Hi have I got a battery or electrical fault do you think.

 

Petrol Vrs 245 bought in Feb 2022.Built Dec.21

 

I don't use the car daily but periodically fit my Ctek charger and charge the battery to full.

 

From a fully charged battery,after about 18 days of not being used the car starts flashing the hazard lights and then the alarm goes off.

 

The Ctek has 3 leds lit when fitted and the voltage is 11.8V .I recharge to full and no more alarm or flashing lights.

 

Surely a 1-2 year old battery should be ok for 3 or 4 weeks.

 

Any thoughts please.

10 hours ago, GrumpyOldGit said:

Hi have I got a battery or electrical fault do you think.

 

Petrol Vrs 245 bought in Feb 2022.Built Dec.21

 

I don't use the car daily but periodically fit my Ctek charger and charge the battery to full.

 

From a fully charged battery,after about 18 days of not being used the car starts flashing the hazard lights and then the alarm goes off.

 

The Ctek has 3 leds lit when fitted and the voltage is 11.8V .I recharge to full and no more alarm or flashing lights.

 

Surely a 1-2 year old battery should be ok for 3 or 4 weeks.

 

Any thoughts please.

Hi you say is 11.8 v and you recharge till full, but is that 11.8 before you put on charge and what is the voltage at "Full" ?

@GrumpyOldGitSadly batteries are not always good for 3 or 4 weeks of no use on many modern cars, even in mild weather.

So it is what it is. 

So could park at airport for 3 weeks and come back to a flat battery then.

 

AGM any better in your experience?

 

@Radiotwo Didn't check voltage after charging but car was good for at least a fortnight.This is only the 2nd time this has happened.Just means with winter coming I'll be charging the battery every fortnight 

1 hour ago, GrumpyOldGit said:

So could park at airport for 3 weeks and come back to a flat battery then.

 

AGM any better in your experience?

 

@Radiotwo Didn't check voltage after charging but car was good for at least a fortnight.This is only the 2nd time this has happened.Just means with winter coming I'll be charging the battery every fortnight 

Hi, Without having the final reading its hard to say but 11.8 volt is not good, it should be at least 12.5 volts, so you have a problem with a short or the battery is faulty, try and get the battery tested (admitting needs to be fully charged) and if found faulty go back to the dealer and get them to change it under warranty 

12 hours ago, GrumpyOldGit said:

From a fully charged battery,after about 18 days of not being used the car starts flashing the hazard lights and then the alarm goes off.

 

Do you mean that you charge the battery with your charger and then leave the car for 18 days or do you mean that after having driven the car for a reasonable journey you considered that the battery was fully charged before leaving it?

 

The latter is a wrong assumption because the battery management system for the Start/Stop function only maintains the battery at about 80% state of charge.

 

If its the former then either you have a parasitic discharge like a dashcam or the Can Gateway not shutting down or the battery has lost capacity, I would expect and have experienced more being able to restart after more than 30 days with a fully charged good battery, sadly cars with the Start/Stop system never have a fully charged battery.

 

You could try disconnecting the shunt resistor which will give a standard alternator charging system, then drive it for a few miles to fully charge the battery and see whether it exceeds the 18 days by any margin.

11.8 volts is what I would expect for a voltage reading taken from a Start/Stop vehicle unless the battery was disconnected or the bonnet switch shunted and the measurement taken after 20 minutes when the Can Gateway will have shut down, that alone drops the voltage by around 0.7v making any comparison to an open cell voltage/state of charge chart meaningless.

Thanks for replying.

 

For clarity this first happened about 2 months ago and I put it down to a one off.Alarm chirping rather than horn blaring and neighbour said lights had been flashing earlier that day.Door and bonnet open checked voltage 11.8v.Fitted ctek Mx 5 smart charger normal car mode and charged to max.

Start stop is active.Car used for one 40 mile trip and a couple of 4 mile trips then not used for about 17 -18 days not exactly sure.

 

Last night wife says lights flashing so fitted charger and charged to max.

 

Will check voltage later for reference with a fully charged battery and bonnet open.

 

No dash cam but a usb wireless charger in place no phone on it obviously

 

Sounds like I need it checking though

What type of battery does your car have. If it is an AGM stop/start battery then you should be using the agm setting on your charger. Secondly are you connecting the -ve lead from the charger to the earth point on the bulkhead as per owner manual and not to the battery, as this can cause problems. 
I would unplug the usb wireless charger when not in use.

Edited 20 October, 20232 yr by Kenny R

EFB so no don't need to use AGM mode.

Yes +ve to battery and -ve to bulkhead.

 

Voltage after exiting car,engine off is 12.3v now.Im happy the charger is doing its job.

 

Is the car alternator and management working correctly I don't know.

Is the battery capacity compromised or is there a short/drain on the battery beyond what's normal again I don't know.

 

Will definitely check if USB should be live or not with ignition off and try unpluging.

1 hour ago, GrumpyOldGit said:

EFB so no don't need to use AGM mode.

Yes +ve to battery and -ve to bulkhead.

 

Voltage after exiting car,engine off is 12.3v now.Im happy the charger is doing its job.

 

Is the car alternator and management working correctly I don't know.

Is the battery capacity compromised or is there a short/drain on the battery beyond what's normal again I don't know.

 

Will definitely check if USB should be live or not with ignition off and try unpluging.

It is very difficult these days as you used to just start the engine and if you got 14.5(ish)  you knew it was ok, but now when you see

the voltages they go up and down, and I think you need to get a Multimeter to check things out like current draw when the car 

is turned off and what would help is do a drop test on the battery its self.

 

and just as a matter of interest my voltage  after it has been stud for a few hrs is 12.46 volts 

6 hours ago, GrumpyOldGit said:

Fitted ctek Mx 5 smart charger normal car mode and charged to max.

Start stop is active.Car used for one 40 mile trip and a couple of 4 mile trips then not used for about 17 -18 days

 

Sadly the battery (mis)management system will have undone all your good work in charging the battery, it will have allowed the vehicle's electrical running load to discharge the battery to around 80% SOC hence the alarm sounding after 18 days.

 

A new battery may well increase the 18 days to ???, get the battery load tested if you can, if you know the car is going to be left you could charge it when its finally parked up, if it were me I would disconnect the shunt resistor and revert to a standard charging profile without the start/stop function, but then I hate that anyway!