Should I replace the battery? AGM, Worth the cost?


I am now starting (pun intended) my 6th year on an conventional Interstate battery in Florida in a black truck. I am surprised it is still starting the truck.

An AGM battery I bought 28 months ago died in the wife’s car. Bought that one from Sam’s Club with a “no excuses” 36 month warranty. Got a new battery but I am NOT impressed with flat plate AGM batteries. Had a spiral cell Optima in one summer-only car for over 7 years. Sold it still going strong. You can’t kill an Optima - that’s what a local tow truck driver told me.


In the Pacific Northwest for me. 25 years in the Seattle area and now in Western OR. Working on a 2011 BMW right now, original battery, car will hardly crank over.

I recommend replacement of any battery that is over 6 years old, whether it tests good today or not. When I had my own shop I recommended replacement and didn’t bother testing them if they were 6 years old. That’s because 25 years of experience show that even if a 6 year old battery tests good today the chances of it failing rise dramatically after the 6 year mark. I rarely see a battery more than 7 years old. 10 years is unheard of.


My record was 1 year on a $70 Wallmart battery. Wouldn,t turn the engine over, wouldn’t take a charge at all. Yeah the car sat in the garage most of the time but still 1 year is a little quick. Then they wanted to argue about it and try charging it for the night. I said the car is sold and I’m delivering it tonight so give me another one. Sheesh.


My 2012 Camry, bought in 2011 is more than 7 years old, still tests good. My daughters’ 2010Corolla is at least 9.
Both test good except at Valvoline Instant oil change where I get my cars State inspection. They don’t do repairs except lights and wiper blades but they did start selling Batteries 3 years ago and that is when they told me I needed one.

The funny thing is, I have had the car inspected there twice more with the same battery and they never told me again that I needed a new one. I must have the special self healing model.


Not exactly. The battery (supposedly) had issue only once and that too I don’t have a first hand knowledge of what actually happened. DW only does one job, driving the vehicle, rest is on me. So I am describing what was described to me. I will when I will have a problem and/or figure out the issue.

Second, I don’t know what others have experienced but my Sentra’s OEM battery lasted for 7 years and was still working well, but I changed after the mechanic suggested me to change, only because the battery is 7 years old. The replaced Kirkland battery is 6 years old and I have no plans to change it until it actually fails at ‘my’ hand.

Forester’s battery is OEM, 4 years old, has not failed at ‘my’ hand but I am following up on DW’s comment. So before I get a new battery, I would like to make sure that it is indeed the battery that failed, and not some odd experience or something else at work.

So yes, I want to test it again.


You don’t need AGM. I use those with motorcycles because they’re hassle-free and unspillable, but it’s overkill for a car.

I would try taking it to a different auto store (I usually shop at Advance Auto Parts) and having it re-tested. To do it properly, they should have asked you to do it with the engine running and have had you rev it.

And yes, it’s completely possible it’s bad. I recently had one go bad at six months (I live in North Carolina). Fortunately, it was still under warranty.


Batteries “fail” for lots of reasons, but lots of short trips is one of the most common. If this car is your family “run around” car try taking it out for a 100 miles or so. That length drive will really help charge it up and refresh the battery. You just should do that every so often.


Personally, I wouldn’t invest 270$ in a baterry. From my own experience even the cheapo’ batteries will do just fine.

Cold temperatures do not negatively affect your baterry. With lead-acid baterries the story is the same as with food. In cold weather, If properly charged, they will last longer. Lithium baterries are exact opposite.

Usually it’s usually already damaged baterry and the fact that the engine is harder to turn in the winter that finishes the baterry in cold weather.

If you use too small baterry, it’s also an issue. Even though you will use the same amount of energy on each start as from big baterry and then the engine recharges the battery right afterwards, strain differs greatly.

Let’s say that you use 40Ah baterry in a car that should have 70Ah baterry. Starting the engine will take just about 30A, but while the 70Ah baterry still has 40Ah left, 40Ah baterry has only 10Ah left. While you took less than 50% from the large baterry, you took 75% out of small baterry. Strain like this will degrade the plates and cause growth of crystals in the baterry.

