Should I change PWM to MPPT solar controller?

[cpedw]

When I first installed solar panels, there were only 2x20W panels (12V, in parallel because they are flat on deck and prone to shading). At the time, the consensus seemed to be that MPPT wasn't worthwhile at such low power.

Subsequently, I added 2 more 20W panels in parallel. Have I moved into the zone where it's worth paying more for an MPPT controller?

Last year, with all 4 x 20W panels and the PWM controller, the batteries just about held up through 4 days not moving. There's 3x100 Ah of domestic batteries. The major drain when anchored is the fridge. Not sure of its consumption but it wasn't hot on the NW coast of Ireland!

The engine (VP MD2030) is the only other charging source apart from very occasional mains in a marina. Do people recommend the Sterling A to B or a similar charge enhancer?

Our sailing is 6-8 weeks at a time, aiming to sail as much as practical but often finding the engine is in use for 4-6 hour stretches. We also choose (or are obliged sometimes) to spend several days anchored from time to time.

Derek

 

[FlyingGoose]

Yes a MPPT is more efficient for your panels , cannot help with the Sterling , some one will come along with some better thoughts on it

 

[Laminar Flow]

In low light conditions a MPPT is more efficient then a PWM. So, for Northern Europe a MPPT is preferable. For Med sailing a PWM is sufficient.
We have this one, the 40A version. It was cheap and has given us, so far, three years of faultless service.

 

[gregcope]

You can get cheap MPPT controller on ebay. Ensure you check reviews, as some are fake and PWM.

At the other end Victron make some great ones; Some have bluetooth and an App. I have a 75/15 (takes 200W)

 

[FlyingGoose]

This might help
Which solar charge controller: PWM or MPPT? | Victron Energy

 

[jaypea]

These guys were good for my panels and mppt https://www.photonicuniverse.com/

 

[LONG_KEELER]

I've been going through the same thought process.

The increase for an mppt appears to be between 10%-30% .

The larger the array the greater the benefit.

I decided that my 55w array did not warrant the extra cost.

 

[AngusMcDoon]

You can get cheap MPPT controller on ebay. Ensure you check reviews, as some are fake and PWM.

At the other end Victron make some great ones; Some have bluetooth and an App. I have a 75/15 (takes 200W)

The Epever ones as shown above are genuine MPPT. Anything less than the cost of those are usually fake.

 

[lw395]

Ideally, we'd all have the best of everything.
You could analyse the gain you might get from a better controller, you'd need to put in the detail of how you use the boat to get an accurate answer.

But if I had to guess, trying to run a fridge offgrid, the first place to spend money might be more or better panels.

If it was me, I'd also be looking at the charge current from the alternator and how that might be improved or not.
Our typical use pattern of motoring out of harbour most mornings, getting some serious amps into the batteries for say 40 minutes makes a huge difference.

One also has to consider how 'precious' the batteries are. If you've spent lots on a big bank of new batteries, and you will live aboard say 9 months of the year, it is imperative to treat the batteries to near-ideal charging, or you are wasting big money on batteries. If, like us, you've got old batteries and the actual number of daily cycles in a season is not so great, then giving the batteries a harder life is not such a big deal, so not worth investing big money to avoid.
In UK waters, it's hard for many people to avoid running the engine now and then to charge batteries. Relying on solar to avoid that will not work on a rainy week. But running the motor a couple of times a year to charge batteries won't kill it or you, doing so every week would be bad.

A look at the demand side, see if the fridge could be made more efficient?

 

[Rappey]

The cheap pwm controler works fine but panels run around 20v so the controler blocks the input above 12v. (Wasted current)
Change to mppt and it converts the whole 20v to amps, hence you get more current at 12v than what the panel is outputting .
At around £65 for the epever I would also recommend it.

 

[V1701]

Of course an MPPT will help but I suspect what you really could do with is to increase the size of your solar array, 80 watts isn't very much. If that's not feasible just accept that you might need to run the engine occasionally to augment the solar which is no biggie...