Take care when adding hydraulic attachments to new electric forklift trucks

If you’re in the process of ordering an electric forklift truck with a hydraulic attachment you need to take special care. Unless it is correctly specified and fitted, you could cut the operating life of your battery by 50%.

Read on and we’ll tell you how a leading company discovered, to its cost, the problems caused by a mismatch between truck and attachment … what caused the problem… and what you can do to avoid it happening to you.

Correctly specified and fitted attachments increase a forklift truck’s productivity.

Increasing functionality

With the cost of fossil fuels rising dramatically and legislation in at least one European country outlawing the use of diesel trucks indoors, demand for the new generation of AC powered electric forklifts is growing fast. Matching that increase is a continuing trend towards powerful, productivity-boosting attachments such as clamps and rotators… The result is a truck that is truly multifunctional – a major benefit in these tough economic times.

But using a powerful attachment requires a battery of sufficient capacity – and precise tuning of the hydraulics – or there may be problems.

Let’s look at a real-life example… A well-established company decided to fit a bale clamp to its existing truck. Everything went well for a while… but pretty soon the shift life was falling significantly – even though the battery was barely two and a half years old.

Identifying the problem

First, the truck was thoroughly inspected… then the attachment… followed by the battery and charger. Close investigation showed that the battery was discharging power much too quickly when working with the clamp. This is very harmful for a battery and was the reason why the battery capacity and life were being affected so severely.

The problem was twofold: a cylinder in the clamp was too big and the pump capacity set for the truck meant the hose diameter was too small. (Note: some trucks generally have slightly slimmer hydraulic hoses for third service connections and this increases resistance. But because the truck owner wanted a fast-acting clamp, the pumping power had been set at maximum. Unfortunately this only compounded the problem as the excess of hydraulic oil actually aggravated the problem by suffocating the flow.)

Preventing a mismatch

As the company in question discovered to its cost, the secret to obtaining the optimum performance is accurately matching the hose size with the volume of the attachment’s cylinders and the truck’s pumping and battery capacities.

Sounds straightforward but, according to a leading attachments manufacturer, it is often difficult to find out how much power the attachment actually needs. A clamp, for example, pulls a greater load than a fork attachment, because it needs higher pressures and more oil. However, there are other factors which are unknown to any supplier – such as intensity of use. The truck has an hour meter… but that doesn’t show how often the attachment itself is in action.

‘Remarkably, nobody ever asks us how much power our attachments will use – even though everyone knows they affect energy consumption!’ said a spokesman. ‘One of the most common mistakes is setting the pumping speed too high. As a result, some of the oil goes to the attachment but a lot of it goes straight to the tank. Reducing the pumping speed doesn’t affect the operating speed of the attachment but does affect the amount of energy consumed…’

And that’s critical because the trend is towards lighter duty batteries thanks to AC technology which means trucks use less energy than previously. A smaller battery is less expensive and can be highly efficient… but is more vulnerable to peak loadings.

Our conclusion

Best practice is to fit a high capacity battery since this also benefits the battery’s water consumption and temperature – helping maximise its operating life while reducing the costs of recharging.