[vina]

Originally Posted by Aroy

Back to the topic. Here is what I would do to get all the information I need

. Ammeter in the battery circuit to monitor the current flowing to and from of the battery.
. Ammeter in the Alternator circuit to know how much it is generating
. Voltmeter across the battery for monitoring voltage
. Temperature meter (I miss the meter) to know how hot the cooling circuit is
. Oil pressure meter to monitor the engine oil pressure

I prefer individual analog meters so that I can check what I want without fiddling with selection knobs, so there goes computerized display.

If I ever get a 4x4 with a low ratio GB, I would add the following (a la Pajero)
. Altimeter
. Tilt meter
. Air temperature meter

At present I have none of these in my Alto K10, and remain blissfully ignorant of what is going on, trusting in God (or MUL) that the car will run perfectly without any divine intervention of any sort, as long as I carry out the maintenance as per the MUL booklet! No meters == Ignorance is Bliss.

If I take my sister as the benchmark - she doesn't care for all this info. Now does my wife and most people I know.

In fact a majority of people on team-bhp (not the enthusiast who keep posting all the time, but a majority of the members) wouldn't care either.

It is not just about whether you know what's going on, but also what do you do once you know.

[Sutripta]

Originally Posted by vina

On the question above - as a designer I have a tough choice. I would really like to tell the user (1) His battery is about to die - as in die from old age (2) His battery has life, but it is about to die - as in die to deep discharge ...
The eternal question: SoC and SoL.
Since you (or rather the manufacturers) are giving only pass/fail - some mix of the above criteria with margins in each case will have to be devised and output. The criteria will also include economics - I think in the two I have listed above (2) will take the cake.

Nothing else?

Originally Posted by DerAlte

^^^
You constrained it to 1 of 2 possible 'what to display'. I was trying to remove that limitation, so that there can be better inferences drawn by the person looking at the telltale. The main objective is to help the person draw the right inferences.

That constraint was thought through. (At least I think so!) Idea was to clarify thoughts about cause and effect, and prioritising what is more important than what.
One other constraint I should have added is that it has to be based on voltage and ampere measurements made at externally accessible points.

Let us go back one step.
How exactly does the ign. warning light work? And therefore, what does it tell us? What does it not tell us?

And the next stage: Can we rewire it to show us more/ more relevant information?

Regards
Sutripta

[sdp1975]

My Punto MJD MID was showing a "AirBag Failure" warning during startup - typically this is indicative of a weak battery or a leak in the electrical system( eg a faulty AC compressor) from what I've gathered by searching here and other forums.

My 3 yrs old battery showed 12.92 Volts - I had shut down the engine at this shop and the fellow checked the reading. He said that the battery was fine - anything above 12.6 should be good as per him. Is he right or my voltage reading is on the lower side requiring a change ?

[aks_karthik]

Originally Posted by sdp1975

My Punto MJD MID was showing a "AirBag Failure" warning during startup - typically this is indicative of a weak battery or a leak in the electrical system( eg a faulty AC compressor) from what I've gathered by searching here and other forums.

My 3 yrs old battery showed 12.92 Volts - I had shut down the engine at this shop and the fellow checked the reading. He said that the battery was fine - anything above 12.6 should be good as per him. Is he right or my voltage reading is on the lower side requiring a change ?

Ask the battery shop guy to load the battery to max and take the reading. It'll differ and lower than the default rating. I too had the same problem and finally found the problem with battery. Once I replaced the battery everything moved to normal.

[Sutripta]

Originally Posted by sdp1975

My 3 yrs old battery showed 12.92 Volts - I had shut down the engine at this shop and the fellow checked the reading. He said that the battery was fine - anything above 12.6 should be good as per him. Is he right or my voltage reading is on the lower side requiring a change ?

Hi,
Given your symptoms, the battery needs to be tested under load. Best would be to temporarily replace with a known good battery and test.

Regards
Sutripta

[Aroy]

Normally a lead acid cell has a voltage of 2.2V per cell, hence for 6 cells the voltage is 13.2, in a fully charged battery with no load.

The problem starts when the battery's internal resistance goes up, hence the voltage drops quite fast with increasing load, especially while starting. So the correct test of battery capacity is to measure the voltage under full load. Older batteries had external connection between cells, hence a "Tong Tester" (essentially a voltmeter with a resistance between the terminals) was used to test each cell. I have yet to see a modern 12V version, so the next best thing is to see if the battery can crank the engine for say 10-15 seconds. If it can then it is OK, else it is on its last legs.

The Ignition light usually indicates
. That there is power, with engine off
. That the battery is not charging, with engine on

The moment the engine fires, the light goes off as the alternators charge the battery even at idling speed.

[DudeWithaFiat]

The Ammeter on my friends RE (Classic 350) is pointed at 'zero' most of the time. What could that mean? Isn't supposed to be inclined towards the '+' more?

Thank You.