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RBM+ Relay Booster Module 12V/24V

The RMB + relay booster module is an optional upgrade kit for the IBS-DBS and DBi-DBS dual battery systems. With IBS-DBS and DBi-DBS, an emergency start from the on board battery (Aux) is always possible if the starter battery outputs 8.5V or more voltage and if the on-board battery has enough charge. With well-maintained and regularly charged batteries, an emergency start without RBM + is possible at any time. If vehicles are driven in hard use, vehicles are on ferries or in the container or the headlights have been forgotten to be switched off, it can happen that the starter battery is discharged below 8.5V due to excessive discharge, cell closure or defective battery housing. In this situation, an installed RBM + helps to be able to carry out an emergency start from the on board battery (Aux) despite the bad starter battery condition. RBM +  extends the range for emergency starting when the starter battery is charging from approx. 8.5V to approx. 5.5V. For an emergency start, the charge on the aux battery should be between 50% and 100%, depending on the size.
The RBM + function is integrated in the IBS products IBS-DBR and IBS-DBM20A and an RBM + is no longer required.


RBM + (Relay Bosster Module +) was developed for applications with very high temperatures and replaces the previous model RBM.
The RBM + (Relay Booster Module +) enables a link start from the on board battery (Aux) even if the starter battery fails completely. RBM + is integrated into the installation next to the IBS 200Amp relay. The RBM + improves the link start support by 100% if the auxiliary battery has a sufficient charge.


  • RBM+: for all new IBS-DBi-DBS and DBS, DBi/12V/24V systems (marked with the logo uC).
  • RBMKIT: for all systems BM3, DBi-DBS, DBi/12V/24V without microcontroller.
    The existing 180A Nagares / IBS relay has to be replaced by the new IBS 200A high-power relay contained in the kit.

In the case of a deep discharge of the starter battery (start up of engine from starter battery is no longer possible), the "Link" button on the IBS battery monitor (IBS-DBS/BM3 or DBi-DBS) is pressed. With the support from the RBM+ at starter battery voltage below 10V the start of the engine from the on board battery (Aux) would be activated.

In very cold weather or when starting capacity is reduced the RBM+ supports the relay to make sure the contacts stay properly closed during link start, this extends the relay life.

The IBS Dual Battery System DBS with RBM+ only performs if at least one battery has enough remaining starting capacity for a start up of the engine.

New IBS Battery Monitors (BM with uC Technology) are equipped with a low battery alarm on both batteries. If this alarm starts to sound, then check your battery system before further traveling. If doing so the risk of having battery problems is very small and RBM+ is only there if things go totally wrong.

For best performance follow next steps:

    • use 25 or 35mm2 cabling between relay and batteries
    • The RBM+ should only be used with the wire as delivered
    • If the relay has not been replaced with stronger 200A relay, a link start with a dead starter battery may still be performed, but the relay might get destroyed. With diesel engines first glow (if possible) 2 times before cranking to reduce stress on relay.

    The RBM+ (Relay Booster Module) has been designed as system optimization for the IBS Dual Battery Systems (IBS-DBS and DBi-DBS). The standard system installed allows a manual link (for a manual link start) if the Starter Battery shows more than 8.5V. We learned in rare cases when the starter battery collapses due to extensive discharge or when cells shorten out the starter battery can go down to 5V. In this case if RBM+ is installed the car can still be started with the manual link function with the support of the on board battery (Aux) (best result are achieved if the auxiliary battery is in good shape and at least charged 50% or more).

    Best link start functionality is achieved if the power wires between the batteries are 25mm2. For winch application we recommend 35mm2 and for Rallye/Trophy/construction trucks 50mm2.

    The other Dual Battery System IBS-DBR needs no external RBM+, as this module is already integrated.

    Schematics of Dual Battery System IBS-DBS with RBM

    Relais Booster Modul RBM+