Charge controller suitability

[Cornelius0511]

I have three 250 solar panels on my narrow boat
Going to 6 leisure batteries
Recent volt controller burnout can anyone suggest suitable replacement

 

[PetiteFleur]

Speak to Photonic Universe, they will give good advice, website very good as well with lots of info. Prices reasonable as well.

 

[CJ13]

You won’t go far wrong with a Victron MPPT.

 

[KompetentKrew]

I have myself only just started looking at solar controllers yesterday, with a view to placing an order later tonight. I think what I write is correct - hopefully someone will correct me if I'm wrong.

The rating of your solar controller depends on whether you wire your panels in series or parallel.

I found these pages helpful, particularly the first (with the photos of the trees and shading).

• What’s The Difference Between Wiring Solar Panels in Series or Parallel?
• Camper Solar Panels - Series vs Parallel
• How to wire solar panels in series vs. parallel

I have a sailboat and, because of the mast, at least one of the panels will frequently be in shade, therefore I will wire the panels in parallel.

I guess your 250W panels will be 20V x 12.5A. You would connect them in series to get about 60V x 12.5A

Therefore the Victron 75/15 would be adequate. However the 100/15 or 100/20 are not much more expensive and would allow you to add an additional panel (or upgrade your existing panels) in future, so you might consider them instead. These models are all around the £100 mark.

If you wished to wire the panels in parallel then you would need a controller of at least 20V x 40A - it is the amps that are expensive and this would cost you a lot more, around £300 for the Victron 100/50.

The SmartSolar is Victron's premium product, with built in bluetooth that allows you to monitor it with an app on your phone. It can also talk to certain other accessories using a "SmartBus" network.

The BlueSolar product is their basic MPPT and, despite the name, it does not have built in bluetooth. It is just blue.

Hope this helps.

 

[KompetentKrew]

I should add that you should check the specifications of your panels - some are closer to 30V, and if you have three of those then the Victron 75/15 will not be adequate.

 

[William_H]

As sort of said it is the amps from the solar panels that demand a higher power (current) controller and the amps that probably fried your old controller.
Now you may already have 40v panels being typical domestic PV panels of around 250w. So it is most likely if you are running to 12v batteries that you have an MPPT controller. (panels sold for recreation tend to be 20v but for domestic houses 40v)
If you have 20v panels then you may have a PWM controller (cheaper) and it is likely that the current you want to put through it is more than controller can take. (quite likely over rated by Chinese maker)
So we would recommend an MPPT controller which can take the 40v panels or all 3 x 20v in series. If 40v panels then perhaps in series is too high voltage (120v) for some controllers but either way you will need a hefty controller. As said Victron are good. Just check the ratings. ol'will

 

[noelex]

I guess your 250W panels will be 20V x 12.5A. You would connect them in series to get about 60V x 12.5A

Therefore the Victron 75/15 would be adequate. However the 100/15 or 100/20 are not much more expensive and would allow you to add an additional panel (or upgrade your existing panels) in future, so you might consider them instead. These models are all around the £100 mark.

If you wished to wire the panels in parallel then you would need a controller of at least 20V x 40A - it is the amps that are expensive and this would cost you a lot more, around £300 for the Victron 100/50.

Unfortunately, that is not how it works. The current rating of solar controllers is a rating that also applies to the output.

So 750w of solar requires a controller with a current rating of at least 50 A (60 A would be better) if you have a 12v system. An alternative that is often a better solution for large solar arrays is to fit multiple controllers (often one per panel). So with a 3x250w array, three 20A controllers is an option.

Multiple controllers allows for better tracking resulting in a higher overall output and adds valuable redundancy. The drawback is slightly more complex wiring. Cost depends on the specifics. It is generally slightly more expensive, but sometimes multiple small controllers are less expensive that a single larger controller.

