The 36-Volt Lead-Acid Powertrain in a Vintage Melex: How It Works, Why It Lasts

By Melex History Editorial Team

The 36-volt lead-acid battery pack

A standard vintage Melex 152 runs six 6-volt lead-acid batteries wired in series, producing 36 volts nominal at the main bus. The original packs were flooded lead-acid — the heavy, maintenance-required type that needed water topped up periodically and tended to off-gas hydrogen during heavy charging.

Three things determine how long a 36-volt lead-acid pack will last in practice:

Depth of discharge. Lead-acid batteries hate being drained below 50
percent of their capacity. A cart that gets driven into deep discharge
on every outing will eat its pack in two seasons. A cart that gets
charged regularly between outings can run the same pack for six or
seven seasons.
Charging discipline. Lead-acid batteries also dislike being left at
partial charge. Every meaningful discharge should be followed by a full
charge to 100 percent within twenty-four hours.
Water level. Flooded packs lose water through normal operation.
Topping up with distilled water every few months is part of the
ownership burden. A pack run dry can fail in weeks.

The fact that Siedlecki picked this powertrain in 1971 — and that it has remained essentially unchanged across the Melex catalog ever since — is a testament to how mature lead-acid technology already was when Mielec started building carts.

The DC series-wound motor

Melex carts use a DC series-wound traction motor — the same motor architecture that was used in industrial forklifts, trolley cars, and virtually every battery-electric vehicle of the era. The series-wound configuration produces high starting torque, which is exactly what a loaded golf cart needs when pulling out of a stop on a slight slope.

The motor itself has only two consumable components worth knowing about:

Carbon brushes. Spring-loaded blocks of carbon that ride against
the commutator of the rotor. They wear down over decades of use and
eventually need replacement. Replacement is straightforward: pop the
end cover, slide the old brushes out, slide new ones in, reinstall the
cover.
Commutator surface. The copper segments on the rotor that the
brushes ride on. Over time the surface can develop ridges or burn
marks. Light surface dressing with brush-seater paper restores it. A
badly burned commutator needs to be cut on a lathe — a more involved
job, but uncommon.

A series-wound DC motor on a Melex will run essentially forever if the brushes and commutator are maintained. There is no electronic control board to fail, no inverter, no power MOSFET to short. The motor is the single most durable component on the cart.

The solenoid contactor

The component most likely to fail on a vintage Melex is the main solenoid contactor. The solenoid is a single high-current relay that switches the full motor current on and off in response to the accelerator pedal. When the pedal is pressed, the solenoid closes; when the pedal is released, the solenoid opens.

Three failure modes are common, all of which a course mechanic could diagnose:

Welded contacts. Heavy current arcing during normal use slowly pits
the contact surfaces. Eventually the contacts weld together, and the
cart runs continuously regardless of pedal position. Replace the
solenoid.
Stuck spring. The return spring weakens with age. The solenoid stops
opening reliably when the pedal is released. Replace the solenoid.
Burned coil. The electromagnetic coil inside the solenoid burns out
from age or moisture exposure. The cart simply does not respond to the
pedal. Replace the solenoid.

A new solenoid costs less than a hundred dollars and is the single most common repair on a vintage Melex. Most owners learn to replace it within the first year of ownership.

Why this architecture has lasted

Modern golf carts increasingly use lithium-ion batteries, brushless DC motors, and electronic speed controllers. These technologies offer real benefits — lighter weight, longer range, lower maintenance — but they also reduce the cart's repairability. A modern lithium-ion cart with a failed controller is largely a junk vehicle until a manufacturer-specific replacement part is sourced. A vintage Melex with a failed solenoid is back on the road for under a hundred dollars.

Siedlecki's 1971 design choice — to use the simplest, most repairable electric powertrain architecture available at the time — turned out to be the choice that gave the brand its fifty-year operational lifespan. Carts that can be repaired with hand tools and generic parts get repaired. Carts that require manufacturer-specific electronics get scrapped.

For a collector evaluating whether to buy a vintage Melex, this is the single most important fact: the powertrain is designed to be fixable, by design, and that design is the inventor's contribution to why so many examples survive today.

Frequently Asked Questions

What voltage does a Melex golf cart run on?

Standard vintage Melex carts including the 152 run a 36-volt nominal system using six 6-volt lead-acid batteries wired in series. Heavier-duty Melex variants such as the 412 utility pickup sometimes used 48-volt configurations.

How long does a lead-acid pack last on a vintage Melex?

Three to seven years, depending heavily on depth-of-discharge discipline and charging habits. Owners who charge after every use and avoid deep discharges routinely get six or seven years from a pack. Owners who run the pack into deep discharge regularly tend to replace after two or three years.

Can a vintage Melex be converted to lithium-ion?

Yes. Drop-in 36-volt lithium-ion replacement packs exist and require no motor or controller changes on the original Melex architecture. Most owners report 40 to 60 percent more range, no water-topping maintenance, and 20 to 30 pounds of weight savings after conversion. Cost is typically $1,500 to $2,500.

How do I know if my Melex solenoid is failing?

Common signs include the cart running continuously without pedal input (welded contacts), the cart failing to respond to the pedal at all (burned coil), or intermittent surging (weak return spring). Replacement is the standard fix and costs under one hundred dollars in parts.

Are the original motor brushes still available?

Yes. Replacement carbon brushes for the DC series-wound motors used in vintage Melex carts are available through general golf-cart parts suppliers and through specialty motor-rebuild shops. Brush replacement is a 30-minute job and typically extends motor life by another decade.

Why didn't Melex use brushless motors or electronic controllers?

Brushless DC motors and electronic speed controllers were not commercially mature in 1971 when Siedlecki designed the original cart, and they remained expensive through the 1980s when Melex was at its production peak. The decision to use a series-wound DC motor with solenoid switching was the conservative engineering choice — and turned out to be the choice that gave the brand its long-term repairability.

Conclusion

The 36-volt lead-acid powertrain that Stanislaw Siedlecki specified in 1971 was, in retrospect, the right call for a vehicle that needed to last fifty years. Modern golf cart designs are faster, lighter, and more efficient — but a vintage Melex with a healthy battery pack, fresh brushes, and a working solenoid will outrun a comparably-aged modern cart in one specific way: it will still be running. For owners willing to invest the modest maintenance burden, that's the real value of the original architecture.