MPPT VS PWM

[chaser]

I believe its called the "load" terminal and yes gives you power straight from the batteries but it is set to cut out if the voltage drops too low.

Martin

What is the load output of a charge controller?

Some charge controllers will have +- load output terminals. These can be used to control a load and have the battery terminal voltage. The output load is commonly used for 12V lighting. Basic control will be to switch the load terminals on/off via a button on the charge controller. Other charge controllers will have the ability to control the load terminals by setting on and off times or dawn to dusk on time, this is helpful if lights need to be switched on/off automatically.

Another function of the output terminals is that if the battery gets to a discharged state (usually around 11V) the load terminals are switched off by the charge controller to prevent over discharge of the battery. The output will be switched on again when the solar panel has charged the battery to around 12.5V.



Please be aware
The maximum load connected to the load terminals will be determined by the rating of the regulator e.g. 10A regulator will equal 10A load, therefore it is not advisable to connect an inverter via the load output of a solar controller as the current draw in most cases may be far too high for the solar controller to handle and could cause serious damage to the solar controller.

mines a 30 amp controller with an inline 20 amp fuse to the inverter.

 

[chaser]

I believe its called the "load" terminal and yes gives you power straight from the batteries but it is set to cut out if the voltage drops too low.

Martin

What is the load output of a charge controller?

Some charge controllers will have +- load output terminals. These can be used to control a load and have the battery terminal voltage. The output load is commonly used for 12V lighting. Basic control will be to switch the load terminals on/off via a button on the charge controller. Other charge controllers will have the ability to control the load terminals by setting on and off times or dawn to dusk on time, this is helpful if lights need to be switched on/off automatically.

Another function of the output terminals is that if the battery gets to a discharged state (usually around 11V) the load terminals are switched off by the charge controller to prevent over discharge of the battery. The output will be switched on again when the solar panel has charged the battery to around 12.5V.



Please be aware
The maximum load connected to the load terminals will be determined by the rating of the regulator e.g. 10A regulator will equal 10A load, therefore it is not advisable to connect an inverter via the load output of a solar controller as the current draw in most cases may be far too high for the solar controller to handle and could cause serious damage to the solar controller.

another question what advantage is a lesser amp controller, wont a 30 amp do just the same as a small one ?

 

[Silver-Fox]

@chaser and @funflair thanks for the answers in a simple way I can understand
Im ok with house electrics but car electrics sometimes have me stumped.
Especially when some live feeds are then seen as parts and stuff like that

 

[sweetie]

Now all the clever stuff has been asked, can I ask a daft question.

Why do the MPPT controllers have an out let for what appears to be a lamp?
Can that outlet been used for something else?

I have connected a double 12v socket for charging phones and occasional use of 300w innverter for wife’s hair tongs.

 

[funflair]

another question what advantage is a lesser amp controller, wont a 30 amp do just the same as a small one ?

Less money

Martin

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[funflair]

mines a 30 amp controller with an inline 20 amp fuse to the inverter.

So a 250watt inverter at a guess.

Martin

 

[chaser]

So a 250watt inverter at a guess.

Martin

see my previous photo, 1500 w

 

[tonyidle]

It is separate thin wire signal loom that plugs into the EBL for that function but most EBL's no longer have connection for it and they don't fit panels that display current any more apart from very high end vans. None fitted in any Hymers now.

Mine has - hence my interest.

 

[funflair]

see my previous photo, 1500 w

Sorry didn't see your photo But 1500 watts on a 12v/20 amp fuse? I guess you don't use many of the watts.

Martin

 

[manda3000gt]

mines a 30 amp controller with an inline 20 amp fuse to the inverter.

Why is the charge controller connected to the inverter ?

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[chaser]

Why is the charge controller connected to the inverter ?

because it was the easist way of wireing the inverter in the rear of the van, bearing in mind this is a diy ambulance conversion with a bulkhead, and as it was wired with large cable.

 

[funflair]

because it was the easist way of wireing the inverter in the rear of the van, bearing in mind this is a diy ambulance conversion with a bulkhead, and as it was wired with large cable.

What do you want the inverter to do as even 500 watts would need about 45 amps and the 20 amp fuse will limit it to not much more than 250 watts.

