For a while, everyone was talking about the 42-V-system. Now one hardly hears anything more at all, probably in view of the enormous conversion costs. One tends to forget that utility vehcles have been driving around for ages, with at least half that amount of tension. After all, 24 V of nominal tension, means, approx. 28 V of on-board voltage, if the generator is charging well.

There used to also be systems which were partly 12-V. This of course, meant higher costs, e.g., for the manufacturers, instead of being able to use an off-the-shelf part fitted out with twice the voltage. Refitted devices were also accordingly expensive.

If then, by using special circuitry, it is possible to switch over from 12 to 24 volts, only the starter is supplied with the higher current, which is due to the size and the compression in Diesel engines. Thus, two batteries, which change over from a serial- to a parallel switching after the start procedure, are necessary.

If then, any wise-guys discover two 12-V-batteries in the battery housing, they might get the idea of buying a 12-V-device and connecting it to only one of the serially switched batteries. The worst thing about crackpot ideas like this, is that, in the beginning they actually do work.

In this case, the device would have to be installed unearthed, e.g., between the casing and the vehicle. Then the sparks would really fly, because then, in the apparently unaffected battery, a possible unfused short circuit could occur. However, as always in such cases, the dummies don't give up and insulate the device reliably.

Indeed, their satisfaction is only short lived. Try to imagine the charging of two serially switched batteries. The same current passes through both batteries, whereby the charging difference is generally not compensated. It would have to be charged for a long period, way over the gassing limit, to enable the charging to occur and through additional heating of one battery, only benefit the other one.

As you can see, it wouldn't take long before one of the two batteries collapses, whereupon both batteries would have to be replaced. A very high priced 'money-saving'. The solution: compare the price of a 24-V-system with that of an additional device ... 11/12