Camper and motorhome

Motorhome power distribution.Charging, distributing, protecting.

In a motorhome, three energy sources feed one house battery: the alternator, shore power and often solar. From there, a switch panel distributes power to the consumers. To make this work reliably and safely, every cable needs the right cross-section and its own fuse, with the main fuse no more than 17.8 cm from the positive post.

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Motorhome power distribution: charging, distributing, protecting
  • 12 and 24 Vmotorhome systems
  • 17.8 cmmaximum to the main fuse
  • 3 %voltage drop for key circuits

The building blocks at a glance

ComponentTaskAt philippi
House batterysupplies the living area, separate from the starter batteryLithium batteries BullTron and Super B
DC-DC chargercharges the house battery from the alternator while drivingDCB DC-DC chargers 12 V and 24 V
Charging relayconnects starter and house battery when the alternator chargesACR 12/24 charging relay
Battery chargercharges from shore powerACE battery chargers
Switch paneldistributes and protects the consumer circuitsSTV 200 vehicle panels
Main fuseprotects the cable from the positive postTerminal fuse SHB, Class T

Charging while driving: DC-DC charger or charging relay

A charging relay connects starter and house battery in parallel as soon as the alternator charges. This is simple, but it only passes on what the alternator delivers. Modern vehicles regulate the alternator voltage variably, so often too little reaches the house battery. A DC-DC charger charges the house battery with its own profile and the right voltage, also for lithium batteries.

The cable to the DC-DC charger carries high current over several metres. The cable configurator calculates its cross-section and the fuses at both ends.

Charging while driving: DC-DC charger or charging relay

Distribution: switch panel instead of fuse box

A switch panel combines switches, fuses and displays in one place. Each consumer circuit gets its own protection matching its cross-section, with fridge and heater separate from lighting and sockets. The series 200 vehicle panels are available in several versions. To see and switch battery, tanks and consumers on one display, use the PCU control unit.

Distribution: switch panel instead of fuse box

Protection: the rules from boat building

Motorhomes have no dedicated standard like ISO 13297 for boats. The principles can be transferred directly, however:

  • Main fuse: no more than 17.8 cm from the positive post, ideally directly on it.
  • Lithium batteries: only the SHB terminal fuse or Class T at the post, because of the very high short-circuit currents.
  • Every cable: protected according to its cross-section, not the device.
  • Voltage drop: at most 3 percent for fridge, chargers, DC-DC chargers, inverters and heater.

All fuse types and their breaking capacity: fuses at a glance. The capacity calculator determines the battery size you need.

Protection: the rules from boat building

Matching products.From our range.

View all ›
DCB 12V charging booster DCB 12V charging booster635,00 €View › DCB 24V charging booster DCB 24V charging booster635,00 €View › ACR 12/24 isolation relay ACR 12/24 isolation relay150,06 €View › Battery Charger ACE 12/30 Battery Charger ACE 12/30449,00 €View › Bulltron LI185B200-12-P Bulltron LI185B200-12-P1.649,00 €View › Lithium Battery SB 12V105E NOMADA Lithium Battery SB 12V105E NOMADA1.759,00 €View › Control panel STV 204 Control panel STV 204147,00 €View › SHB fuse SHB fuse15,51 €View › Flush-mount standard socket with hinged lid ESD 12/24 Flush-mount standard socket with hinged lid ESD 12/246,35 €View ›

Categories.The full range.

Frequently asked questions.Short answers.

Do I need a DC-DC charger in a motorhome?

In modern vehicles with variably regulated alternators usually yes, and with lithium house batteries almost always. A charging relay only passes on the alternator voltage; the DC-DC charger charges with its own profile matched to the battery.

How do I protect the house battery?

With a main fuse no more than 17.8 cm from the positive post, ideally directly on it. With lithium, only with an SHB terminal fuse or Class T. The rating depends on the cross-section of the main cable.

What cable cross-section do I need for the DC-DC charger?

That depends on current and length, as the outgoing and return cable both count. At 12 V and 3 percent voltage drop, 16 to 35 mm² quickly add up over several metres. The cable configurator calculates the exact value for your charger.

Do I need a battery main switch?

It is strongly recommended: it disconnects the house battery during storage and for work on the system. It does not replace a fuse, however; both belong together.

Read more.In the philippi Academy.

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