Battery health %- when to replace?

[Nukeman7]

See Post #9 in this recent BITOG battery thread if you are a Sam's Club member. Better price than the EverStart MAXX (exact same battery if the MAXX battery serial no. starts with "EP") at WalMart with an identical warranty. The sale ends tomorrow.

 

[Patrick0525]

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.

At a bare minimum u should equip ur daughter’s
Mazda with a pinch weld adapter so the uncouth Gorillas at road side assistance doesn’t flatten or damage the rocket panel. Makes me sleep a whole lot better at night.

Pinch weld adapter plate

 

[SC Maintenance]

What is the resistance value? What is the CA value, and what is it rated at.

The % health is a bit misleading. Its just a divisor from the CA / rated and measured at a temperature that is not probably correct. I had a 24F from Walmart (the $50 specials when they had them) that was only 80% when brand new.

If it was low resistance, like 5 milliohms, I would keep it. If its quite a bit higher than that, I would replace.

 

[Sequoiasoon]

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.

Maybe I'm in the minor percentage but in over 45 years of working on vehicles I have not come across any batteries that failed as a short that I recall. Declining percentage getting too weak, many. Lights left on killing them, many. Over 99% able to jump start except when the jump pack was low on charge.

Just because it's my vehicle, my ~60% battery in fall lasted through 2 winters until I changed it. For me it was a combo of lazy, no change in cranking speed, Jump pack and jumper cables in trunk. I also back in driveway all the time and have a slight downhill on the driveway. My '17 Accord is a 6MT so 2nd gear, let it roll a bit, let clutch out. My son and daughter did that just as practice a couple times in it. Their cars unfortunately automatic so no option for that.

 

[eljefino]

If you get a lithium jump starter, keep it at 50-60% SOC. Roasting those things in the hot glovebox at 100% runs THEM down quickly too.

They are great for non-car people, with reverse polarity protection, "good connection" LEDs, etc. And OP's progeny might wind up jump starting someone less fortunate, without using cables, and without potentially damaging her car.

Incidentally, when I went to college, Security jump started peoples' cars if they needed it because they sat unused between breaks. "But I found a great parking spot." Driving the car every week or two will keep the brake rotors clean as well as battery charged and tires from flat spotting.