Battery health %- when to replace?

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Are there any general rules of a threshold of battery health to warrant replacement? My daughters 2022 Mazda CX-5 reads at 71% on the OE battery and I’m debating on replacing it prior to her heading back to college.
 
60% warning, 50% to replace, per Midtronics and their high-frequency tester.

Since you have a tester, it seems appropriate to log the results during every maintenance visit then buy the battery when you see a sudden drop off in rated capacity. In other words it might hang out at 71% for years then drop like a stone.
 
If your daughter is going back to college out of town, replacing that battery with a $70 EverStart Value battery from WalMart is cheap insurance for peace of mind.
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Otherwise, I'd get her a jump pack and teach her how to use it.
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The % once again is a "megapixel conundrum" like output, where man wants one number to judge goodness (I assume this is based on CCA vs original?).

It's no different than glucose or cholesterol--199.999 OK! 200.001, DANGER! It's not like that at all.

If I had one other number, I'd want to know the internal resistance. But why not factor all the numbers together? Voltage, resistance, CCA, what it's going to be used for and under what conditions.

The last alternative is to not worry about the above and simply replace. There are folks here who throw away good tires based on age. So if someone is of means, they can also not worry and just do. That's another possibility.
 
If your daughter is going back to college out of town, replacing that battery with a $70 EverStart Value battery from WalMart is cheap insurance for peace of mind.
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Otherwise, I'd get her a jump pack and teach her how to use it.
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This. I think a new battery is in order (I usually recommend replacement at the 4 year mark) and a lithium jump starter for the glove box is a must.
 
Again - this is for a college kid away from home - very different standard than the car in your driveway.

What’s it cost for her to get AAA or a local garage to come jump it for her fall break drive home? How long will that take?

Would you trust one of her 19 year old classmates to jump it from their Dad’s car without frying the electronics?

Does she even have jumper cables or a jump pack?

How much is a new battery, again?

Why try and stretch out another year on this battery and risk all of the above?
 
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Are there any general rules of a threshold of battery health to warrant replacement? My daughter’s 2022 Mazda CX-5 reads at 71% on the OE battery and I’m debating on replacing it prior to her heading back to college.
As a suggestion buy the Walmart battery replacement and a BatteryMinder 2012 or 128CEC2.

Spend the next 3 months BM maintaining the battery. I restored a 21 RX350 from 74% to 100%. See link below and 1 yr of data

RX350 battery

I am confident that u can restore the battery and use it as a backup.
 
As a suggestion buy the Walmart battery replacement and BatteryMinder 2012 or 128CEC2.

Spend the next 3 months BM maintaining the battery. I restored a 21 RX350 from 73% to 100%.
See link.
She’s taking the car back to college - so, the car won’t be in the OP’s driveway to do all that.

So, why try and restore/extend the life on this one?

How many of you have received the call from a kid, hundreds, or thousands, of miles away, that starts out with, “Dad, the car won’t start!”.
 
She’s taking the car back to college - so, the car won’t be in the OP’s driveway to do all that.

So, why try and restore/extend the life on this one?

How many of you have received the call from a kid, hundreds, or thousands, of miles away, that starts out with, “Dad, the car won’t start!”.
I am suggesting replacing the battery. Peace of mind and near zero midnight emergency calls.
A cheap Walmart battery $70, $110, $140 depending on the warranty desired.

It is highly desirable to charge the battery before installation. U can snapshot the Soh and internal resistance as the baseline new condition. The dealer and independent normally won’t do it since it is time:money and the alternator is now less stressed.

Take the Mazda OE battery and use a BM to restore it. This will a be spare backup battery.
It is a long term science project and use the BM to top off the other batteries in the household.
 
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Is it the original battery from 2022? 3 years is about replacement time. How far away is college? What experience does she have jumping with a jump pack?

Piece of mind - change it now while convenient and easy, in daylight, dry day.
Piece of mind #2 - get that Gooloo jump pack anyway so she has it with her. Make sure she knows how to use it with the "override" if needed. Keep it charged, toss on charger every 3 months. My daughter used hers multiple times to help friends and a couple times for herself.

Caveat - check vehicle for opening/accessing where she plans to store it. My daughter is very good with ability and phone call if needed. She left her lights on one night and didn't get back to the car for a couple days. There wasn't enough power in her pretty new battery to unlock the doors or do the electronic hatch release. There is no cable release to her hatch (08 CRV) and the hatch blocks the cover to access spare tire area. She ended up having to crawl through and pop the little emergency access cover and move the manual lever to open the hatch. The jump pack now resides between her front seats under her little console tray the CRV's have.

If you haven't already show your daughter how to change her tire with only the tools included with vehicle or if you get a longer breaker bar etc that will always stay with it. If she has help she trusts great but having to rely on someone else or AAA may take a while and risks to her. My daughter did that and if in a situation will also have at least a knife/pepper spray on her in case something goes wrong direction by somebody stopping to "help". She likes not having to rely on someone.

