CX-5 System died then ok after jump start but driving range shown is huge

[bandanaman]

In the UK for this one - I filled up with petrol and 2 days later when I went to the car, it was dead - the door would open (weirdly) but could not open boot or nothing on dash - I got a jump start and everything OK except radio memories wiped! - drove the car to ensure battery was ok - but it took 20 mins for the range gauge to rise from 0 and it went all the way up to 506 miles (!!!!) - never shown anything higher than 435 miles - what could have caused this? - how reliable now?
When I switch engine off and restart the car the petrol gauge shows a range of 506 miles ....
Car starts OK but I am wary - the key fob working OK - but it wouldn't before the jump start.
Not sure the battery was dead - it appears more that the 'systems' were dead which 'woke up' once the car started.
checked battery with multimeter and it read 12.3V - battery was new in November 2021 - start / stop battery (replaced when the original battery also died on me but it then charged up and is still working well
Ideas please

 

[HyFlyer]

Your "miles to empty" history was wiped (same as your radio memory). It'll take some driving before it is more accurate.

I'd say your battery is near the end of it's life. A good battery should be 12.6 volts at rest if I recall. (Battery has 6 cells @ 2.1 volts each)

 

[Conrad 16.5]

12.3vdc is low. What does the voltage look like with the car running?

Should be over 14vdc while running, if the alternator is doing its job.

 

[ADS-B]

Mine shows 13.5 "ish" on a hot day, 14 only when it's cold outside.

 

[Conrad 16.5]

Mine shows 13.5 "ish" on a hot day, 14 only when it's cold outside.

Was the AC on when you tested on the hot day?

 

[ADS-B]

I have a multi USB port plugged in with live voltage reading and yes, AC is on most of the time because 29 N latitude, you know. It would be difficult without it.

https://a.co/d/3Cj58YX I recommend one of these.

 

[Conrad 16.5]

I have a multi USB port plugged in with live voltage reading and yes, AC is on most of the time because 29 N latitude, you know. It would be difficult without it.

https://a.co/d/3Cj58YX I recommend one of these.

Checking the alternator voltage should be done with the AC, and all other accessories, off.

 

[ADS-B]

I agree and I will check it just out of curiosity. But mine definitely works or I would not get anything above 12-12.5 VDC.

 

[bandanaman]

Your "miles to empty" history was wiped (same as your radio memory). It'll take some driving before it is more accurate.

I'd say your battery is near the end of it's life. A good battery should be 12.6 volts at rest if I recall. (Battery has 6 cells @ 2.1 volts each)

Thanks Hi Flyer - the battery has a 5 YEAR WARRANTY

 

[bandanaman]

Your "miles to empty" history was wiped (same as your radio memory). It'll take some driving before it is more accurate.

I'd say your battery is near the end of it's life. A good battery should be 12.6 volts at rest if I recall. (Battery has 6 cells @ 2.1 volts each)

Thanks Hi Flyer - the battery has a 12.9v now - Went to Halfords to query the battery - put it on a battery health test and the battery came up as 610 Ah (new 640 Ah) - we plugged the 'diagnostic probe' in and there were a few error messages (historic) - cleared all historic and probe showed nothing amiss..?
So still not sure what the problem was / is - range has now come back to 'reality' of 450 miles (as it gets used to driving style).
Will have to wait and see if it dies on me again ....

 

[youri]

Honestly, it just looks like you forgot to turn it off all the way and the battery died. Or you might have a dome light that was left on. All the symptoms are similar to a dead battery that needed to be jumpstarted.

 

[bandanaman]

Honestly, it just looks like you forgot to turn it off all the way and the battery died. Or you might have a dome light that was left on. All the symptoms are similar to a dead battery that needed to be jumpstarted.

Hi Youri, yeah it sounds like that - but it is keyless so as you get out it switches off - if lights are left on then it buzzes as you leave - to stop all that - anyhow living with the question mark at the moment

 

[youri]

I accidentally put mine on ACC mode once (pressed the start-stop before putting the car in park) and left the car without noticing it was still on. Battery died.

 

[bandanaman]

Mines a manual - 'Park' is where I go to feed the ducks .....

 

[youri]

Lucky you for even having that option!