Which MPPT Controller?

[Gypsyjoss]

Hi Guys
I want a MPPT controller for a 50 Watt solar panel.

The cheap £15 ones on ebay appear to be fakes. I'm looking at Victron Blue and the Ep Solar tracer range at £60 plus.

Has anyone had any experience of these or any other make that they can recommend, please?

Cheers!

Pete

 

[laika]

...and if anyone has recommendations for one for up to about 300W, ideally with at least 2 separate inputs, I'd be interested in that too

 

[gregcope]

I have recently purchased a Victron Blue 75/15 which can take upto 200W of panels.

http://www.kurandamarine.co.uk/bluesolar-charge-controller-mppt-7015

A few notes;
- All the electrics are encapsulated within the housing
- You need to have a dump load connected
- Has different modes but I will use it as standard
- Only has a connections for dump, panels and output. You have to do your own multi-input wiring
- Larger models have MC4 connectors which means you can buy the MC4 multiple connectors (2 to 1 or more)

Overall pleased. Not cheap, but well made and looks like a quality product.

 

[VicS]

I have recently purchased a Victron Blue 75/15 which can take upto 200W of panels.

http://www.kurandamarine.co.uk/bluesolar-charge-controller-mppt-7015

A few notes;
- All the electrics are encapsulated within the housing
- You need to have a dump load connected
- Has different modes but I will use it as standard
- Only has a connections for dump, panels and output. You have to do your own multi-input wiring
- Larger models have MC4 connectors which means you can buy the MC4 multiple connectors (2 to 1 or more)

Overall pleased. Not cheap, but well made and looks like a quality product.

I think you mis understand the purpose of the "load" connection It is not for a "dump" it is an automatic load disconnect feature which offers an option to connect a load or loads ( 15 amps max ) via the controller in a way which will prevent over discharge of the battery.

from the Victron data sheet

Load output
Over-discharge of the battery can be prevented by connecting all loads to the load output. The load output
will disconnect the load when the battery has been discharged to a preset voltage​

You can use it, if you wish, to prevent something like a fridge, for example, over-discharging the battery.

 

[William_H]

Yes I have looked at MPPT controllers from China. Some bravely show a picture of the internals.
What is an essential part of an MPPT controlleris an inductor or transformer which effectively transforms the switched DC from the panel down in voltage (so up in current) to that voltage needed for the battery charge. (often in 3 stages of voltage like a charger or altenator controller.
When you look at the printed circuit board there is in some cases clearly no inductor so not true MPPT.
Even with a switching inductor circuit the really mysterious part of the MPPT controller is this max power point tracking.
The switching transistor takes bites of DC from a capacitor charged from the panel input. This transistor is switched at a variable rate which determines how much power is extracted from the capacitor and hence from the panel.
Some sort of microprocessor checks periodically and determines just what voltage and current the power should be taken from the panel to give max power. This is an area that is very difficult to measure or decide just how good the MPPT controller is. This aspect becomes more critical in low panel output conditions.

I am using one of these at home for a solar installation fairly successfully.
http://www.ebay.com/itm/DC-to-DC-Bu...188382?hash=item566fc23e5e:g:-RYAAOSwpdpVbX0R
It has the transforming function at reasonable efficency and is set to give a voltage to the battery of 14.1 so the battery will not be overcharged. It does however reduce the charge current as the battery gets more charged so reducing efficiency of charge.
The switch transistor in this simply switches on for a longer time if more output voltage is required. So as the sun power fades it sucks more power from the solar panel till it looks like a near short circuit ie low voltage high current means much less power. So it is definitely not MPPT.

On the othe rhand if you use a PWM type cheap controller it will provide the full panel voltage or nearly so to the battery meaning that every bit of current goes to charging the battery regardless of battery charge.
Disregarding the fact that about 20 % of the panel voltage (power) is wasted in the panel internal resistance.
The PWM type should only start to limit charge current when voltage of the battery rises to near 14v
Or you could use direct connection of the panel with no limiting. (risking battery overcharge)
All very complicated and us mere mortals may never know if the MPPT controller we buy really does what it claims in terms of accurately tracking max power point and converting voltage and current at that point
to what our battery really needs. Especially given that solar power seldom has enough power to recharge batteries fully. good luck olewill

 

[Poecheng]

I have a Victron 75/15 (as above) and am very pleased with it - it works as expected in that it provides a good charging voltage at the battery and works through a charging algorithm eventually arriving at a float charge.

My understanding of its workings accords with that of VicS; I have two wires for input (from one or more panels) and two for output. That's it.