A small air compressor, plug in, not rechargeable, in case tires need top off or TPMS pops on while driving, air gauge you trust. At least 1 spare key to keep in her dorm room/apartment or on vehicle. OBD2 plug in with a phone app and how to use to check/reset a code if needed. All my cars have the VeePeak BLE+ in glove box and all of family has OBD Fusion app.

Obligatory BITOG- make sure she knows how to check and top off oil in her vehicle and does so at least before trips along with tire pressure and other fluids. If going north with winter potential, make sure windshield washer is an antifreeze type for when temps drop. drain and refill with that if you were using summer version. make sure the antifreeze version is through the lines.

Normal checks of brakes for pad life, tires for depth, change the wipers, check air in spare. Make sure she keeps tank at least 1/2 full in case she needs to go somewhere unexpectedly. Easy to schedule or do it when she gets there. If going north where snow/ice may be a factor, true winter tires on rims for when she gets home towards thanksgiving if she does. Some better rated all-weather versions at least otherwise. Real snowbrush/ice scraper if the area warrants that.

Most of that is only a couple hundred bucks except tires and will put here way ahead of many in preparation.

Search on me for streetsurvival it has links to pictures/videos for her to get some good emergency experience. My kids tell their friends to do it.
 
She’s taking the car back to college - so, the car won’t be in the OP’s driveway to do all that.

So, why try and restore/extend the life on this one?

How many of you have received the call from a kid, hundreds, or thousands, of miles away, that starts out with, “Dad, the car won’t start!”.
That call came a couple times along with "my TPMS light is on but I have a test in 15 minutes"" My steering is making a weird noise and is harder to turn (rusted metal PS line)""my car is pulling more to the right (rusted brake pads)"

Make sure she communicates any oddities from her normal experience so it's easy check when available.

Also coat of wax on vehicle if possible, at least a spray on ceramic detailer and Rain-X all the windows.
 
I should have mentioned, she’s only 80 miles away and I see her several times a semester, with her coming home once in awhile and my Wife and I going there for home tennis matches. That’s the only reason I’m on the fence. If I only saw the car on semester break, I’d change it.
 
Are there any general rules of a threshold of battery health to warrant replacement? My daughters 2022 Mazda CX-5 reads at 71% on the OE battery and I’m debating on replacing it prior to her heading back to college.
These days batteries just fail with no warning
 
I should have mentioned, she’s only 80 miles away and I see her several times a semester, with her coming home once in awhile and my Wife and I going there for home tennis matches. That’s the only reason I’m on the fence. If I only saw the car on semester break, I’d change it.
Very different situation than I had imagined…My youngest has her car in Boston, a mere 10 hour drive up…

But my oldest had her car in Salt Lake City - so, effectively out of range for Dad to help directly, though I did apply my Visa more than once…
 
Part of going to college is learning to be an adult. A battery at 71% is NOT all that bad off (assuming the rating is true). Tell her that if the vehicle sits parked for long periods of time, it will kill the battery. Maybe then, she will volunteer to drive on beer (wine) runs for her friends to keep the battery charged.
 
Put a Walmart Everstart MAXX in it, and if the vehicle battery area permits, upside it to a larger size. It probably has a group 35, and the larger 24F probably will fit.

The MAXX will be more reliable longer than the lower tier Walmart batteries.

As others already mentioned, a college students vehicle may sit unused for many days.

Don't pay more money for the same battery made by the same manufacturer with different stickers and maybe what looks like a beter warranty at other stores.

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By the way, a battery that test 71 % in July ain't gonna make it through next winter.
 
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If your daughter is going back to college out of town, replacing that battery with a $70 EverStart Value battery from WalMart is cheap insurance for peace of mind.
View attachment 291615

Otherwise, I'd get her a jump pack and teach her how to use it.
View attachment 291616

Even the best jump pack won't start a battery that fails as a short, and sometimes old batteries fail suddenly as a short. My sister has a 1000 Amp Gooloo jump pack and I remind her to charge it every 3 months. It was fully charged and only a year old and it could not start her 2019 CR-V when the 51R battery failed as a short. Her husband connected it up properly and his attempts dropped the charge of that jump pack from 100 % to 71%.

I put a new MAXX 51R in it.

BTW, I had previously disconnected the ground wire and scraped away the paint where it mounts with a 1/8 inch flat blade screwdriver and also scraped clean the lug and clean the battery connections and coated all connections with a lite coat of Corosion X Aviation grade electric contact cleaner, and added the green and red battery corosion preventing pads, and put it all back together.


Put that money towards a Walmart MAXX, and forget about it for 3 years.
 
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