Hi Larry, sometimes it is hard to sort the wheat from the chaff information. I still do not know how my BS 6000 is charged. I have charged it from the red and black screw on terminal, BUT when removing the charger there is no voltage at those terminals. We have been touring for shortish (up to 10 days) trips since Jan 2014, and have had to learn a heck of a lot and received help on every topic from Cindy's forum here.

Worst part is I still do not know our van in every important detail. I am quite disabled now so I tend to ask first before I start pulling things apart to find out how things work. That was how I used to operated before my accident 7 years ago. I probably wrecked more than I fixed BUT I felt good about having a go!!!! My health does not allow me to doing things more than once, called energy management!!!   That accounts for my highish post count. 

Aussie Paul. 

Do you have the three sheets of instructions that come with the unit? If not you can download any missing ones from here.

The instructions seem clear to me. You were trying to read the battery level by putting your meter across the input to the trickle charger:

CHARGING

Charging of the Breaksafe battery can be done via the tow vehicle auxiliary line (Breaksafe black wire) or by connecting
a small battery charger (8 amps maximum) to the red and black terminals on the front of the Breaksafe box. The orange
charge light next to the red terminal will illuminate when the Breaksafe battery is connected to 12 volts for charging. The
charging system in the Breaksafe unit is a trickle charge circuit only and it may take several hours for the battery to fully
recharge.

Was the orange charge light on when you were charging the battery through the front panel terminals? Some chargers require a few volts at their output before they commence to charge. Find yourself a charger that will produce at least 12 V at its output when not connected to anything. Alternately you could try removing the house battery from its cradle and using that to see if you can get some charge into the battery.

The other thing to check is the "hot wire" connection from your tug to the Breaksafe unit. If need be you can stick pins through the black (positive) and white (earth) wires to check you have battery power from your tug when hooked up. If you get that working properly you can recharge your battery charged whilst you drive (if you drive for long enough.) Another alternative would be to get yourself a 12 V power brick with a 1 - 2 A output and use that to keep your battery in good nick.

TEST BUTTON
 
Use the test button to test the condition of the built-in battery. This should be checked each time the trailer is used.
Depress the button momentarily and check the battery level lights. The test button will also energise the trailer brakes and
brake lights.

As you can see, when you press the test button you put a considerable load (quite a few amps on a 7 Ah battery is a considerable load.) With that in mind pressing the test switch when the battery is down a little may not produce a green light. This does not mean the battery is stuffed, a battery with a rested voltage of 12.3 V most likely would not produce a charged indication on the test lights. It may just need recharging.

-- Edited by PeterD on Monday 6th of April 2015 03:26:52 PM

The following fitting instructions would suggest that the positive charging terminal could be used as a sensing terminal for a remote monitor:

http://rvelectronics.com.au/image/data/BREAKSAFE%20REMOTE%20MONITOR%20FITTING%20INSTUCTIONS.pdf

This means that there cannot be a diode in the path. Instead I'm wondering if the charging input is separately fused, and if this fuse is open. However, this doesn't explain why an automatic charger cannot sense the battery voltage in a known working unit, as the OP's Internet research would suggest.

Nice to see you, too, PhilC. Hope you're well.

I notice that the documentation states that the battery can be charged by the vehicle's charging system via a black Auxiliary wire. I'm wondering how the two charging sources are isolated from each other, and this leads me to thinking about diodes again.

Aussie Paul,

I just had my first taste of breaksafe battery hassles today. My understanding is that the 6000 unit, which you and I both have, has its own charger in the box, Therefore it doesn't require an external charger like I believe earlier models did, but simply a 12 volt supply to the red and black terminals. Someone has suggested that the instruction sheet is a bit misleading on this point. It may be that the use of a charger on the 6000 won't work.
I'm still at the stage of charging my battery on the bench, so I can't offer information as fact, just a maybe.