12V DC Lights pulse annoyingly

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samuel
samuel Solar Expert Posts: 80 ✭✭✭✭
I'm using a LaCrosse BC700 battery charger (AA and AAA batteries) at my cabin.

Installed in the cabin is a set of four cigarette outlet (12V DC car auxiliary outlet) for a charging station for cell phones, iPods, etc... Since every electronic device has a car charger this was an easy way of charging small devices without the need for running the inverter and using a 110AC charger.

One of our 12V charger plug-ins converts 12V to the 3V and plugs into the BC700 battery charger.

My 12V DC distribution box (Blue Sea fuse box) feeds my 12V auxiliary outlets AND a 1200lumen LED light fixture in the kitchen (see diagram for more).

When I have the battery charger plugged in and it is charging batteries the lights in the kitchen pulse roughly every second. I'm assuming this "pulsing" is related to the way the battery charger operates to charge AA NiMH batteries. Is there a way I can eliminate this "pulsing" or should I only charge my batteries during the day?

Thanks, Sam

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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    My understanding is that NiMH batteries require a pulsed charge for best results and proper charging. Therefore you'd be less bothered if they were charged during the day when no lights were required.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    i am assuming this is in fast charge. have you tried the slow charge rate? do any of the other lights pulse or just the kitchen? what kind of wire gauge are you using?

    these chargers will pull a good deal of current in fast charge for all 4 batteries and i think the higher current draw is causing voltage drops to other circuits when that extra power is pulsed through to the batteries and is why i believe the dimming is taking place. additional v drops can be from the switch or the timer.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,493 admin
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    Re: 12V DC Lights pulse annoyingly

    I would suggest moving the DC LED lighting circuits directly to the battery bus bar (with their own fuse/breaker at the bus bar per wire/circuit, for safety).

    Leave the "pulsing" loads where they are. If you get too much pulsing on the loads (causes a battery charger to reboot, etc.), then use heavier/short wire back to the battery bus.

    LED's and some CFL's are very sensitive to voltage variations. And your eyes are very sensitive to changes in lighting flicker. Adding some filter caps at the DC fuse box may help too. Also, different LED's may use different internal electronics for ballast control... Some may be more insensitive to input voltage variations.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    My suggestion would be to put a diode in series with the light and place a capacitor about 16v and 2000uf across the + and- between the diode and the light fitting.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: 12V DC Lights pulse annoyingly
    john p wrote: »
    My suggestion would be to put a diode in series with the light and place a capacitor about 16v and 2000uf across the + and- between the diode and the light fitting.

    that may help too by smoothing out the surge caused by the charger's high loading pulses. its working would depend on how deeply the drops are that are occurring and the time intervals of these pulses so a higher value may be needed for the electrolytic cap. possibly better wire gauges used to the lights in question as well as the other suggestions others and myself gave. i note the switch may be of an ac design and they won't handle dc as well so that could be another sore spot.
  • jagec
    jagec Solar Expert Posts: 157 ✭✭
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    Re: 12V DC Lights pulse annoyingly
    niel wrote: »
    that may help too by smoothing out the surge caused by the charger's high loading pulses. its working would depend on how deeply the drops are that are occurring and the time intervals of these pulses so a higher value may be needed for the electrolytic cap. possibly better wire gauges used to the lights in question as well as the other suggestions others and myself gave. i note the switch may be of an ac design and they won't handle dc as well so that could be another sore spot.

    Caps are probably cheaper/easier than re-running wires. He could use a car audio cap at the fuse block to stabilize voltages throughout the system. I'd bet that even the smallest car audio cap that money can buy would still be massive overkill for this application...those guys deal with SERIOUS voltage sags.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,493 admin
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    Re: 12V DC Lights pulse annoyingly

    I am not sure caps are a great solution here... First in a low impedance situation (lead acid batteries and heavy cabling), the amount of surge current that can be supplied by the caps is limited relative to that supplied by the battery. And remember that capacitors actually have to cycle voltage to sink/source current. A battery bank actually "holds" voltage without regard to current (for sake of argument here) because of chemical activity.

    In the end, I believe that the changing voltage is because of relatively small/long wiring between the battery and the Light/Chargers-cycling-load connection points.

    Just moving the lighting wiring from the remote fuse panel, and re-wire back to the common battery bus (with appropriate fusing) would do a much better job of isolating the voltage surges (and, leaving the existing long/small wiring in place back to the rest of the loads will also help isolate the battery bus by reducing surge current from the remote loads (I*R drop of wiring reduces current surge, plus some inductive losses too in the wiring).

    I would only address the load wiring (heavier/shorter) if the loads themselves are having other issues (voltage cycling causing loads to reboot, RF noise, audio noise, etc.).

    Lots of capacitors on a short/heavy wire run against a large lead acid battery bank are almost useless.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • samuel
    samuel Solar Expert Posts: 80 ✭✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    Thanks for options.

    The battery charger is charging at 200mAh per battery.

    I'm using #18 wire for most of the run, heavier wire buried in the ground. 10Amp main fuse (at batteries), 5Amp fuses for the aux lines in the fuse box in the cabin.


    Well, the main buss bar is in the garage. The fuse box is in the cabin. I told myself I'd never dig another trench between the garage and cabin so we buried a spare line - one end is in the garage attic, the other in the cabin basement. Despite that, I'm not sure I'm looking forward to crawling back up into the garage attic to grab the wire and run it back down the wall to the batteries and go through all the fuss of more fuses and connections to get rid of a pulse that I can work around.

    I think right now the best option is to charge during the day or plug the charger in when we turn the lights out for the night. In the future I might work up the ambition to take advantage of that second buried wire.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    samuel try as on post#5 its a few cents to buy the parts and I really think it will work. it cant hurt anyways
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: 12V DC Lights pulse annoyingly

    johnp,
    i'm not so sure 2000uf will do it for his application as 2000uf would be good at supplying sufficient current for the time intervals required by 60hz ripples. his pulsing may be in seconds. i would say if you try it to go with as high of a uf value as you can and not go below a 16v rating and of course without breaking the bank as i wouldn't put more to this fix than the cost of running another wire would be.
  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
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    Re: 12V DC Lights pulse annoyingly

    I don't agree with your use of #18 wire. I'm surprised that you only have that one problem.

    For one thing using wire smaller than #14 AWG is a code violation . Another problem are those, like you are now encountering, with anything on that circuit that draws more than a few milliamps.