc transformer is protesting.

A capacitor maybe helps but the inrush current for the capacitor and the leds, can shutdown your dc/dc transformer. so this only works if you can switch every string seperated.

Greetings from Greece8)

Brock · March 2010

Re: problem with 12 volt lights flickering...

Ok, that makes since now.

Then I see three options.

1. Get a second converter and separate the strings.
2. Get a larger capacitor to put on the output side to smooth out the chops, but I would think you will still see a pulse even using a large cap.
3 Go back to a battery idea. In this case even using a relatively small battery would smooth out the chops. I am thinking a 12v 7 amp SLA ups type battery. No maintenance, readily available and relatively inexpensive, just about any large box or sporting goods store will carry them; I think even Target and Wal-Mart. Just be sure to also fuse the power to the battery.

Milopez · March 2010

Re: problem with 12 volt lights flickering...

unfortunately, Peterako's reply may not fit, as I'm still using the halogen bulbs and haven't yet switched to the lower wattage LEDs.

Brock, why is it that you don't seem to think a capacitor will work and that I'd be better off adding a 12v 7 amp SLA ups type battery instead?

Also, why do you suggest only using a 7 amp battery, since the full set of lights will draw 25 amps, won't there be a problem?

Sorry for such basic questions, but I'm still learning all the details related to the electrical stuff....

BB. · March 2010

Re: problem with 12 volt lights flickering...

As long as the minimum voltage at the battery is >12.8 volts or so (have to make sure that the voltage dips you are trying to filter out are also >12.8 volts)--the battery is not discharging. It is acting more like a capacitor.

-Bill

Brock · March 2010

Re: problem with 12 volt lights flickering...

The voltage on a cap would probably still flick or bounce as it turned on and off and while the cap would smooth out the on and off's I don't think it would carry the 30 amps for off time without seeing the dip. I could be wrong and maybe a big enough cap would work without seeing anything. For example say right now the voltage is going between 12v and 0, with the cap it might bounce from 12v to 11v as the cap discharged and the converter came back up to voltage.

I am just thinking cheap. At 7 ah 12v sealed battery could carry the light for maybe 20 minutes by itself. Obviously a larger battery would be better, but the battery should only be acting as a HUGE capacitor for the very short time converter is cycling in the "off" mode. So the line voltage might go from 12v to 11.9v when the converter was in the off cycle.

As Bill said I would up the voltage to the float voltage to the battery, around 12.8 or so, so basically the battery would sit at a full state all the time and just even off the blinking.

mike95490 · March 2010

Re: problem with 12 volt lights flickering...

When i first mentioned caps - I specificly said Low ESR caps. They have lower internal resistance than batteries, and in fact, are used as battery savers, they will supply brief surges better than batteries can, and it saves peak power from damaging the battery plates. Get as much capacitance as you can afford, at about 1.5x the working voltage (12V system, 18V or higher caps)

Milopez · March 2010

Re: problem with 12 volt lights flickering...

Well, in talking with the manufacturer of the voltage regulator, it looks like we're going to try a $7 aluminum electrolytic capacitor (30 volt and 5000-10000 uF, from www.digikey.com; 565-3313-ND) to see if that works. If not, then he'll walk me through the surgical removal of the built in current limit resistors on the board, as he said that it shouldn't be too difficult to remove them, if necessary. Hope this works!!

In any event, I'll also plan on swapping out at least a few of the halogen bulbs for the more efficient LEDs. Over time, as the halogens burn out I eventually work towards switching them all, but don't want to jump to that too quickly. I'll let you all know how things work out. Thanks for all the input!!

problem with 12 volt lights flickering...

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