Flickering LED ceiling light when heater start/stop.

[Henrik]

Hi,

I've got a T6 fitting with a 110Ah AGM battery. This is then connected to a fusebox via 2 x 70amp cables (plus and minus). To the fusebox I have amongst other things 6 x LED's and a Webasto Air Top 2000 heater connected. The LED are fine, they work as curtesy light and can be switched on "manually" from a switch in the back. Only issue is now that when the heater starts up / cools down the LED flickers... Having read multiple post at various VW fora, it has been sugested it could be a voltage drop and yes, there is a slight drop when the heater starts up (around 0.3V), but that does not explain the flickering. Others have sugested it have something to do with the fuel pump and back EMF from the coil in the pump... So far, I have found no one that has cured this issue. As a side note, I also have a flexible stalk LED reading light fitted to the fuse box and that seem to not be affected at all.

I am hoping one on all you people here has come up with a solution, and would be grateful for any comments.

Regards,

Henrik

 

[Pauly]

Are the LED lights turned on or off when said flickering occurs ?

 

[Henrik]

They are ON! I have none of the "normal" LED issues like glowing when they should be off etc. That has all be taken care off.

 

[Pauly]

It can only be voltage drop/voltage surge surely.
I know you say you have measured 0.3v drop but an inrush startup current on the heater and the associated volt (downward) spike would be so quick I think it would be immeasurable ?

I not really sure how to combat it but I am wondering if some form of capacitor on the LED circuit would help smooth the supply (and possibly a suppressor if you are suffering floating EMF ?)

I'm sure @travelvolts would be able to give some professional advice

 

[Henrik]

Thanks for your comments Pauly. You may be right, guess I need to get an oscilloscope on it to see what is really going on. I have already spoken to @travelvolts, but even he has no answer to this one! He has the same heater, but no issue with flicking LED. Come to think of it, he did mention trying to suppressor (for car audio),. Thanks again for your inputs.

 

[Mccoatup]

I had the same problem with my MV Airo Heater during the Ignition cycle, which I have now solved. My remote dimmer controlled light switch also stopped working about a month after I fitted it. Although I didn't have access to an oscilloscope to confirm what was happening, being a retired electronic engineer I divined that the heater was putting some significant spikes back onto the AGM Leisure battery supply line, both over and under voltage during the Ignition cycle. You wouldn't see these on a multimeter as the spikes are too short duration. LED bulbs are very fast reacting so you could see the effect on these, whereas, with traditional tungsten bulbs you probably wouldn't, as they don't respond quickly to change.
I therefore fitted 2 devices: a 12V - 12V converter in the supply line to the LED bulbs to remove the voltage fluctuations,

https://www.amazon.co.uk/dp/B01LCHOZ00/ref=pe_3187911_185740111_TE_item​

(£12.99) and a Surge Suppressor across the Leisure Battery terminal to remove and damaging over voltage spikes, https://www.maplin.co.uk/p/kemo-overvoltage-protection-dc-12v-n22dd, also £12.99.
I have had no problems since fitting these. Having a guaranteed 12V supply to the LED bulbs is probably a good idea in any case as it will maximise their life, since the unregulated battery voltage can rise above 12V quite significantly in normal usage. The DC-DC Converter I chose provides 3 Amps, which was more than enough to power all my LED bulbs, but you would need to ensure this is enough to cater for your set of bulbs. You can buy higher current converters if needed.
Hope that helps!

 

[Henrik]

Thank you so much for all that info! I will keep my fingers crossed. And report back when I have tried it. Parts already ordered...

 

[Mccoatup]

No problem - happy to help. Next month I am going to borrow an oscilloscope from a former work colleague so I can take some screenshots for the Forum of 'before' and 'after' the modifications, so I have some definitive evidence of what's happening to the 12v line.
And whilst I'm posting on the forum, here is a shameless plug for my Charity Fundraising Climb of Mount Kilimanjaro which I am doing next week! www.justgiving.com/bobdalgleish. (The trip is all self-funded so 100% of contributions go to the small charity, Fanconi Hope, which I now run).

 

[Henrik]

I have just fitted both the Overvoltage Protection and the Voltage Regulator to the LED's and there is no more flickering when heater is starting up!
The Overvoltage Protection across the battery on its own, didn't have any effete on the flickering but adding the VR sorted it out. I have not tested the VR on its own. Thank to every one for your inputs.

 

[Mccoatup]

Good to hear this has sorted out your problem! The Overvoltage protection device won't have any direct effect on the LED lights flickering but it will protect any sensitive electronic devices you have connected to your leisure battery, so for the sake of £12.99 it's worth it for peace of mind.

 

[Mccoatup]

And thanks very much indeed Henrik for making a donation to my Fanconi Hope charity, sponsoring me for my Kilimanjaro climb!