# When do you Replace the Battery in your Car? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [June 8, 2025, 7:38pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343 "2025-06-08T19:38:21Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [June 8, 2025, 11:09pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/21 "2025-06-08T23:09:01Z")
> [@engineer\_comp\_geek](#): > > But if you have the space, get a bigger battery. My battery compartment is very tight. The E-350 battery for my RV had lots of room and I got the biggest one I could fit in there. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 8, 2025, 11:31pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/22 "2025-06-08T23:31:34Z")
> [@TriPolar](#): > > I get a new battery when the old one won’t start the car. Don’t get one ahead of time. Car batteries have an expiration date and secret technology that makes them fail on the first day after that date that you need to go somewhere in a hurry or sometimes if it’s just raining or really cold out. I don’t think this is good advise because any failure away from your house/tools leaves you stranded. You’re right about the secret technology that knows when to mess with you. I had a battery short out in a very bad place. The car died while on the highway so that there was no residual voltage for the alternator. > [@Dewey\_Finn](#): > > When I get the car serviced, one thing they do is to measure the charging capacity. When it’s below some threshold, it’s time for a new battery. This. there is a definable voltage reading (at rest) that signals the end days of a battery. It’s 12.4 volts at rest (engine not running). When running it should be above 13 volts. The rise in voltage tells you your alternator is working. If it doesn’t rise above the resting voltage then you will be stranded in the very near future while on the road. [I have a USB plug-in charger that measures voltage](https://www.walmart.com/ip/Cusimax-Car-Charger-5V-3-1A-Quick-Charge-Dual-USB-Port-LED-Display-Cigarette-Lighter-Phone-Adapter/414149104?wmlspartner=wlpa&selectedSellerId=101133085&selectedOfferId=5DAEC8DC0A3B38F1A2F5E47D1BB1F54C&conditionGroupCode=1&wmlspartner=wlpa&cn=FY25-ENTP-PMAX_cnv_dps_dsn_dis_ad_entp_e_n&gclsrc=aw.ds&adid=22222222297414149104_101133085_0000000000_21407473164&wl0=&wl1=x&wl2=c&wl3=&wl4=&wl5=9015822&wl6=&wl7=&wl8=&wl9=pla&wl10=553143410&wl11=online&wl12=414149104_101133085&veh=sem&gad_source=1&gad_campaignid=21690411341&gclid=EAIaIQobChMIz5Ht4_zijQMVczUIBR2buwGNEAQYBSABEgJVevD_BwE). If you buy one get it with a red LED readout and not blue. Blue is hard to read in the daytime. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [June 9, 2025, 12:07am UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/23 "2025-06-09T00:07:31Z")
> [@OldOlds](#): > > So now the battery is in the passengers footwell and I predict it will sit there until the current one dies. Either you’re not understanding LSLGuy or I’m not understanding you. Are you just going to leave the battery in the footwell untouched until you need it? If that time is a few months from now, it’s possible that your new battery will be completely dead and of no use for jumping the truck or replacing the old battery. You’ll have spent money on a new battery and let it turn into a useless brick. Your plan is somewhat viable if you put a trickle charger on it every few weeks, but I don’t see anywhere that you said you plan to do that. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [June 9, 2025, 12:18am UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/24 "2025-06-09T00:18:12Z")
> [@engineer\_comp\_geek](#): > > Car manufacturers tend to undersize the batteries in cars a bit these days, partly to save on manufacturing costs and partly to save weight. If you replace your dead battery with the largest battery that will practically fit in your vehicle, you’ll probably never have to replace the battery ever again (unless you accidentally kill it somehow). Interesting. (Johnny Carson) _“I did not know that.”_ Thanks. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [June 9, 2025, 1:01am UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/25 "2025-06-09T01:01:50Z")
> [@OldOlds](#): > > So now the battery is in the passengers footwell and I predict it will sit there until the current one dies. I understand avoiding work, but if you are just going to own the new battery as it dies, it doesn’t have to be in the passengers footwell. You can put it somewhere else to die, where it won’t be in the way. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [June 9, 2025, 1:47am UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/26 "2025-06-09T01:47:14Z")
Why not just store the new battery in the auto parts store? In other words, don’t buy it until you need it. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [June 9, 2025, 1:59am UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/27 "2025-06-09T01:59:11Z")
My annoyance is that EVs and PHEVs don’t start without a starter battery but they generally come with really crappy ones that die early. And the terminals to jump them are not always easy to figure out. Not sure why the big batteries can’t be designed to trickle charge them? ---
**Author:** ![pullin](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@pullin](https://boards.straightdope.com/u/pullin)\ **Post date:** [June 9, 2025, 12:42pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/28 "2025-06-09T12:42:15Z")
I replace batteries on a schedule (same as tires). They’re never run till failure. Since the truck’s electrical system is often running additional lights, electric brakes, charging coach batteries and powering dashcams 24/7, I don’t trust it to last as long. So it gets a new battery every 3 years. > [@engineer\_comp\_geek](#): > > Car manufacturers tend to undersize the batteries in cars a bit these days, partly to save on manufacturing costs and partly to save weight. If you replace your dead battery with the largest battery that will practically fit in your vehicle, you’ll probably never have to replace the battery ever again (unless you accidentally kill it somehow). Not sure about “never again”, but I replaced the original battery with the largest AGM I could fit in the space. ---
