5 July 2016

How to properly maintain your classic’s battery

You’ve been waiting for this drive all week. You turn the key and instead of a V-8’s roar, the only sound your car makes is click-click-click-click. Venturing into your garage for an early morning drive only to hear the sickening whine of a dying starter motor puts an anticlimactic end to any driving adventure before it begins. Maintaining your lead-acid battery is not vintage motoring’s most exciting aspect. Unfortunately, though, it is necessary for classic cars that might sit dormant for long periods of time between excursions. Weeks and months of downtime can result in battery discharge. The good news is that maintaining a battery is easy and inexpensive.

The wet cell lead-acid battery hasn't changed all that much since its introduction in the 1800s and neither has the maintenance of adding distilled water, cleaning up corrosion and charging. Lead plates inside the battery react with electrolyte or battery acid to store and discharge electricity. Sulfuric acid vapor and hydrogen gas can exit the battery vents as a byproduct of charging. Resulting battery terminal and post corrosion can interrupt incoming and outgoing current flow. Cleaning up the terminals and posts can help keep corrosion at bay. Corrosion, time, cold temperatures, mystery shorts or a recalcitrant map light can discharge a battery between drives.

Modern lead-acid automotive batteries offer more cranking power, longer life and less maintenance – thanks to sealed cases – than traditional batteries. But even Absorbed Glass Mat (AGM) and Gel batteries, both of which stabilize the electrolyte and eliminate adding water, still require periodic post and terminal cleanup. Classic car purists often stick with the traditional-appearing, basic black lead-acid battery for aesthetic reasons. Spending time and money on a period-correct restoration and bolting in a Day-Glo pink topped Extreme 2000 battery under the hood just isn't right. Original-appearance or restoration-specific AGM and Gel batteries are available, but chances are great that a wet cell lead-acid battery provides your classic car’s spark.

Assuming your car’s charging system is in working order, avoiding a dead battery in the dawn before cars and coffee or at sunset after a long and winding drive is simple. Maintain and clean the battery terminals and posts. Add distilled water to the cells as needed. Charge the battery using a 2-10 amp charger after a load or voltage test. If your classic car or motorcycle sits under cover or in the garage for extended time periods, nothing beats the slow or trickle charger – a determined device that not only keeps the battery charged but also helps prevent battery-killing sulfation. Exercise through charging and occasional rest is a good cycle. With proper care and maintenance your lead-acid battery can provide years of faithful service.

maintaining a classic battery
Posts and terminals clean up with this inexpensive tool. One side of the tool cleans up terminals, the other side...

maintaining a classic battery
The other side of the tool is made for cleaning battery posts for improved contact.

maintaining a classic battery
Dielectric grease helps prevent new corrosion, repel water, and improves contact.

maintaining a classic battery
Low electrolyte levels can wreck havoc. Add distilled water to the cells. Do not overfill.

maintaining a classic battery
A battery load tester checks voltage and simulates a heavy current draw.

maintaining a classic battery
The automatic battery charger brings the battery back to a full charge quickly.

maintaining a classic battery
Slow or trickle chargers maintain battery charge and can prevent battery-killing sulfation.

maintaining a classic battery
A 1-lb. baking soda to 1-gal water solution neutralizes acids and helps prevent corrosion.

maintaining a classic battery
The slow or trickle charger is ideal for use if the car sits for long periods between drives.

