Are any MPPT controllers buck+boost?

I think they are pretty much locked into their long thin form factor. They
Aim ate them into. Weather seled sandwich from the factory.

I have been getting by using a manually adjustable DC-DC converter to measure max power point which works, but most controllers can't really follow the max power point as well as the manual method if Vmpp jumps around too quickly. Seems like a decent strategy with no local shading is to just scan the voltage range, find the global max, then track it as it moves around with some local hill climbing. But there are situations such as shading of one or more panels where the system max drops down to just a local max and hill climbing is trapped trying to find the top of the wrong hill.

Jim

HiTech wrote:
Right I could just put my two 12's in series and get 24. I'm not yet convinced in the real world for my panels, whether serial or parallel connection would do better. It would be nice to have the option and be able to compare real world performance, if I go MPPT.

Jim

Perhaps when my PWM arrives I can send you my MPPT for trial and look see inside.

Now, question, any chance your panels can be cut shorter? Maybe folded?

O&S

A watt is a watt is a watt. A MPPT controller cannot induce perpetual motion. Because the operation of MPPT is a bit esoteric methinks a lot of hype has found fertile ground to sprout.

IMHO the MAIN advantage of MPPT is it's ability to deliver maximum watts potential over long distance using significantly smaller conductors.

When someone delivers "The Goods (also referred to as proof)" with overlay charts and graphs showing WATTS delivered to the battery by the controller then the situation should become a lot more clear.

Same system, wire sized for PWM, establish a kWh graph, then overlay the performance of a MPPT. I'm not talking about comparing a 48 volt panel with wire sized for 12 volt operation to a 12-volt panel with perhaps 20voc.

When a 20 volt panel is showing a working 16 working volts potential, and the battery bank is at 12.2, then something's not right.

Right I could just put my two 12's in series and get 24. I'm not yet convinced in the real world for my panels, whether serial or parallel connection would do better. It would be nice to have the option and be able to compare real world performance, if I go MPPT.

Jim

If you are going to go with an MPPT controller why not go with 24-volt panels and problem solved.

It is hurricane season again so time to take it to the next level.

Absolutely solar panels are current sources over most of their range but the max power point is right around where they stop being a near ideal current source and the current falls off a cliff. Once Vbatt is even a few tenths past Vmpp the current and therefore power produced drops to minimal levels.

I have read that some controllers will run at the max power point and step the voltage up to charge the battery when needed, but I cannot find any examples. For me with either PWM or MPPT, if I run my panels in hi temps but in the shade, I get good power production due to the good temp profile of the Unisolars for power. But once the charging voltage gets up into productive territory of 14.0+ volts, there are situations where the Vmpp is there too. So I'm getting better power production from the panel than MPPT in that case (no DC-DC losses with PWM), *but* that low Vmpp is limiting the controller's ability to run the charge up to 14.5v or 14.6v. An MPPT controller with Buck+boost converter circuitry could do it.

I could also wire it up to be able to switch the panels from parallel to serial at that point and skip the problem, since it may not need all the amps once it wants to charge at over 15 volts, and that would give the controller 28v to work with even in the worst conditions. But it could be that best shade output could really be had by an MPPT that can step voltage up or down. I have a converter I can test this with - one panel on buck and one on boost into the same battery.

For my usage to run just fridge I have excess watts on sunny days and plenty of battery for many rainy days in a row, but yield in rain and shadow are actually at a premium and could conceivably cover a significant portion of my needed 20-24 amp hours a day from just the 136w of Unisolars.

It may be academic though. When the batteries really NEED a good charge, the panels dropped down to a Vmpp of 14v in the shade means a partially discharged battery will be drawing very nearly the max power out of the panels anyway under PWM. It's not to uncommon for me to see 4 amps charging on a cloudy day depending how thick the clouds, and 20+ amp hours back in go a long way toward break even, even on a day with no sun.

I need to figure out what Vmpp and amps produced at Vbatt are on the panels under various rain conditions.

Jim

:D

Doubt it. Solar panels are current sources. All the MPPT has to do is take less of a load from the panel and the voltage will go up.