**Author:** ![OldOlds](https://avatars.discourse-cdn.com/v4/letter/o/a3d4f5/32.png) [@OldOlds](https://boards.straightdope.com/u/OldOlds)\ **Post date:** [June 9, 2025, 12:46pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/29 "2025-06-09T12:46:40Z")
I’m a little surprised by the lectures on it being wasteful to buy the battery and not install it. It’s not like I don’t know that- I intended to install it and then got hit with a lazy spell and wondered whether others replace their batteries proactively or not. Also, I’m a little surprised that this one has lasted a full 6 years. ---
**Author:** ![octopus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/octopus/32/3716_2.png) [@octopus](https://boards.straightdope.com/u/octopus)\ **Post date:** [June 9, 2025, 12:49pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/30 "2025-06-09T12:49:35Z")
Unfortunately, that is my policy as well. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 9, 2025, 1:11pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/31 "2025-06-09T13:11:29Z")
> [@engineer\_comp\_geek](#): > > Car manufacturers tend to undersize the batteries in cars a bit these days, partly to save on manufacturing costs and partly to save weight. If you replace your dead battery with the largest battery that will practically fit in your vehicle, Agree completely that modern cars are fitted with the smallest battery they can get away with. I question that there is _any_ space left in a modern car’s engine compartment to fit a physically larger battery in there. Maybe on something like an F-350 pickup the under-hood area is so vast there’s a spare inch somewhere. But under the hood of a modern passenger car? You’d be hard-pressed to squeeze a pack of gum in there alongside the battery. Just buy the size the car is designed to accommodate and be done with it. IMO / IME / YBLMV\* * * * \* Your Battery Life may Vary 😉 ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [June 9, 2025, 7:17pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/32 "2025-06-09T19:17:04Z")
> [@LSLGuy](#): > > I question that there is _any_ space left in a modern car’s engine compartment to fit a physically larger battery in there. Point of fact - not all modern batteries are even in the engine compartment. The physical starter battery (as opposed to the traction battery for the EV range) of my wife’s new PHEV is in the wall of the rear hatchback area! I will grant that there are “jump” points in the engine compartment, but not the battery itself. And yes, it’s undersized. > **[Article](https://www.toyota.com/owners/warranty-owners-manuals/digital/article/rav4-prime/2023/om42e79u/ch07se030405/)** ---
**Author:** ![OldOlds](https://avatars.discourse-cdn.com/v4/letter/o/a3d4f5/32.png) [@OldOlds](https://boards.straightdope.com/u/OldOlds)\ **Post date:** [June 9, 2025, 7:21pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/33 "2025-06-09T19:21:24Z")
I had a Buick LeSabre with it under the back seat and the trunk is not at all uncommon. ---
**Author:** ![Lancia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lancia/32/17174_2.png) [@Lancia](https://boards.straightdope.com/u/Lancia)\ **Post date:** [June 9, 2025, 7:46pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/34 "2025-06-09T19:46:40Z")
Certain generations of VW beetle are (in)famous for having the battery under the back seat. I had a 1989 Toyota van with the battery under the floor under the middle row seat. I also had a 2007 Chevy HHR with the battery shoved next to the spare tire under the trunk floor. That was a massive pain in the ass to access. So yeah, no a new thing. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [June 9, 2025, 7:58pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/35 "2025-06-09T19:58:34Z")
Yes, I remember the underseat battery in VW cars. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 9, 2025, 8:11pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/36 "2025-06-09T20:11:11Z")
Many Corvettes had the battery in the trunk. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [June 9, 2025, 8:42pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/37 "2025-06-09T20:42:00Z")
> [@Dewey\_Finn](#): > > Yes, I remember the underseat battery in VW cars. And the hole in the floor eaten out by the battery acid. Find an old VW bug with an intact floor pan and you got a rarity. And a person sitting on the back seat may just short out everything, good times. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [June 9, 2025, 8:51pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/38 "2025-06-09T20:51:21Z")
I replace batteries in both cars and the tractor every three years. I used to do it when the car died and I was stranded and had to call for expensive on-site help and had to cancel appointments and miss obligations. Then I figured out every three years is much cheaper and much easier. ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [June 9, 2025, 8:55pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/39 "2025-06-09T20:55:23Z")
I don’t proactively change out the battery. Anytime I have trouble starting the car, the first place I go is to the auto parts store to get it tested. But sometimes there is no warning and the car won’t be able to start. If I’m at home, I remove the battery and drive it to the parts store in my other car. If I’m out, I have my wife come get me and give me a jump if I don’t have a jump starter device with me. In case you’re not aware, they make portable jump start devices that are basically huge USB device chargers that can also jump start a car. For instance, > **[NOCO](https://www.amazon.com/stores/NOCO/page/7428E5DB-99DF-42C9-8687-789F696FFDF3)** > > Innovation, performance, & quality. That's noco. If I’m driving out of town or leaving the car at the airport, I have this in the car with me. As a bonus, you can use it as a device charger for your phone or tablet. If you get one, be sure to get a good one. The cheaper ones start to flake out after a while. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [June 9, 2025, 9:49pm UTC](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343/40 "2025-06-09T21:49:29Z")
> [@ParallelLines](#): > > Point of fact - not all modern batteries are even in the engine compartment. Maybe ten years ago, I tried to help out a person with a dead battery, in the parking lot of a nearby restaurant. They had a BMW (I can’t remember which model), and were looking under the hood, confused, because they couldn’t locate the battery. I wound up looking up the car model on my phone, and discovered that it was in the trunk (something that the owner never knew until then). [Previous page](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343.md?page=1) [Next page](https://boards.straightdope.com/t/when-do-you-replace-the-battery-in-your-car/1019343.md?page=3)