Solar regulator confusion

From the evidence supplied it is not possible to determine whether the regulator is faulty or not.
Many regulators require the battery to be connected in order to decide their charging parameters, and will give erroneous results if that rule is not adhered to.
Most modern regulators incorporate a blocking diode as do many panels, make sure your system has at least one to prevent backfeed at night.
As you have access to a voltmeter, why not connect the battery during daytime and see what voltage you have then.
Two things should happen when you have the battery connected:
1. The panel volts should drop to that of the terminal voltage of the battery.
2. The battery voltage should begin to climb fairly rapidly, this will only be surface charge, but it will indicate that the controller and panel are working.
If you then disconnect the panel and check with your voltmeter across the solar input terminals of the controller you should have a very low (millivolts) or no reading on the meter. If you are getting more than that then you probably need to install a blocking diode in the line, there may already be one at the panel but an extra one won't make a lot of difference to the charge regime.
You might also check charge current with the meter as well just to ensure that the panel is actually outputting a reasonable current.
Is it possible that the battery is at fault?

Hi Chris,

Sounds like the regulator is at fault and the panel is not far behind.

Can you do an amps reading with your meter on the panel first to see what sort of amps it is producing then an amps test on the regulator output.

I assume the battery is about an N70 size (truck battery size) and if that is the case then a 50 watt panel will never do the battery justice.

I have read that a flooded cell battery will lose 4% of its charge per week whereas AGMs only lose about 4% per month.

This means that a flooded cell battery will need to be charged sufficiently on a regular basis or continually as you are doing, but, in my opinion that 50 watt panel is not big enough. I would be using something in the order of 150 watts for the above battery and certainly nothing under 100 watts for a small car battery.

If you need to get a new regulator then you could do worse than one of These cheap LED display units.

I am not sure where your budget takes you so I have suggested a cheap one but if you can afford better try a Fangpusun regulator as I have a couple and find them excellent despite them being a PWM.

Here is a link to a Fangpusun
20 amp regulator. I like them because they have a clear indication of SOC, Panel output,
Reg output etc and show the SOC in a tank gauge like indicator.

I have used several different types of regulators and I find them one of the best as there circuit board is virtually a Stecca type board.
For the uninitiated Stecca is a well respected brand of Solar regulator.

Cheers, Bruce.

The panel is there to keep a fully charged battery topped up on the off season (fishing) so battery is never flat when I connect solar panel.

It's a marine battery

Chris85
If you have had the panels charging and disconnected the battery terminal, then the regulator will have been open circuit.
Possibly this has damaged the regulator and it uses some current instead of blocking.

I may be wrong but a couple of my regulators say "Do not disconnect while solar is active" othewise it fries the reg. You have been testing the reg open circuit output while solar is active, not good.

Try a new regulator.