Brat not Charging on the bench.

[Darwould]

I have two new Brat Controllers to be installed on our cabin.  Each will be connected to one 250 watt panel.
In order to test them before taking them to the site, I have connected a gel cell battery to the battery terminal, which reads 26.4 Volts, and am simulating the solar cells with a 28.6 volt power supply. 
The Brat units flash their sequence, and then the blue load light comes on which gives me battery voltage on the load terminals.
The problem is, neither unit will charge their battery.  There is no Yellow light, and no charge current going to the battery. The only light that is on is the blue one, indicating power available to the load.   
When I jumper the power in to the battery, bypassing the Brat, it charges the battery at just under 2 amps. 
Is it that I don't have enough voltage differential to initiate a charge?... or what can I try?   
I would like to know that all of the circuitry external to the Brat  is working before I take this out to the site, thus the test.  (The panels are already mounted)
(I have permanent meters in the circuit, and also a 12 hour timer on each after the Brats, so to get lights, the button has to be pushed before 12 hours so that lights are not left on accidentally.) 
Alan

[Darwould]

Did some more testing by raising the input voltage simulating the PV input to 34 volts, and both Brat units immediately showed a yellow light and started charging .  It appears they need more than 28 Volts to get them going!. 
If anyone knows what the threshold voltage between the PV and the battery voltage is for this unit, it would be useful.

Also tried a dead 12 Volt cell in series with a good one, as the instructions say it will charge a dead battery.  It charged for about 30 seconds, then stopped for a minute, then charged for another 30 seconds.  This sequence added about 2 volts to the dead battery, so could possibly continue.  Didn't let it carry on to find out. 
 
I guess I will have to wait until it is installed on the panels to see how it really works!.
Alan

[CDN-VT]

Lets hope you don't have 12V style panels . P/V INPUT VOLTAGE MAXIMUM - 60 volts

VT

[brad.midnite]

The Brat waits until 110% of battery voltage is available open-circuit at the PV input. This is done to reduce hiccuping between charging and not charging and also because there's very little power available when the open circuit voltage is near battery voltage.

Using a power supply is not a true test in this case. Also, there 's a 10 second delay before it starts charging and voltage filtering, so the actual threshold was lower than 34v. It just appears higher because you were increasing the voltage.

The Brat transitions to lower power modes when not charging. Some margin above battery voltage is also meant to guard against The Brat uselessly 'charging' a battery while acting as a larger load than the panel can provide.