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Discussion Starter · #1 ·
Battery losing charge intermittently

I have a 2005 Volvo V50 T5 M6 with 108K miles. Recently the 5 year old battery gave up the ghost. I jumped it a few times and it would work for a little bit and then die again. Replaced it with a nice AGM battery. Everything went great, but then just the other day the new one died. The car stated the moment the jumper cables were attached. I'm guessing it only need .1 volt more to get the starter going. Now over the last week I have tested the battery and charging every day. Each time the battery rest at 12.96 to 13.01. When running I'm getting over 14 volts.

Any thoughts on what might intermittently be draining the battery? I always have the dome on full OFF. Could some other light be getting stuck on? Intermittent short? Alternator getting touch, but just working the last week? I have all usb dongles out of the 12v ports.

I'm at a dead end on this one. :what:
 

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It sounds to me like your alternator might be bad. I'd say that's probably the issue since you've already replaced the old battery. I doubt something would simply be draining it enough to keep killing your battery unless you've recently installed amps for a sound system or something else that requires a lot of energy.
 

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Discussion Starter · #4 ·
No new installs. It is still in stock configuration. I've only replaced, wipers, brake pads, tires, shocks, and the pass side motor mount. I don't think any of those would cause a drain.

However, I did replace my fuel sensor, but that was a long time ago. I did just install new HID bulbs as one had burnt out, but not really thinking that would do it.

Next I'm going to check all the connections on the starter and alternator.
 

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Get your alternator tested at an auto parts store. They have portable units to test in car with the engine running. That's how I found out the diodes were bad in mine and not charging the recently replaced battery.
 

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Just get ready to pony-up for an alternator. They're almost all going out around this age. Tasca has a good price, but you can also get a rebuilt one from Denso (if that's your alternator, that is). If it is a Denso unit, check their website and order through a local auto parts store.
 

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On the t5 the alternator job takes a few hours but it's doable (from what I can tell). On the 2.4i, it's a simple drop-in job and takes maybe 30 mins. Either way, $800 is a rip-off but much better than it was even a year ago when a new OEM alternator was $800 alone (!). Since yours is an early chassis, I suspect it'll be a FoMoCo / Denso unit. If that's the case, check my other thread on alternator woes and you'll find lots of information about which denso unit works.
 

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Discussion Starter · #13 ·
Wanted to see if any of you knew how the alternator starts charging. Should it go form zero to charge the second the engine starts or slowly ramp up over about 5 seconds?

On my jeep, in less than 1 second it goes from resting charge to full alternator charge.
 
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