Question on breakaway battery monitors

Submitted: Wednesday, Sep 12, 2018 at 15:30
ThreadID: 137242 Views:870 Replies:6 FollowUps:4
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I am building a van with a breakaway system but, being in NSW, I have to install a battery monitor which gives a visual and audible alarm if the breakaway battery goes low.
I have a Hydrastar electric over hydraulic system but the Hydrastar folks, being Queensland based, have no knowledge of breakaway battery monitors as they are not required there.
My question is, given that I have a big 400AH LiPo4 battery system going in with 990 watts of solar on the roof, do I need a separate battery for the breakaway system or can I run it off the house batteries?
I have a feeling I have to install a separate battery and connect it to the house batteries. If that's the case I'll put in a tiny LiPo4 to keep the charge and float thing compatible.
But does anyone know for sure?
Thanks in advance.
Keith
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Reply By: kgarn - Wednesday, Sep 12, 2018 at 16:48

Wednesday, Sep 12, 2018 at 16:48
Here is an extract from the NSW Vehicle Inspectors Bulletin
Requirements for large trailers equipped with electrically operated brakes
"The Road Transport (Vehicle Registration) Regulation 2007 requires that all trailers with a Gross Trailer Mass (GTM) exceeding 2 tonnes be provided with a braking system which will operate automatically and promptly upon breakaway
of the trailer from its towing vehicle, and that such application should be maintained for at least fifteen minutes.
Such trailers, if fitted with electrically actuated braking systems, must be equipped with a device which applies the brakes in the event of a breakaway from the towing vehicle and maintains application for at least fifteen minutes. It is
essential therefore, that an energy source, such as a battery, be carried on the trailer and that means be provided to ensure that the battery is maintained in a fully energised condition. In this regard, it will be satisfactory if any trailermounted battery is constantly charged by the towing vehicle and a warning device is fitted to warn the driver (from the normal driving position) if the trailer battery charge falls to such a level as to render the trailer brakes incapable of
meeting the requirements."


My reading of the requirement is that an energy source (battery) is required in the trailer but not necessarily a separate dedicated battery.
However that energy source (battery) must be maintained in a fully energised (whatever that means !!). It is stated that this requirement can be achieved by charging from the towing vehicle.
I am not sure that if solar panels on the van were the only means of charging the battery the requirement would be met. - If you were driving at night, there would be no charging of the battery even though you may be OK due to the 400Ahr capacity of your system.


Ken
AnswerID: 621169

Follow Up By: Frank P (NSW) - Wednesday, Sep 12, 2018 at 22:55

Wednesday, Sep 12, 2018 at 22:55
I agree with Ken's interpretation.

IMO, the document clearly states that, to be compliant, the breakaway battery must be charged by the tow vehicle when driving. So if you're using a 500amp hour lithium house battery supported by 700 watts of solar to run the brakes and breakaway, you still need a charging system from the tow vehicle to the house battery. And the monitor, of course.

That is what I have. It has been inspected and found compliant.
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Follow Up By: Motherhen - Friday, Sep 14, 2018 at 22:56

Friday, Sep 14, 2018 at 22:56
RMS confirmed to me some time ago

"The method of charging the batteries is not really relevant, provided the batteries are maintained in a state of charge that allows the brakes to operate safely and the driver is able to monitor that state of charge.

- - -

The fact that the trailer battery or batteries are charged by solar cells rather than by the towing vehicle’s alternator, does not change those requirements."

The Inspector's Bulletin (the only document on the subject) states

"Such trailers, if fitted with electrically actuated braking systems, must be equipped with a device which applies the brakes in the event of a breakaway from the towing vehicle and maintains application for at least fifteen minutes. It is essential therefore, that an energy source, such as a battery, be carried on the trailer and that means be provided to ensure that the battery is maintained in a fully energised condition. In this regard, it will be satisfactory if any trailermounted battery is constantly charged by the towing vehicle and a warning device is fitted to warn the driver (from the normal driving position) if the trailer battery charge falls to such a level as to render the trailer brakes incapable of meeting the requirements."

