Trailer brakes, breakaway systems and battery indicators

Posted on 04 Mar 2015 by

First a caveat - the following is general information only and is not to be taken as legal advice or comprehensive, chapter and verse, detail on the rules relating to trailer brakes.

There, with that out of the way, here are some thoughts on trailer breakaway brakes.

The NSW rules require a trailer over 2 tonnes GTM to have brakes that can be applied from the driver's seat of the tow vehicle, and that can apply themselves automatically if the trailer breaks away from the tow vehicle, and STAY APPLIED FOR AT LEAST 15 MINUTES. The RTA guidelines can be downloaded at , and the RTA vehicle inspector bulletin (VIB6) can be downloaded  at  

The RTA NSW requirements also require the towing vehilce to be equippped with an electrical circuit to automatically maintain the trailer (breakaway) battery in a fully charged condition, and to be capable of warning the driver if the condition of the trailer battery is such that it MAY not be capable of meeting the requirements.

Now, applying a set of brakes for 15 minutes on a big caravan or heavy trailer is a tough task, and the batteries that do this are usually around 7 to 9ah capacity which, in perfect condition, might run a headlight globe for about an hour and a half, so you'd have to hope that the brake system doesn't draw more power than, say, 4 or 5 headlamp globes. If that wasn't enough, though, the other problem is the battery condition, which takes more than a voltage reading to check. This comes down to an analogy - if you take the lid off your petrol tank and smell petrol, how far can your car go on the petrol that you smell? I'm guessing that you know that you don't have enough information, you need to know how much petrol is in the tank, and the same is true of lead acid batteries. If you test the voltage on your battery and it reads 12.8 volts, is it any good? Nobody knows, because all the voltage tells you is that there is a battery there and it doesn't have failed/shorted cell, it tells you nothing about the capacity of the battery, or the usable power stored within the battery. The real test is to apply a load to the battery and see what happens then. A good battery will withstand the load that it is expected to handle, and a weak battery will drop voltage quickly, even if it starts at a (fully charged) 12.8 volts.

We hear people complaining about regulations, and how the trailer braking rules are making life difficult, and people also say that if your trailer has broken away, things are probably going to happen a lot more quickly than the next 15 minutes but, regardless of whether that is true or not, it is important to adhere to the rules, and it is a requirement of the trailer registration process that these things be checked. We'd much rather see this being done right, than it being done on the cheap in the hope that any effort is good enough.

Dealing with the issue of an indicator of battery condition first, we aren't keen on LED lights that do nothing except indicate the presence of a battery, and we aren't keen on voltmeters that show the voltage of the breakaway battery. Neither provides the information that you need. What we do like is the Breaksafe 5000/6000 combined with the RM6000 remote monitor. This setup basically has the breakaway system components talking to each other, a simple way of keeping the (integral) battery charged from the tow vehicle, an additional way to keep it charged from the trailer battery system (if there is one) which keeps the battery in a good state of charge when the trailer isn't being towed (otherwise it will be deteriorating all the time it is below peak voltage) and, cleverly, the system automatically disconnects the charging system, briefly, each time you press the brakes, then applies a load to the breakaway battery to check it is capable of withstanding a load, and then gives a green light if all is good, and a red light and 10 second buzzer if the trailer breakaway battery isn't good. 

Easy for an appropriately skilled person to fit, easy on the pocket and, we think, an appropriately well thought-out solution to meeting the RTA requirements. Call us on 02 9970 6996 if you'd like to chat it through, or to order parts. We do a roaring trade in breakaway units, and each one we sell is going to make the roads just a little safer. Lovely!