Battery low on 3.0 Tdi

[prophet]

Two days later I re measured the battery. It’s now reading 12.16. I haven’t used it or started the car in two days. So it’s dropped from 12.45. Is that normal?

[lynalldiscovery]

Its not happy motoring its ******, this is the joys of internet advice
Seriously its going to let you down on the wettest coldest night going, you know the kind of night where you are gagging for a dump miles from home but think Im home shortly so walk past the last loo just as they are closing the doors only to find the car wont start! and theres nothing worse than an unreliable car.

So either buy a new battery or some spare toilet roll

[lynalldiscovery]

See this chart theres many like it and all vary slightly but all will tell you 12.16 is knackered.

[prophet]

See this chart theres many like it and all vary slightly but all will tell you 12.16 is knackered.

Thanks for that. I take your point that 12.16 isn’t great. I’m still trying to work out though if that means a knackered battery, or something in the car is draining it. That Bosch battery is £279 from EuroCarParts. It’s a lot to spend when it’s only two years old, if that doesn’t cure the problem.

[niall campbell]

you need to do two things

1) take the car to any garage that does a FREE battery check . Google your local area. They will test for a dud cell ( s) . New batterys off the shelf can have them & so can a 12 year old one. Its just your luck & why you have to hold onto your receipts

2) Check the output of your alternator. SHould be 14.5 volts under FULL LOAD. All lights on, Full beam, rear demister on, heater in car blowing full speed. Measure the volts at alternator

then measure with everything switched off, but engine running

This will check the " clutch " on alternator is working & the brushes are not worn down, regulator working etc. New cars have a " clutch" system so the alternator only charges when the car tells it to do so.

[c4a5er]

As said earlier in the thread if a battery terminal is getting hot there is a resistance. You should remove the the battery connection and clean it and then make sure it is replaced tightly. Also check that the cable itself is secure into the cable connection.
May or may not be the final problem but definitely the thing to eliminate first.


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[niall campbell]

yes I agree


this could be due to alternator overcharging the battery, causing a dud cell (s) ........................ bad regulator in alternator

[lynalldiscovery]

No its not it isnt great, trust me its knackered, I change loads at work and in my eyes anything thats below 12.4/5 will cause slow start cranking and as 2 batteries are cheaper than the middle of the night breakdown callout plus the two batteries they will fit it just makes sense to fit new ones whilst its in the shop.
People always think as its a 12v battery anything over 12v means its good, but its 2.1v per cell x6=12.6 minimum.
If not convinced remove the battery off of the car, charge it again over night, leave standing for 12 hours and recheck voltage that way you have eliminated the car from the equation


As for 279 quid thats got to be the biggest psis take ever!
One for my disco 90 quid and one for the wifes last audi 3.0tdi was 90 quid as well, both from Tayna batteries iirc.
Search for 019 battery, you can pay well over a ton as you have found out, but a normal everyday one will still do the job

[swalker]

I work for a medical device manufacture in the R&D department. a team of engineers spent a year validating the 18V battery. serious bit of black magic in battery technology.
In short the best way to tell the capacity is the open circuit voltage, for an 18V battery anything less than 19V is a fail.....

[prophet]

As many suggested on here, I took my car to my local trusted garage. They tested the S5 battery and said it was knackered. They also said it hadn’t been coded to the car. Don’t know if that has caused any of its issues. It has now been replaced with an Exide battery.