The batteries in a golf cart are such an important part of the operating equipment that I think their role is often underestimated. Keep in mind that, right now, I am talking about conventional lead-acid batteries (the ones that for years and years have come as standard equipment in a new golf cart). These batteries are unique and have some special characteristics about them and some special needs. To try to stick some other kind of battery in there to replace them with (usually price motivated) is rarely a satisfactory solution.
The most common attempt is to try to replace them with much less expensive Marine type deep cycle batteries (3, 12 volt batteries instead of the original 6, 6 volt batteries). They will make the cart run, but with a whole new personality. This type of battery is designed to have a relatively low amount of energy used out of them for long periods of time and even to be almost fully discharged before the energy is replaced (recharged). One of the ways that these batteries are used is to operate trolling motors. They draw a relatively small amount of current. Just cruising around at a slow speed, the motor might draw more like 10 to 30 amperes, but need to be able to do it for hours and hours, between charges. This is basically the opposite of a golf cart battery, which is designed to have larger amounts of energy taken from them for shorter periods of time and to have the energy replaced right away. When you fist put the pedal to the metal in your golf cart, current can surge to over 200 amps. Trying to reverse their roles in life (lead acid and GEL types) not only adversely affects the performance of the golf cart, but also distracts from the life expectancy of both types of batteries. One of the main reasons for this is because most people stick with the original cart’s charger, and the optimal charging routine is quite different for each of them.
The original chargers that came with early golf carts were only “automatic” in that they had a knob on them to set the charger to shut off after a selected time of charging had lapsed. How much current was being supplied to the battery and at what voltage it was driven by, was totally controlled by the charge state of the batteries being charged. When you first turned the charger on, the batteries would represent quite a low resistance (impedance) to current flow, so the charger would “give it everything it had” to supply the current (I = E / R where I is current, E is voltage, and R is resistance). As it did this, its voltage would be pulled down to whatever it could provide. As the charge continued and the batteries accepted more and more current, the current flow would lower (because the resistance of the batteries would rise). With the reduction in current flow, the charger’s voltage is pulled down less, so the voltage increased. As the charge cycle continued, the current would continue to lower and the voltage would continue to increase until the mechanical timer that was set with the knob timed out and the charger shut off. Once again, the amounts of voltage and current were determined solely by the resistance that the batteries offered to the amount of current flow, and of course, the limitations of the charger. If the charger was left on too long, the batteries could be “over-charged” and damaged. Large amounts of electrolyte could be “boiled out”.
As time went on, manufacturers wanted to make the charger more “user friendly” and have the charger shut off automatically when the batteries were reasonably charged, so they added an automatic charger “board” (circuit board) to the charger. It would monitor the voltage during the charge cycle and after the batteries had reached the point where the voltage got up about as high as it was going to get, and stayed there for a calculated amount of time, the charger would shut off without any user assistance. This was a huge improvement for battery performance and life expectancy.
However, for the most efficient charge cycle for lead-acid batteries, some things could be improved. It was discovered that if the charge cycle were broken into different phases, each of which had different purposes, more energy could be safely transferred into the batteries, and their life expectancy could be lengthened even more.
The first phase of the charge cycle is called the Bulk Charge stage. During this part of the charge cycle, the voltage and the current are allowed to “do their thing” kind of like the chargers mentioned above, with the resistance of the batteries pretty much setting the voltage and current levels (with some limitations built in to prevent overheating the batteries). This phase constitutes roughly 80% of the total charge cycle.
The next phase is called the Absorption Charge stage. In this part of the charge cycle, the voltage is held at a constant value and the current is allowed to vary as the condition of the batteries improves. This phase is allowed to continue until the charge state of the batteries is up to about 90% of its completed charge.
The next phase of the charge cycle is called the Float Charge. In this part of the cycle, the voltage is lowered and the current is allowed to “trickle” to complete the charge cycle.
Another phase that may or may not be part of a complete charge cycle, depending what kind of charger is doing the charging is called the Equalization Charge. It is where the batteries are intentionally “overcharged” at a slightly elevated voltage in order to promote de-stratification and de-sulfation, two conditions that are detrimental to the performance and life expectancy of lead-acid flooded cell batteries .
In order to facilitate and control these phases, manufacturers came up with “smart” chargers. These are microprocessor controlled chargers which sense and dictate voltage and current levels during the charge cycle. There are many different makes and models of these and it can be confusing trying to select the right one for the application at hand. Most of them now have a way to select the type of batteries that are going to be charged. That is very important because there is a big difference in how these phases of the charge cycle need to be handled for different types of batteries.
With the advent of GEL filled batteries and absorbed glass mat (AGM) type batteries, the rules about how to adjust voltage and current during the charge cycle all changed. They are real picky about not being overheated or held at too high of a voltage for any length of time. If the voltage, which is the driving force for the current flow into the batteries during the charge cycle, is raised too high for the batteries to accept the amount of current being supplied, the electrolyte (gel) can actually get dried up in the process. Major damage can occur in just a short time. The maximum voltage used and the heat developed in the batteries must be limited. They require a different algorithm to be used by the processor.
Bingo, another reason for not trying to use the lead-acid type and these newer type batteries interchangeably, without addressing the charger that is going to be used with the batteries. Unfortunately, most people who consider this changeover (GEL or AGM for lead-acid) don’t even consider this aspect of the equation. So, the old charger doesn’t match the correct configuration at all, so the batteries are not charged in a way that will provide them with optimal performance or life expectancy.
Fortunately, some of the newer chargers can be “set” to accommodate a variety of different types of batteries. Some of them have switches that must be configured according to the owner’s manual, or some other of method of telling the charger what type of battery it is dealing with, but if you still are using the original charger that came with the cart, it probably doesn’t match what you need.
Put it altogether, and this idea of just saving a few bucks by sticking some cheaper marine batteries in a golf cart to replace the lead-acid type is VERY problematic.
For information about books written by Ron Staley about both electric and gas driven golf carts and their repair, visit the following links.
Electric Golf Cart Repair, both as an eBook and in Hardcopy:
Book: Ronald L Staley: 9780578560557: Amazon.com: Books
Gas Golf Cart Repair, both as an eBook and in Hardcopy:
Gas Golf Cart Repair Book: Ron Staley: 9798987911303: Amazon.com: Books