Delay between ignition and headlights coming on

MikeMl said:

Then you have another problem, like a parasitic drain when the vehicle is parked, or a diode out of your alternator. My 2004 K1500 GMC Pickup is driven infrequently (once a week, on average) and still has the original battery. My 2006 Toyota is driven daily, and still has the original battery.

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I tend to very much agree with MikeMI on this. Now I don't have always on headlights but on many trucks (I guess cars also) I have noticed that when cranking to start the headlights actually are cut out (off) during crank till the key is released. My truck doesn't do that and I just got the wife (who now thinks I am nuts) to stand in front of the truck while I had the headlights on and started the truck. The lights remained on.

I generally get 5 to 6 years on a 5 to 6 year battery also. When they finally do fail it seems always the coldest day of winter!

Ron

The current load from the lights is small (perhaps 10-15A) compared to the starter amps (perhaps 150A) so whether the lights are on or not when you start the engine likely doesn't make much difference in the starting power or the life of the battery.

My motorcycle had a relay that cut out the headlight whenever the starter was engaged to eliminate its load. Perhaps with the small battery in a motorcycle, eliminating the load from the lights was more critical.

If your car battery lasts only 1 year then it is no good, the charging system is no good or something is always turned on at night and is draining the battery.
A capacitor draws zero current from a battery unless it is shorted.

A car battery lasts 4 years if you take good care of it and it lasts 5 years if you ignore it.
Hey! My car battery is nearly 5 years old and I think I looked at its battery one time. Maybe I should not look at it. It still works perfectly.

MikeMl said:

Boncuk, Our temps run 95 to 105degF (35 to 40degC) in the summer, so not that much cooler.

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Alright Mike,

Thailand has three seasons: the hot season, the very hot season and the f... hot season, which is now - the sun "crosses" Thailand on it's way North.

Summer time in Utah is probably four months per year at the most. Here it's 12 months per year. May be that "slight" difference causes batteries to quit earlier.

Regards

Boncuk

My last failed car battery failed on a very hot day many years ago. It was "sealed" but i think it simply dried up. I also dried up on that hot day.
I wonder if cheap Chinese no-name-brand car batteries on E-Bay do not last long?

And I live in Hong Kong, where along with the temperatures of Thailand, we get the humid season.

Two months of rain.

Well, i'll go with the circuit Eric posted. Many thanks. Can someone please give me a shot by shot explanation of how it works? I'm still on basic RC circuits.

Zephyr said:

And I live in Hong Kong, where along with the temperatures of Thailand, we get the humid season.

Two months of rain.

Well, i'll go with the circuit Eric posted. Many thanks. Can someone please give me a shot by shot explanation of how it works? I'm still on basic RC circuits.

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hi,
Ref the image I posted previously.

When the ignition is OFF the circuit is not powered.
At ignition ON, the C1 cap charges via R6 and R1, R6 is a variable so that you can tweak the delay time.

As the voltage on C1 reaches the switch on voltage at the Gate of the 2N7002, [the delayed period] current flows thru the diode of the opto coupler, R2 and thru the 2N7002.

The current thru the opto diode makes it emit light [IR],, this is detected by the opto transistor and current flows thru the opto transistor, R3 and into the Gate of the SCR.

The SCR switches ON and stays ON, the current thru the SCR also flows thru the headlights.

When you turn OFF the ignition, the SCR switches OFF.

The diode D1 and C2 cap provide simple filtering, the diode also reduces the effect of the battery voltage falling as the starter motor is used.

Is this enough.?

MikeMl said:

Why not just sense the battery/alternator voltage? With vehicle parked, battery will be <12.6V. Key on, prior to start, it will drop lower. During cranking, it will go <11V. Only after engine is running at fast idle or faster will the battery voltage come up to >13.0V. During driving, the voltage will always be from 13.2V to 14.5V.

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Thats exactly what i'm looking for. Can anyone tell me how i can make a simple cheap circuit to do just that? Thanks

Come to think of it, I have never seen a car/truck which didn't use a secondary contact on the starting key switch to turn off all ancillary loads (headlights and running lights included, radio, air conditioner, heater blower, etc ) while the key is in the START position.

it may be an exception but here in canada batterys last generally 8 to 11 years of life, they put bigger batterys for colder temperature and they last long. Make a quick test, disconnect positive battery wire and tehne put an ammeter in series with it to see how much current is drawn when car is stopped, it should be under 30ma.

Carmusic,
Are you in mild Vancouver?
I am near hot and cold Toronto where domestic car batteries here last only 5 or 6 years. I don't know how long Korean car batteries last.

You could try a simple Voltage sensing circuit with a Zener diode.

I use a 12.6 Volts zener and 180 ohm's resistor in series.
From the Z + R midpoint I drive via a 470 ohm resistor the base of BC547 transistor.
This one can trigger a small 12 Volts relay which can switch your lights on when the accu voltage is over 13.2 Volts.
I use this for an hour meter to record engine running hours.

In case a lot of idling happens and the accu voltage may drop to below 13.2 Volts the threshold may have to be set to 12.8 Volts by changing the Zener diode. ( you can actually make good Zeners from a couple of led's in series )
As long the 10 mA zener current is not exceeded it should work well.

audioguru said:

Carmusic,
Are you in mild Vancouver?
I am near hot and cold Toronto where domestic car batteries here last only 5 or 6 years. I don't know how long Korean car batteries last.

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no im from quebec where we get often -25C so we need big batterys to start engines!

I've emailed the OP, that I have a design with PCB that I could modify to do the following:

1. Maintain the on/off feature of the existing headlamp switch. i.e. It can be turned on when the car is off.
2. Keep the headlights off during start
3. Start timing when your back to ON. Well not exactly.

The assumptions for the vehicle is that the headlights are turned on with a relay that switched +12.

He needs to take two diodes and attach the anodes together. Cut the existing wire to the relay. The two anodes go to the relay. One cathode goes to the original headlamp switch. The other cathode, goes to Delayed out of my device.

So, nothing is different,so far if nothing is connected. If you connect +12 to wire that goes to my device, the lights will turn on. A wire OR. (i.e. a high level OR gate)
Ground needs to be found.

The IGN ON circuit needs to be found. This is the trigger. A circuit which is only on when the car is running such as gauge.

As long as you don't linger at IGN ON for 10 sec on your way to start, your fine.

(ACC ANDed with Ignition ON) would be a better trigger source, but it should not be necessary. It avoids the above problem. Remember tat while your starting the vehicle, cirtain circuit go dead, like the radio and heater goes off.

Start has to be found, so that the timing interval can be reset during the start phase. That part can be easily added.

The timer is already transient protected against the automotive environment andhas a VERY fast reset time like under 1 mS. It also has some inherent undervoltage lockout and short circuit protection.

Avery simple circuit to add would be a lights on reminder. With a buzzer and a few diodes, I created one on my old car that would buzz if I opened the Driver's door witht he lights on.

The circuit isn't simple. The electrical environemt is harsh with +50 and -200V transients at least in the vehicle.

Seems to me you could just power a relay from the start supply and use the NC contacts to control the lights. You may have to add a cap and diode to the coil to keep it from dropping out when starting. Andy