Caravans or specialised trailers are often equipped with their own battery. This battery is used to supply power during standalone operation without a towing vehicle. Power is required, for example, to operate auxiliary devices such as manoeuvring aids, refrigerators, interior lighting, winches, etc.

During driving, the trailer’s battery is charged via the so-called charge line. However, when the towing vehicle’s engine is switched off, there is a risk of discharging the towing vehicle’s battery.

For this reason, a voltage monitor was previously installed in the charge line. This ensured that the charging connection was established only when a defined minimum charging voltage was reached. Similarly, the connection was interrupted when a defined minimum cut-off voltage was reached. In some wiring harnesses, this charge line function with a voltage monitor was already fully integrated. However, in most cases, an additional extension kit (e.g. article number 22400509) was required. This resulted in additional costs for materials and installation.