car batteries - why do they still suck?

I just replaced my battery in my car. It was 2 years old.

My car doesn’t have any problems that I know of, with the alternator or anything else. I can accept that perhaps I got a bad battery. It happens.

However, what I don’t understand is why can I never get a battery to hold a charge after it has run down? It seems that if a battery is drained, or perhaps passes a point of no return with some juice left in the battery, that’s it. The battery is dead and there is no way to save it.

This has been this way as long as I can remember. Why haven’t there been any technological breakthroughs in vehicle batteries to permit the recharging and reusing of them? They are obviously capable of doing this: this is what an electric car battery has to go through on a continual basis. So why the always failing car or truck battery?

I’ve not known anyone to ever recharge and reuse a battery successfully, although I’m sure it has happened. Just seems strange to me that a battery can be recharged through the night, and gain a charge only to lose it when it is taken off the charger.

if you drain a lead-acid battery way down, a layer of lead sulfate can build up on the plates that a charger may not be able to “break” through.

Sorry, but there isn’t a rechargeable cell that I’m aware of which can survive abuse. if you drain a NiMH cell in a series pack, it can be forced into polarity reversal which ruins the cell. Li-Ion cells have protection circuitry to prevent you from draining past the “point of no return.” Which is good, since most failure modes for lithium rechargeables results in “burning the hell up.”

because those electric car batteries have sophisticated control systems in there to prevent the cells from ever being over-charged or discharged too deeply. The starter battery in every car out there is just wired in parallel with the rest of the system and has basically no protection whatsoever.

A general comment about car batteries: if you’re going to leave it sit for an extended period, disconnect the ground terminal. I’ve left batteries in this state over the winter and the vehicle has always started on the first crank after reconnection.

further, in all the cars I’ve messed with in my family, only once has a battery not lasted at least 5 years. I don’t know what you’re doing to the poor things.

I think a lot of it has to do with marketing and weight requirements.

First off, consumers have been conditioned by advertisers to believe a battery having high cold cranking amps (CCA) is indicative of a “better” battery. So how does a manufacturer increase CCAs for a given volume? Simple – by increasing the number of plates. But because the volume is fixed, the plates must be made thinner. Thinner plates fail much quicker (compared to thicker plates) when the battery is drained. In other words, for a given volume there is a tradeoff between CCA and susceptibility to corrosion when the battery is drained.

Secondly, automobile designers are under a lot of pressure to shave off weight wherever they can. A small battery with lots of thin plates may meet their weight requirements. But drain it once and you’ll need a new battery.

I’ve become convinced that the manufacturers all put crappy batteries in cars as original equipment, probably to save money. Upmarket and economy marques alike. I’ve seen this scenario several times:

1 - buy new car.
2 - battery craps out in 1 - 2 years.
3 - replace with battery from auto parts store.
4 - replacement lasts until car is sold.

Batteries, of course, are generally not covered under new car warranties.

Bad batteries don’t just happen. Was this a maintenance free battery, or did it have filler caps on the top of it, and if it had filler caps, did you check the electrolyte level periodically? You could also have something in your car that is draining power from the battery even when the car is off. All cars do this to some degree, which is why you need to either use a battery tender or disconnect the battery if the car is going to sit for a while (note - some car stereos and alarm systems aren’t very happy at having the power removed - follow your manufacturer’s instructions if you have one of these). You may have even had something like a stuck relay, which left something turned on when it shouldn’t have. Now that the relay isn’t stuck any more you may never see the problem again (I’ve had the fan relay in my Cadillac stick on exactly twice in the past ten years).

Lead acid batteries really don’t suck. Most people have very few problems with them. The only time I’ve had to replace any batteries in the past couple of decades is when I’ve left a vehicle sit for too long and I’ve killed the battery as a result. Overall though, lead acid batteries are dirt simple, rugged, work over a wide temperature range, and are generally pretty darn reliable.

I suppose if a battery was cheaply made it might not be sealed as well as it should be. That is going to cause you to lose electrolyte which will eventually destroy the battery. Are you willing to pay more for a battery? Most people want cheap, so batteries are made cheap. You can’t make it both high quality and cheap at the same time. Pick one or the other.

They do make lead acid batteries that don’t self destruct quite as easily. They are called “marine batteries” or “deep cycle batteries”. The lead plates inside a car battery are intentionally made pretty thin. For a given weight of lead, if you make the plates thin you get more cranking amps (more plate surface area) but the battery doesn’t have as much “reserve” in it. A deep cycle battery has thicker plates, which for the same amount of lead gives you fewer cranking amps, but you can discharge the battery much longer before it self destructs. If you want the same amount of cranking amps, a deep cycle battery would therefore have to be much heavier than a regular car battery, which, like anything else that adds weight, is going to negatively impact your gas mileage. But if you want a battery that doesn’t “suck” as much, there you go.

