Dim and Flickering lights with Diesel Generator

Dim and Flickering lights with Diesel Generator. Not strictly a solar question, but I’m open to any comments or solutions!

System is very straight forward ‘genset’, Outback VFX3024 inverter/charger with FW250 (great piece of kit if you've not played), Outback MATE, Exide OPzS 1320 Ah batteries and a Deutz single cylinder 1500rpm diesel 5.8kW generator.

When the generator runs the incandescent lights in the house go dim and flicker, when the generator goes off (battery/inverter power) the lights are noticeably brighter and do not flicker.

I have checked the earthing, cabling, voltage inside the house, fuel lines, and current and can’t find anything odd. I have searched the web and found a reference to ‘Flicker Transient Phenomena’ linked to diesel engines. Basically a 1500 rpm engine has a frequency of 150Hz, and it seems the harmonics of this frequency can influence the quality of the power output?

Two questions, has anyone come across this, and do you know of any filters that can remove it.


  • BB.BB. Just some guy Posts: 23,887Super Moderators admin
    Re: Dim and Flickering lights with Diesel Generator

    Single cylinder diesels, from what I have read, are known for flickering lights... Basically, one power stroke for every eight 1/2 revolutions (one revolution of the 1,500 RPM alternator is two full AC cycles--two revolutions for every power stroke--assuming 4 cycle engine).

    The output voltage of the alternator may (should?) be adjustable.

    Is there a flexible coupling between the alternator and the flywheel/engine? If the coupling is loose/failing, that could cause weird harmonics between the motor and the alternator.

    Can you add a larger flywheel to the alternator (option?)?

    Lastly, the only way I can think to stop the flickering with the current genset is to use a large AC to DC battery charger (maybe a used forklift charger sized to ~50% of the generator's capacity) to charge/run your battery bank loads and just use the inverter for your AC loads.

    Other than using a continuous converting UPS between the genset and the loads (really the same as an AC battery charger to your battery bank setup)--I cannot think of any device/filter/ferro-resonate transformer that could be used to "clean up" your AC directly.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrockBrock New User Posts: 591Solar Expert
    Re: Dim and Flickering lights with Diesel Generator

    Can you see what the voltage is out of the genset?

    If it were me I would just use a good 24v charger and charge the batteries directly from the genset and let the inverter power the loads. I like iota chargers and would suggest one or two (you can parallel them) of these http://store.solar-electric.com/ioten25amp24.html
  • mike95490mike95490 Title:User Posts: 6,127Solar Expert ✭✭✭
    Re: Dim and Flickering lights with Diesel Generator
    Two questions, has anyone come across this, and do you know of any filters that can remove it.

    Perhaps looking into your alternator, is it a 2 or 4 pole unit ? 2 pole units exhibit more flicker with a 1 cyl diesel, but 4 pole will still show it. It's inherent with the way the flywheel speeds up/slows down and the single power stroke.

    New electronic ballast CFL's may hide it, but any magnetic ballast lamps will show it too.

    Maybe turning the genset into a battery charger only, is the way to go, unless you need it to start a large motor.

    Sometimes, the internal voltage regulator is too "lightweight" and does not respond fast enough, and "pulses" the exciter winding, some other electronic regulators feed the winding with a more sine like signal, and that helps reduce the flicker.

    You may find more info here: ST-3/5 regulator plans available



    (note because of spam, Listerengine has a strict sign up process, PM me if you need help getting in to post there)

    PS Listerengine is a very slow site, it may take several tries to get pages to load.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||

    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
  • icarusicarus Super Moderator Posts: 5,070Super Moderators
    Re: Dim and Flickering lights with Diesel Generator

    You don't say what kind or style of generator you have, but if it has brushes, check the brush rigs for arcing. Many older style generators had both DC and AC brushes and they would arc as they wore. Check the armature/commutator for signs of damage.

  • adasadas New User Posts: 136Solar Expert ✭✭✭✭
    Re: Dim and Flickering lights with Diesel Generator

    Aloha, check your cycles as well. My diesel genny will run very slow and still operate appliances, but I need to rev it up a bit to get 60Hz and run more effeciently
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