981 dash display battery volts 15.2 whilst driving?

[andygo]

I'm sure my 2016 GTS used to show mid 14v when driving, but over the last couple of trips it been up at 15.2v for some time. Is this OK or should I be taking it to the OPC.

It's had a new Porsche battery a couple of months ago as the original was showing low charge after being left overnight, down in the 11.8v range.

[elan362]

That sounds too high - AGM battery charging voltage is around 14.7-14.8v
Was your new battery coded to the car? (It should have been)

[andygo]

elan362 said:

That sounds too high - AGM battery charging voltage is around 14.7-14.8v
Was your new battery coded to the car? (It should have been)

Who knows if it was recoded, it took the OPC over 2 hours to fit.. Mind you there are 2 battery terminals to undo plus the battery retaining clamp.

Your figures reflect my feelings on normal charging voltage. I have just bought a CTEK charger to keep the battery up to spec as (unfortunately) the car isn't my daily driver and less likey to be as it becomes time for the gritters to spread rust enhancer on the roads.

[Snowy999]

voltage is temperature dependent. I've seen 15.2v when v cold outside, just assumed it was part of the programme.

[andygo]

Snowy999 said:

voltage is temperature dependent. I've seen 15.2v when v cold outside, just assumed it was part of the programme.

That's good to know, very little about this on the net TBH. Thanks

[gsewell]

Could be the voltage regulator on the alternator.

[elan362]

gsewell said:

Could be the voltage regulator on the alternator.

That would be my thought. Something is not right
15.2v is tools high. It will cook the battery.
Get it checked out

[Snowy999]

When the scale says 15.2v my Lithium Battery's BMS (I run a Liteblox) tells me it is actually receiving 15.0V.

[elan362]

Snowy999 said:

When the scale says 15.2v my Lithium Battery's BMS (I run a Liteblox) tells me it is actually receiving 15.0V.

15.0v sounds way too high for a lithium battery too!
I have a 205Ah LiFePO4 lithium battery in my campervan and I have a votronic vcc1212-50 B2B charger that is set to a steady 50A charge at 14.2v.
I appreciate there are different lithium battery chemistries available, and my charger has 4 lithium charging profiles (13.9v, 14.2v, 14.4v and 14.6v) to accommodate these, but I've never heard of lithium iron phosphate battery charging requiring 15v. What is your lithium battery chemistry?

Edited by elan362 on Tuesday 6th December 12:10

[elan362]

^ https://en.liteblox.de/technology/
LiFePO4 chemistry. Data sheet says 15.2V max charging (but that is not necessary to be that high) current, which is 3.8V per cell
Surprised it is that high TBH. But at least a LiFePO4 battery has an onboard BMS, That should prevent overvoltage charging.
15.2v is way too high for AGM Batteries and will cook them

[andygo]

OI spoke to the OPC today who said it was fine. If its overcharging a warning light will come on. (And lets face it, the OPC should know, they are always overcharging!)

My new Ctek charger arrived today as well. Hooked it up, only lit up first 3 lights of 7, with 7 to show full charge. Left it for 4 hours or so and it showed 7/7, fully charged. When running dash Voltmeter shows 15volts. I'll see what develops, but at least I have told the OPC.

Edited by andygo on Tuesday 6th December 20:22

[cay]

Mine shows 15+ after the car has been left standing for a while. This is after car gives a 'low battery' or similar warning when starting.

After a good drive ( over an hour ), it drops back to 13 odd.

[WG]

This prompted me to look at my Macan volts today. It showed 15.2 volts when driving. Make of that what you will !

[SkinnyPete]

andygo said:

I'm sure my 2016 GTS used to show mid 14v when driving, but over the last couple of trips it been up at 15.2v for some time. Is this OK or should I be taking it to the OPC.

It's had a new Porsche battery a couple of months ago as the original was showing low charge after being left overnight, down in the 11.8v range.

It's totally normal.

I drove over 100 miles yesterday with it reading 15.3 all the way, going to 15.4 briefly at one point.

Car is on the original battery and starts first time every time.

[Snowy999]

Consistent with what I have seen, it is cold out there! If you do a big journey then when you restart I expect you will see that it stops being so high and drops into more usual mid 14s like I've seen.

The Liteblox has a BMS which can deal with up to 15.2V, thus I have watched this pretty carefully. However, they did design the battery I have for the GT4 and when I asked them they said don't worry.

Here is an AGM data sheet showing charging voltages at different temperatures. 0 degrees C is 15.1V.

[andygo]

Thanks for the help chaps, appreciated as usual...

[Luckyscoob]

My Cayman 981S read 15.2 on its last trip out. It hadn’t been used for 3 weeks and it’s only around 2 degrees. When the car is used more and the weather is warmer its lower.

[ATM]

andygo said:

I spoke to the OPC today who said it was fine. If its overcharging a warning light will come on. (And lets face it, the OPC should know, they are always overcharging!)

Well done

[jeebsy]

I've got a 718 but in sport mode it seems to sit about 15v. Normal mode it's usually 13-14.