This was a maintenance free battery, and it was a brand new battery in a two year old car.

Now, the one thing I did do was leave the battery connected and it sat for an extended period of time this summer. This was not planned, but just worked out that way. Perhaps this was the reason for the battery draining. Still, I would think that a battery that is just keeping the car in a non-running state, where the drain on the battery would be minimal, it seems rather surprising that it died. Completely. Drained out.

Question. If I want to avoid this in the future, which terminal should I remove from the battery while the car sits? The positive, the negative, or both?


The good thing is, a dead battery is worth $10 at a metal scrap shop. Cash. (Or at least it used to be.)

Are you in the South? It’s been really, really hot this year. I’ve heard that heat can kill a battery. I’m not sure why.

If you have a garage and a plug-in handy, a battery tender is really the way to go for any car that may sit for weeks or months without being started. They only cost $25-$35 and the battery will always be ready to go, and in good health. And as already mentioned, some important controls do not recover well from a loss of power.

If you think of a battery as a storage vessel that can be emptied of charge and then re-filled with charge without harm, then you are thinking of it the wrong way. A battery is a chemical reaction that needs charge to continue. Each full drainage weakens the reaction.

Much better to keep a trickle going through, like keeping a plant watered. You wouldn’t expect to let a potted plant dry out and then come back to life once you add water a month or so from now, would you?

Better to keep the battery and the plant alive with a little trickle of juice.

Tell me about it. Car batteries are a favorite target of drug users and general thieves hereabouts. They steal them and sell them to the local scrap dealer who knows they’re all criminals, but never asks questions. Pain in our collective asses.

If you leave your car set for extended periods and don’t have a tender, then I would suggest once a week starting the car and letting it run for 15 minutes or so. Not a bad idea, not only for the battery, but to keep seals from drying out and internal parts from freezing up.
If you are going through mulitple batteries I would suspect you have a parasite circuit somewhere. Something is using power while the car is off. Do you have any electronics installed that were not from the factory? A stereo perhaps. If so, double check the wiring and put a meter on it when the car is off to see if it is pulling power. Also, as mentioned above it is possible you have a relay, switch or contact that is not working properly. This would certianly explain why your battery is draining.

It’s safer to remove the negative, as a slip of the hand that touches the wrench to other metal on the car won’t cause a short. Only one cable need be disconnected. First make sure you have any anti-theft codes, if applicable.

If your problem is just sulfate there is a Technological solution
I have several of these and use them on all my heavy equipment that sits for more than a few weeks.
It truly revives totally sulfated batteries.
It won’t of course fix opens or shorted cells, so you have to understand what the issue is.

I suspect that a lot of car manufacturers these days are putting in very lightweight and cheap batteries, partly to save cost and partly to save weight. Maybe one of our resident car expert dopers can chime in and say how often they see newer batteries fail compared to replacement batteries.

Cars vary, but in general I think modern cars do tend the drain the battery a lot faster when turned off than an older car. You’ve got some power being drained to keep your radio from losing its memory, and the car’s engine computer also has to take some power to retain its settings as well. If the car has a wireless remote for the alarm or just to unlock the doors then that takes some power as well.

In my experience, most cars will go a couple of weeks without being started with no problem. After that, it depends on the car. Some will kill the battery after a couple of weeks, some will last a couple of months before killing the battery.

I think most folks disconnect the positive, but it really doesn’t matter. You can disconnect either one.

As was already mentioned, you can also use a plug in battery tender.

Depending on how long the car is going to sit, you may want to add some fuel stabilizer to the gas tank and put the car up on jack stands so that the tires don’t develop flat spots.

I have had good luck reviving batteries. I had a one year old Walmart battery that sat for a week with a light on in the car. The voltage was actually slightly reversed on my meter. I carefully charged it and used it three more years in that car and still have it on the floor here as a backup jump starter for people in winter. (It never failed at below zero temps.) And I have saved a few others over the years. The exception is if it freezes or has been freezing. I don’t even attempt to charge such a battery.

Guess I’m way ahead of the game.

My OEM battery lasted five years. Auto store replacement lasted two. I’m on my second auto store battery, the first was replaced under warranty. Ditto for the wife’s car. It seems like when car batteries fail, it’s quite sudden. Car is running fine when shut off. Then when you go to start it, you either get nothing or the dreaded click click click.

Exactly. I’ve just replaced the original battery in my car. 5 years old and it went from being perfectly fine to dead overnight. Past experience tells me don’t bother recharging even partially ‘dead’ ones because they’ll just fail again very soon, and when it will cause lots of inconvenience.


modern batteries just die. no warning.