3 tips for storing car batteries

Kyle Smith

No, this is not an article about EVs. The vast majority of internal-combustion cars have been equipped with some type of electrical storage device for over a century, yet few understand the details of them or how to properly care for the various types you might encounter.

Maintaining a battery to last for years is not an exacting science, but it is a science. We won’t pull you aboard a time machine and drag you back to your senior-year chemistry class, but with the weather changing and cars heading for slumber in parts of the country, it’s a good time to review what you should know about this vital automotive component.

Batteries are important for a variety of reasons. They provide the current needed to spin the starter motor, ensure the ignition has proper voltage, excite the charging system, and more.

Technology has advanced significantly over the years, but many of the principals around how batteries work, and how to best care for and feed them, have not. Knowing these best practices will save you money, peace of mind, and even time.

Lead acid vs. AGM vs. lithium ion

Acid for a lead acid battery
Lead-acid batteries often ship dry and the user has to fill the acid properly themselves. Kyle Smith

The first thing to talk about is construction. Most batteries look more or less the same—the exterior is commonly a plastic case with two terminals, one positive and one negative.

The most basic and common battery that you will encounter in vintage cars is a flooded lead-acid. These consist of multiple electrode plates suspended in a case flooded with a mixture of acid and distilled water.

The next step up is an absorbed glass mat (AGM) battery, which is functionally the same a flooded lead-acid. The biggest difference in an AGM battery is that the positive and negative plates are separated by fiberglass mats that absorb the mixture of acid and water to prevent it from sloshing.

AGM batteries can be sealed, and thus are often easier to mount since the acid is captured in the fiberglass mats. You can position them with the terminals facing any direction—up, down, or sideways—without worrying about leaks. By comparison, a standard lead-acid battery requires venting as they do emit gas during regular charge/discharge cycles. That vent dictates how the battery needs to be mounted.

Optima redtop AGM battery
The Optima Redtop is an example of a AGM battery. These are much more durable than flooded lead-acid ones but carry the same weight and packaging size. Optima

For even more benefits, you can leave lead-acid behind completely and switch to a different chemical makeup—lithium ion. These batteries are smaller, lighter, can handle being fully discharged much better, and operate better across a wider range of temperatures. Of course everything comes with a drawback, and the big one here is that lithium-ion does not tolerate being overcharged, as I found out a few months ago.

A lithium-ion unit is often smaller, lighter, and even more durable, but that all comes at a cost. Antigravity Batteries

All three of these types work well in automotive starting applications, where the rate of discharge and charge are not extreme and large amounts of storage is not required. Each has strengths between cost, ease of use, and lifespan that owners will need to balance when selecting the right one for their ride.

Trickle vs. maintenance vs. regular charging

Type “battery charger” into your search engine of choice and you will be inundated with options and likely paralyzed by choice. Depending on what you do, there probably is not one single charger that will fit all of your needs. Here is a quick breakdown of the three types.

Regular: This is meant to quickly top up a battery that has been discharged. Bringing one back from fully empty to a usable level takes time, and a regular charger is your best bet to get back on the road the fastest.

However, it is not the right tool for keeping a battery in top charge while not being used. Proper use would require using a regular charger for a short period every 30–45 days, depending on discharge rate. Remembering to connect and disconnect the charger appropriately can be tough and could lead to damage if the battery is overcharged or let go until it’s completely flat.

Kyle Smith

Trickle: A trickle charger slows down the rate of charge being put into a battery, increasing the voltage slowly. It can sometimes revive batteries that a regular charger would damage. The trickle charger is perfect for long-stored cars, but there is still no cutoff which means if left on indefinitely, this type of charger could still damage your battery.

Maintenance: The maintenance charger was created to solve the problem of overcharging. This is essentially a “smart” trickle charger that detects battery voltage and, when it senses the battery is topped off, tapers or stops charge flow periodically. When the maintenance charger cuts charge, it allows the battery to discharge naturally. When the voltage drops low enough, it will begin charging again.

This prevents both overcharging and the battery going completely flat by taking the guesswork out of putting a charger on and keeping track of voltages. This is our recommendation for any car that is not regularly driven. Both six-volt and 12-volt maintenance chargers can be found for prices that won’t break the bank. (Certainly for less than the cost of a new battery every few years!)

