The first technical question...EVER!!!

[AndrewS]

How long should it take your car alternator to fully charge the battery?

I ask because my starter motor is getting slower and slower on the recent cold mornings, and i'm soon going to be pushing my car to work in a morning (thank god I live at the top of a hill).

I bought a new stereo/CD player in January, and it uses power even when the ignition is off, which is slowly draining the battery. I drive for about 30 mins to get to work on a morning, and the same coming home, which I would have thought would be enough to re-charge the battery.

Can I fit a more powerful alternator maybe? Any other suggestions?

[Junior]

The first Tech Response ever ...

You could try the following ..

A) Get a new Altenator
B) Get a battery for a diesel car more heavy duty
C) Get a different radio

[Eirik]

First, use a multimeter to determine how many amps is pulled out of the battery. Remove the ground connection up at the battery and fit an amp instrument between the wire and the battery. Let's say it drains at a rate of 1 amp per hour, your battery would lose 14 hours during the night (approx.). Your alternator is perhaps giving only 400 watt = 28 amp. That would be just enough to charge your battery in 30 minutes IF no other sources demanded juic(which they do, of course).

With drain established, check how many volts the car is charging with. Reading amps is not easy with a multimeter - it will fry - so you need something much bigger to read charging amps. But if it charges with about 14v, give or take a few tenths, it should be OK.

If the drain isn't too great and the charging system OK, suspect an ageing battery.

[pat byrne]

My 1st post here, guess I'm a little late joining this thread.

Andrews how old is the car? If more than 2 or 3 years it's most likely that the battery is low in acid in one or more of it's cells. If its a maintenance free unit you can usually look at an indicator on top to check it's status. If bad replace it! :(

If it's not maintenace free it's better as you can add steamed, condensed water to the low cells. This as far as I know can be bought in a chemist, seriously.

The best way to charge a battery after it going flat is to remove one lead and use a battery charger overnight to charge it. This is know as trickle charging. Flat battery perfer this to a mad busrt which comes from an alternator. http://www.eforecourt.com/UBB/bounce.gif

[This message has been edited by pat byrne (edited 12 April 2000).]

[This message has been edited by pat byrne (edited 12 April 2000).]

[Smiler]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>I bought a new stereo/CD player in January, and it uses power even when the ignition is off, which is slowly draining the battery.<HR></BLOCKQUOTE>

Not true. When the ignition is off the power used is hardly anything and certainly not draining your battery. (I run a head unit, CD Stacker and AMP).

How old is the battery?

[AndrewS]

The car is 2 years old, the battery 3 months old, so there shouldn't be any problems there.

The manual for the CD player states that 'if the car does not have an electrics position on the ignition switch (which the Fiat Punto doesn't) then the unit will drain the battery. Contact Sony for more information'.

I contacted Sony and they were no use whatsoever. It's not as bad if I always remove the removeable face plate (which I should do anyway!). That way it doesn't seem to be draining the battery quite as quick.

[Ballyfermotman]

Car is two years old and the battery is three months old??????????????

My oul lad has a 1991 323 Mazda since new and it still has the original battery.

[BrianF]

The alternator wont charge the battery, it just re-circulates the current back to it, so if you have a flat battery, its not really going to get any better until you charge it!!!

What type of a head unit is it?? Will it switch on when the ignition is off??

If so you may need to rewire it. The only thing that should consume power while the car is switched off is permanent power to your Head Unit, and that should be minimal!!
Bring it to a Car Audio Place - there is a good one at the Red Cow Roundabout.....

[BeCos]

"The alternator wont charge the battery"

Huhhhh!!!. Of course it charges the battery. It IS an "Alternator" i.e it converts alternating current into DC and supplies this to the battery at about 13.5-14.5 Volts.

Obviously a proper trickle charger is better when the battery is totally flat,charging slowly for longer is better than a "quick burst" as pat byrne said earlier.

But to make the above statement without qualifying it is not correct.

[This message has been edited by BeCos (edited 31 May 2000).]