Liftgate problems solved by Trailchargers

Liftgates can be extremely useful, as they can be more efficient than ramps, allowing operators to be more effective. However, if electric-over-hydraulic mechanism is failed, by dead or dying batteries for example, then it becomes entirely redundant. At worse, it can be costly, as when the batteries fail when the gate is lowered, and it is unable to be raised, which can necessitate an SOS to a call-out service.

Drivers are often known to leave the engine idling, as this keeps the alternator rotating, which in turn keeps the auxiliary batteries charged. However, Bruce Purkey, president of Purkey's Electrical Consulting, observes that many local laws are legislating against idling engines. This leaves the batteries with sole responsibility for the liftgate, and the more often that a truck has to stop and start, the less time there is for the running engine to recharge the batteries. Given that a liftgate is useful for delivery trucks, such as midesize volvo trucks, this can present a problem.

It is vital to get the charging time correct; equally so to get the voltage quality right. Fortunately, there is a recommended practice, as proffered by the Technology & Maintenance Council of the American Trucking Associations. It kindly suggests that the batteries be powered by no less than a half a volt, regardless of the wiring's length. The problem with this is that long trailers can sometimes have gaps of up to 60 feet between the battery units. Even if it is not quite that long, it can still be problematic because resistance can be caused by a variety of other variables; incorrect wire gauges, fuses and loose connections. The voltage used for charging should be at least 14, if not more, but more often that not, according to data which Purkey collected, dips to 13.25. The lower voltage leads to a superficial charge, depletes battery life and can also damage some of the small motors inside the the lifting mechanism of the liftgate.

Purkey says that there are a variety of charging circuits available, each of which has their own pros and cons.

Single pole circuits entail an independent positive connection between the tractor and trailer batteries. The fifth wheel of the tractor acts as the ground, and so depends on the state of the fifth wheel, for example corrosion and dirt .

Dual pole circuits entail a positive cable and a negative cable, acting as connections between the tractor and trailer batteries, in cahoots with an insulated plug. The current is able to flow in both directions, and whichever battery has the lowest amount of charge will draw the current. The engine being started will catalyse the the trailer battery into trying to assist in powering the starter motor.

Reefer charging entails trailer batteries with parallel connections to the battery, which allows the the reefer engine to charge the batteries when it runs. Unfortunately the reefer can overload and then the voltage can drop. If the reefer unit is inactive, then there is no charging.


According to Purkey, there is a solution, and the solution is the Trailcharger, which is a DC to DC converter. The Trailcharger, made by SurePower Industries, will boost an input from between 9-16 volts, and will stabilise or correct it to 14 volts, which keeps the batteries properly charged. It is also capable of compensating for varying temperatures.


Trailchargers are available in 20 and 50 amp versions. In order to test which one will be most appropriate, Purkey says that you should factor in what is the heaviest load that they will handle, and then measure the amperes, and the time that it takes the motor to raise and lower the gate. The Trailcharger is located near the auxiliary battery, and is the wired to the charging circuit, whichever one is present.

Sometimes Purkey will add an 'extender', which is an electronic device that optimises the Trailcharger when used with a dual-pole circuit. When the engine is not running, the extender ensures that the trailer batteries are kept charged. It also ceases to take a charge for a period, in order to read the voltage available, and then decides whether to keep charging.

Purkey has installed hundreds of Trailchargers into a variety of vehicles, including volvo trucks, iveco trucks and renault trucks. The feedback has been universally positive, helping as it does to solve all of the most common problems inherent to liftgates.