Removal vs. maintaining in place

This one is less about the battery and more about the vehicle. We all agree that maintaining a battery is important, but is leaving it out in a cold car still acceptable? Most batteries want to be kept at temperatures of around 75 degrees Fahrenheit. If your car rests somewhere much chillier than that for extended periods of time, you risk decreasing the capacity of the battery. Maintenance chargers can help by keeping the voltage at a level that won’t degrade the battery or damage the electrolytes, but the decision is more involved than simply stringing up a charger and ducking out of the snow.

Modern cars, with all their techno-wizardry, often need a constant battery connection and voltage in order to keep the computers happy. While removing the battery might seem ideal to keep the battery at proper temperature, it might be better to leave it in place and find a way to keep it charged appropriately.

For vintage cars that don’t even have a clock to reset if power is disconnected, the removal option should be considered in order to extend the life of the battery. Everything in life is about trade-offs, and replacing a battery more often—remember, a battery is a consumable wear item, like tires—in order to keep the finicky computers happy might be the right choice.

Batteries are often overlooked until the moment they die or otherwise leave us stranded. An ounce of prevention is worth a pound of cure though, which means properly selecting and caring for your car’s battery can give you years of trusty starting and driving.

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    The advent of the “smart maintenance charger/tender” is one of the high points in my automotive life! I went through those years of chargers and trickle chargers, and removing vs. leaving in-car, and I bought more batteries over 45 years than I can remember. Since the “tender” type of charger came out, I’ve bought several and now keep batteries from mowers, 4-wheelers, motorcycles, boats, tractors, and of course, my not-driven-in-winter vehicles in primo shape year after year. Of course, I sometimes trip over extension cords strung to all of those things when trying to fumble through the dark barn…🤔

    Same experience here. I have several batteries that have lasted 8-9 years now that I use a ‘smart’ chargers. Before using them I never saw 6 years on a battery and I have about 10 of them that get stored for the winter.

    I have found the best way to maintain your battery – and the vehicle it is in – is to run it at least every 2 weeks. Even if the weather is too bad to bring my toys out to play, I still try to run them every week or so. I have watched numerous people cook the life out of batteries by trickle-charging them even with very good trickle chargers

    The Die-Hard in my ’66 Pontiac is nearing its 15th year anniversary (bought 2008) and spends 95% of the winter on a tender. It does get started a handful of times during those months – for instance, we have a New Year Day Cruise/Show in honor of an old local rodder (R.I.P. T-Willy) – but for the most part, it’s the minder/charger that carries the load.

    The general consensus is you shouldn’t start you stored car during storage unless you can take it out on a 20 minute drive. I use to do it but noticed that I had to replace the exhaust system often due to moisture trapped in it from starting my car and letting it run for about 15 minutes every month in the winter. If there is moisture in the exhaust I would imagine it would be trapped in the oil pan, etc of the motor too. I use battery tenders and have never had a problem.

    The following story is to the best of my memory.

    In the mid 1970s, I purchased a “Forever” Firestone battery for my 1968 Chevy; Firestone advertised one will never have to buy another battery for their car. Around 1990, my second “Forever” failed.

    I had the original warrantee and sales slip and wanted it replaced free of charge. Local Firestone dealers would not honor the warrantee and asserted I had to go to a Firestone owned store.

    I contacted the nearest Firestone owned store (about 160 miles and three hour drive) and they insisted I drive my 1968 car to their location. I asserted I would be there on Saturday.

    On a Saturday, I put my daily driver battery in the car and drove to the Firestone store. I carried my really clean “Forever” battery, warrantee, and sales slip into the store. No one could help me, only the manager could authorize the replacement. After about two hours, the manager did come to the store. He did authorize a replacement battery (about 500-600 cold cranking hours, not the 700-800 cold cranking hours of the “Forever” battery). He then voided my warrantee and issued a new sales slip.

    Firestone insisted the “Forever” warrantee was not for antique or classic cars. I have never purchased a Firestone product since then.

    But your 1968 car wasn’t an antique or classic in 1970 when you bought the original battery! Firestone should be ashamed of that tactic…

    About your lifetime battery… I always thought the shops got reimbursed from the franchiser for the warranty work. Apparently not. Side note: I got an AAMCO transmission with a lifetime warranty and had it rebuilt three times for nothing. Expensive when I got it, but saved a fortune over time.

