We were requested to design and build a power management system to retrofit into a 2016 Hymer A-class motorhome.


The customer required to be off grid for long periods of time in hot climates. He needed a system that would allow him to use his Dometic Freshjet 2200 air-conditioning to keep the motorhome at a comfortable temperature.

2016 Hymer power management upgrade

2016 Hymer power management upgrade


The first stage of the installation was to disconnect all the existing battery charging methods as these would not be suitable to charge Lithium. This was done in such a way as to allow them to be easily reconnected if the Lithuim system was removed to return the motorhome back to standard.


We then installed an island system that was completely separate to the Hymer system. We installed a Victron Orion DC/DC transformer with an output voltage of 12.5 volts, this would fool the Hymer control system into thinking that there is a fully charged battery installed. This isolated converter also put a barrier between the Lithium battery and the Hymer system to ensure the battery was protected.


We installed the Victron 300ah Lithium Battery in a temperature controlled enclosure. We installed a blower fan that would operate automatically if the box reached 45 degrees to ensure the battery did not over heat


We installed a Victron 2Kva Multiplus charge inverter. This unit has a 2kva inverter and an 80 amp charger. This unit can also be set up to charge Lithium Ion batteries


We installed 580 watts of solar on the roof, due to the other items already installed on the roof this was the most we could fit. We achieved the 580 watt by installing 5 panels and connecting them in series. These were then connected to the battery using two Victron 100/30 MPPT charge controllers.


We installed a split charge system allowing any surplus alternator current to charge the Victron Lithium battery. This vehicle was fitted with a 130 amp alternator so potentially we could receive between 100 and 110 amps of charge to the Victron Lithium battery while the vehicles engine was running.


As this Motorhome is being used all year round unfortunately we could not rely on the solar alone to charge the battery. We installed a Dometic TEC29LPG generator in the garage area of the motorhome. We also installed 2 Alugas cylinders in the gas locker and 2 under slung gas tanks this gave a total of 110 litres of LPG. This LPG can be used to run the Dometic generator and all the heating and cooking requirements.


We installed a Victron BMV-700 shunt and monitor. The BMV 700 shows the battery level and charge and discharge currents.


To monitor the system we installed a Victron Colour Control. The Victron Colour control can perform many tasks, these include the following:
• It shows the AC input from shore power
• It shows the AC loads being used
• It shows the amount of PV being generated
• It shows the battery level
• Is shows the DC draw from the battery
• It shows the water and waste tank levels if fitted with a VE. Can resistive tank sender adaptor
• It can automatically start and stop the generator using programmable parameters. These include programmable quiet times, starting automatically when the battery reached a certain state of discharge and stop when the battery is recharged.
• Using a Wifi module it can be remotely checked to ensure the system is operating correctly, this includes history reports.


We also installed a Dometic Freshjet 2200 air conditioner to keep the customer cool