Does your radio go off during engine start?
 

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.

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.

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

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.

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

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? :p 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.

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.

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.

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

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.

I'm sure in my younger days I hooked up a radio by running a wire straight to the battery.

My Subaru does this (radio shutoff when cranking the engine) and I always figured it was for the reason Diesel_Dave posted above. Interesting that your circuit worked. I'm annoyed by the 3-5 seconds it takes for my Subaru (Clarion) radio to re-boot after an engine re-start but not annoyed enough, yet, to try a fix. Maybe later. Good work.

Oh, meant to mention that maybe you'd want a current limiting resistor between D2 and C1 to limit in-rush current when you first charge C1 but, heck, if it works and doesn't blow Fuse F1 then ... far out!

I just have a tape deck in my Forester.

I wonder if I actually own any tapes...

I did not have a car when I lived in Germany, I just listened to Internet radio, just like I am doing right now, but it always seemed like the German stations played American music with German commercials.

I always found it to be amusing. People always change channels for commercials, but I never had any idea what they were selling! :D

First off, yes, it was a problem on my '97 Civic. Restarting the engine caused the radio to shut down and reboot. The problem was worse when listening to CDs or when listening to any spoken material - if you miss a couple words you can lose the whole thought.

Another project provided insight into what was happening. I installed TWO deep cycle batteries in the trunk and deleted the underhood battery. I installed a new stereo and had the option of powering it from whichever battery I chose.

One battery powers the starter motor and headlights. The other powers everything else, including (currently) the STEREO. This works well. Key-starting the engine does NOT reboot the stereo. However when I wired the stereo to run off the battery that powers the starter, key-starting the engine DID cause the stereo to reboot.

So I deduced -
Nothing in the car's logic circuitry cuts power to the stereo when keying the engine. However, the voltage drop of starting the engine does cause the stereo to cut out and reboot.

Note - this installation has both positive wires for the stereo powered by the same battery. There is some possibility that by running these two leads off different batteries one could also avoid engine-start stereo shutoff, but I didn't take the time to test the various possible combinations.

Modern car stereos have one positive "constant power" lead which keeps the clock and memory going, and also provides the necessary current for its other electronics. The other positive lead could be called an "enabler". It is switched on/off by the ignition switch. The stereo will run or can be turned on only if that lead has power, but it really only permits the stereo to run, doesn't provide a significant amount of power. I didn't take the time to wire the two leads to separate batteries to see what would happen.

list parts?
 

@arekkocowicz: I have the exact same problem with my Mini cooper and a new head unit (Kenwood). I don't have a good oscilloscope to check the voltage drop from my battery, so just for testing purpose I connected the yellow +12v constant cable from my radio to a stabilized power supply, with the ground attached to the chassis of the car. and as you guessed when I start the engine the radio didn't turn off anymore.
so I need to create the same circuit as you did. :D

Did you made improvement to your circuit?

could you provide a list of the parts you used with their respective values?
I know you used Su'scon 5.5F 2.5V x6 for the capacitors, but what about the diodes and fuse?

and where did you bye the Su'scon capacitor?

thanks for your help! :thumbup:

The start position of every car I've seen, cuts power to accessories. Even if you disconnect the starter, and there is no power draw, the start ignition position will kill accessories. If it was really a current draw issue, then the headlights would shut off long before a stereo that draws only a few amps. And my headlights certainly don't shut off when I'm cranking the engine(I bet yours don't either).

The solution is to reroute the ACC feed to the stereo, so that it isn't going through the start position.

headlamps are connected to a constant +12V in every application i've ever seen. this is why you can accidentically leave them on with the ignition off and kill a battery.

i'm sure there are exceptions to this now though.

Yes, and no. Subarus all have them wired through the ignition switch, ON position. VWs have the parking lights wired straight, but headlights wired through the ON position. A few other cars have similar things.

When I have bothered to put a stereo in a car, I always got the 12v power from the reverse light circuit. That way you don't have to run a wire to the battery, just to the fuse block, it's protected by a fuse, there is rarely any other draw on the circuit, and whenever I have done it the reverse lights were one of the constant power circuits (as in they stay on when you start the car), but the circuit will shut down when you turn off the key so you don't have to worry about leaving the stereo on and killing the battery.

The radio shutting off when cranking is not a problem.
The radio is supposed to shut off when cranking. It is switched to do so.

This is because the inductive current draw from the starter can put a massive voltage spike into the electrical system when cranking stops. By shutting off electrical accessories that are sensitive to power spikes, the manufacturer avoids the chance of damaging them.

Ok I made a similar circuit for the constant yellow +12V cable but I placed just 1 Diode Schottky followed by the cap (6x 2.7v 5Farad in serial) and now it work like a charm!
The radio does not switch Off/On anymore when I ignition the engine.
And yes when I remove the key it switch off normaly.

Thank you very much! :D

I have never noticed that before in any car' I will have to test them all!