Solar panel output lags load change

[John Boy]

I have noticed that the output of solar panels lag a change in load and then the battery is drained for a short while. Does anyone have any ideas to prevent this occurance<

[Guest]

14 minutes ago, John Boy said:

I have noticed that the output of solar panels lag a change in load and then the battery is drained for a short while. Does anyone have any ideas to prevent this occurance<

Welcome John Boy.

It is perfectly normal. MPPT's cannot adjust that fast. Takes them a few seconds to catch up. You can also see the opposite when the load is high and is switched off, the MPPT takes a few seconds to back off.

 

[___]

MPPTs usually back off quite fast, but they don't always spool up that fast. Back-off is easy, you just pull back on the PWM ratio. But increasing power sometimes involve a scan for the maximum power point and that might take several seconds.

[Guest]

1 hour ago, plonkster said:

MPPTs usually back off quite fast, ...

You must have seen what a induction plate / microwave does ... man, like mine goes -650w - 0w - +650w all the time.

Not "quite fast", lets settle on not too slow - the point is, it does go over and under all the time.  

[___]

9 hours ago, The Terrible Triplett said:

Not "quite fast", lets settle on not too slow - the point is, it does go over and under all the time.  

Yeah, but in our case it should be pointed out that the ESS loop with the Multi is the slow part. The power value is low-pass filtered from 1-second spaced readings and communicated to the Multi at 2.5 second intervals, so that swing is usually a 5 second operation

[Guest]

3 minutes ago, plonkster said:

... in our case it should be pointed out that the ESS loop with the Multi is the slow part.

AHA!!! See, there we now learn something new.

We both then good replies. You because you talk about things you know, me because I see stuff not knowing the intricacies ... like so many others here.  

[___]

There is also this old video I made years ago. I had the discharge power limited on the Multi, which caused the MPPT to limit its current. Then I increased the discharge current so that the MPPT was forced to go hunting for max power, and you can see here how the PV power sweeps down and up a few times. Victron MPPTs scans three times, which is clearly visible here. While it is scanning, you will dig into battery power at times

 

Edited February 21, 2019 by plonkster