How To Check Is200 Alternator/charging System?

[blahmartinblah]

Hi

Recently had a problem with my Battery going completely flat after it came back from the body shop getting the rear bumper resprayed. I'm not sure if they left the lights on or something to flatten it, or it is unrelated, but... I want to check my car out to make sure it will be OK. I want to check first the Battery is getting charged properly, and then that there is nothing unexpected which will flatten the Battery.

Can anyone help with rough numbers for what to expect here?

1. Battery voltage when car is idling (I.e. from the alternator). - Should this drop much when headlights etc turn on?

2. Current consumption when the car is turned off completely, with all interior lights off, etc.

3. Current consumption when the car has the ignition turned to 'on' with some specified number of accessories running?

Thanks

Martin.

[P38Aaron]

Hi

Answer to number 1 should be about 14-16v (closer 16v)

If i am wrong then im sure somebody will step in and put me right.

Have you checked the acid level and strength of each cell?

Aaron

[blahmartinblah]

Hi

Answer to number 1 should be about 14-16v (closer 16v)

If i am wrong then im sure somebody will step in and put me right.

Have you checked the acid level and strength of each cell?

Aaron

Hi Aaron.

I haven't checked the batteries acid level and strength. It is only 9 months old and I took it back to the the supplier (Unipart) today for testing. They said it is fine, and recharged it for me for free! :winky:

Thanks for the tip on the voltage, but 16V seems really high to me. Is it based on measurements of your car?

Martin.

[DJ Wozza]

anywhere between 13-14 vols is where mine is normally with my sound system on low.

16v sounds outrageous;y high to me.

[DJ Wozza]

anywhere between 13-14 volts is where mine is normally with my sound system on low.

16v sounds outrageously high to me.

[blahmartinblah]

Thanks DJ Wozza. Thats about more what I'd expect.

How about the current draw from the Battery when the car isn't running to make sure nothing is draining my Battery when it is parked up? Anyone got a rough idea what to expect?

Martin.

[rossastra16v]

Once you start the car it should charge the Battery @ around 14v. if the car is idling then its unlikely that the engine will be spinning fast enough to charge the Battery @ 14v so if you put the headlights on then you should expect a drop in voltage but as long as the voltage goes to around 14v when you rev it you should be fine

[KevLex]

Modern alternators can output their regulated supply down at quite low engine speeds. Certainly at a fast idle of about 1000rpm you should be getting about 13-14V depending upon where you measure it. Alternator regulators are normally set for either 13.8V or 14V on a 12V system. This will be the voltage that the alternator tries to regulate to at its output. The higher the current being drawn from the alternator and the further away from the alternator that you measure (on the high current path) the lower the voltage that you will measure.

Quiescent standby current should be quite low. If all electrical loads are turned off you will be left with the alarm, central locking and various other controllers. The total load on an IS200 is about 0.5W, this equates to about 50mA. If you lift the earth terminal off the Battery and insert an ammeter this is what you should measure. Make sure that the doors and boot are closed and that you don't activate the central locking or any other load or it will take out the low current fuse in your ammeter ;-)

As for the standard running current it will depend on what is active at the time you measure. The ignition system will take about 60W and the fuel injection another 40W. That equates to about 7A but I would not be surprised to see even higher current than this. Be very careful if you plan to measure this using an ammeter in series with the supply. If the Battery becomes disconnected from the the charging circuit whilst the engine is running damage may result to the various electronic modules still connected to the supply. This is because the Battery will no longer be in circuit to smooth the AC waveform coming from the alternator.

So in summary to your original questions:

1. 13.5V +/-0.5V

2. 50mA

3. Hard to say, of the order of 10A but I would not test this.

The best way to test your Battery is to check the specific gravity of the cells with a hydrometer (from a car accessory shop). The original Toyota/Lexus Battery had a built in hydrometer but it only gave an indication from one cell. It is not uncommon for one cell to fail and you will see this when you measure the gravity.

Alternatively if you load the Battery after it has been sat overnight by turning the headlights on, it should still measure about 12V across the terminals. Each cell is 2V nominal, so if you are only getting 10V then this may indicate that a single cell has failed.

[blahmartinblah]

Kevlex, top post mate thanks.

Here are my measurements:

Battery voltage after being parked for ~24hrs: 12.56V

Battery voltage with the car idling @ 935rpm and all accessories turned off: 14.30V

Battery voltage with car idling @ 847rpm with headlights and rear window heater turned on: 14.23V

Battery voltage with car turned off completely after ~5mins idling: 13.62V

Current consumption with car turned off, all doors closed, all accessories off, doors unlocked, alarm off: 93mA

It all looks OK to me, although the current consumption is a bit higher than the 50mA you specified. Where did that number come from, and does anyone have comparative measurements to see if mine is really different? My only electrical modification from standard is changing the headunit to a Pioneer CD/Bluetooth device. It definitely turns off when the car is off. Perhaps it has a higher Iq rating that the standard player?

I don't think 93mA is going to do that much damage to a 60Ah Battery anyhow.

Martin.

[KevLex]

Martin,

I wouldn't worry about the 93mA standby current on your car. I measured the 50mA on my own unmodified IS200. There is likely to be car to car variation as well as model year to model year differences.

93mA being drawn from a 60Ah Battery still equates to about 1 month.

Your other readings look reasonable (within 5% of tolerance).

If you have any further problems then I would get a hydrometer and test the gravity of the Battery electrolyte.