Also, It’s really easy to just murder your baterry straight away. It usually won’t take more than three complete discharges (by leaving your lights on or running your laptop for too long) to kill the baterry. So if it happened to you, that you have completely discharged the baterry twice (or once and left it alone for a while), your baterry is likely to be seriously damaged or dead. Then, if you’re prone to do these discharges, there’s no point in buing high grade baterries, you’ll murder them anyways.

Short trips and frequent starts with only short time in between also kill your baterry. Although some people may recommend to you to switch the engine off on junctions. Even though such behaviour can save you gas, it won’t save your baterry.

Start/Stop systems also murder baterries. Special baterries are requred for cars like those. Also modern fuel saving cars can kill your baterry by improperly managing charging procedure, leaving your baterry dry.

So to prevent baterry damage, if you drive mostly short trips, no motorways etc. it’s perfectly ok to go and charge your baterry every now and then. If you can, charge it every day, it won’t hurt it. The one thing that kills lead-acid baterries is leaving them empty.

When it comes to diagnosing baterry, one way is to charge it, put it in the car, and start after 24h. If it starts it’s probably ok. Another problem could be the oil. If it’s worn out, it will be harder to turn the engine. You also may want to use some synthetic oil that starts with low number like 5W30 or 0W40 to have easier cold starts.


What is a ( baterry ) ?

Stupid spell check, I was being facetious about the spelling . I know what a battery is.


A container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power.


Thank you @StarSword,
The vehicle was off when the battery was tested. I will try another store.

Ye, totally agree. Most of her trips are short, less than 20 miles, but the car does go out for more than 100 miles at least once a month.

This is EXACTLY what I wanted to know.
And thank you for the explanation. That helps a lot.


Seriously, charge the battery on a daily basis. I do short trips and the original battery lasted 6 years . How is someone who lives in an apartment supposed to do that .
Also oil that is labeled 5w30 can be just plain regular or synthetic.


There is no car engine out there that has a starter that requires only 30 amps to operate.

Actually the exact opposite is true. That’s why replacing a battery on a modern car may require you to register the battery to the car, so the car can properly maintain your new battery.

You should always use the oil recommended in your owner’s manual for your temperature range.


The charging system is tested with the engine running, the battery can’t be tested with the engine running.


They did for me. I was having power flickers. The nice lady at Advance Auto came out with a computerized testing tablet the size of a textbook, checked the voltage, then had me start the engine, and then rev it a few times. She tested the battery, found it bad, and also tested the alternator (which was a used part with 110+ thousand miles on it so it could’ve been that, too, but it wasn’t). The warranty replacement of the battery solved the problem.


She tested the battery before you started the engine and tested the charging system when the engine was running.


This thread is moot since the OP wants to wait until the battery fails completely before replacing it.


Also the OP is making this decision of replacing the battery a lot more difficult then it needs to be.

The first time a battery shows a reluctance to start any of our vehicles I get a new battery . Problem solved before there is one.


Well you can always try to drag your car in to your apartment, but I find it easier to remove the battery out of the car and carry just that. Then you put it on some well ventilated place and just charge it.

In case somebody will actually do that:
Use gloves (because lead), don’t put the battery against your clothing (because acid), put it on well ventilated place (because hydrogen), put something under the battery (because leaks).

I used to remove the battery out of the car on regular basis for charging so it’s well tested method.


That was an example.

I got it from battery manufacturer who shared his thougts on start/stop systems and the battery types used for those. Not my Idea.

Car manufacturers typically make veeeery good deals with oil manufacturers. That’s why my engine started with 10W40 semi-synthetic and now I’m supposed to pour 5W30 full synthetic in there. Nothing changed, the car manufacturer just made a new deal with the oil company.

So, with older cars with large mileage (forgot to mention that) it’s ok to use your imagination a bit. With older worn engines it’s possible to switch to higher second number in xWxx to catch the now slightly loose clearances.

But sure thing if you really love the car it’s always a good idea to check with a car mechanic of your liking.