BATTERY FACTS
If you are shopping for a new battery, it is usually because your last one is failing. Why did it fail? The number one answer to that question is NEGLECT. Premature failure of a battery often has very little to do with the brand of the battery. Once you get past the first week all automotive starting batteries should far outlast their advertised pro-rata warranty period IF you treat them right.
What does that mean? How do we treat a battery right?
Batteries MUST be used as they were designed to be used, or they will perform badly and quickly fail. You must keep starting batteries close to fully charged ALL the time.
Most automotive type starting batteries are intended for STARTING duty. They are sold by Group Size and rated in Cold Cranking Amps. When we go shopping for a battery we want the best we can afford. Most of us will look for the highest CCA rating that will fit in the brackets. But simply buying the highest CCA rated battery is probably NOT the best choice for your tractor battery.
How do you use your tractor? If it often sits for several days, weeks, or even months between chores, the battery with a lower CCA rating is often the better choice! Why? In order to get maximum CCA ratings, the lead plates must have a very high surface area. Lead plates designed for starting duty are thin, light, almost sponge-like. In normal starting duty, starting the engine only draws down about 3 to 5 percent of the charge. Then, the battery is immediately recharged by the charging system. We rarely use more than 5 percent of the capacity in a typical starting battery and the battery is in this slightly discharged state for a VERY short period of time. HOWEVER, when you let that same battery sit for several days, weeks, or months, it will self-discharge as much as 5 percent per week! After only two weeks some batteries will be at only 90 percent charge. This is called "Deep Cycling" and the thin lead plates are not designed to do that. They simply are not made to withstand the rigors of deep-cycle duty, and will quickly start to fail!
The battery with a lower CCA rating is going to be a slightly less aggressive design. The lead plates should be more forgiving of the occasional foray into a deep-cycle mode of operation. I generally buy the less-expensive batteries, and I have always gotten good service out of my batteries. I have three 48-month batteries in service right now that are all well past their warranty, one is over 10 years old!
True Deep-Cycle batteries are rated in Amp-Hours and are usually much more expensive than starting batteries. A deep-cycle battery is a better choice for your tractor from a performance standpoint, but maybe not for a reasonable cost. Some MARINE and TRACTOR batteries are a hybrid design that falls somewhere between starting duty and deep-cycle. These types of batteries should be a little more forgiving of an occasional deep discharge than a typical automotive starting battery, but they are also more expensive.
BRAND NAME MYTH
Ask any group which battery they think is best, then step back and listen to everybody argue about the merits of their favorite brand. This may be hard to swallow, but Brand Name battery quality has a lot more to do with what part of the country you are in than what brand you buy.
Paying more money for a particular brand name generally just buys a label. The vast majority of all brand name batteries in the United States are made by just TWO battery manufacturers. It is a very good bet that your favorite brand name battery was manufactured by either Johnson Controls or Exide. In fact, many of the popular brand name batteries are made by BOTH Johnson Controls and Exide. The only real difference in many of the familiar brand name batteries sold by the national retailers is the color of the plastic and the decal or logo printed on the case! Batteries are ordered by retailers in large quantities from the manufacturers. Those orders and contracts often vary by region and frequently change. So there is no guarantee that the DieHard currently in the store was made by the same manufacturer as the one in your car.
All automotive batteries sold by every major retailer should last about as long as their warranties say they will last, PERIOD. Treat any manufacturer's battery just a little better than average and it will last MUCH longer.
AGE is MUCH more important than Brand Name. A battery might be new to you, but it could have been sitting on some dealer's shelf for a couple of years. Buy your new battery from a place that sells a lot of them so they turn their inventory over frequently. You can check for yourself. All automotive batteries shoudl have date codes stamped in the case that will tell you the date of manufacture. Look for something like a letter (A = January, B = February), and then a number (7 = 2007). Don't buy a battery that has a "BORN ON" date more than six months old.
THE CONCRETE FLOOR MYTH
A concrete floor is no better or worse than any other common flooring material for modern batteries in plastic cases. All automotive type Lead-Acid batteries DO self-discharge over time regardless of what you set them on. For some types of batteries this self-discharge is as much as 15 percent per month! Even if you put your battery on a charger once or twice a month, your could be dipping into a deep-cycle type of operation. I still try not to set batteries or anything else directly on the floor. It is much easier to clean if everything is stored on a sturdy shelf.
Here is a voltage chart for a 12 volt battery. It indicates the relative charge for each volt reading. These are static readings with the engine off and no-load on the battery.
Divide the voltages by 2 for a 6 volt system.
IN CLOSING - My tractor is rarely used more than 2 or 3 times a month and can occasionally go two months without being started. So, MY choice is to buy the least expensive automotive starting battery I can find. When there is a choice, I choose the lower CCA rated battery. I never buy PREMIUM name-brand batteries.