 

[gregcope]

I think you mis understand the purpose of the "load" connection It is not for a "dump" it is an automatic load disconnect feature which offers an option to connect a load or loads ( 15 amps max ) via the controller in a way which will prevent over discharge of the battery.

from the Victron data sheet

Load output
Over-discharge of the battery can be prevented by connecting all loads to the load output. The load output
will disconnect the load when the battery has been discharged to a preset voltage​

You can use it, if you wish, to prevent something like a fridge, for example, over-discharging the battery.

I asked the Victron technical support about the LOAD and they said;

"Do not connect motors or loads with high inrush currents."

I have (re)asked if you HAVE to connect a Load. Call me dim, but it is not clear if you must in the manual ...

Still pleased with it. Nicely made. I liked the Blue internal encapsulation.

Greg

 

[VicS]

I asked the Victron technical support about the LOAD and they said;

"Do not connect motors or loads with high inrush currents."

I have (re)asked if you HAVE to connect a Load. Call me dim, but it is not clear if you must in the manual ...

Still pleased with it. Nicely made. I liked the Blue internal encapsulation.

Greg

Inverters are specifically mentioned in the data sheet as unsuitable loads. If necessary control circuits can be connected to the load terminals though.

A snag , if that's the right word, with these controllers which recently came to light on these forums is that the voltage from the solar panel must exceed the battery volts by 5 volts before they begin to operate. This means that with lower output panels / low light conditions/ partial shading they may not charge whereas a PWM controller will. However the problem can be overcome by connecting two, or even three, panels in series as the controller will accept up to 75 volts input.

 

[ianj99]

Inverters are specifically mentioned in the data sheet as unsuitable loads. If necessary control circuits can be connected to the load terminals though.

A snag , if that's the right word, with these controllers which recently came to light on these forums is that the voltage from the solar panel must exceed the battery volts by 5 volts before they begin to operate. This means that with lower output panels / low light conditions/ partial shading they may not charge whereas a PWM controller will. However the problem can be overcome by connecting two, or even three, panels in series as the controller will accept up to 75 volts input.

You could even wire a switch to change from parallel (during the summer) to series during the rest of the year, thereby having max charging current when you need it and not have a problem with insufficient panel volts the rest of the time.

 

[VicS]

You could even wire a switch to change from parallel (during the summer) to series during the rest of the year, thereby having max charging current when you need it and not have a problem with insufficient panel volts the rest of the time.

With these MPPT controllers I don't think there would be any advantage in switching to parallel during the summer. They optimise the operation of the panels and use electronic jiggery pokery to convert what they get out of the panels into what you want for battery charging.

 

[gregcope]

Tech support replied that I do NOT need to connect anything to the LOAD.

The tech support is very prompt on email, if some things are lost in translation.

Also the supplier and panel manufacture both recommended parallel panel connections.

I appreciate in some shading and low light the mppt might not start due to the 5v differential. My usage is mostly summer based and my 72W should be more than enoughto charge my 250AH bank during the week. I also plan to add another 100W or so.

David Berry wrote an article in Jan 2015 PBO here where he fitted a 75/15 to compare;

http://www.victronenergy.com/upload/documents/Fitting-solar-panels-to-boats.pdf

 

[VicS]

Also the supplier and panel manufacture both recommended parallel panel connections.

A little surprising because the instruction manual says

3.2. PV configuration

● The controller will operate only if the PV voltage exceeds battery voltage (Vbat).
● PV voltage must exceed Vbat + 5V for the controller to start. Thereafter minimum PV
voltage is Vbat + 1V.
● Maximum open circuit PV voltage: 75V.
The controller can be used with any PV configuration that satisfies the three above
mentioned conditions.
For example:
12V battery and mono- or polycristalline panels
● Minimum number of cells in series: 36 (12V panel).​

In particular

● Recommended number of cells for highest controller efficiency: 72
(2x 12V panel in series or 1x 24V panel).​

 

[gregcope]

A little surprising because the instruction manual says

3.2. PV configuration

● The controller will operate only if the PV voltage exceeds battery voltage (Vbat).
● PV voltage must exceed Vbat + 5V for the controller to start. Thereafter minimum PV
voltage is Vbat + 1V.
● Maximum open circuit PV voltage: 75V.
The controller can be used with any PV configuration that satisfies the three above
mentioned conditions.
For example:
12V battery and mono- or polycristalline panels
● Minimum number of cells in series: 36 (12V panel).​

In particular

● Recommended number of cells for highest controller efficiency: 72
(2x 12V panel in series or 1x 24V panel).​

I think their recommendations are due to issues with shading.

