solar panels

Alan,

I wonder if you were actually measuring the AMPs delivered to the battery? With an MPPT type controller you might get something approaching 8-9 amps. If the reading is erratic, it suggests to me that the controller and the digital (?) meter are interacting. (This type of controller regularly disconnects the load momentarily to check on operating conditions. A digital meter samples a few times per second and may occasionally do so during this dead period to produce erroneous readings.)

Most non-MPPT controllers simply disconnect the battery from the panel once it reaches a fully charged voltage (typically 14.4 - 15V)

Did you have the battery connected when you got that voltage measurement? The output of the controller would be pretty unpredictable if not.

The straight answer to your question -

At the battery terminals with the solar gear connected and assuming the battery isn't dead flat, you should be seeing at least 13 - 14.5 volts.

With the panel disconnected from everything (including the controller) you should see about 22V at the panel.

Suggest check the open circuit (disconnected from battery and controller) panel voltage, looking for at least 20V, and the short circuit panel current (ie connect a current meter with at least 10A capacity directly across the panel - again with NOTHING else connected) - you should see about 7A in strong sunlight. If these tests are ok, your panel is ok. (Important - return the meter to its voltage measuring state, ESPECIALLY plugging the leads back into the voltage measuring terminals BEFORE making any voltage measurements! If you don't, all the smoke will be let out!)

Then I'd check the battery voltage with nothing connected - should be around 11.5-13V, depending on recent history. If it's much lower than this, there is a battery problem - very flat or maybe you had the solar wiring wrong way round?


HTH

John

Alan, would suggest you test the solar panels output first.
Disconnect panels from battery and using a multimeter put the probes on the + and - wires and you should get 18 to 21 volts, if you do not take the panels back to where you bought them.
If it does hook the panel back up to the battery ( i can only assume this battery is in a healthy condition i e not stuffed) ensuring that you have the positive wire to the + on battery and the negative wire to the + on battery.
You do not say if you have 1 x 120 watt panel or 2 x60 watt which you have coupled together ensure they are coupled together correctly if it is the latter.
Try this for starters
Farouk

Alan
My understanding is that the solar panel will only chagre at what the battery will let it. I can hope you got the unit from a 1/2 decent dealer, and you may be able to contact them fro help.

I could be wrong, but I have been lead to believe that it may well be the controller that is playing up, as most panels are ok but it's the controller that makes the difference.

Have you tried the panels on another battery ?

Cheers
Bucky