    That is exactly what you should have done. I had exactly the same experience except the brand was Sears Diehard lifetime warranty.
    They replaced it once with a 5yr inferior battery and I’ve never set foot in a Sears store since.

    Sears Auto Centers had their empoyees on a small salary/ comission based pay plan. They had their pay based on selling new stuff. They were caught having a spray can full of oil under the cars and they would spray oil on shocks and othe replacable items, than bring the customer into the bay to show them that “Your shocks are leaking”. They were forced to stop the practice by paying the mechanics what they were worth and no comissions.

    Exactly what happened to my 2011 Challenger- sprayed the front strut and told me it needed replacement. I’ve been driving it for miles, no handling issues, tires wearing fine.

    Meidas used to run a commercial on TV where an old man in a model T would drive in and demand a replacement muffler per their lifetime warranty. They would scratch their heads and comply. As he left the service guy asked ‘you ever gonna sell this car?’ The man replies, ‘ohh, I’d never sell Annabelle! See you again, boys!’ Nothing lasts forever. They figure you will sell the car first. But Firestone should have honored your replacement. Still, you did get 15 years on a battery…

    “Like to give you boys the business!” My old man lived to 98, and was still laughing at that one about 30 years after they quit running it. The difference between a ‘clever’ ad and a ‘genius’ ad is whether you also remember who the ad was for…

    Toyota had a lifetime guarantee on mufflers back in the 90s here in Canada. The muffler on my ’88 Extra Cab pickup ran from the converter to the back of the truck. Paid for the first one, got 2 free then sold the truck after 10 years and 290k miles.

    I say that’s a bunch of B.S. If I were the manager, the fact that you still had all the paperwork as well as the documented vehicle, I would have honored it. That’s the shame about these phony warranties that are no longer honored. First they try to make you give up, then they tell you to never come back. Craftsman tools are the same and when they do honor the warranty they hand you garbage replacements with no warranty.

    Someone will warranty your Craftsman tools and your right about the quality. Today Home Depot swapped out the 18” x 1/2 breaker bar for a 15” as they do not carry a 18”. Ok. The one they’re swapping is a year old broken with the Allen pin that holds it together. I found on a eBay supplier. The one I sent to him as defective was 40 years old and had a drift pin holding it together. Got it when I was 17. The new ones are poorly designed and made to break. We have no choice but to buy Chinese products and corporations don’t care about quality. D.

    I was “ convinced “ by a Jobber that I could buy a whole set of 3/4” drive sockets for the price of one or two Gray brand ( quality). Well when the rather loose fitting Chinese socket slipped while reefing on it only 6 stitches were required. Now I only buy the best and you can find Made in North America
    ( Canada / USA)

    Lol, I also bought a “Forever” battery in the mid 70’s for my 68 Corvette. It died about 6 years later and I took it to the local Firestone dealer. They did replace the battery and told me they would not do it again. I tried to reason with them about the “Forever” part, but the dealer would not honor the warranty after one replacement. That was also my last Firestone product.

    I hate to say it but I went through the same sorry song and dance with a Firestone “Forever” battery. What a pathetic way to do business and I too, have never bought another Firestone product, nor will I ever.

    I guess my luck’s been better. In 1976 bought a JC Penny’s Lifetime Battery for my 1972 TR6. Currently on my eleventh battery. JC Penny no longer handles batteries, and let Firestone do the adjustment. The receipt is getting pretty raggedy and some locations what to see the title. I think I’ve gotten my money’s worth.

    Always make a copy of your original warranty & sales receipt. For those cases where you’re getting a hard time the best thing to do is take good photos of the battery, warranty & sales receipt & don’t give up the battery. I’d file a complaint with the state consumer protection division. I’d also file in the local small claims court for the cost of a new similar battery & would add as much punitive damages to the max of the small claims court limit. If they don’t show up, a judge may award up to the amount asked for.

    This will date me…who remembers what chain stores did to sell batteries in the the 1970’s ?

