MPPT Controller Explanation For Dummies

[Emmalina]

Its all about algorithms and the biggest advantage I have found is the ability to series up your panels to 150v VOC so you can reduce cable diameter on big arrays.. Seen a lot of these "cheap" Mppt charges from a certain country and they don’t even weigh enough to make decent paper weights.
Yer gets wat yer pays for !!

[goboatingnow]

Originally Posted by Emmalina

Its all about algorithms and the biggest advantage I have found is the ability to series up your panels to 150v VOC so you can reduce cable diameter on big arrays.. Seen a lot of these "cheap" Mppt charges from a certain country and they don’t even weigh enough to make decent paper weights.
Yer gets wat yer pays for !!

There's no particular reason for mppt controllers to be large or heavy though

Dave

[Emmalina]

Originally Posted by goboatingnow

There's no particular reason for mppt controllers to be large or heavy though

Dave

True but you are dissipating a lot of excess energy so you need a large heat-sink or fans. I prefer a large heat-sink as it has no moving parts. You also require a certain amount of inductors and other fairly heavy passive components to boot.

[Emmalina]

This vid explains a lot about quality without being too biased...

WELLSEE fake MPPT controller guts - YouTube

[goboatingnow]

Originally Posted by Emmalina

True but you are dissipating a lot of excess energy so you need a large heat-sink or fans. I prefer a large heat-sink as it has no moving parts. You also require a certain amount of inductors and other fairly heavy passive components to boot.

Mppt with switched mode shouldn't be dissipating hardly anything, high frequency inductors are small , and really heat generation should be low.

Dave

[Emmalina]

Originally Posted by goboatingnow

Mppt with switched mode shouldn't be dissipating hardly anything, high frequency inductors are small , and really heat generation should be low.

Dave

Well alll the main players I deal with are pretty big and heavy that includes outback morningstar BZ etc but then again we go for 45-80A systems
Switch mode power regulation doesn't dissipate much heat !

[nimblemotors]

Originally Posted by goboatingnow

Mppt with switched mode shouldn't be dissipating hardly anything, high frequency inductors are small , and really heat generation should be low.

Dave

This $100 SPV1020 controller board has no heat sink, has 97% efficiency.
In fact, if you read about them, it uses four small inductors, so it doesn't need a larger electrolic capacitor, which tend to have short lifetimes (1-3 years) in the heat.
I see both the circuit boards in the videos have electrolic caps.
Note however, it is JUST a MPPT controller that outputs a fixed voltage,
it is not a battery charger.

[noelex 77]

There are lots of poor quality MPPT regulators.

MPPT can be implemented in many different ways and some of them of very inefficient.
If you want an MPPT it needs to be good quality. If you want a cheaper regulator it is generally better to get to a non MPPT regulator, but make sure it is PWM not just an on off regulator.

There are some moderately priced MPPT such as Gensun, but MPPT circuitry is complex and I would recommend avoiding the cheaper MPPT regulators.

[T1 Terry]

Originally Posted by Emmalina

This vid explains a lot about quality without being too biased...

After actually testing these two controllers, the WellSee didn't perform that well, but it crapped all over the 2 BZ units I had, one MPPT250, the other MPPT250HV. The output display on the BZ units tells very large lies, at a reading of 25 amps it was actually putting out 18 amps. If you could actually get it to output 25 amps the thing would need to be water cooled, it generates that much heat, even mounted in an old inverter case with 2 fans running, the transistors finally failed.

Unless you are charge a big lead acid battery pack or you have a big mismatch between panel voltage and battery voltage, there is bugger all to be gained. If you are charging Li batteries, it's actually a backward step, the energy wasted as heat in the MPPT controller is greater than the gain from impedance matching. Li batteries don't have the big voltage changes between discharged and charged, and there is no bottle neck as far as resistance against current entering the battery, the PWM type controllers work fine, up to 80% conversion efficiency.
Unless you can keep the solar panels below 25 deg C while in full sun, there is not enough difference between Vmpp and Li terminal voltage, but enough to over come wiring resistance.
For those that want to work it out, for ever deg over 25 degC reduce the Vmpp by 0.462%, panels in full sun in T shirt weather will climb to around 75 degC, that brings the 18v Vmpp @ STC (Standard Test Conditions, a light box in a lab with flash readings so the panels don't heat up) down to 14v Vmpp NOCT (Normal operating Cell Temp) not much impedance match to be had there.

T1 Terry

[FlyingCloud1937]

Originally Posted by endoftheroad

I used a meter yesterday at mid day and my 140 watt panels were 20 volts each entering each mppt controller. Was I seeing things?
The battery was 14.3 volts (if I remember correctly).

My batteries are full mid morning while I'm running refrig, vhf and 12 volt fans.
I'm charging every electronic gadget possible during this 6 or 8 hour period although it's not necessary.
I'm new to solar and mppt, it's been a better than expected experience.

2-Kyocera 140
2-genasun mppt controllers
4-Trojan T-105's in series.

Victron battery monitor soon to be installed.

It's raining here in Key West at 3:00 pm, grey skies and stormy weather and my panels are 14.4 each and the batteries are 12.7 volts.

Looking forward to the Victron.

Endoftheroad,

I don't want to burst your bubble,

but food for thought.

Solar panels can easily fool a volt meter, especially if you never plug-in to shore power.

