12V Guru – Caravan Breakaway System Battery

Question to 12V Guru

Hi 12V Guru,

It was interesting to read the segment in issue 600 of Caravan World regarding the breakaway system batteries.

My Question is: Why does the manufacturer insist that we use a 7Ah battery when most vans have a minimum of 100Ah house battery? The only explanation I can find is that the system must be able to hold the brakes for a minimum of 15 minutes in the event of a breakaway.

When you consider that the 7 Ah battery must keep energised (usually) 4 magnets as well as the brake lights I find this to be hard to believe. Also when you consider that it is admitted the life span of the 7 Ah battery can usually be measured in months not years as the house battery, this system seems flawed in design. What are the implications of using the 100 Ah house battery instead? I note some vans actually do this.

John McNamara, Gold Coast

12V Guru answers:

Hi John, you have hit on one of my favourite topics – caravan safety breakaway systems! Many years ago, we took the BMPRO team to Queensland for the week on the road of research and better understanding market needs. One of the key findings from our research and countless one-on-one interviews was just how many RVers either did not understand their breakaway system or did not manage it at all.  In fact, if was quite disappointing to see the level of indifference that existed amongst travellers when questioned about their systems.

Caravan breakaway battery – out of sight, out of mind

What we discovered was alarming – most systems were installed in locations that were ridiculously difficult to gain access to or were in an empty cavity that encouraged “burying” the unit with pillows or spare bedding. The systems were not connected to a reliable charging source.  Many RVers thought that their system just charged when connected the towing vehicles AUX connection at the hitching point.  Upon inspection many were not even wired in this manner but even if they were, the battery inside could be dead flat before the start of the trip thus rendering it useless in case of emergency.

Finally, over 90% of those we met and interviewed had never run a system check or replaced the battery.  It was a matter of “Out of Sight – Out of Mind” which for a safety device sounds incredulous.

There are three angles to consider this on – size of battery, suitability, serviceability of system.

Breakaway system battery capacity

Picking up on your point regarding the battery capacity.  Out testing has shown that a fully charged and brand new 7Ahr battery does provide power to the 4 brakes and the brake LED’s for the required 15 minutes but only if the battery meets the first two requirements – NEW and CHARGED. 

As you rightly point out these batteries are cheap and last only a few months – especially when not maintained properly. Each brake magnet draws 3.6A and the total of the LEDs is at maximum 1A.  Therefore, the system would require 15A of power to turn on four electric brakes and the RV lights. The technical specifications of these batteries state that it will provide this power – but only just.  Not if the battery has not been regularly replaced or kept charged.

Breakaway system battery suitability

Secondly, suitability! These smaller 7Ahr batteries are not adequate. Safety systems should be designed with a margin of engineering and real-world safety – not to meet the minimum requirements because as the research proved, RVers don’t understand or maintain their vans essential systems.  You can certainly use a 100Ahr 12V battery – normally the house battery, if you have a breakaway system that is designed for this setup such as the BMPRO TrailSafe.

We would not recommend a simple substitution of batteries as this is not how the system would have been designed and therefore may operate outside its specifications. However, if your setup has been configured suitable to work with the house battery of the RV this provides a more reliable power source as it is more likely to be properly maintained and charged.

Breakaway system battery serviceability

And finally, serviceability.  Like all critical safety equipment such as brakes, bearings, wheels/tyres, couplings, SwayControl etc., the Emergency Breakaway system should be serviced regularly.  It is prudent to check the connecting cable, check the pull pin at the trailer hitch activates the system and that the battery is charged with the capacity to perform 15 minutes of activation before you start the trip.  Recommend systems that provide you with this feedback that everything is safe and ready when you are at the front of the A-frame hitching up the RV to the car.

Stay safe and hope you are never in circumstances where the Breakaway system needs to be used – 12V Guru.

safe towing: caravan breakaway system battery charged


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