I bought a 'new' (2004) Subaru Forester last week. The other day, I took it in to have the wheel alignment checked, and once they had finished aligning it, they came back and said "the battery was flat when we tried to start it to take it off the ramp" - and lo and behold, when I tried to start it to leave work later the same day, it was indeed flat. The car hadn't shown any signs of a weak battery beforehand, and when I got home, I measured the voltage on the battery and it showed a healthy 12v (and started again happily), so had presumably charged itself up fine on the way home.

So the question is, what on earth did they do to the car, in 20 minutes, to flatten the battery?

(needless to say, I won't be going back to the same tyre shop!)

  • How did you start the car at the shop? – chilljeet Jun 5 '15 at 9:03
  • They did so, before they told me about it... – Nick C Jun 5 '15 at 9:07
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    You'll want to rule out a battery drain issue by measuring the current draw when the car is 'dormant'. It could be that a circuit has shorted which is causing unusual, possibly intermittent, battery drain. How long did you leave the car off at home before trying to start it up again? – Zaid Jun 5 '15 at 10:06
  • I agree with Zaid.. but who knows if the service centre was mischievous. – Shobin P Jun 5 '15 at 10:33
  • Yeah, though there was no sign of any such issue beforehand...(It'd been sat unused from Sunday to Tuesday, and started on the button) It had only sat for a few minutes, but it's now sat for two days since, so I'll see if it still starts tonight... – Nick C Jun 5 '15 at 10:43

How old is the battery (if it has a date stamped on it)? If it is over five years old, I'd replace it as a maintenance item. Remember too, a healthy battery should actually be over 13vdc at rest and fully charged. If your battery was only reading 12vdc, this is an indication of a weak battery to me. It may have a bad cell and accumulate what I call a surface charge, where some of the time it has enough power for a short burst of energy which is enough to get the car started. Some of the time it doesn't and all you get is clicking from the starter (if even that). I would take the battery and have it load tested. This is the easiest way to get a good idea of the health of it.

  • Good point, I've not checked the age, I'll have a look later... – Nick C Jun 5 '15 at 13:28
  • Well, the battery appears to only be two years old (it has 03.2013 stamped on it), but certainly appears to be kaput. I'll get a new one this week... – Nick C Jun 8 '15 at 9:56
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    New battery seems to have solved it - proof that even a relatively new battery can lose it's ability to hold charge... – Nick C Jun 16 '15 at 14:14
  • @NickC - Glad to hear that. When you have a completed outcome (one which is not wishy-washy), it always bodes better in my book. – Pᴀᴜʟsᴛᴇʀ2 Jun 16 '15 at 16:11

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