Member Since: 16 Jun 2021
Location: Cambs
Posts: 22
Weird battery charging issue.
I have one of those volt meters which plugs into what used to be called a cigar lighter socket. I don't use it very often but after having a Red restricted performance warning which IId reported as steering angle sensor which I'm told is common if the battery is on its way out. The volt meter reported battery voltage of 12.2 volts which I believe is a bit low. Had the battery tested and was advised it needed replacement which is fair enough as it is the original battery (63 plate Disco 4). Had a new battery fitted and it read 12.7 volts. Plugged the meter in again this morning and it only read 12.2 volts again. Left it in while driving and it fluctuated between 12.2 - 12.1 volts and therefore was not being charged. I then noticed that when the car was creeping ie not touching accelerator it shot up to 13.8 volts so was charging but as soon as I touched the accelerator it dropped back to 12.2 volts. Could I be lucky and the (original) aux belt is slipping or is it the alternator? By cruel coincidence over the last couple of days I have also had the Red restricted perormance warning (and performance very restricted) due to "manifold absolute pressure mass or volume air flow correlation" which I guess is split manifold.
13th Jun 2024 5:12 pm
eightfoot
Member Since: 12 Apr 2015
Location: sunny essex
Posts: 798
sounds like normal behaviour to me,do a search and read up on the kinetic recharging system it uses as what you are describing is the same as mine when the battery is fully charged hopefully nothing to worry about 12.2 with ign on but not running is also normal please excuse any grammer/punctuation mistakes,i'm thick,thankyou
current vehicles 2005 d3 2013 d4
13th Jun 2024 6:19 pm
Manorbleak
Member Since: 16 Jun 2021
Location: Cambs
Posts: 22
Many thanks for your reply but is 12.2 volts normal with ignition off? I suspect not when it was 12.7 volts on the new battery when fitted.
13th Jun 2024 8:37 pm
Tyty
Member Since: 18 Aug 2022
Location: South West
Posts: 79
The charging system is a bit more complicated than most cars. The BMS module will request a certain voltage from the alternator to charge the battery.
Did the BMS get reset when installing the new battery?
14th Jun 2024 12:48 pm
Manorbleak
Member Since: 16 Jun 2021
Location: Cambs
Posts: 22
Thanks for the reply, yes the garage said they had reset it but to be sure I did it myself with my IID tool when I got home.
Bearing in mind it's only 3 days old the battery took over 3 hours to charge fully using my Ctek charger this morning and is now at 12.7 volts.
I don't have any fault codes relating to the charging system and the alternator light is not on.
14th Jun 2024 2:02 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8194
The only way to accurately measure the voltage is with a multi-meter and the battery disconnected, you not only need volts which is only a guide but more importantly you need amps although that should not be a problem with a new battery.
A plug in device to the cigar lighter is only a guide.It can when others can't,
It will when others won't,
It goes where others don't.
14th Jun 2024 6:33 pm
Manorbleak
Member Since: 16 Jun 2021
Location: Cambs
Posts: 22
Reply much appreciated but I have bigger problems to worry about as in both manifolds split
14th Jun 2024 11:42 pm
Tyty
Member Since: 18 Aug 2022
Location: South West
Posts: 79
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