It's called surface charge.


If you have a 440 amp-hr bank and draw out 100 amp-hr over-night.

Now add 2 solar panels that generate 12 amp's per hour. Total by 12 noon in your latitude is going to be not more then 48 amp hrs added back...leaving a deficit of about 52 amp hrs.

If your bats are showing 14+ voltage you have a surface charge. And the real state of charge is....something less than 100%

Amps out overnight X 125%, plus amps in from the solar = net re-charge.

So now if this is a day in day out occurrence and you have a negative, then, at some point the deficit is going to come home to roost.

Lloyd

[goboatingnow]

Originally Posted by noelex 77

There are lots of poor quality MPPT regulators.

MPPT can be implemented in many different ways and some of them of very inefficient.
If you want an MPPT it needs to be good quality. If you want a cheaper regulator it is generally better to get to a non MPPT regulator, but make sure it is PWM not just an on off regulator.

There are some moderately priced MPPT such as Gensun, but MPPT circuitry is complex and I would recommend avoiding the cheaper MPPT regulators.

What do you mean PWM versus on off , the PWMsokar regulators are an on off charger design.

Dave

[goboatingnow]

Originally Posted by T1 Terry

After actually testing these two controllers, the WellSee didn't perform that well, but it crapped all over the 2 BZ units I had, one MPPT250, the other MPPT250HV. The output display on the BZ units tells very large lies, at a reading of 25 amps it was actually putting out 18 amps. If you could actually get it to output 25 amps the thing would need to be water cooled, it generates that much heat, even mounted in an old inverter case with 2 fans running, the transistors finally failed.

Unless you are charge a big lead acid battery pack or you have a big mismatch between panel voltage and battery voltage, there is bugger all to be gained. If you are charging Li batteries, it's actually a backward step, the energy wasted as heat in the MPPT controller is greater than the gain from impedance matching. Li batteries don't have the big voltage changes between discharged and charged, and there is no bottle neck as far as resistance against current entering the battery, the PWM type controllers work fine, up to 80% conversion efficiency.
Unless you can keep the solar panels below 25 deg C while in full sun, there is not enough difference between Vmpp and Li terminal voltage, but enough to over come wiring resistance.
For those that want to work it out, for ever deg over 25 degC reduce the Vmpp by 0.462%, panels in full sun in T shirt weather will climb to around 75 degC, that brings the 18v Vmpp @ STC (Standard Test Conditions, a light box in a lab with flash readings so the panels don't heat up) down to 14v Vmpp NOCT (Normal operating Cell Temp) not much impedance match to be had there.

T1 Terry

Yes terry but Vmp also moves with illumination levels , and a small mismatch in voltage can mean you are moved away from the Vmp pointb( which is dynamic)

I don't get your comments re Li at all. Li with its capability of demanding full charge right up to the end is a n ideal candidate for MPPT , whereas for LA , its only useful in bulk charge phase , yet many people buy panels for absorption charging , ie finishing off the battery and with big panels for this use MPPT is useless as the panels arnt delivering anywhere near full power anyway.

Dave

[noelex 77]

Originally Posted by T1 Terry

If you are charging Li batteries, it's actually a backward step, the energy wasted as heat in the MPPT controller is greater than the gain from impedance matching. Li batteries don't have the big voltage changes between discharged and charged, and there is no bottle neck as far as resistance against current entering the battery, the PWM type controllers work fine, up to 80% conversion efficiency.

With LI batteries the gains from MPPT controllers will, overall, be higher than for lead acid batteries.

The lower battery voltage during charging that is characteristic of Li will make the gains from voltage conversion inherent in the MPPT process higher.

A suitable algorithm for charging Li batteries can be programmed into the better MPPT controlers, but not all of them.
Many of the medium and low priced controllers are not suitable.

On all the current MPPT and non MPPT controllers the battery voltage hysteresis is a bit too high for my liking, but this will only be a factor near 100% control.
I think we will see controllers released in the future with tighter voltage control which will be better for Li

[goboatingnow]

Originally Posted by nimblemotors

This $100 SPV1020 controller board has no heat sink, has 97% efficiency.
In fact, if you read about them, it uses four small inductors, so it doesn't need a larger electrolic capacitor, which tend to have short lifetimes (1-3 years) in the heat.
I see both the circuit boards in the videos have electrolic caps.
Note however, it is JUST a MPPT controller that outputs a fixed voltage,
it is not a battery charger.

The SPV1020 chip , that's the eval board , is designed as a fully fledged , Just feed that into a PWM solar regulator and hey presto mppt charger ,( well , maybe a buck stage might be useful ) ,

Interesting chip , designed as a mppt per panel application replacing bypass diodes.

Interesting its even a 4 phase switcher , which should mean no nasty failure prone big caps on the output to control ripple

I see a project in my future. !!

Dave

[noelex 77]

Originally Posted by goboatingnow

What do you mean PWM versus on off , the PWMsokar regulators are an on off charger design.

Dave

There are three types of solar controllers/regulators. From cheapest to best they are:

1. On/off.
2.PWM
3.MPPT (which are generally also PWM)

There are no suitable collective nouns to describe these different types of regulators, but it is important to distinguish between them.

Calling PWM regulators On/off, or bang bang, is very confusing as it blurs the first two categories of regulators.