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I've had my Mazda 3 2013 since 2016. This winter in Massachusetts it's died on an almost daily basis in the morning, and sometimes at night if it's particularly cold out.

I mostly drive to school, work, and to a friend's house, each commute only taking about 30, 8, and 10 minutes respectively for distances at most 12 miles. So I'm aware that I drive short distances and use a lot of amperage to get it started in the cold.

How do I know whether or not I need to completely replace the battery or just give it a good charge? I have an external jump starter (one of those small battery packs) and I typically only need to leave it connected for 30 seconds-2 minutes before I can jump start my car. The battery indicator in the dash is also not lit, and my leads don't have corrosion.

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    Checking the voltage of the battery before starting and monitoring the voltage when the car is running (the alternator voltage at that point) can be good to monitor battery health. They make voltage readouts that plug into your cigarette lighter outlet for constant monitoring or you can use a multimeter. – JPhi1618 Mar 12 at 17:11
  • @JPhi1618 but would this tell me the difference between a dead battery that just needs a charge and one that needs to be replaced entirely? I'm worried that the voltage tests will only tell me the current charge and not the overall health right? – Otanan Mar 12 at 17:23
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    Well, if the battery voltage is under 12, and it doesn't seem to charge up, it could be because of the short trips or poor alternator performance. Then maybe it just needs a good charge. If voltage is good, but it still won't start, the battery is probably "weak" and needs replacement. An auto parts store will normally do a load test for you as well. But... these complaints normally end with buying a new battery. – JPhi1618 Mar 12 at 17:27
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    Welcome to Motor Vehicle Maintenance & Repair, btw :o) – Pᴀᴜʟsᴛᴇʀ2 Mar 12 at 17:37
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    Check out this related question about how long to drive to charge a battery. – JPhi1618 Mar 12 at 17:39
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Typically, an automotive battery lasts about five years at the longest. If you still have the original equipment battery in your vehicle, there is a very high likelihood it needs to be replaced. Considering a battery usually lasts that long, anything past five years is bonus, so consider yourself lucky.

As for how to tell, what you're suggesting of needing to jump start the vehicle every morning is a good indication the battery is most likely toast. In cold weather, the battery suffers from reserve energy loss, as it can only muster about (depending on the temp) ~50% of the full charge, and that's any battery, not just an old one. If you go to utilize it when its cold, its reserve capacity is way down, doesn't want to let the car start, and there you go. When this consistently happens you need to check the voltage of the battery before you jump it and before you try to use it. If it's below 12vdc, it's a candidate for replacement. If it does show above 12vdc, try to start the car. If it doesn't start, check the battery again and I'll bet it's now below 12v, more than likely by quite a bit.

When you get this far, take the battery to a parts retailer and have them test it. They should have a device which can tell you what the reserve capacity of the battery is, or basically tell you what kind of shape it's in. Like I said earlier, if it's over five years old, you've gotten full use of the battery.

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