Charge controller issue???

[bpdchief]

When checked at plug in back of van panels show 19.6v output to charge controller. Checked at the PWM charge controller screws it drops to 13.2v.....why the drop? Also, it SEEMS to take longer to reach the 13.7v float or the max 14.4v . After solar shuts off the batteries settle at 12.8v. Do I have a controller issue or am I concerned about nothing?!

 

[John61CT]

That is how PWM works, why MPPT gets you maybe 15-25% more power.

 

[Trebor English]

A drop of 6.4 volts from the solar panel to the solar charge controller solar input is too much drop.  Could you be measuring the battery connection at the solar charge controller?  If you are measuring the battery voltage that is not necessarily wrong.  

Can you post the charge controller particulars?  Brand, model, what is the programming?

 

[John61CT]

No put a 40+V panel on PWM, it will just drop over half the power and keep output V the same.

That is why no point in buying panels for PWM, over say the normal 21-22Voc rating for 12V panels.

If you had a big (1+V) voltage drop between two ends of the same circuit, then that is worth investigating.

And none of this has to do with, is the SC actually charging the battery properly?

Need an ammeter to check that.

 

[QinReno]

When checked at plug in back of van panels show 19.6v output to charge controller. Checked at the PWM charge controller screws it drops to 13.2v.....why the drop? Also, it SEEMS to take longer to reach the 13.7v float or the max 14.4v . After solar shuts off the batteries settle at 12.8v. Do I have a controller issue or am I concerned about nothing?!

When you say "checked at plug", this was with the panel disconnected from the controller and therefore the "open-circuit" voltage? If so, that's normal. Eg, on this page, it says "Open-Circuit Voltage (Voc): 20V Short-Circuit Current (Isc): 6.45A".
- https://www.amazon.com/Renogy-Monocrystalline-Solar-Panel-Design/dp/B078J42WL7

Otherwise, everything else you say is how my little 100W system works. Solar panels are "current sources", so when you hook them to a load like a battery, the output voltage will drop down to near the battery voltage, eg 13.2V. Then, as the battery charges, the input voltage to the PWM controller will rise to the 14.4-14.6V range. Then, when the solar power goes away, eg sun goes down, the battery voltage will show 13V or so initially.

Solar panels are *not* voltage sources, which means the voltage output will stay approx constant when you apply a load.

 

[bpdchief]

Thanks to all who responded. Yes, that 19.6 was an open circuit. I understand now and will have our company electrician check with ammeter tomorrow. An MPPT controller is in my near future.