Many caravans have their breakaway connected to the house batteries. The only drawback is if the pin is accidentally pulled when you are not there, the batteries will deplete quite quickly.

Motherhen

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Reply By: Keith B2 - Wednesday, Sep 12, 2018 at 17:41

Wednesday, Sep 12, 2018 at 17:41
Thanks Ken. Your words are encouraging. I have a 60 amp dc-dc charger from the tow. I guess I'll have to check with the inspector.
Keith
AnswerID: 621172

Reply By: MarkHugh - Wednesday, Sep 12, 2018 at 19:20

Wednesday, Sep 12, 2018 at 19:20
Hi Keith,

Yes, in NSW you need a monitor that checks the breakaway battery voltage. I had a simple hard-wired monitor (via a single wire through the trailer plug to the dash) but replaced it with a Hummingbird wireless monitor. It costs considerable more but there are no wires to put through the caravan or tow vehicle and it can monitor several batteries, not just the breakaway, in a colorful display with user-set alarms. In my case I monitor the vehicle's main battery, my deep-cycle secondary battery as well as the caravan's main battery and the breakaway. Small transmitters are connected to the batteries (but not the vehicle's main vehicle battery because it is monitored via the Hummingbird's power supply, say the vehicle's cigarette lighter socket). The transmitters' range is pretty good, maybe 50 metres or more.

Cheers, Mark
AnswerID: 621173

Reply By: Mick O - Wednesday, Sep 12, 2018 at 22:47

Wednesday, Sep 12, 2018 at 22:47
Keith, a separate battery should be required. Many units for breakaway systems actually incorporate a battery monitor so there is no need to install one. I have one on the tandem trailer very similar to this unit on fleabay.

Breakaway Battery

As a side issue, one of the main problems with plugging a Bluetooth wireless monitor onto those small batteries is the drain. It may be only milliamps but over a period of months it will drain the battery if it is not connected through your vehicle plug or charged regularly. On a 400A/H, not a worry but a small 4 or 6 A/H, mate it will be dead flat in no time.

Cheers,

Mick
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Follow Up By: Frank P (NSW) - Wednesday, Sep 12, 2018 at 23:06

Wednesday, Sep 12, 2018 at 23:06
Mick,

In NSW you don't need a separate battery. You can run the electric over hydraulic brakes from the van house battery as long as the supply to the brake actuator is uninterruptible, meets the other wiring requirements and is monitored and is charged from the tow vehicle.

Mine is set up that way, has been inspected numerous times and is compliant.

Cheers
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Follow Up By: Mick O - Wednesday, Sep 12, 2018 at 23:18

Wednesday, Sep 12, 2018 at 23:18
OK Frank, re read everything and realised he is talking about the 400A/H system in his caravan which would obviously negate need for a separate battery on that platform.

I was thinking plain trailer over 2 Tonnes like my tandem which you would need to fit a separate power source (battery) to ensure brake operations in event of a breakaway (heaven forbid!).

Cheers
''We knew from the experience of well-known travelers that the
trip would doubtless be attended with much hardship.''
Richard Maurice - 1903

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Reply By: Mikee5 - Thursday, Sep 13, 2018 at 08:50

Thursday, Sep 13, 2018 at 08:50
I read the extract carefully. Itstates : It is essential to have the battery on the trailer, but not essential to have the charging system on the trailer. It is satisfactory to have the charging stystem in the tow vehicle. Now if this second phrase was not included, the rules would demand the charging system be on the trailer too. Therefore by having the charging system on the trailer you have met and exceeded the requirement.
AnswerID: 621180

Reply By: Keith B2 - Thursday, Sep 13, 2018 at 16:04

Thursday, Sep 13, 2018 at 16:04
That just about settles it. Thanks everyone for your help.
This is a great forum for getting informed and sensible answers.
Thanks again,
Keith
AnswerID: 621191

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