Solar charge controller weird voltage reading

[Maddin123]

Hello,

I have 2 x solar panels installed. Each with 25V and 3,7 amps.
The solar charge controller is called "CMT 30" and is supposed to be PWM.

Now, if I read the voltage on the controller on the solar connection I see a value of about 12.7 Volt when the sun is shining. But then.. every 5 seconds the voltage spikes up for about a tenth of a second. The value is between 12.7 and 16 volts.
At the battery connection the voltage stays constant.
Is this spiking for purpose? Is the controller trying to average the input voltage somehow?
I don't know if its defective.. In the manual it says it charges the battery with 14.4 volt but I never read this value. Is the battery taking damage from this behavior?
It never gets full by the way. In the evening I get a reading of like 12.5. As I bought it it had 12.7

[red31]

OP, the concept is both battery and panel voltage should rise to 14.4v. Then battery voltage is held there for 10 mins (per info in above link), then the battery is allowed to drop to 13.6v and held constant. Measured panel voltage after the battery gets to 14.4v will rise as the panel is now operating at battery voltage and panel Voc On and off rapidly.

Adding loads at any time to the above charge cycle may extend any mode and/or not allow the controller to change modes for instance if battery v never gets to 14.4v then the next 2 modes never happen. A draw down from 13.6 float to 13.2v restarts the charge cycle.

[time2roll]

I doubt the voltage spike will create any harm. The 12.7 max volts could be indicating the controller has failed. Even 6 amp charging should allow the voltage to rise.

I would jump the controller to connect panels direct to the battery. Need to monitor this and you should see voltage rise steadily over a couple hours. Post the results.

[TomG2]

pianotuna wrote:
Welcome to the forums.

The panels are about 95 watts @ 25 volts. But the PWM controller drags the voltage down to just 12.7.

Not all PWM controllers act that way. Mine (HQST) boosts at 14.4 volts and floats at 13.8 volts. My 100 watt panels provide about 75 watts each under normal conditions. The OP's should do as well.

To the OP: Some controllers scroll through various readings. Yours may be looking at one reading and then another?

[pianotuna]

Welcome to the forums.

The panels are about 95 watts @ 25 volts. But the PWM controller drags the voltage down to just 12.7. That may yield less than 50 watts of power per panel.

The system may maintain the battery bank and slowly recharge them when the RV is in storage--but won't do much charging at all when the RV is in use, given that the parasitic loads may be consuming more energy than the panels harvest in perfect solar charging conditions.

You could improve things by getting an MPPT controller--but it may be best to ebay this system--and replace with something that has a lot more capacity.

[BFL13]

https://www.aliexpress.com/item/32453845196.html

The instructions here (scroll down) say it is one of those that must have the battery connected first or the controller will be damaged.
It is PWM.

PWM does control the panel voltage by shorting it on and off once the batteries reach the set high voltage 14.4 or whatever. Until then, the panel voltage will be the same as battery voltage.

Not enough info why the batteries are not getting charged to 14,4 volts. If there is too much voltage drop on the wires between battery and controller, the controller will "see" 14.4 and stop voltage rising further, but the battery voltage will be lower than that set point.

Your array is quite small so if you have a bigger battery bank the array would not be enough to get the batts up before dark.

Your panels must in parallel, not in series, or the total voltage could fry the controller, and if it did still work, you are only getting half the amps you should be getting when they are in parallel.

Not enough info about your set-up and the camping scenario to know what's what.

I had a similar controller in one of my past set-ups and it did the job, even though it was an "eBay special". Can't just blame the controller for what it is and ignore other possible factors.