    Had a new ’72 4wd Chevy Blazer as a 2nd car. Ex #1 & I mainly used it for camping so it got little use & sat outside in a field. Bought a K-Mart battery with a LIFE-TIME warranty for as long as you owned the car.

    Got 15 years of batteries for the price of one, until the car was sold.

    Not to change the subject – but regarding “Lifetime Warranty – as long as you own the car” – my experience with a “lifetime – as long as you own a car” from a national muffler company. I asked “are you SURE it is as long as I own the car?” (they didn’t know me!) – and they said YES. Got 5 mufflers out of them (over 23 years and 360k miles) until the last visit when the manager told me “I never want to see you again” – The “Midas touch” wore out I suppose…

    I’ve got too many cars to drive regularly, so keeping the batteries charged is a challenge year round. Made even more challenging because they’re parked in a condo parking lot, and I’ve got nowhere to plug in a charger. And when the choice is the Corvette, WS6 Trans Am, or one of the others, the others mostly sit. I’ve got battery disconnect switches in all of my cars. Best idea I’ve come up with under the circumstances.

    2008 Mustang GT. Had the original battery on a maintainer, along with a heavy duty timer which activated 4 hours a day. Battery lasted until this past spring. Did this even during months car was driven, and doing it now with the new battery. It always cranked over like a champ.

    Do the other residents of your condo complex mind that you are taking up so many parking spaces for your personal stable of cars? I sure wouldn’t be happy if I lived there… Sounds like one person using more than their fair share of resources.

    I cannot say enough praises about Deltran’s Battery Tender, either the Plus or Jr version. I’ve had one on my John Deere tractor now for 10 years and the original battery still goes strong. I attach it whenever I’m not using it, summer or winter. I have them installed on my stored cars too. Unreal.

    My classic 1965 Dodge Coronet has an Optima Red Top AGM battery dated labeled 4/12 or going on 11 years since installation. In addition, I always attach my automatic Battery Tender to it whenever it is sitting in the garage, which may be weeks at a time. My un-scientific experience says that Optima makes one heck of a battery, and the battery tender makes a big difference towards the life of the battery. The initial cost of the Optima is twice the cost of the lead acid version in my daily driver, but I don’t have to replace it every 4-5 years. Heck yeah, this combination pays dividends over time. Still shows no sign of battery failure.

    My experience with optimas if you run it down its lifespan is over,went back to lead acid dinosaur batteries,work better for me.And they are always kept on a charger/maintainer now,batteries too darn expensive.

    Our experience, too, Rick. My Packard, Cord and other old six-volt car owning friends have gotten good service from Optimas. Our Red Top 6-volt, 800 cold cranking amp batteries do not leak, off gas, and are eight times more resistant to vibration than traditional lead/acid batteries, not that the this is a problem in Packards or most old luxe road cars. Turns my gear-reduction starter easily. Got just shy of a decade from my last one, looks like more of the same from present one. Know of a ’41 Cad that got 14 years from his Optima, and a Cad V-16 starting just fine on an Optima.

    The best maintenance charger we found was a CTEK UC-800. Connect it, forget it. Orange light charging, green floating full up. No, don’t work for Optima, but when we find a good product that helps keep our wheeled alter egos rolling, we believe in singing its praises.

    For those of you who appreciate the wisdom of “weight is the enemy” in all cars, not just dragsters and racers, six-volt Optimas weigh only 18 1/2 lbs. A little here, a little there, it adds up.

    A good Thanksgiving to all those here gathered.

    I agree about Optima batteries. The longevity of them is great. One of the things that most impresses me with AGM batteries is that they take a charge very fast, and that means my alternator doesn’t work very hard and it will last. One of my cars is twenty-six years old and still has the original alternator.

    Your photo that says, “Notice that these are trickle chargers, not maintainers,” is incorrect. The Battery Tender (including the Junior shown) is a maintainer, not a trickle charger.

    I see new Battery Tender Junior’s marketed as both charger and maintainer but the two pictured are clearly labeled as chargers only. Maybe there was a change behind the scenes?

    Also I have discovered there are some battery maintainers that don’t live up to their claims.

    I had an Optima Red Top battery that self-destructed, spewing acid from one of the vents, and building up enough pressure to cause the negative terminal to jut out of the top about 1/8″, while installed in my vintage car. Fortunately the damage was contained to the battery itself and a moderately corroded battery cable, as I discovered it during a monthly check.

