Cheap 10amp PWM- am I overloading?

[Leo3]

This SCC was stock in my travel trailer. It’s a 10amp and you can see in this pic it says 14amp. Trailer has one solar panel and I connected another in parallel. Hopefully the pic attached. I’m have bad service. It’s the readout in the SCC showing 14.6 amps input. It got up into the 15’s. So since 14/15 is a lot higher than 10, am I going to damage something or overheat a wire?

SCC specs:
-accepts up to 190 watts of solar at 12V. .
-LCD display shows Charging Current, Battery Voltage
-max solar panel input voltage 25V.
-max solar array current 10amps.
-battery voltage range 6-15.5volts

Here are the two panels:
Panel on trailer (maybe)
Voc 21 V
Vmp 17.5 V
Imp 5.68 A

SP120 Maxoak/Bluetti

• Voc 23.7 V (so 2 would be 47.4V)
• Vmp 19.8 V (so 2 would be 39.6V)
• Imp 6.06 A (so 2 would be 12.12A)

 

[snoobler]

No pic attached.

 

[Leo3]

Just picture the SCC screen reading 14.6 amps. I can upload pic due to poor service.

 

[snoobler]

You sure it's not reading volts? 14.6V is a common bulk/absorption voltage..

 

[Leo3]

You sure it's not reading volts? 14.6V is a common bulk/absorption voltage..

Yes. Positive.

 

[snoobler]

Sounds like a defective controller. I wouldn't trust it to properly charge a battery.

 

[Leo3]

A pwm is not supposed to lower the amps to 10 right? It should be like an error code instead? I really need to get a 20 amp controller don’t I. Assuming wiring can handle. I will try to get some more data and when I am back in good service I can post.

 

[Whinny]

How are the panels configured, you said 2 in parallel and then indicated you have 3? Are they all mounted or are some ground deployed?
Do you have 1 or 2 sp120's.

• Voc 23.7 V (so 2 would be 47.4V)
• Vmp 19.8 V (so 2 would be 39.6V)
• Imp 6.06 A (so 2 would be 12.12A)

You don't get to double both current and voltage when combining panels-it's one or the other depending on series or parallel

 

[chrisski]

Yes get a bigger controller, also get an MPPT that as you add on more panels, you don’t need to keep panel voltage below 22 or whatever your PWM is rated for but have options to put the panels three in series and not only have to use three in Parallel. I was surprised what that did to wire sizing and voltage loss.

Recommend getting an SCC about what you think your system will grow to. For me, that is to run my propane heater fan overnight takes a lot more energy than anything else I use.

I only use an MPPT controller, but if it output more than it was designed for, I would not keep the SCC and replace it.

The MPPT I have has a couple of features where it automatically limits output amperage to the rating of the charge controller, and I can adjust that down.

Perhaps your PWM doesn’t have that. Looking at two of your panels, at peak solar output stepped down from 18 to 14.6 volts could be close to 14.6 amps. When I hear 10 amp SCC though, I think of all the components designed on the SCC that could be overheating because the 10 amp rating is exceeded. I’d be worried about my travel trailer burning down. If this were set up somewhere where it burnt, a fire would not spread, then maybe.

 

[Leo3]

I just have two panels hooked up in parallel with a branch connector. One is an SP120 and one is a flexible panel that came with my trailer. The sp120 is just sitting on the roof alongside the mounted flexible panel.

How are the panels configured, you said 2 in parallel and then indicated you have 3? Are they all mounted or are some ground deployed?
Do you have 1 or 2 sp120's.

• Voc 23.7 V (so 2 would be 47.4V)
• Vmp 19.8 V (so 2 would be 39.6V)
• Imp 6.06 A (so 2 would be 12.12A)

You don't get to double both current and voltage when combining panels-it's one or the other depending on series or parallel

 

[snoobler]

The SCC shouldn't be able to send more than 10A to the battery. Thus it shouldn't pull more than 10A from the panels. If it is, something is broken OR the calibration is so bad, it's 40% off.

 

[Leo3]

Finally good enough service to post my pic!

 

[mikefitz]

A pwm controller will send whatever current the panels can deliver, if the battery can accept the charge. The pwm is just a fet switch connecting the panel to the battery. The PWM can only control the on time, not current directly. The two panels will only generate 12 amps in ideal conditions, so there is a display error in the unit. I would expect in practice around 8 amps.

am I going to damage something or overheat a wire?

I dont think so, the worst that could happen is that the controller will fail. Provided you have a fuse suitable for the cable connecting the battery to the controller at the battery end of the cable, nothing can catch fire. The major source of energy is the battery that could generate 100s perhaps thousands of amps into a faulty unit or a cable short.

If you buy a true MPPT controller you will get more power from the existing panels.

Mike