My battery warning light stayed on for longer than normal after starting yesterday, so I started looking at the health of my battery and alternator.
First the battery, it appears to be running at around 12.3V. Charging it overnight got it to 12.7V (immediately off the charger) but this dropped back to around 12.3V with the ignition on for about 30seconds.
So, that to me doesn't sound like a particularly healthy battery. Would you agree?
I ask as it is a decent battery (Bosch S4 010) and the date code on it is october 2022. So I am a bit surprised it is looking tired after only 8 months.

That lead me to look at the alternator. Engine idling it was charging at about 13.5V. This was after I had charged the battery overnight so, although on the low side, I figured it wasn't unreasonable if it thinks the battery is charged. I noticed the manual says 13V to 14.8V at idle.
Again, any comments from those that have experience of what this system is supposed to do?

Lastly, as I was looking, I wondered if the alternator sprag clutch (overrun pulley) was ok, not least because there is a bit of noise coming from that area, particularly when cold.
So I popped of the cover on the pulley and tried turning the alternator with an 8mm hex in the shaft. It would not turn, either direction.
Again, I've never played with an alternator with a overrun pulley before but am I right is saying that is not correct, I should be able to turn the shaft freely in one direction?

btw. battery is not AGM, no BMS, or extra earth lead for that matter. Although with engine running the voltage drop from the alternator body to the battery negative was much less than 0.1V. So I think my earth is good. FL2 2007 2.2d Auto SE. Baltic Blue.

Yeah, battery is on it's last legs and the FL2/LR2 is a battery hungry hog. Assuming your alternator is the same as mine, the alternator pulley bolt could also be the culprit if it loosens. @p_gill has a lot of helpful posts and thread re the alternator.

My battery woes are described in this thread.

Once the battery started to show problems and struggled to give a decent resting voltage it just got worse and worse. I followed Nodge's advice and fitted a larger battery, there is plenty of room for an 80Ah+ replacement.

https://www.freel2.com/forum/topic38965-15.html FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 76k+ miles) (MY2015)

12.7v immediately off the charger is way too low. That shows it is most likely a battery issue.


My car is 14.4v & very consistent. About 50 amps charge after 30 seconds according to Kyoritsu 2046 clamp meter.

Neighbour's battery at about 18 month had a dead cell, in a Honda. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Thanks everyone. That confirms that the battery is a bit dodgy so I am resigned to buying a new one. I'll take the advice and go for a decent capacity one, it isn't worth saving a few quid on.
I have had a read of some of the other threads on the subject and there is some good info there, although expected charging voltages vary quite a lot.

That just leaves me wondering what caused the battery to go so quickly. I need to do some more tests but it is looking like I probably need to get access to the alternator and check stuff like the famous blue wire. Although is sounds like if I can get to that (fuel filter removed) then I am half way to getting the alternator out so I might go the whole hog and replace that too. FL2 2007 2.2d Auto SE. Baltic Blue.

If you worry about your car battery you can always fit something like this https://www.ebay.co.uk/itm/195536761700?ha...R4LQoJCtYg
It makes checking the voltage as simple as opening an app and you can check historical data as well. There are plenty of variants, I chose this one when they were cheaper and fitted one to each of our 2 cars.

Well, I just got a chance to test the battery/alternator a bit better. I have a traditional style battery tester - the sort that puts a 100A load on and measures the voltage with an analog meter.
So, initially (no load, just unlocke the car) the battery was at about 12.6V - much better than yesterday, so it must have recovered while being left.
I then put the load on for 10s and it dropped to just under 11V. Not great but just about in the range the tester claims is ok for a 700CCA battery. It recovered to over 12.5V in about 10s.
I then started the car and left it at tickover. The battery voltage was then at about 14.3V. So again, charging more than it was yesterday.
I then stopped the engine but left it at ignition 2. ie dash lit up.
The voltages started at around 13.2V (again, better than yesterday off charge) but over about a minute dropped to less than 12.5V.
So my conclusion from that lot is that the battery is indeed tired, but not completely dead. So I still agree it needs replacing but first I want to be sure I know what killed it.

To that end, I started the car again, left it on tickover (charging at about 14.3V again) then turned on the lights, windscreen and seats. Voltage stayed at around 14V. I then turned off all those loads but used the battery tester to load the battery (ie a 100A load) (only briefly!). The engine revs immediately dropped and there was a nasty rattle from the alternator area. The battery voltage also dropped to around 12V.
I was going to conclude that this meant the alternator was not charging very well, but then realised that expecting it to give over 100A at tickover was probably pushing it a bit and it actually did pretty well.

So I am still not convinced I know what killed the battery, or what caused the charging light to stay on for while after starting it a few days back. Obviously the sprag clutch needs fixing but otherwise I am tempted to get one of those monitor things BossBob linked and see what it finds.

Is there anything I have missed? FL2 2007 2.2d Auto SE. Baltic Blue.