PWM controller not charging correctly with 300watt panel?

Hawaii_Joe
Guest

PWM controller not charging correctly with 300watt panel? Mar 8, 2016 1:11:56 GMT -8

Post by Hawaii_Joe on Mar 8, 2016 1:11:56 GMT -8

Here is my system:

300Watt 24v panel (36volt nom, open 42v)
1 12V 330ah SLA Battery
Renogy 30A Positive PWM Charge Controller
30' of #10 MC wire from panel to controller.

Controller is mounted 16" from the battery with #10 wire to battery

According to some quick calculations, My battery to Panel ratio is pretty good. I believe a 300watt panel is sufficient to keep up with demand at 500-600watts Total consumption per day on days of near/full sun. I can adjust my loads easily to suit the sun I am getting.

My problem is that, I wake up and the battery is reading 12.5 after settling for several hours after the inverter is turned off. When the sun hits the panel and the current starts to flow the battery voltage reaches 12.9-13.0v very quickly, Say by 10am. However the voltage never rises above this even if with no draws for the entire day. The voltage just sets at 12.9-13.0. Then when I turn on some loads at night the battery falls immediately down to 12.5/12.4. What i mean by loads is perhaps 30-70 watt hours of AC out of the inverter.

I feel that the battery voltage should reach 14.00+ with the PWM if the battery is nearing full. I've used a voltage meter on the terminals. And today it was full sun all day and i had no loads on the system for 5 hours during peak sun times, Inverter was OFF. The terminals to the panel on the PWM, read 13.5V, the terminals to the bat read 13.0v, These voltages remained for 4 hours with no change.

I am not sure what could be wrong, can someone look at my specs and let me know what they think?

spiderbob
Solar Addict

Posts: 229

PWM controller not charging correctly with 300watt panel? Mar 8, 2016 7:42:08 GMT -8

Post by spiderbob on Mar 8, 2016 7:42:08 GMT -8

Joe, don't know if this will help much, but some explanation for you, but in practical terms, most solar power systems don't reach their full potential current load. During the morning hours, before the sun gets high and powerful in the sky, the batteries get quite a bit of charge. Usually, by the time the sun is really cranking out maximum energy at noon, the time when the system could be producing max amps the batteries have already gotten pretty well charged and are starting to ask for less and less current from the controller. Yes, the charge controller has already begun to throttle the panels back a bit and less current is flowing through the system, you sound pretty much on with your numbers, even 12.5a is a good place to be with your battery when not charging. You will get to 14.5, but not every day, as the controller tries to clean the batteries, but then again, not sure if the MPPT30 has that feature. I use a 40, a technician will come in sometime today and help out here.

Last Edit: Mar 8, 2016 7:45:51 GMT -8 by spiderbob

jsb2000
Solar Addict

Posts: 169

PWM controller not charging correctly with 300watt panel? Mar 8, 2016 7:46:05 GMT -8

Post by jsb2000 on Mar 8, 2016 7:46:05 GMT -8

Just verifying a few things: Your controller is mounted 16 INCHES from the batteries using #10 wire, not 16 feet?

Is the battery new or used? Either way, it might help to have it tested. I've had a few "new" batteries in my time test bad. Manufacturing/handling/storage methods do sometimes contribute to a "new" battery not behaving as such.

Other than that, your calculations appear sound. There might be a problem with the controller and/or panels. Can you measure the input current from the panels to the controller? And the output current from the controller to the battery? One of the first things I purchased after my Renogy kit were two of these. They really give me a good view of what's going on at all times.

Admin
Administrator

Transitioning to new forum. This forum will be locked September 3rd.

Posts: 387

PWM controller not charging correctly with 300watt panel? Mar 8, 2016 10:57:33 GMT -8

Post by Admin on Mar 8, 2016 10:57:33 GMT -8

Hello Joe,
The charge controller you have is a PWM controller and not an MPPT controller correct? If that's the case then connecting a 300 watt panel will result in a loss of 180-200 watts. This is because the PWM controller will simply cut the excess voltage. In order to make full use of your 300 watt panel I would recommend a 30A or 40A MPPT charge controller. The controller seems to not be charging properly since you mentioned it was charging at 13.0 volts for 4 hours. The voltage should have gone up in those 4 hours. If you can contact us at (909) 517-3598 we can replace the controller if it was purchased within a year.