16 Reader Comments

  • 1
    Nolan Pahud Santa Rosa, CA July 7, 2016 at 13:08
    After disconnecting my battery to clean corrosion off the +terminal and reconnecting the cables I found not all the power windows worked properly. My 2006 Mazda6 can lower the two front windows with the key fob to let hot air escape. That feature didn't work and neither could I lower the passenger side window from the driver's seat. After checking fuses I read the owner's manual and the solution required a simple re-program of the windows which was explained in the manual. Glad I didn't rush to Mazda service and look foolish. When in doubt...
  • 2
    Mark T. Baltimore July 7, 2016 at 13:19
    I was under the impression that trickle chargers carry a real risk of fire. I believe I read that in one of Hagerty's own articles. I'd rather have a dead battery than burn my house down (and my classic car). So, what's the insurance company's take on this?
  • 3
    Brenda Long Beach, CA July 7, 2016 at 14:25
    I have a BMW, battery under the back seat. How can I use a solar panel in the window to keep it charged?
  • 4
    Charles Hammer Whidbey Island, WA July 7, 2016 at 10:06
    I was taught when I was a kid just learning about cars to completely disconnect the battery from the car (or boat) that you were putting away for the winter. Charge it up completely and then store it on a block of wood, checking the charge every couple of months along with a good charge before connecting it back up before a drive. Dad said this was the best way to keep the battery healthy and the battery compartment or area clean. Was this just an old wive's tale?
  • 5
    Hal Smith Citrus Heights, CA July 7, 2016 at 10:11
    I have a '56 Thunderbird that I drive about once every 2-3 weekends. Rather than face the headaches you describe above, I have a switch located right on the battery box to turn off the battery between cruises. Even with that taken care of, I know a battery can go dead just sitting unused, so I give it a slow charge about every month.
  • 6
    Alan Weverstad Suttons Bay, Michigan July 7, 2016 at 10:22
    I believe that a battery maintainer is much better for your battery. A trickle charger will continue to charge but the battery maintainer floats from high to a lower state of charge and back. More like batteries experience in use
  • 7
    Johnny Canterbury, CT July 7, 2016 at 10:42
    I remove the positive (+) lead from the battery.
  • 8
    Peter Dyson Illinois July 7, 2016 at 11:10
    Who wrote this article?? Never use a trickle charger or a battery charger for long term storage. ONLY use a Battery Maintainer. Trickle chargers are deadly to lead/acid batteries, sulphate the cells, and cause rapid evaporation of the water in the battery. Be sure you use a good quality Battery Maintainer. Read up on them before buying.
  • 9
    Danny Boy Chicagoland July 7, 2016 at 11:11
    Don't place battery chargers or trickle chargers above the battery as it is being charged.
  • 10
    Ike Mayer Covington, LA July 7, 2016 at 11:41
    I have two classics and have trickle chargers on both. A great device; and, I have not experienced any dead battery disappointments on the weekend drives.
  • 11
    Bob Cabaniss North Carolina July 7, 2016 at 11:44
    Seriously..I' an aviation mechanic and inspector. I have many customers who fly only a few times a year, similar to not using your vintage car (I'm guilty too) as much as we wish. Please think about using a de-sulphateing trickle charger, rather than a plain, cheap charger. A few dollars more, but your batteries will last much longer..works on motorcycles also. AGM batteries ar soooo much better than the old style lead acid type. No corrosion, last much, much longer.
  • 12
    David Carter Texas July 7, 2016 at 12:26
    Worth also saying that where a car sits for extended periods of time, especially outdoors/barn, covered shelter, there are many advantages to simply disconnecting the battery. Slow discharge is unlikely, and if a mouse or some other beast should gnaw the wiring, you won't lose your car to a fire. Quick disconnects can be bought, motor-sport competition suppliers have them, or just undo the live battery clamp and secure it away from the terminal. Takes a few seconds.
  • 13
    Catherine Klimenkov North Las Vegas Nevada July 8, 2016 at 20:00
    Some say use a spray on anti corrosion I say do not or you will run into a discharged battery as the stuff will prevent proper contact and that is commeing from an electrical engineer (my Dad) so do not let any Auto service tech put that stuff on your battery clamps.
  • 14
    William D Justis Olympia WA July 9, 2016 at 14:48
    Use caution with a trickle charger. Even a 2 amp charge over enough time can overcharge the battery and boil the electrolyte away ruining the battery. The battery "tender" or "maintainer" will keep the battery charged but only when needed avoiding overcharging. Read the specs.
  • 15
    Dick Maddux milton,fl July 10, 2016 at 08:59
    I used a maintainer (of good quality) on my airplane battery while on vacation. When I returned I was greeted with a corroded battery box,support tubes and rudder cable. No more for me ! I disconnect the battery and let it sit. It will last a long time that way. My two Triumph TR3's have disconnected batteries and they have lasted for many years.I short charge prior to driving and you are ready to go!
  • 16
    Chuck Minn. August 29, 2016 at 00:16
    Do NOT buy Sears maintainers. I own eight of them and found most of the time the batteries are less than the full charge of 12.6 volts, often high 11 volts and yet the maintainers are on "green light" refusing to recharge the batteries to the proper level. I have better luck with Harbor Freight .5 amp. chargers. They are called maintainers but are actually continuous chargers but at a level that does NOT boil the water out of a battery even when left on for an entire winter. If you buy ANY maintainer make sure to check the voltage on the battery after the maintainer indicates it is charged but do this a few days later to check if the charger is keeping the battery up. Schumacher maintainers seem to be another questionable maintainer as a friend has had the same trouble with two of their maintainers. If your engine starts after you see your maintainer shows "green" you will think the maintainer worked but not necessarily so. A good battery will hold a charge for months but other batteries that need a little assist from a maintainer often do not get it.

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