I understand these vehicles electrical systems are sensitive to battery voltages. Just noticed my iidtool shows my battery at 11.8 to 11.7 and in red when key on. But engine off. Charges fine and no problems starting. Battery getting too old for this car?

What is the charge like from the alternator?

Test with engine running across battery terminals... .
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Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

I will test across terminals when I get back home. Iidtool gives me a 13.8 to 14 v when engine running. Turn engine off and iidtool reads 12.2 and trickles down to 11.8 in about 3 min. When it drops below 12v the color goes from green to red.

Your charging voltage seems OK-ish. I'd be expecting 14.2 or a touch more just after starting. Static voltage of anything less than 12.6 V is less than ideal on a Fatty and can lead to starting difficulties and/or error messages.

If your static voltage is dropping to 11.8 three minutes after stopping engine then you have a current drain somewhere or your battery is knackered and isn't holding a charge.

Do bear in mind, though, that the IID tool itself consumes power so it is better to use a multimeter across the battery terminals to get an accurate reading. 2006MY 4.2 SC
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Thanks. Yes I was wandering how much the iidtool could be using. I will test across terminals tonight after everything stops whirring and buzzing.

How old is your battery ?

Buy a new battery , put it on charge first till fully charged just to be sure then fit to Range Rover and see what readings you get onto no6 Range Rover

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There is a huge load on the battery when you start. An old, weak battery might be able to show 12 V on a meter, but not sustain it under a big load. There are fancy machine for testing batteries under load, but such a rapid loss of voltage would tend to indicate further investigation is warranted.

Can't read the battery year. I'm guessing about 3 yrs old. PO would have put in new battery when purchased in parts. Resting volts across terminals is 12.33v. Only thing drawing power is the LED on the USB charging outlet.

I have been playing with my IID today and have almost the same readings. After a few mins with the ignition on to allow reading of VIN and to allow unlocking of the new tool the voltage drops from 12.3V to less than 12V, shows red , pops back up to 12V and shows green and back again. Engine on shows 14.2V.
So, its either normal or we both have tired batteries.
Doclees, did you change your battery?

No I haven't changed the battery. I get 12.3 v across the terminals and it stays there through the night. The instrument cluster reads 12.3 v on startup too.

doclees wrote:

Can't read the battery year. I'm guessing about 3 yrs old. PO would have put in new battery when purchased in parts. Resting volts across terminals is 12.33v. Only thing drawing power is the LED on the USB charging outlet.

Yes I get that. I mean obvious things. Thanks though.