Martin

 

[chaser]

What do you want the inverter to do as even 500 watts would need about 45 amps and the 20 amp fuse will limit it to not much more than 250 watts.

Martin

not doubting your figuers but i have all sorts of drills and things working off it but in reality its only for charging laptops and stuff.

 

[Bobby22]

I have just caught up with this thread and for a system of only a 100w panel a PWM controller is good an MPPT has only got an advantage if the solar array is 150w or over.t
The text below is taken from the Victronenergy website. The information is also available elsewhere.
So @ShiftZZ if you have not already bought a controller you might want to read what the experts say.

3. Conclusion

PWM

The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).

MPPT

To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

The summary above and the full white paper, has been written and compiled by Reinout Vader.

John Rushworth

 

[Bobby22]

More research from " World's Leading Solar Controllers and Inverters". Morningstar.
They have a great PDF that explains all things solar controllers and indeed MPPT controllers are well represented but is the PWM a BETTER chioce for low power (specifically low current) motorhome arrays?

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[andy63]

PWM a BETTER chioce for low power (specifically low current) motorhome arrays?

Thats not necessarily so bobby..
Ive read the white paper with an open mind and dont come to that conclusion...
The mppt at worst acts as a pwm controller but under some circumstances even at low wattage installations (100w in the example used ) it can still out a preform a pwm...even if only by 10% using their example...@25 degC.
The final conclusion of that paper you quoted even states.....
.........................................

An MPPT charge controller is therefore the solution of choice:
a) If cell temperature will frequently be low (below 45°C) or very high (more than 75°C).
b)If cabling cost can be reduced substantially by increasing array voltage.
c) If system output at low irradiance is important.
d)If partial shading is a concern.

.........................

At least 3 of those points are fairly crucial and applicable to a mh installation applicable to our climate.. and would make a mppt controller....even a smaller one worth considering...

Andy...

 

[Guigsy]

Thats not necessarily so bobby..

I think the reasoning is that if you have a very limited budget, it's a waste to get an MPPT controller if your remaining cash ends up only stretches to a dated basic 30w panel. In that case you're probably better off going with 100w and PWM. With the dropping costs of MPPT chargers and panels, I'll agree that the 'go PWM' zone is shrinking.

 

[Bobby22]

Thats not necessarily so bobby..
Ive read the white paper with an open mind and dont come to that conclusion...
The mppt at worst acts as a pwm controller but under some circumstances even at low wattage installations (100w in the example used ) it can still out a preform a pwm...even if only by 10% using their example...@25 degC.
The final conclusion of that paper you quoted even states.....
.........................................

An MPPT charge controller is therefore the solution of choice:
a) If cell temperature will frequently be low (below 45°C) or very high (more than 75°C).
b)If cabling cost can be reduced substantially by increasing array voltage.
c) If system output at low irradiance is important.
d)If partial shading is a concern.

.........................

At least 3 of those points are fairly crucial and applicable to a mh installation applicable to our climate.. and would make a mppt controller....even a smaller one worth considering...

Andy...

If you get a chance read the pdf of Morningstar, ( quotes from them above #165 ) the graphs on MPPT show poorer harvesting on low power systems.

They are saying that in low current situation the PWM may have equal or better energy harvest.

After looking into both controllers i would suspect that an MPPT is the better choice if a van has more than 300w of solar.
The PWM can actually be a better choice for anything under 200w as the efficiency of an MPPT is poorer at these powers.

I have often wondered if getting an MPPT controller would benefit my system. I have a 120w of solar with a PWM and never had a problem with power.

 

[andy63]

If you get a chance read the pdf of Morningstar,

Cheers bobby...ill try and get round to that...
Andy..

 

[Guigsy]

After looking into both controllers i would suspect that an MPPT is the better choice if a van has more than 300w of solar.
The PWM can actually be a better choice for anything under 200w as the efficiency of an MPPT is poorer at these powers.

I'd suspect that's down to the capacity of the controllers. It might be the controlled Morning Star chose for the test was for mega-amps maximum with an array of panels, so it wasn't that efficient at low power. You don't drive a truck to the shops.

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