Electronics question unrelated to ebikes.

[jonathan75]

There is often wonderful electronics advice on this forum, I know a lot of you are naturals on that (perhaps why you've gravitated to ebikes!), and so I wanted to ask for advice on an un-ebike-related matter on which I need a bit of help.

Just bought a new car stereo, and after I fitted it, took the 'faceplate' off and locked the car, it drained much of the car battery in an hour. So trying to salvage my investment (sadly I bought it in the summer so it's too late to return it I think), it struck me I could fit a switch on one of its power wires. I realise there are 'proper' technical solutions, but my time is fairly limited (hence the stereo sitting around for 6 months). So:

• Assuming the red and black wires (I'll check the schematics...) are in the right place, which one would be right to put a switch on?
• Could this solve my problem acceptably?

Thank you!

 

[Zlatan]

The red. The black will be earth, could grab a partial earth through dash and cause overheating if you put it on black.
Shouldn't drain battery tho...I,d get a car electrics bloke to look at it.

But if I were fitting it I,d find an ignition live and put an inline fuse from that to power it. Wont work when engine switched off...

 

[Deleted member 4366]

There's a few things that don't add up;

Even a small battery has about 60 amp-hours, so to half drain it in an hour, you'd have to take 30 amps out of it. There's no way in the world a car stereo can take 30 amps. The wires would catch fire, and when you tried to connect them they'd be sparking.

My guess is that it takes one or two amps at full power and less than 0.1 amps on standby if it were possible to switch it on with the front panel off. If your battery was already completely knackered, you'd still be able to leave it on overnight before your car wouldn't start.

The on/off switch is normally on the red battery wire, so when it's switched off, the battery is isolated. There doesn't seem to be much point in putting another switch on the red wire because your problem must be somewhere else.

Could you give us a few more details about what exactly you have and how you wired it up?

For now, rather than put a switch on it, disconnect the red wire, take off the front panel and touch it on the battery connection. If it sparks a bit, it's taking current from the battery, and if it doesn't spark, it isn't.

 

[Danidl]

There's a few things that don't add up;

Even a small battery has about 60 amp-hours, so to half drain it in an hour, you'd have to take 30 amps out of it. There's no way in the world a car stereo can take 30 amps. The wires would catch fire, and when you tried to connect them they'd be sparking.

My guess is that it takes one or two amps at full power and less than 0.1 amps on standby if it were possible to switch it on with the front panel off. If your battery was already completely knackered, you'd still be able to leave it on overnight before your car wouldn't start.

The on/off switch is normally on the red battery wire, so when it's switched off, the battery is isolated. There doesn't seem to be much point in putting another switch on the red wire because your problem must be somewhere else.

Could you give us a few more details about what exactly you have and how you wired it up?

For now, rather than put a switch on it, disconnect the red wire, take off the front panel and touch it on the battery connection. If it sparks a bit, it's taking current from the battery, and if it doesn't spark, it isn't.

Hi unless we know the make and type of the stereo no one here can answer the question properly.
D8veh analysis that it will take only 24watts will be true if it is one of the simple stereo radios , on the other hand if it were one of those really high-powered jobbies intended to wake the dead with thumping bass, it could drain a battery under an hour.

 

[jonathan75]

The red. The black will be earth, could grab a partial earth through dash and cause overheating if you put it on black.

Good stuff, thanks

the make and type of the stereo

It's a very basic stereo, nothing fancy, it's this one. http://www.pioneer-car.eu/eur/products/mvh-280dab

Yes I think you're right - it's just that my car has funny electronics which get unhappy after not much drain - so I didn't really describe the whole picture. Battery is quite new, top of the range.

If your battery was already completely knackered, you'd still be able to leave it on overnight before your car wouldn't start.

The on/off switch is normally on the red battery wire, so when it's switched off, the battery is isolated. There doesn't seem to be much point in putting another switch on the red wire because your problem must be somewhere else.

Could you give us a few more details about what exactly you have and how you wired it up?

For now, rather than put a switch on it, disconnect the red wire, take off the front panel and touch it on the battery connection. If it sparks a bit, it's taking current from the battery, and if it doesn't spark, it isn't.

Very interesting. I think I must have not switched it off properly, not knowing which was the off button, and instead just removed the front panel and assumed that powered it off. I'm going to test that. And I'm going to read the damn manual.

Yes the drain issue I think is because my car is a Peugeot 1007 which after moderate use of electronics, even just the internal light for an hour (at least before I replaced the battery), goes into 'economy' mode, and refuses to move its electronic sliding doors without a 'reset' which requires the engine being started. So the battery doesn't have to drain much to fall below the threshold at which the car is unhappy. It's odd but livable-with.

 

[Danidl]

Good stuff, thanks



It's a very basic stereo, nothing fancy, it's this one. http://www.pioneer-car.eu/eur/products/mvh-280dab

Yes I think you're right - it's just that my car has funny electronics which get unhappy after not much drain - so I didn't really describe the whole picture. Battery is quite new, top of the range.



Very interesting. I think I must have not switched it off properly, not knowing which was the off button, and instead just removed the front panel and assumed that powered it off. I'm going to test that. And I'm going to read the damn manual.

Yes the drain issue I think is because my car is a Peugeot 1007 which after moderate use of electronics, even just the internal light for an hour (at least before I replaced the battery), goes into 'economy' mode, and refuses to move its electronic sliding doors without a 'reset' which requires the engine being started. So the battery doesn't have to drain much to fall below the threshold at which the car is unhappy. It's odd but livable-with.

Ok
I have a peugneot 3008 diesel with the same type of battery protection, even 15 minutes of the radio on with the ignition off will cause it to go into eco mode and the radio will switch off until the motor is turned over again. This is to protect the motorist.. the primary purpose of the battery is to start the engine so using it for other purposes which could negate this are discouraged. Think of it this way , it is mildly annoying when the radio cuts out, but this does not compare with the flustration when the car won't start.

The radio claims 200 watts output, that would be 18 amps ,...... But this is an instantaneous power output and the average power would probably be 20watts real 2amps