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Old 28th October 2014, 16:25   #31
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Default Re: Listening to the car radio when the engine is off - Bad for the battery?

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Originally Posted by reignofchaos View Post
You don't need to reach 9.6V to reduce the life of a battery. If the battery has reached 9.6V, its as good as gone. Actually anything below 45-50% discharge of an SMF battery will reduce its life span drastically. At 50% charge, the voltage will be down to 12.1V or so.
* 12.1V at 50% charge is OPEN CIRCUIT voltage - no load connected. One cannot discuss in Open Circuit terms for practical usage, since one never measures Open Circuit. Even the battery-wala measuring the voltage (with his charging box) after taking out battery does it with a nominal load, since otherwise they cannot account for / detect "cell failure"

* The "nominal 12V" is actually 12.66V at 100% charge, measured at open circuit at 20C. Open-circuit voltage is measured 12 hours after charging to allow surface charge to dissipate and enable a more accurate reading

* The voltage at 0% charge is 11.7V, again measured Open Circuit at 20C

* Since OC voltage of Lead Acid batteries is negative temperature coefficient (-0.022V/DegC), the voltage reading will be lesser at higher temperatures

* ALL automotive electronics is designed to operate reliably in the range 12V +/- 20%, i.e. 9.6-14.4V, since operational conditions are never "open circuit". Different loads can pull down 12V line to as low as 9.6V, but the voltage recovers once the load reduces

* "Deep discharge" affecting the life of the battery would be over-stressing it. An SMF battery usually has a life of 400 discharge cycles (down to 0%). The usual charge range in mixed (day + night) usage is 40-100%

* Very few people allow the battery to go to deep discharge state. No sane driver does it deliberately. Oversight may cause it, like forgetting to switch off parking lights (headlights usually go off when key is removed), or interior or engine bay light. BUT this is a rare happening, if at all it happens. Under such circumstances, "life" of battery is not a big concern

* If the driver is listening to the radio at a low volume (that's what they do when parked in office / basement parking), he can do it for a few hours and still the charge condition will not go below 40%. The starter will be able to crank the engine even at 10% charge, albeit it will be hard labour and one can hear it. Modern controlled-injection engines are able to start even in that condition, and charge reaches 30-40% in 10 minutes driving

It will be a different story if he is tripping away listening to item numbers at a loud volume, especially if the owner has fitted good ICE. Then he can discharge the battery in 2-3 hours, and will face the wrath of the owner when it is time to go home. Some drivers are indulgent, but very few are that stupid.

Last edited by DerAlte : 28th October 2014 at 16:27.
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Old 28th October 2014, 20:57   #32
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Default Re: Listening to the car radio when the engine is off - Bad for the battery?

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Originally Posted by DerAlte View Post
* "Deep discharge" affecting the life of the battery would be over-stressing it. An SMF battery usually has a life of 400 discharge cycles (down to 0%). The usual charge range in mixed (day + night) usage is 40-100%
Agree with most of your points other than this one. Try deep discharging an SMF to 0% 20-30 times and it'll lose most of its capacity. After that, its a dud - it'll only be good for 30% of its original rated capacity. The manufacturer rated specs are mostly at 50% discharge not 0%. SMFs just can't take the mechanical strain of deep discharge unlike flooded batteries.
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Old 29th October 2014, 00:10   #33
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Default Re: Listen to car stereo with engine OFF?

Guys, I noticed off something a little strange off late.

When I stop at a traffic light and I switch off the car and I start it again the music system stops functioning momentarily so that all the battery's power can be directed towards starting the engine. Basically, music stops for about a second when I am cranking the engine. I understand that this is normal.

But sometimes I notice that the music system switches off temporarily even when I am moving the key from the off position to the ignition position. So, basically music stops for about a couple of seconds once the key is being turned from 'off' to 'ignition' and again when I am cranking.

Is this something I should be worried about?

PS:
Car: Maruti Suzuki Swift VDi (2008)
Battery replaced in 2011 oct with Amaron DIN 6X(Don't remember correctly).

Edit: Forgot to mention the the car covers less than 500kms a month now-a-days due to change in usage pattern. Also, distances covered ar usually pretty low, around 5-15kms whenever it goes out. I can't remember if the problem occurs even after a longish drive.

Last edited by scuderiamania : 29th October 2014 at 00:12.
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Old 29th October 2014, 16:47   #34
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Default Re: Listen to car stereo with engine OFF?

Quote:
Originally Posted by reignofchaos View Post
... Try deep discharging an SMF to 0% 20-30 times and it'll lose most of its capacity. After that, its a dud - it'll only be good for 30% of its original rated capacity. The manufacturer rated specs are mostly at 50% discharge not 0%. SMFs just can't take the mechanical strain of deep discharge unlike flooded batteries.
Considering that generally no one in their right mind does that to their batteries "20-30 times", that is just a rhetorical expression. The manufacturer cannot refuse to service or replace in warranty if the battery doesn't recover from an occasional deep discharge. But yes, there is no end to paranoia.

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Originally Posted by scuderiamania View Post
... When I stop at a traffic light and I switch off the car and I start it again the music system stops functioning momentarily ... I understand that this is normal. ...
Yes, that is the standard modus operandi.

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Originally Posted by scuderiamania View Post
... But sometimes I notice that the music system switches off temporarily even when I am moving the key from the off position to the ignition position. So, basically music stops for about a couple of seconds once the key is being turned from 'off' to 'ignition' and again when I am cranking. ...
Most likely there is a random loose connection (or more precisely, a short to ground) in the key (lock) switch.
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Old 29th October 2014, 22:14   #35
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Default Re: Listen to car stereo with engine OFF?

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Originally Posted by DerAlte View Post
Most likely there is a random loose connection (or more precisely, a short to ground) in the key (lock) switch.
What do I need to do to stop the problem from re-occurring?
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Old 30th October 2014, 13:59   #36
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Default Re: Listen to car stereo with engine OFF?

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Originally Posted by scuderiamania View Post
What do I need to do to stop the problem from re-occurring?
First ask the service guys to establish if there is a short. If it is a switch fault, you have to replace it.

This is a rare occurrence, so it is unlikely to recur.
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