Flat Battery
 

hi

I'm a new owner of a beautiful Volvo XC90 2017 R-Design, which i've owned for less than 3 weeks. After returning from abroad yesterday following a weeks break we suffered a flat battery. Really surprised as never happened before in 25 years of driving and most certainly didnt expect that in such a new car! Anyone else suffer similar issues?

Volvo assistance service wasn't anywhere near as good as BMW breakdown...

There have been a few people on here lately who have experienced flat batteries, one only left car overnight.

That's really dissapointing, if not a bit shocking on such a new car.
There are reports of this on other threads and no doubt, owners will let you know their findings on the issue.
For other reasons, I was unhappy with my car and made it absolutely clear to the supplying dealer within four weeks that I was going to reject the car and insist on its collection. My dealer has falling over themselves to get my car fixed and make sure I am totally informed on the fixes and satisfied with any subsequent work required (my posts are all on excessive tyre noise thread)

As for Volvo assistance - again, it seems you have had an unfortunate experience.
My wife's Volvo threw a drive belt in Norfolk. The assistance van arrived within an hour, on a filthy day in November. The engineer jacked the car, removed the front offside wheel and the inner arch panel to access the pulley and tensioner - all whilst lying on the ground in pouring rain and my wife and myself standing over him with golf umbrellas. Poor bloke was drenched wet by the time he had fixed the car but by lord, did I write him a glowing report - and all that after he just would not "take a drink" from me - and then drove onto his next call in Felixstowe.

Hope you get to the bottom of this issue. Enjoy your new car.

Every morning recently when I have gone to start the car it give either "12 volt battery charge low" or "12 volt battery low will soon enter power save mode". The technician has told me to make sure I lock the car each time I leave it as this forces the electrical system to shut down more quickly.

Usually after a 2 - 3 mile run the battery has been charged enough for the message not to reappear until the following morning

It is going in on 9 Jan for technician to have a look unless I need Volvo Assistance sooner!

Luckily so far it has not failed to start, but I have taken to carrying a 12v starter pack with me in case.

By recently I mean every morning since 11 December.

I noticed this warning (the power save one) for the first time today. I assumed it was because I do short journeys 95% of the time. Does this mean I am at risk of the car not starting then? That is a little disconcerting if so.

Did you use the VOC app at all when you were away?

You are very much at risk

Short journeys are a killer on any car battery on any car.

The effect of the starter motor load plus the entire vehicle electrics cannot be sufficiently compensated by the alternator due to the short charging times available.
As a rule of thumb, you need around 15 minutes to replace the charge in the battery that was used to start the car. Very approximate, as this depends on engine temperature (cold start requires much more power than warm start) and on the total electrical load in the vehicle (on cold wet winters days with demisters running, wipers front and rear, heating fans running, lights on, etc - this all reduces the available reserve charge for the battery).

I would recommend you get into the habit of connecting an intelligent charger once a week to ensure your battery has sufficient reserve capacity to see you through your daily drives.

If you do not have the ability to do so because e.g. you park on the street, then aim for a 30min to 1 hour drive every weekend to top up the battery.

Whilst I tend to do 80% 30min drives in my MY2009 XC90, I know my battery is the original now 8 year old battery, and I give it a top up charge in my garage every now and then - around once a month - just to be sure. I use a CTEK charger, they are one of the best connect-and-forget chargers on the market, and also support the AGM type batteries in the new XC90s. I connect mine to the convenient 12V power outlet in the boot space.

Whilst I only have a 5A charger, as I only top up my battery every now and then, running 5A for 10 hours overnight will put 50Ah back into my 90Ah battery, which is sufficient to bring it to full charge

The newer XC90s use 80Ah or 95Ah batteries, so a 5A CTEK charger is sufficient for overnight use. Otherwise choose a 10A charger if you wish to top up the battery faster.
Remember too that the modern XC90 with start-stop has 2 batteries: an auxiliary battery provides the extended power for the start-stop function. The auxiliary battery is however only 10Ah.

Here's some more math:

A car battery in the 2015 XC90 is a 80 or 95 Ah rated AGM battery, depending on model

An alternator in a XC90 is typically about 210A

Thus we can see that running 210A alternator for 1 hour will easily fully charge a 95Ah battery from nearly flat to full.

However many other factors also come into play:
The full alternator output is not available until around 2000 RPM
At 1000RPM, most alternators are at about 50% output

The amount of electrical load on the car will increase the time to fully charge the battery, as less power is available for charging

Assuming 50% of power is used for running the car, and then engine is running at 1000 RPM, the the available current to charge the batter is 210A x 50% x 50% = 52A. On a short run of only 15min every day, you can only put 50-ish amps into the battery for 15min, which is the same as 12Ah (50A for 15min = 12A for 1 hour), and if the battery is already depleted, you may find over time that this is insufficient to maintain a full charge.

Hence my recommendation for a smart battery charger

NOTE: The 2015 and newer XC90 use AGM batteries, your charger must be capable of charging AGM batteries. The charging parameters are different.

Note:
On the new XC90'S the 12v socket in the boot is disconnected when you turn off the ingnition so connecting via this will not charge your battery,

Just had this message come up on my 3 day old car. Max journey we have done until this morning was about 20 minutes, with heated seats, steering wheel etc and also some time playing with sensus on my drive, so i guess this was to be expected based on the above. Slightly worrying though after just a few days, perhaps my other cars batteries were the same but they didnt have the ability to tell me.

Anyone know what power save mode actually is? Presume it shuts down non-essential services to maintain a charge to start your car