In the service of the environment: Alternative drive systems in commercial vehicles of Daimler AG - PART IV


Stuttgart, Germany, Jul 16, 2008

Quick-change battery system: The LE 306 and 307 E electric vans

In 1972 Daimler-Benz introduced the LE 306 electric van, equipped with a quick-change battery system: through a flap fitted on the side between the axles, the set of batteries, mounted beneath the cargo area, could be pulled out on one side, in no time at all, while on the other side a new set of batteries was being inserted.

The van, which was still from the Hanomag-Henschel range, could handle a payload of exactly one ton with a maximum GVW of 3.5 to 3.9 tons and a battery weight of 860 kilograms. Depending on the style of driving, one battery charge enabled a radius of operation of about 50 kilometers. The electric motor developed 35 to 56 kilowatts; top speed was 80 km/h, climbing ability was 13 percent. The electronic controls were from Kiepe. All in all, 59 units of the electric van were manufactured.

However, it turned out that the complex crosswise replacement system normally was dispensable. In the successor, the 307 E, the manufacturer contented himself with a lifting device incorporated into the battery holder which permitted removing the storage batteries downwards with the aid of conventional hoists. Each of the two battery sets generated 90 volts. With a payload of 1.45 tons the van attained a speed of 70 km/h and a climbing ability of 20 percent. The traction motor managed an output of 30 kilowatts. The braking energy could be fed back into the batteries.

The German postal service used 22 vehicles of this type in a practical test in Bonn in 1983. The results, however, were rather sobering: the energy costs were almost twice as high as the cost of comparable diesel vehicles. Another concern of the test, sponsored by the German Federal Ministry for Research, was to try out various methods of drive control and power transmission. A battery switchover device with electronic field control and hydrodynamic torque converter was tested as a more cost-effective variant compared with the usual electronic armature and field control with a fixed gear ratio. The third and fourth variants were a conventional manual transmission and an automatic transmission, respectively.

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