Just saying what I was quoted.

 

[gregcope]

Oh, and I plan to fit them with T shaped connectors, so I can go from Parallel to Serial if I want.

 

[aluijten]

I bought one of these:

http://www.ebay.co.uk/itm/Regolator...ello-solare-/261798309452?hash=item3cf4652e4c

Delivery was excellent. The item looks pretty nice, did some experiments but not used in anger yet.
You can actually watch the regulator seeking for the optimum point in power harvest from the panel.
I opened it up and the electronics look pretty well layed-out, no cheap assembly.
There are several versions of this regualtor available (different max. currents)

 

[charles_reed]

I bought a BZ 500 about 5 years ago, direct from the States - input up to 72 volts, capable of 500 amps @ 12v. Switchable float from 13.5v to 14.8v, complete with readout for battery volts/amps/panel amps.
Input is optimised @ 48v but I use 24v.
Charges @ about 1v above system volts and put out up to 18 amps (in pulse mode) from 328w of PV panel into seriously discharged batteries, dropping to about 8 amps into charged batteries, before going into float - that's @ 35-40 N. @ noon in summer.
Cost was $US 348.

 

[ip485]

I have fitted an Outback MPPT - its been excellent and very robust with 800W of solar. They do a number of smaller controllers I believe, but highly recommended.

 

[Javelin]

So with two 100w panels mounted on top of the cockpit spray hood what controller does the panel recommend?
Getting a little confused with all the options and the cost differential seems massive between the options.

Use will be UK waters, East Anglian coast predominately.
The boom I guess will cast a shadow on one or the other panel at some stages of the day.
Battery bank is 4 x 110amp deep cycle plus a small high crank engine battery.

 

[Poecheng]

So with two 100w panels mounted on top of the cockpit spray hood what controller does the panel recommend?
Getting a little confused with all the options and the cost differential seems massive between the options.

Use will be UK waters, East Anglian coast predominately.
The boom I guess will cast a shadow on one or the other panel at some stages of the day.
Battery bank is 4 x 110amp deep cycle plus a small high crank engine battery.

In that scenario I would put the panels in series (24v but probably about 28v if both working well; if one good and one less good then you are still getting more than 14v) and push it into a Victron 75/15 MPPT.
These can take 75v max (so no problem)
These can take 15A max (again no problem as 2x100W/24v = 8.33A or 200w/28v = 7.14A)

It has alternative settings and a small metal jumper piece but you want their recommended setting which (IIRC) means you remove the jumper - takes longer to explain than to do!
Connect the Victron to the battery (or permanently connected distribution busbar) and it identifies whether you are 12v or 24v system.
Then connect up the panel(s) to the input and off you go.
If you are as sad as me - spend lots of time looking in awe at the battery voltage (multimeter) and the lights (victron unit) :encouragement:

It should cost about £70 and you know you have the real thing.

 

[ianj99]

In that scenario I would put the panels in series (24v but probably about 28v if both working well; if one good and one less good then you are still getting more than 14v) and push it into a Victron 75/15 MPPT.
These can take 75v max (so no problem)
These can take 15A max (again no problem as 2x100W/24v = 8.33A or 200w/28v = 7.14A)

It has alternative settings and a small metal jumper piece but you want their recommended setting which (IIRC) means you remove the jumper - takes longer to explain than to do!
Connect the Victron to the battery (or permanently connected distribution busbar) and it identifies whether you are 12v or 24v system.
Then connect up the panel(s) to the input and off you go.
If you are as sad as me - spend lots of time looking in awe at the battery voltage (multimeter) and the lights (victron unit) :encouragement:

It should cost about £70 and you know you have the real thing.

That's daft! Putting panels in series halves the current available from the two panels. ie the OP will in effect just have one 100watt panel with (potential) 24v charging ability.

I recommend a Victron or similar multi stage charger with multiple outputs so the engine battery can be charged when the main batteries are charged.
Its a false economy to spend a few hundred on panels, skimp on a decent charger and then wonder why your battery life has been shortened and effective capacity reduced by regular undercharging.

I checked out the reasons for putting the panels in series and Victron's argument relates to the drop in panel output voltage with temperature and also being able to use thinner cables. You can read more here:

http://www.victronenergy.com/upload...Which-solar-charge-controller-PWM-or-MPPT.pdf

But their example shows a 24v 100watt panel (ie yours in series) only provides 66w, so you are sacrificing charging current most of the time in UK waters simply to maintain better charging at high panel temps, which may rarely occur. In the Med, for example, there is possibly a case for their recommendation.