A commonly asked question in the golf cart industry is “how do I convert a 36V golf cart up to 48V”? At first thought, this may seem like a simple question, but there is more to this conversion than many may think.
Within modern golf carts, there are three basic classifications of common electrical systems present at the 36V voltage level.
36V series wound with electronic speed control,
36V series wound with resistor coils, and
36V separately excited with electronic speed control.
There are also AC powered systems now available in the golf cart market and at www.golfcarcatalog.com, but they are all 48V or higher and are significantly harder to modify than the systems I’ll cover in this article.
In this short article, I cannot cover all of them, so although I may touch on each, I will for the purpose of this tutorial, focus on 36V DC systems with either a “series” wound or “separately excited” motor and controller.
The 36V DC series wound system with resistor coils was the original design of early electric vehicles and golf carts dating back to the late 40’s and forward all the way until
the late 80’s when electronic speed control technology was “borrowed” by golf cart manufacturers from the material handling industry (i.e. scissor jacks, electric forklifts, etc.). This system employed a speed control “wiper” board connected to the accelerator pedal. When the pedal was depressed, it would move a wiper arm with contactor across a series of stationary contacts on the board. Each contact was connected to a resistor coil and then ultimately to the motor. By using resistor coils in series which have successively less resistance than resistor before, more power could flow to the motor, thus increasing the speed. Primitive? Yes, but effective and simple. However, although it is possible to upgrade these vehicles to electronic speed control at either the 36V or 48V level, I would not recommend it due to the cost associated with the conversion.
You can buy a modern 48V cart for far less money than the conversion.
That being said, let’s move on to 36V DC separately excited and series systems with electronic speed control. I should first explain the terminology of “separately excited”
vs. “series”. Whereas a typical DC powered ”series” motor has power that flows in series in one side and out the other, a separately excited motor has power applied separately to the armature and field. This allows for many unique features that DC series wound motors cannot provide such as regenerative braking, roll away protection, and others. Those are all complex topics for later tutorials. Without getting into manufacturer specifics of Club Car, E-Z-GO, Yamaha and others, upgrading a 36V DC separately excited system from 36V to 48V is generally possible, yet slightly more complicated and costly than a 36V DC series system.
• Upgrade controller: This is one of the largest expenses of the upgrade. Typically,
since separately excited systems are more manufacturer design specific, they are rated for an exact voltage rather than a range. More often than not, series controllers are rated for a voltage range, such as 36-48V. If so, you can keep the same controller, save lots of money, and just run a higher voltage through the unit. If not, the controller must be replaced in the upgrade with an aftermarket substitute rated for that voltage (Alltrax, GE, Curtis, and others are available from www.golfcarcatalog.com).
• Upgrade solenoid: Solenoids are high amperage switches typically installed between the battery bank and controller. They are much less expensive than controllers and are designed to fail rather than the controller in a surge situation. Generally, they are voltage specific so if upgrading from 36V DC to 48V DC, you’ll need to source a 48V solenoid rated at the same level as your controller’s current (amperage).
• Upgrade solenoid diode and resistor: Most golf carts with electronic speed control have a diode across the small terminals of your solenoid and a discrete pre-charge resistor across the large terminals. Each time your solenoid is engaged or disengaged, there is an internal spark although you do not see it. The pre-charge resistor is used to dissipate this spark in the form of heat to prolong the life of your solenoid contacts. At the 36V level, a 220-250 ohm resistor is common, while if you upgrade to 48V, you need to source a 470 ohm resistor as the replacement. The diode is installed across the smaller terminals as polarity protection. A diode is a one way gate for electricity. So, it effectively prevents power from flowing in the wrong direction and damaging components. Controllers under the 300 amp level use a 1 amp diode while anything larger uses a 3 amp diode. Be sure to size your diode according to your controller amperage.
• Upgrade motor: Most DC motors, whether series or separately excited are rated for a range of voltage such as 36V-48V. Be sure to check your motor rating. If it’s rated for up to 48V, it does not need upgrading. If it is not, you’ll need to source a 48V separately excited or series motor, depending on your application.
• Upgrade batteries: Of course, to covert from 36V up to 48V, your battery bank must be changed. This can be accomplished in several ways. Be sure to tailor your battery bank to you application and needs. You can use four 12V batteries, six 8V batteries or eight 6V batteries. Be sure to note that the more lead present in your battery bank (lead acid only and weight aside), the further your distance travelled on a charge (range). Six 8V batteries will have a greater range than four 12V’s, while eight 6V’s will produce the greatest range of the three, all else being equal.
Last but not least, with any voltage change, regardless of the electrical system, a new charger must be sourced. A 36V charger will never fully charge a 48V battery bank regardless of how much time you allow. This is a large expense that many people often overlook. The voltage must match your battery bank exactly, although the charger amperage can vary. The higher the amperage, the faster the battery bank will charge, but also the greater risk of battery damage. Be sure to select your charger carefully based on the brand, voltage, amperage, and type of batteries you use.
So, now that I’ve covered the basics of how to upgrade from 36V to 48V, let’s wrap it up
with a brief word about what you’ll gain. The single largest misconception in the golf cart industry is that 48V cart will go further than 36V versions. You will NOT gain more range if you convert from six 6V batteries to six 8V batteries, but you WILL gain range if you use eight 6V batteries due to greater amount of lead. It all depends on your battery bank.
All else being equal you will gain more speed. If you increase the voltage to any electric motor, it will spin faster. The voltage change alone will NOT increase your torque; this
can only be accomplished through installing a 48V motor capable of higher torque, or installing a 48V controller with a higher current limit (amperage). When DC power is discussed, amperage equals torque and voltage equals speed. Both are also inversely proportional to each other. As one increases, the other decreases. Be careful and enjoy your 36 to 48V DC golf cart upgrade!
Michael Williams, Product Development Director, (www.golfcarcatalog.com)