 

[Cornelius0511]

Thank you one and all for your prompt response reference solar panels controller will today follow up

 

[Poey50]

Unfortunately, that is not how it works. The current rating of solar controllers is a rating that also applies to the output.

So 750w of solar requires a controller with a current rating of at least 50 A (60 A would be better) if you have a 12v system. An alternative that is often a better solution for large solar arrays is to fit multiple controllers (often one per panel). So with a 3x250w array, three 20A controllers is an option.

Multiple controllers allows for better tracking resulting in a higher overall output and adds valuable redundancy. The drawback is slightly more complex wiring. Cost depends on the specifics. It is generally slightly more expensive, but sometimes multiple small controllers are less expensive that a single larger controller.

On our 32 footer there is limited space for solar so, to maximise, each of two 80 amp panels (in batwings configuration) has its own MPPT and a third MPPT takes care of a 30 watt panel plus a roving 100 watt panel that can be connected in parallel. As you say this also allows for redundancy if a controller dies and, for the batwing panels, avoids one panel in shade taking down both if they were connected in parallel. The greater ability to harvest sunlight of my lithium pack also helps but that's another topic.

 

[stuartwineberg]

I got an Epever controller from photonic which is excellent.

 

[KompetentKrew]

Unfortunately, that is not how it works. The current rating of solar controllers is a rating that also applies to the output.

So 750w of solar requires a controller with a current rating of at least 50 A (60 A would be better) if you have a 12v system. An alternative that is often a better solution for large solar arrays is to fit multiple controllers (often one per panel). So with a 3x250w array, three 20A controllers is an option.

Multiple controllers allows for better tracking resulting in a higher overall output and adds valuable redundancy. The drawback is slightly more complex wiring. Cost depends on the specifics. It is generally slightly more expensive, but sometimes multiple small controllers are less expensive that a single larger controller.

Many thanks for your reply, and I apologise to anyone misled by my ignorance (which is, as you will see deep and wide). I shall piggyback this thread.

I presently have 4 solar panels, and I recently discovered they are supplying no power. Shortly afterwards I read here that you should never disconnect the batteries from the charge controller without first disconnecting the solar panels (or switching to shunt?). No doubt this is the cause - I must have killed the solar controller when installing the SmartShunt and replacing a battery cable.

I find my panels were installed in 2013, the Solara model S80M36 - they are 23 Wp, 19V at max power and 22.6V open circuit, 1.21A at max power.

Consequently I have ordered a SmartSolar 100/15 to replace the dead controller - this model is little more expensive than the 75/10 and I thought it would give me additional capacity to replace my existing panels in the future - Solar's current model is 2cm longer on one side, but has 50% more output.

My current panels could be connected in series for 80V x 1.21A; total output about 100W, so the controller will put out about 12V x 8A (and this is with specification). Or they could be connected in parallel for 20V x 5A, doesn't make any difference.

If I were to upgrade to the new S140M42 panels, they are 35 Wp, 24.4V (28.6V open circuit) and 1.38A. So I guess the 100/15 would be able to cope with these too because I guess I woulds use the 24.4V figure if connecting them in series, and this is just below 100V. The total power of four panels is 140W and, whether they be connected in series or parallel, this is 11.5A on the 12v side, which is again within spec.

Does this seem right?

 

[noelex]

Many thanks for your reply, and I apologise to anyone misled by my ignorance (which is, as you will see deep and wide). I shall piggyback this thread.

Boats are complex and no one can know everything. That is what the forum is for. Hopefully the collective wisdom produces the right answer .

I presently have 4 solar panels, and I recently discovered they are supplying no power. Shortly afterwards I read here that you should never disconnect the batteries from the charge controller without first disconnecting the solar panels (or switching to shunt?). No doubt this is the cause - I must have killed the solar controller when installing the SmartShunt and replacing a battery cable.

As you point out, disconnecting the battery when the solar panels are connected is not good practice for most solar controllers. It can damage the controller, but this does not commonly happen. Most controllers survive. So double check there is not another fault in the system before forking out for a new controller.

