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How-To Choose and Maintain a Battery
Here's how to extend the battery life for cars that aren't driven every day
You probably don't think about your Mustang's battery very often. In fact, many of us don't think about it at all--until, of course, you turn the key and the engine won't start.
Maybe the starter turns over for a few seconds or maybe there's only silence. In any case, you're going nowhere fast, and that Saturday-afternoon cruise you planned a few days ago isn't happening until you schlep down to the local auto-parts store and buy a new battery.
But wait, didn't you buy a new battery for your car less than a year ago? Often that doesn't matter, and that's where this overview comes in. In a general sense, we're going to discuss how to help a battery last as long as possible, but note you might not have much control over battery longevity. Some batteries take a final exit sooner than expected or sooner than they should.
We'll also offer a few tips on choosing the proper battery for a vintage Mustang, both a show-oriented car as well as on a daily-driver where appearances are less of an issue. Of course, maintenance suggestions apply to the battery in any car, not just vintage or late-model Mustangs.
While in one sense a battery is a relatively sophisticated component with various bits and pieces, it's also a simple piece of equipment that must provide enough cranking amperage to start a car. Once the car is running, the electrical system provides the current to operate the car while the alternator keeps the battery charged. However, the alternator only charges the battery when the car is running. When a car is stored for any extended period of time, the battery is just sitting with it. Over time, a battery's ability to maintain a charge adequate to start the car will diminish. In fact, for any battery, even a brand new one, there will come a time when it will simply die and must either be recharged or replaced.
That's where a proper charger comes in. In short, the best way to maintain a battery in a car that isn't driven on a daily basis is to keep it connected to a charger that has a "trickle" setting. In other words, you ideally want to have a charger that not only charges a battery, but also one that maintains the charge. The idea is to have a battery fully charged, and once it's there, the charger keeps it in a fully-charged state.
An excellent general purpose charger that also doubles as a top-notch maintenance-type trickle charger is the CTEK Multi US 3300. This Swedish-developed charger does both the recharging and maintenance processes. It's an ideal choice for any 12-volt automotive battery.
The CTEK uses "switch-mode" technology, a four-cycle process for optimum battery charging and maintenance. The CTEK "recovers" or "wakes" a discharged battery.
The bulk charge mode is a standard charging circuit that ranges from 0.8-3.3 amps, which is where about 80 percent of the battery's energy is returned. The charger delivers an almost-constant current until the battery voltage reaches a set level.
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The absorption mode applies a peak charge of 14.4-14.7 volts until the battery is fully charged. The charge current then tapers, and voltage is kept constant at a set level. The final pulse mode sends out current pulses, and charging ranges from 95 to 100 percent. The battery receives a pulse if its voltage falls. This stage keeps a battery in good condition although it's not being used on a regular basis. The compact CTEK charger is fully sealed and weighs just over one pound.
National Parts Depot also offers the Deltran Battery Tender, primarily a maintenance-type charger. Its 1.25-amp constant-current reaches and maintains a full charge indefinitely by automatically switching to a storage charge. It won't overheat or overcharge a battery and it adjusts for temperature. In addition, the
Battery Tender has microchip circuitry that avoids shorting or sparking if the clips inadvertently touch each other. For example, if storing a car for the winter, NPD suggests removing the battery from the car and leaving the Battery Tender connected while the battery isn't in use. NPD also has a Battery Tender Jr., a more compact unit with a 750-milliamp current rating. It will also charge and maintain a battery.
A general-purpose charger, the sort sold at any auto parts store, is also worth considering and is usually available at a budget price. A good example is the Schumacher SE-82-6 dual-rate charger that we purchased at a local Southern California Kragen Auto Parts store for 25 bucks. The difference between a typical charger such as the Schumacher and the others mentioned is its higher amperage output. At its 6-amp charge rate, it'll charge a battery in about 6-8 hours. And while its 2-amp slow-rate setting is good for smaller batteries, this is a manual charger that will continue to charge even after the battery is fully charged. A visual check of the ammeter is required to know when the battery is fully charged. This unit is not as suitable for long-term low-amperage trickle charging on a stored battery.
Battery Maintenance Tips
We asked National Parts Depot's Rick Schmidt what he does with the batteries in the numerous vintage Mustangs and other collectible cars in NPD's collection, many of which are rarely driven. His advice applies to any battery and car, whether part of a large collection or--for like most of us--in a collection of one.
"If you're not driving the car regularly, it's best to completely remove the battery from the car," Rick said. "Batteries sometimes act like ticking time bombs, and you never know when a case is going to crack or vents are going to spew while a battery is not being used. From our experience, batteries will do funny things just sitting there, disconnected and motionless. So, get it onto a shelf or bench unless that's impractical because the car is driven more often than once or twice a month. Also try to store batteries in a cool and dry space.
"For a long time, we've done a scheduled regimen of slow-charging our batteries on a rotational basis, usually just a 2-amp charge until fully charged, about once a month. However, we're currently revamping equipment to utilize full-time Battery Tender trickle-chargers. Either way works well, but the Battery Tenders are less work and less to keep up with. You just hook them up and forget it.
"For old-style acid-wet batteries, keep up with the water level on a regular basis. Don't overfill, and it's good to loosen the caps while in storage rather than relying entirely on the pin-hole-sized vent, which can sometimes act as a high-pressure spray nozzle.
"Our experience is that batteries in general are fickle and inconsistent. Some batteries last 10 years and others only 10 months, for seemingly inexplicable reasons. Some batteries will slowly degrade, while others will just short-out and die. We've probably bought more batteries over the years than bottles of wax, despite our maintenance attempts. But then again, we didn't keep up with our batteries as well as we do today. Unless you're driving it, get it out of the car, and keep a low-amp charger on it or trickle-charge monthly in a dry and cool area. After that, the battery will decide how long it wants to stay with you.
"We've still got the original battery in our '97 Saleen S351, and with relatively light use and charging maintenance, it still cranks strong after nine years. We've had other batteries that were maintained religiously, and they flamed-out and sprayed acid all over a car's engine compartment within six months. In the final analysis, a slow maintenance-type trickle charger is the best way to extend battery life for a car that isn't driven on a daily or weekly basis."
Choosing a Battery
For vintage Mustangs, choosing a battery for a regularly-driven car isn't too difficult. The most popular size battery for vintage Mustangs is a Group 24. Most small-block V-8-powered cars with 260, 289, 302, and 351W/C engines came with a Group 24-sized battery.
When big-block Mustang production started in 1967, they were mainly equipped with dimensionally larger Group 27 batteries. Thus any '681/2-'70 428 Cobra Jet car was equipped with a Group 27 battery. Anything larger was relatively unusual in the realm of early Mustangs. The huge Group 29 battery mounted in the trunk on '69-'70 Boss 429s is the most notable exception.
Most of the time when shopping at an auto parts store, you'll be steered to a Group 24 battery for almost all small- and big-block V-8 Mustangs, which usually works fine since the cranking amperage for modern batteries is considerably better than earlier batteries, regardless of size. For example, the Group 24 Autolite battery we purchased at a Kragen Auto Parts for our '69 Mustang project car has more cranking amps (835) than any Group 27 battery sold in 1969.
For a restored show car where appearance is important due to show judging, Antique Auto Battery offers raised-letter batteries that have hard-rubber script cases and correct Autolite red caps. AAB also has an epoxy-type material called Poly Tar for its reproduction tar-top batteries. It duplicates the appearance of the old-style tar material that got sticky, dirty, and sometimes leaked acid, but without these obviously undesirable qualities. For vintage Mustangs, AAB essentially has all the cars covered with G24FA, G27FA, and G29HR sizes.