Boosting a dead battery in a truck or tractor and allowing the alternator to restore its charge could shorten its life. In fact, some battery information sources suggest doing that just 10 times will kill a standard vehicle-starting battery. (Deep-cycle batteries, however, are a little different.) Taking steps to keep your battery’s voltage up and prevent it from fully discharging can extend its life.
When farm trucks or self-propelled machines are put into storage for winter — or any extended period — their batteries will slowly begin to discharge, even without parasitic drain from the machine’s electrical system. A battery will typically lose one per cent or more of its charge per day through natural self discharge caused by a chemical reaction inside the cells. During winter storage that causes another risk: freezing.
The electrolyte in a fully-charged battery consists primarily of sulphuric acid, which is resistant to freezing except at very low temperatures. In a fully-discharged battery, however, the electrolyte has a high pure-water content allowing it to freeze in much less severe conditions. At just -7 C, electrolyte in a fully discharged battery could freeze. Compare that to about -67 C when at 100 per cent charge.
When a battery is discharged, lead from its plates and sulfur from the electrolyte combine to form lead sulfate on the plates inside the cells. If it’s left in that state, the sulfate becomes dense and hard. It then cannot be converted back to its normal state through charging. This inhibits the normal chemical reaction required to produce electricity and can gradually reduce a battery’s ability to take a charge or deliver voltage, eventually rendering it unusable. When that happens, the battery is said to be “sulphated.”
Taking batteries out of vehicles during winter storage and putting them somewhere where they can’t freeze and can be frequently recharged will prevent these problems. But that involves some work. And just hooking them up to an economy trickle charger could be just as lethal. If the charger doesn’t cut out when full charge is restored, which seems to happen far too often, it will permanently damage the battery.
If you use AGM (Absorbed Glass Mat) or gel-cell batteries rather than standard wet, lead-acid types, they have special recharging requirements and an older battery charger could damage them or fail to recharge them properly.
There is a better alternative to the typical trickle charger in almost every farm shop. The “smart chargers” that have hit the market in the last few years are well suited for long-term maintenance charging. They will safely recharge and keep batteries in a fully-charged condition if you go away and forget about them — although manufacturers still recommend that charging batteries be checked at least weekly to ensure nothing has gone wrong.
Smart chargers are also generally compatible with AGM or gel-cell batteries and they can also be used on ATV or lawn tractor batteries when set to a lower output. Most popular smart chargers are even capable of reconditioning some sulfated batteries — if they’re not too far gone. But if you test a 12-volt battery that reads nine volts or less when not under load, it’s probably nothing more than dead weight. Just replace it.
The primary difference between ordinary trickle chargers and the newer smart, maintenance chargers is the way they increase battery voltage. Smart chargers are microprocesor controlled and use a four-stage process to bring batteries up to 100 per cent charge. After restoring full voltage, smart chargers continue providing a small current that is slightly higher than a battery’s fully-charged voltage rating, usually around 0.1 volts more. That small amount, however, won’t cause the electrolyte to begin gassing off and keeps the battery topped up.
With some newer vehicles, you may need to disconnect the battery before using an ordinary charger in order to protect the high-tech electronic circuitry. But smart chargers won’t damage sensitive electronic systems — at least, so their manufacturers claim.
Some smart chargers are waterproof and vibration resistant, so they can be permanently installed on a vehicle and just plugged in like a block heater when the machine is parked in storage. If you prefer to put all your equipment batteries together inside the farm shop for the winter, some models can handle a bank of several different batteries at the same time.
A smart charger capable of handling one battery at a time can run you $80 to $130. There are several on the market. †