Battery Discharge

[davevm]

Does creeping speeds, such as at busy round-abouts, drain the battery ?

 

[Skullion]

If you battery is Leaking then I suggest you get a new Battery

Your Battery is only used for Electrionic's of the car so the more you have working at the same time, the more you'll use up.

You can Start the car up and remove the battery if you are worried you'll use too much juice in it

But I'd say get a new battery

 

[pgarner]

While the engine is running the alternator supplies the battery and electrical items on the car. Some don't work that well at tickover can still charge

 

[indiaman]

Does creeping speeds, such as at busy round-abouts, drain the battery ?

Depends on your usage, If you have the A/C on all the time, plus headlights and other accessories,then creeping speeds may discharge your battery, your best bet would be to install a simple voltmeter , which should read at least 12.5 to 13 volts when the engine is idling with electrical load.

 

[HDi fun]

If the charge current is inadequate the battery warning light will come on.

I advise against removing the battery with the engine running. It is used as a giant capacitor to smooth out supply spikes and troughs. It's also a 12v reference for lots of other equipment. Removing it could cause damage.

 

[Country Bumpkin]

Many years ago vehicles were fitted with what was called a dynamo, they would put out very little charge at idle and were very dependent on engine speed. They were generally replaced in the mid seventies by what we currently have, alternators, which are not dependent on engine speed to produce a continuous charge. [some manufacturers had them earlier, some later depending on the model of car]
The first check though is to ensure that the battery is in good condition, it's called a drop test, most garages will be able to perform this for you. Secondly, you need to be certain that the alternator is charging at between 13.75 [min] & 14.5 [max] volts.
If you are suffering from low battery charge at low speeds i would suggest fitting an ampmeter, you only need a temporary one to locate a problem, then with all your usual electrical items running, turn them off one at a time to isolate the drain. When you find the cause, check it out as an individual item, it may be faulty. Modern cars are designed to be able to cope with the demands of the systems fitted to them.

 

[HDi fun]

Dynamos.

Yep - about pre-1974 most cars used dynamos, which are DC generators. Alternators have replaced them now - most are 3 phase devices for low speed efficiency.

 

[turbonutter69]

Just sitting still idling the engine with everything on shouldn't drain the battery at all.

 

[HDi fun]

Just sitting still idling the engine with everything on shouldn't drain the battery at all.

If it's a small basic car with lots of user fitted electrics it's possible for the current drain to build up to a point that there's not a lot of spare juice left to charge the battery.

Although it's still unlikely to be a problem, so I do agree with you.

If the battery light doesn't come on then the net current is into the battery, not from it.

I don't understand the point being made about A/C. The A/C compressor is very demanding but it is directly driven via a belt and pulley, the compressor imposes no electrical drain at all.

 

[Country Bumpkin]

Something to add regarding A/C units. The engine will automatically adjust and raise idle speed to compensate when the car is stationary anyway, it's controlled via the idle control unit.

 

[dpsubaru]

The Musso is a monster for eating batteries and had a feeling that its partly the way its driven, not often about 2000 rpm so had understood that the alternator may not have been spinning fast enough to charge up the battery properly - the batteries were dying after about 6 months each time - does this sound feasible (note we were typical driving with two amps running, headlights on) ?

 

[Bheki Mazibuko]

Re: Battery Discharge
I once experienced that problem with the BMW I once owned. My solution was; I connected a the breathing pipe into a waiting small tank, tight sealed it. When the engine is not running water will automatically evapourate back into the battery.