Bucking and MPPT?

KJINTF wrote:
red

Buck conversion and tracking are separate but tied together functions
Cheap MPPT controllers might simply have a manual user adjustment for setting tracking, while high end units have a CPU dedicated for the job of tracking sweeping etc..... Yes buck conversion can and does happen without tracking changing.

BLF
What is this mystical MPPT function you are going on about?
Remember the PWM function (which is an integrated part of both PWM and MPPT controllers) is for battery charging not DC to DC conversion

I am going on about the very thing you told red about--the tracking thingy. My controller has the automatic type. ISTR some members have older Blue Sky models that have a manual setting requirement.

I am not questioning how the thing works as such, only whether what I saw is a normal sort of amount for when MPPT is engaged.

red

Buck conversion and tracking are separate but tied together functions
Cheap MPPT controllers might simply have a manual user adjustment for setting tracking, while high end units have a CPU dedicated for the job of tracking sweeping etc..... Yes buck conversion can and does happen without tracking changing.

BLF
What is this mystical MPPT function you are going on about?
Remember the PWM function (which is an integrated part of both PWM and MPPT controllers) is for battery charging not DC to DC conversion

red31 wrote:
If it's bucking in float the panel output is higher than the battery, what allows this tracking of voltage higher than battery voltage? ie how can it buck without tracking?

The story is that when it is not in MPPT (which it only does in "Bulk") it is in PWM in "Absorb" and in "Float" Other brand MPPT controllers do the same.

I am not asking whether that is true or whether it was in MPPT or not, just whether the "improvement" was about right for proper MPP tracking similar to what any other MPPT controller does.

I don't know what exactly the array vs battery was at the time, but testing that day with similar numbers in Bulk were with the panel rated Voc 36.8, Isc 8.3 at actual Voc 34, Isc 8.4 with battery 13v, amps 14, watts showing as 182ish. (Question there was why the lower than usual amps and watts--see thread Heat1 Mppt0)

If it's bucking in float the panel output is higher than the battery, what allows this tracking of voltage higher than battery voltage? ie how can it buck without tracking?

MPPT is NOT a function of the device it's the name of the device

MPPT controllers functions include but are NOT limited to
Buck conversion
Array Tracking
Battery charging typically PWM battery charging

As I said above please give us the required data
Measure the array Voltage and Current at the same time you measure the Battery Voltage and current

It was previously established in other threads that MPPT controllers have bucking and MPPT as separate functions. Many( most? all?) only do MPPT in Bulk. In Float they still buck to get the amps up to meet the demand.

In this case, where panel Isc is 8.3, there was 12.4 amps developed. That was from bucking. Then the controller went into Bulk so MPPT was engaged and amps jumped. That made the watts show higher too with the voltage the same.

I just wondered if that jump in amps was "about right" for MPPT "effect" from whatever power point it might have been on in Float without the MPPT engaged. Might be a way to tell if the controller is acting properly if the observed effect (if that was all MPPT effect) is about right.

Will try to answer however I am confused as to what EXACTLY you are asking

MPPT: Maximum Power Point Tracking
A proper unit can be thought of as a traditional PWM controller on steroids.
Up front ahead of the traditional PWM charging function there is a BUCK converter that down converts higher DC voltage from the array to the DC voltage the PWM charging section needs to properly charge the battery. Part of that BUCK conversion stage is a "tracking" function that attempts to find the Vmp of the array. If the Array voltage drops to low the "BUCK" conversion is simply bypassed - it becomes a traditional PWM controller.

You will need to measure the ARRAY voltage and ARRAY current as well as the Battery Voltage and Battery Current to see how the buck conversion stage is functioning.

Running a 12Vdc nominal panel with a MPPT controller IMHO is a majority of the time a waste of $. A parallel wired array with 12Vdc nominal panels in MOST Cases is best suited for a PWM controller.

You were simply drawing current dropping the battery voltage which dropped the controller from float to a different charge stage.

MEASURE your array voltage / current give us the details needed to properly comment.