Looking for some opinions, fitted a new bosch s5 in september over the last 2 weeks the car started throwing up the usual faults when the battery starts playing up, auto park brake not available, special programmes not available etc, etc. But after 30 secs of running it all resets, apart from today when it took a few goes to start after a short run, got home and battery voltage with engine off was 11.8v and car wouldn't start just starter motor clicking, charged the battery up for 2 hrs and it was showing a charging rate of 2amps the whole time after that the voltage was at 12.6v so put it back and car started first time running voltage was 14.6v, just wondered if anyone else thinks my new battery has gone or do the symptoms show an alternator problem, it's an 08 tdv8.

Could be - give it a full overnight charge - then if it happens again, I'd take the battery back to where you bought it and ask them to test it

you need to monitor the voltage that is put out by the alternator as you load it up, it might show 14.4ish volts as it idles after starting, but what does it do when you throw some load at it. try it with the heater on full, the screens on and the heated seats front and rear, and see if the voltage drops significantly under load.

If the battery is that new I would be taking it back for testing as Alistair suggests.

as a basic voltmeter use the vehicle signals page under the hidden menu and you can monitor it on the move. It is strange that a battery that is only a couple of months old should fail though. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
Fiat 500x 1.4 multiair Lounge 2015
2010 LR D4 Commercial 2.7 TDV6

That was my thoughts on a new battery failing, I was going to see if the voltage dropped significantly overnight to see if there's a major drain somewhere, I'll do the full load test tomorrow and see what happens battery was from europarts so I may just take it back on Monday and exchange it , at least to eliminate the battery. Just strange as all this started when the temperature dropped about 2 weeks ago and from experience cold always shows up a bad battery. Thanks for the replies.

If you have a multimeter with amps you can test for a drain without waiting for it to go flat overnight

Could be a bad cell on the battery , or could be an alternator fault , and don't rule out belt-slip during cold weather ...

The problem is , an alternator fault or a slipping belt will often ruin a battery

Checked this morning, overnight voltage had dropped from 12.5 to 12.1 then as soon as key turned to first click dropped to 11.8, started it up and voltage up to 14 after a minute after 5 minutes on tickover 14.5 v. So turned everything on all heated seats and aircon and voltage dropped to 14 so don't think anything wrong with alternator, turned car off waited for a while then disconnected negative and put multimeter across it and showing 0.8 amps, this then popped the 500mA fuse in my multimeter leads (spares are at work) so tracing the fault stopped for now, but have had a problem with some corrosion on the light control module but never got round to getting it changed, so swapped it for the second hand one I had, I couldn't check the drain current due to my blown lead so I'll see what happens to the voltage overnight, I'll also get a decent tong ammeter from work this week as I think 0.8 amps seems a bit high to not completely flatten the battery in a couple of days. I'll update this when I know more definitely what's at fault.

sounds like the alternator is ok with those voltages, just under 1A drain would almost completely flatten a battery in about 4 days, when you have your leads check if it stops 10 mins after shut off, everything major should have shud down by then. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
Fiat 500x 1.4 multiair Lounge 2015
2010 LR D4 Commercial 2.7 TDV6