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Do we need to drive vehicles at least once a month to keep the battery and alternator working?

I'm reading anything from every four days to once per month.

@viciousviscosity Not necessarily drive, but it is a good idea to go out and start it up and let it run for about 10 minutes

@viciousviscosity The longer it sits idle the higher risk you run of the battery dying and needing to get a jump or replace the whole thing

@witchfynder_finder
I have chronic "forgot to turn the headlights off", so I have a jumper with me I charge at least once a month. 😅

@viciousviscosity Haha oh noooo

Definitely go out and run your car for a few minutes today, Val =P

@witchfynder_finder
Hehehe, oh I've been driving my car all week. My SO has been working from home, so I may go out and idle in it a bit. 😁

@viciousviscosity i'd go for once a week, if you aren't going anywhere just idle it up to running temperature + another 5 minutes at least. "cars are meant to be driven"

the much easier and less wasteful alternative is to just disconnect the battery. for times longer than a month, totally disconnect & remove it and bring it inside out of any extreme temps.

@viciousviscosity when I was working as a generator mechanic, we set all the generators we sold to exercise for 20 mins once a week

@RobinHood
Oh neat. I didn't know generators had a maintenance mode like that.

@viciousviscosity the ones that are permanently installed do. The smaller ones on wheels don’t have that mode, mostly so they don’t start up in someone’s garage or shed

@RobinHood
That's a very good reason - there are already waaaay to many incidents of CO² poisoning with indoor use.

@viciousviscosity Depends how old your battery is, and also newer cars tend to have a lot more things that run even when the ignition's off (infotainment systems etc). I've heard once a week, 10-20 minutes fairly consistently from mechanics though. And you really do want to move it around a bit or your tires can be damaged from sitting in one spot too long, plus your brakes can rust and seize.

@viciousviscosity The advice on this seems to vary wildly.

I guess it depends on how old the car and the battery are... Our car is now parked all the time, but I go out grocery shopping about every ten days or so. That's when I take the car up to the next town and back before going to the supermarket, that gives it about 20 minutes of driving to stretch out a bit. :-)

@viciousviscosity one winter, after the third time I needed my car jump-started, the exasperated expert told me to drive it around at least 20 minutes a week.

@viciousviscosity I usually opt for every 2 weeks, but can go a month if need be, depending on how old your battery is.

1/n @viciousviscosity when new, a car battery will self discharge at about 5% per month (very roughly) of there is no load attached. Repeatedly drawing the battery down to a low charge state will both increase the rate of self discharge and reduce the total capacity of the battery. A lot of things affect this behavior: temperature, battery construction, material quality, how the battery is used and charged, and more.

@viciousviscosity 2/n
Both these things, self discharge rate and maximum capacity also naturally degrade over time.

Charging is especially important. As a rough rule of thumb, if you don't draw your battery down below 80% of capacity, and charge it to 100% of capacity once or twice a week, it will last a very long time.

Batteries charge more efficiently in warmer weather than in cooler weather, and conversely can provide more power when it's warmer, less when cooler.

@viciousviscosity 3/n
So in the winter, right when you need more power to start your car, the battery doesn't produce that power as efficiently, and doesn't charge as efficiently, so it will need a longer charge cycle than in the summer.

Also, the battery charges more easily at partial charge than when it's close to full charge. The time to go from 99% to 100% can be as long as the time from 95% to 99%, which is as long as the time from 85% to 95%.

@viciousviscosity 4/n

Stuffing electrons into a battery is like stuffing socks into a drawer. It's easy at first, but then you have a harder and harder time finding room for the new ones, and the last few are especially hard to squeeze in, both for electrons and those heavy tiger striped padded ski socks.

Rate of charge is also important - fast charging can degrade a batteries long term performance as well.

Where was I going before I got all battery pedantic here? Oh, yeah...

@viciousviscosity 5/n

Anyway, a new battery might be ok with being started every month and driven for 20 or 30 minutes. But over time, as the self discharge rate increases, and the total capacity decreases (along with the rate at which the battery can accept a charge), and the weather gets colder, it will need more frequent starts and possibly longer charge times.

Eventually, though, it just wears out and needs replacing. I usually assume 5 years, even for long warranty batteries.

@viciousviscosity 6/n

One thing that can help vehicles that are seldom driven is to disconnect the battery between uses. Modern vehicles have a lot of things that just draw a little power all the time, even when the car is turned off.

Another useful widget is a battery tender, which uses a trickle charge to keep the battery close to 100% charged, compensating for self discharge and for those always-on things. You have to remember to unplug it before driving off, though!

@MightyBigCar
Thank you for all the insight into automotive batteries! 😊
Knowing what to do is good, understanding why to do it is ideal.

Thanks!

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