The battery on my wife's car died this week, which was annoying as these things always are. She'd been shopping and when she got back to the car in the evening, the zapper wouldn't even open the door! We had all the usual trouble of leaving the car where it was overnight (thirty kilometres from homes), returning to the scene of the problem the next day, locating a dealer, hanging around, etc., and my question is this. CAr dashboards can tell us when petrol is low or a door is open (straightforward I suppose), and they can measure tyre pressures, work out present fuel consumption instantaneously and a dozen other things. So why don't/can't they point to a failing battery or worn tyre-treads as well? Surely this would be much more useful? Or is it just not possible? I though anything could be done with a computer.

My car does point to a failing battery. I have a battery light on my dashboard that will turn on if the alternator is not charging the battery. That lets me know that my battery is going to die.

Older cars used to be equipped with an ammeter which showed when the battery was being charged and when it was discharging. Unfortunately even when the alternator is doing its job and "trying" to charge the batery, if the battery has outlived its usefull life, neither lights nor meters are much help. An expiring battery gives some hints that it is not doing its job when the lights get dimmer and the starting effort gets weaker or hesitant. Of course, since the computer and everything else depends on the battery when the engine is stopped door-opening solenoids, etc. can't function.

its possable to install meters into the battery
to check the power of each cell. but that will come at a cost to you and me.
there are lots of stuff they can add to the auto to tell if everything is ok , BUT look at that word for a bit, it will cost us more $$$$$$$.$$ per auto now do you want to pay more $$ for that cheap auto that will last you only a couple years. then if the darn thing breaks
you know where you got to take it to. yep the dealer and more $$$$$$$.$$ to fix the dam thing
BUT they can get those things for you.

Your automobile association probably has an inexpensive procedure they will do, it's called a 'safety check' but they check for a lot more than just safely, at least here in B. C.

I got in the habit of having an annual checkup when I lived in Vancouver but there is no branch office here so I just have it done at my favorite auto repair place. The other good thing it does is warn me, up to a year in advance, about repairs to be ready for, e.g. failing radiator. Helps with budgeting.

This won't utterly prevent being stuck at night somewhere with no wheels, but it will reduce the frequency.

I drive a 1990 toyota 4 cyl. manual trans. pickup. Way too old to have a zapper (the truck is, that is ) . So I'm assuming your wife's car is newer. My battery is over ten years old, never recharged except during driving. Maybe yours is all right, just needs to be recharged and suspect an alternator repair is in order?

best thing to do is check your battery and cables every year . expect battery to last about four years. then replace it and replace cables at the same time and you wont have to worry about that part of the car it will allways work right. check oil and water everyday tires ect.

Thank you all for responding. For your information, the battery (and the car) are 2 years 11 months old. The dealer who fitted the new battery said that it came with a one-year guarantee and that nowadays a lifetime of three years is all you can expect. Years ago, the rule of thumb was between 3 and 5 years, then if you had problems starting the car, change the battery. Sadly for us, this one just died without warning.

The batteries self charging. Jump start it, drive around with no music on, no lights, nothing that drains it, basically no electrics and it should be fine.

Plus check the tread on the tyres to find out if they are road worthy. They come marked.