If I were to upgrade to the new S140M42 panels, they are 35 Wp, 24.4V (28.6V open circuit) and 1.38A. So I guess the 100/15 would be able to cope with these too because I guess I woulds use the 24.4V figure if connecting them in series, and this is just below 100V. The total power of four panels is 140W and, whether they be connected in series or parallel, this is 11.5A on the 12v side, which is again within spec.
Does this seem right?

Unfortunately not. Nearly all solar controllers will self protect themselves if the maximum current rating is exceeded. So a 100/15 controller will not be damaged (although it is not good practice) if it is connected to a solar array that is delivering more than 15A. The controller will reduce the current, so energy is lost, but no damage is done.

The same is not true of voltage. If the maximum input voltage is exceeded even slightly and momentarily the controller is likely to be permanently damaged. For this reason manufacturers recommended allowing a buffer of 10-15% over the open circuit voltage. The buffer is because under some rare conditions (such as very cold temperatures) the voltage can be higher than the specifications. The higher open circuit voltage rather than the lower maximum power point voltage should be used because if the controller is disconnected and reconnected, the maximium open circuit voltage will be present briefly. So a 100/15 controller should only be connected to solar array with a maximum open circuit voltage of less than about 90v. 28.6x4=114.4v and this way too high.

 

[KompetentKrew]

Many thanks for your kind and helpful reply.

Unfortunately not. Nearly all solar controllers will self protect themselves if the maximum current rating is exceeded. So a 100/15 controller will not be damaged (although it is not good practice) if it is connected to a solar array that is delivering more than 15A. The controller will reduce the current, so energy is lost, but no damage is done.

The same is not true of voltage. If the maximum input voltage is exceeded even slightly and momentarily the controller is likely to be permanently damaged. For this reason manufacturers recommended allowing a buffer of 10-15% over the open circuit voltage. The buffer is because under some rare conditions (such as very cold temperatures) the voltage can be higher than the specifications. The higher open circuit voltage rather than the lower maximum power point voltage should be used because if the controller is disconnected and reconnected, the maximium open circuit voltage will be present briefly. So a 100/15 controller should only be connected to solar array with a maximum open circuit voltage of less than about 90v. 28.6x4=114.4v and this way too high.

But I could connect them in parallel, which would mean four of the new S140M42 panels would still put out less than 30V 6A on the solar side?

 

[noelex]

Many thanks for your kind and helpful reply.


But I could connect them in parallel, which would mean four of the new S140M42 panels would still put out less than 30V 6A on the solar side?

Yes that would be fine. Parallel also on average gives a higher total output on a sailboat.

A combination consisting of two groups of panels in series and then connecting the two groups in parallel would also be OK.

Keep in mind that series connection requires thinner wiring than parallel connection. Changing from series to parallel connection may involve replacing wiring unless you do some forward planning.

 

[rotrax]

In early May I installed 400W - 2X 200W - of rigid panels to the rear of our pilothouse roof, wired in parallel. I used the Epever 30 Amp MPPT Controller.

We left May 22nd for the West Country and Ireland with two fridges and a freezer going 24/7/365. Not needed a battery charge from the generator or shorepower since. Even in dull and rainy weather it more than balances the draw. Each fridge draws 4 amps when running, the freezer 5 amps.

Well Pleased. All in cost was £450.00, Panels, wiring, fuses, connectors and terminals, mountings, fastners and other ancillaries.

From Craig Solar. Reccomended from direct experience.

 

[KompetentKrew]

As you point out, disconnecting the battery when the solar panels are connected is not good practice for most solar controllers. It can damage the controller, but this does not commonly happen. Most controllers survive. So double check there is not another fault in the system before forking out for a new controller.

Many thanks - water had entered the structure of the doghouse and the crimps (where the panel's wiring joins the twin-and-earth to the controller) indeed appears to have corroded to nothing.