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EF/EL: System B+ voltage results 

 

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 Post subject: EF/EL: System B+ voltage results
Posted: Sun Jan 13, 2013 12:42 am 
Parts Gopher
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Age: 38

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Joined: 24th Jun 2009

Ride: EF XR6

Location: Bendigo
VIC, Australia

Thought I'd document the actual voltage of what we call "+12V" in EF/EL's.
Needed to optimise LED resistor selection when fitting LED illumination especially the cluster.
If you run the LED's at max current to get full brightness from them, and calculate the resistors for 12.0v, they'll pretty quickly start to flicker and fail.
Or you can keep them "dim" with higher resistance, but that's not a good solution.. wouldn't be much better than using the old filament lamps.
Best idea is to grab the exact max voltage they're exposed to and calculate resistances from that.. which I'm documenting here for reference (cause I can't remember what it was from last time I did it)

Results taken with fully charged, as-new Optima Yellow-Top Sealed battery.
Measured with no accessories, engine @1500rpm.

At battery: 14.1v
At Illumination circuit: 13.8v


You can see the voltage is above 12v, no wonder so many ebay LED's die.
I'll admit to cooking a few hand-made ones from being too keen with the LED current.
Anyway hope it helps..

cheers
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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Sun Jan 13, 2013 11:49 am 
Technical Contributor
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So good points.
I've had LED's flicker and fail in the past - blaming production quality maybe was the wrong area to look at.

 

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96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl
97 EL Futura S/W: LPG, Alarm, LED int Lts, Trip Comp, F/Lane Dome Lt, Climate Ctrl, T5 Conversion

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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Sun Jan 13, 2013 3:22 pm 
Parts Gopher
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Location: Bendigo
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Yep that's usually the way they fail. Most OTS leds are deisgned for 12.0V, and usually the resistors are under-calculated, probably to get more brightness, running them way above rated current.

It's not a production issu. It's a design issue.
It's interesting to know how they QA LED's from the factory.. they bin them according to colour/shade and intensity/watt. Never had a LED that failed under proper current conditions, only seen DOA LED's.

I bought a heap of diff LED bulbs for stop/ind/parkers etc and found most of them ran the LEDs at over 90*C (some started self-cooking quickly at >120*c) as measured in the LED with an IR meter!!

Now 50-60* seems to be okay in terms of life/reliability (though they'll dim as they age) but any higher and they'll self-destruct eventually.

The over-voltage issue is one factor in this problem but there's inherent problems with the resistance used in most Ebay LED's. No simple fix sadly... a month-old LED tail light died on me the other day and apart from replace it again I dunno what else to do.
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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Sun Jan 13, 2013 10:43 pm 
Technical Contributor
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NSW, Australia

Guess I'll have to get an IR meter and start checking - Ebay cheap $15.

 

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96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl
97 EL Futura S/W: LPG, Alarm, LED int Lts, Trip Comp, F/Lane Dome Lt, Climate Ctrl, T5 Conversion

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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Sun Jan 13, 2013 10:52 pm 
Parts Gopher
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Location: Bendigo
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A finger also works as a poor-man's guide to LED's that will fail.. if they feel hot after 5 mins, they're overloaded :)
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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Mon Jan 14, 2013 5:09 am 
Stock as a Rock
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I use the L.E.Ds from Jaycar and have never had an issue . the ones in my dash have been there for over 3 years now without a single replacement .
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 Post subject: Re: EF/EL: System B+ voltage results
Posted: Mon Jan 14, 2013 10:26 am 
Getting Side Ways
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VIC, Australia

Simple solution is use 12v regulators.
They're cheap as hell on ebay, and easy to wire in.
I've used them on LEDs that would be a pain to replace.

 

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