    Since then, I’ve stopped using battery maintainers while the batteries are in the cars. I’ve also upgraded from the big-box store brand maintainer to the NOCO Genius-10 which is expensive ($130 ~ $150), but has hundreds of highly satisfied customer reviews for its ability to do maintenance and bulk charging, and when necessary, repair failed / damaged batteries that other chargers cannot revive.

    So, buyer beware. The above battery incident could have had a worse outcome. The battery could have failed more violently, causing major damage to my irreplaceable classic car or caused a fire. Time will tell how the NOCO Genius-10 holds up. I like it so much though, that I bought a second Genius-10 to serve as a maintainer for another classic car.

    The unit that destroyed your Red Top battery was not a maintainer, it was a trickle charger, and that’s why it did that.

    Interestingly one of the earliest batteries were by far the best. About 100 years ago Edison sold the nickel-iron battery and built a plant to produce them. The batteries lasted truly a “lifetime”. My grandfather had a 1913 Detroit electric which had run for more than 60 years on the original batteries when he sold it to the Denver museum as I was told. Jay Leno had a similar automobile and has a similar longevity depiction. The plant was sold to another car battery company when Edison was tied up on the Niagara Falls power plant. They destroyed the plant and never returned to the Ni-Fe batteries. There is a company making them again for home power backup.

    I’m a fan of the NOCO Genius intelligent chargers. My cars that sit all winter (October – April) have batteries that have lasted over 10 years and were replaced as a preventative measure, not because they died. Both of my Honda Accord Coupe V6 6-speeds had batteries that lasted 10 years even without tenders on them. Not sure if they use a higher quality battery or the charging circuit is stronger but that’s certainly way above average.
    Regarding the lifetime warrantee; years ago Sears figured out that it was cheaper to replace the paint for the few people that changed paint colors than develop a paint that would actually cover in one coat. The battery people probably figured that most people would sell the car before the battery actually died.

    Many good points raised. Batteries (lead acid) simply don’t last long anymore in my opinion. That being said a conscious effort to maintain them properly can coax some extra life out it for sure. I work with an engineer in the early days of EV’s versus hydrogen powered cars etc. His mantra for batteries at that time (“batteries like the same temperature as humans”) coincide with what Kyle said. In regards to quality my original John Deere tractor battery from 2001 lasted until 2015 with the care outlined in the article. My replacement lasted just over 4 years with the same care…Mmnn? And, in regards to computers in cars I stored a 3 year old car (Saturn Vue) for a year without the battery (put it in the house) that was in perfect shape before storage. Didn’t run when I put the battery back in. Ended up being the body controlled module (BCM). Why was this? Because battery was out? It was on its way out anyway? I’ve always wondered if it needed power through the storage process. Side note I coaxed 5 years out of one my lithium motorcycle batteries, again stored at room temperature. My $.02

    Batteries die from depth of charge and number of cycles.Our old cars didnt have phantom loads like newer cars so much fewer cycles and less depth of discharges.That said seems like quality has also slipped but unsure if thats really true as how we use them for sure has changed.

    I looked into battery storage to extend the traction battery in our Prius. And your engineer co-worked was basically right. I learned that the optimal temperature to store batteries is 60F. Actually, 59. something. While I don’t air condition the garage during summer it stays cool from being highly insulated. From late fall through early Spring have the garage heat set at 60F. The Prius is nine years old now and so far, so good. While I haven’t tested the traction battery, the fuel mileage hasn’t gone down over the years.

    A modification of a trick used in the Navy… I leave my “regular” metered charger ON my FacFive Cobra… but… it goes through a lamp-timer. That turns it on for about 45 mins ONCE-PER-DAY, then shuts off… basically a smart charger in function, it NEVER overcharges, BUT as we found out all those years ago in “The Canoe Club”, getting the full-current BUMP is better than a constant or intermittent trickle.

    Some definitions of ‘battery maintainer’ lectric-splain that every once in a while they deliver a more powerful jolt than just the cycle of trickling, to prevent sulfating. It works, for sure. Before buying a storage-charger, I read the fine print to make sure they know that trick.

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