Flat battery

[Caroline Sheppard]

I have a 2010 Subaru Forester that often gets left for a few weeks without use.

i lock it with the key manually as mentioned in my handbook, when I come back to it the Battery is flat, this has happened now three times this year. I had the Battery replaced in February. The most recent time it happened I had been doing mostly local driving of two miles here and there, with four  journeys of eight miles there and back over a period of two weeks. I then left it for two weeks and came back to a flat Battery again ??? 

There is nothing left on to drain the Battery except the alarm system. 

Can this be normal or is there something wrong ?? Would diagnostics at a garage be able to tell ??

kind Regards Caroline 

[Pethurr]

This is a very similar problem to one I have with my Subaru VX. I did a electrical draw test on all  the fuses and found that the ABS system (Fuse SBF8) is drawing power all the time, the current reading was 260 milliamps. It flattened the Battery overnight. I now have to track the fault in the wiring that is causing this. Going to try pulling the fuse when the car is not in use so no power is drawn.

Peter

[Mr B]

around 30mAh +- 10mAh would be a more normal expected range of current drawer while vehicle parked and modules sleeping .
You need get that checked or check it yourself if have a DMM .
Parasitic drawer is quite a issue on vehicles the newer you go, partially as poor electrical engineering choices allowing for higher parasitic values and partially the trend for pointless low quality electronic systems .
Go back to pre 2002 and parasitic values be 10 to 20mAh and you could leave these vehicles months and they still start and Battery lifespan be longer because of it too .
My Battery recycling volume has gone through the roof thanks to poorer quality batteries and car electrical systems that function inefficiently ...

[Justin Time]

On 9/21/2022 at 7:34 AM, Caroline Sheppard said:

I have a 2010 Subaru Forester that often gets left for a few weeks without use.

i lock it with the key manually as mentioned in my handbook, when I come back to it the battery is flat, this has happened now three times this year. I had the battery replaced in February. The most recent time it happened I had been doing mostly local driving of two miles here and there, with four  journeys of eight miles there and back over a period of two weeks. I then left it for two weeks and came back to a flat battery again ??? 

There is nothing left on to drain the battery except the alarm system. 

Can this be normal or is there something wrong ?? Would diagnostics at a garage be able to tell ??

kind Regards Caroline 

There are loads of Subaru Battery drain issues discussed all over the internet so it's a know problem.  To be fair it might also happen to other modern vehicles, but I've not searched for these too.

As Mr B pointed out, modern cars effectively never switch off and have loads of stuff going on, electronically, in them all the time even when they're parked up and locked.  I was aware of this before I bought my Outback (2020), and picked up a few ideas as how to manage this which have worked ... so far...!

First up, if you drive such sort mileages, more 'juice' is likely to be taken out of the Battery, than the alternator puts back in, especially since it seems many modern cars have charging algorithms that try to flatter mpg figures by not engaging the alternator (to recharge the battery), until necessary.  Aside from avoiding lots of short journeys, one 'hack' is to always drive with the side lights on (or the Air Conditioning, or some other high draw of current) as this forces the alternator to start up from the get-go and constantly recharge the Battery.

Secondly, if you have a modern Subaru, go into the options in the infotainment system that allow you to switch off things like allowing the car to search for internet connections for software updates and the like. 

Also, look for hidden  'factory mode' or 'dealer mode' on the infotainment display (see Subaru forums, especially in the US as how to do this for your model) and click on the menu that shows the Battery state of charge, so as to regularly keep an eye on things.

Also, and I'm not sure if this really helps but I do it anyway - switch off the key fob (press and hold lock which simultaneous pressing the blue 'open' button twice) when you lock the car up for the evening.  I think this stops the car trying to search for the fob all the time, but I may be wrong...it saves the fob battery anyway...I think!

Do you have an electronic boot? Don't leave it open for too long.  If you need to leave it open do the karabiner trick (see Subaru forums/Youtube) to fool the car into believing it's closed.

You might also, tape over the boot light switch, or disable it completely, so it can't be inadvertently knocked into 'always on'. Better still, switch all internal light onto permanently off during British Summer Time, when you're less likely to need them anyway.

Lots of forums suggest investing in a charged, battery jump start kit to keep in the car.

Apparently, according to some, Subaru batteries aren't the best (I'm not sure if that's true or not), but it seems some people recommend alternative brands as a replacement. However, with all of the above issues you're only delaying the inevitable even with a bigger, better battery, unless you drive longer journeys.

Hope you get it sorted permanently.

[Justin Time]

Just been notified that the Class-Action in the US over Subaru Battery issues seems to have been settled with Subaru agreeing to compensate.  I wonder about the implications for Europe, if any!

Here's the link:

Subaru Battery Issue