Does your radio go off during engine start?

[arekkocowicz]

Hi guys,
I had this problem - in exact moment when engine starter were switched on voltage in car's installation goes so low that radio goes off. Half a second later it is back on but it has to boot again and cash list of mp3 on SD card which takes almost a minute - too long.
I found a easy solution which works fine for me, I described it here electronics engineering notes: Blaupunkt Melbourne 120 vs voltage dip during engine start If you tell me that it is not only me who has this problem than I will improve circuit and design a PCB for it. Please feel free to give some feedback to this topic. I know - it may be not that strongly related to ecodriving but I try to switch engine off when I expect that waiting for green light will take some time, when it repeats - than it becomes ecodriving related topic.

[Daox]

Yeah, happens to me too in my Paseo. I just live with it. Its only a second or so delay and it is back up and doing its thing.

[Frank Lee]

I don't know- it's hardly ever on. Might as well delete it.

[RobertISaar]

a possible design tweak for you: since you're losing ~.7 volts through the D1 diode with the engine running(or key in run or accessory, really), i would suggest a relay(or better, a FET) that is only active when the ignition is in the run position(and not active when in crank) to supply an alternate current path, that way your diodes won't be dropping voltage when not needed.

[user removed]

I generally use the Radio to check the traffic conditions so I don't get stuck on the Interstate between exits for a hour or more.

How about starting the car then turn on the Radio. Starter motors are over a hundred amps drain and battery voltage drops accordingly even when everything is new. In older cars the starter draw can double the drain before they fail typically.

regards
Mech

[arekkocowicz]

RobertISaar: I have chosen Schottky diode so it will be a little less than 0.7V, at 1A it will be about 0.45V (and 0.65 at 5A) but anyway - you are right - there is much to improve, I will consider using ignition signal.
Frank Lee: Pragmatism! That's the spirit.
Old Mechanic: With 4GB SD card it boots for around one minute (sic!) and the thing is that I stop the engine quite often. When I listen to FM radio that it boots up within one second but you know, I live in Germany, would you like to listen to german radio? So I have to listen to the music from sd card.

ISO7637-2 defines couple of conditions which car's equipment has to withstand. Voltage drop during engine start is simulated with ISO Pulse 4 and as far as I know the voltage can fall down to even 5 Volts or something.

[NoD~]

Good find! My Cd player has gone through a lot... was a high-end one in it's day, but these days, a startup can make it lag for minutes at times (on a CD)! So I'll definitely be looking into this.

[SentraSE-R]

Yes, cranking the starter motor always kills the radio in all of my cars. It's been that way in every car I've ever owned, IIRC.

[user removed]

I most cars when you are starting the engine, the car uses direct battery current to the ignition system, once you go to the run position on the ignition switch the current is regulated to prevent damage to the ignition circuit. Cars used to have ballast resistors for that purpose to prevent an overcharging alternator or generator from frying the points and condenser.

Ancient tech but still used just controlled differently. Helps you get the car started when the battery-charging system is weak.

regards
Mech

[Diesel_Dave]

I always figured it was just because "non-critical" electrical draws are shut off during cranking to ensure the maximum allowable energy is left available to get the engine started. If you can't get the engine started, the radio doesn't matter.