What is wrong with these solar charge contollers?

[Thresher]

What is wrong with these solar charge contollers?
Someone, in another post said that they should be thrown away and replaced with a proper battery management system.
What happens if you don't replace them?


Amazon.co.uk

I hope the link works.

 

[robmcg]

They are standard generic PWM solar charge controllers. Nothing inherently wrong with them but not in the same league as a decent MPPT controller which will ultimately give you better results from your solar installation.

 

[PaulGooch]

The Amazon reviews will give some clues. I's spend a bit more on something decent. As the OP has them fitted already, i'd treble check that they are working as they should and if they are, maybe wait until they break before replacing.

 

[vyv_cox]

I have had a PWM dual bank controller for longer than I care to remember, this one about 15 years I think. It is reliable and does everything I want it to do. There may be small power advantages with MPPT but there are other disadvantages, and in Greece there is no shortage of sunlight.

 

[geem]

I have had a PWM dual bank controller for longer than I care to remember, this one about 15 years I think. It is reliable and does everything I want it to do. There may be small power advantages with MPPT but there are other disadvantages, and in Greece there is no shortage of sunlight.

We find the output of our Victron MPPT amazing. We often exceed the rating of the panel due to the performance gain of good MPPT.
Now we are on a lithium battery we cook with an induction hob. We can use all the power we make. With 920w of solar we harvested 4.9kw yesterday.
We made 100 litres of drinking water, a tank of hot water, meals, cups of tea and still ended the day at 95% charged

 

[Chiara’s slave]

‘You last bought this item on 24/4/2021‘ it tells me. So yes, I have one, yes, it works, and reasonably well. Clearly I’m not a liveaboard like Geem, it’s just mucking about. Our battery is always fully charged when we arrive. We have 2 x 80w panels. One replaced recently. Cutting the wires to the old one froze the controller, I just disconnected everything and started again as per instructions, and it restarted normally. I’ll give it 8/10 for function and value. We could pay 8 times as much for an MPPT, to get 20 odd % better output.

 

[geem]

‘You last bought this item on 24/4/2021‘ it tells me. So yes, I have one, yes, it works, and reasonably well. Clearly I’m not a liveaboard like Geem, it’s just mucking about. Our battery is always fully charged when we arrive. We have 2 x 80w panels. One replaced recently. Cutting the wires to the old one froze the controller, I just disconnected everything and started again as per instructions, and it restarted normally. I’ll give it 8/10 for function and value. We could pay 8 times as much for an MPPT, to get 20 odd % better output.

And possibly longer battery life with correct voltages for bulk, absorption and float for your batteries plus temperature compensation of those settings.
It may not be relevant on a boat with cheapo batteries but if you have expensive batteries, it may make more sense

 

[noelex]

If you are going to buy a cheap solar controller, a PWM (not MPPT) model like this one is the best choice. The circuitry for a PWM controller is relatively simple and a reasonably reliable unit can be built and sold at a relatively low cost.

Try and pick a model with proper three stage charging (bulk/absorption/float) and user adjustable voltage set points.

I have not downloaded the manual, but this model appears to only do one stage charging (although the set point is adjustable) so there better choices than this particular model.

Keep in mind that this type of controller can only be used with so called 12v solar panels. These will typically have a Vmp of around 18v.

MPPT controllers will produce a higher yield, around an extra 15% is typical, but to do this a MPPT has to track the maximum power point accurately. The cheap MPPT controllers do not do this and are not worth bothering with.

 

[William_H]

The proper 3 stage regulation is fine if in fact you have enough solar power and sun shine and relatively small enough batteries that the batteries are charged and then go to float charge. However it seems to me that in many cases with small panel, large batteries limited sun,the system seldom goes to regulation. ie it runs flat out all the time the sun shines and still does not fully charge batteries. In which case the stepped regime becomes irrelevant.
If you have enough sunshine and solar power then yes the stepped regime can be useful but mostly full bore is ok with cut off of charge when and if full voltage is reached. Note that essentially a solar panel will try to charge at a voltage close to 16volts but pulls down to battery volts. That means that it will charge as hard as it can. Unlike say a mains charger where charge volts are critical ie 14.5 then down to 13.5 float.(aprox.)
So the PWM controller will charge at full panel capacity until regulation voltage is acheived (battery full) when it will switch on and off at at ratio that keeps the battery at appropriate float charge. So if mostly it is running full bore due to lack of sunshine or small panel large low charge battery then all good.
Now MPPT charger has this ability to convert what it gets from panels to the very best voltage for battery charging. So you can get some charge at low light levels and some improvement in charge by converting your 16v panel output to 14v needed to charge the battery. This can be even more enhanced by having 20v (12v) panels in series to provide 40 v to controller. So even in lowest light it can provide more than 14v to put charge in. Yes MPPT controllers also have the stepped charge regime which may or may not have any real value.
So to the OP what you have is fine. You may get more charge to convert to MPPT but then you could get more charge fitting more larger panels. ol'will

 

[noelex]

Three stage charging is important. There are plenty of PWM solar controllers that offer this ability so there is no need to spend lots of money, simply check the specifications to make sure you only buy a controller with this feature.

Without three stage charging the single voltage set point is chosen as compromise voltage between the ideal absorption and float voltage. This means the solar controller is much less likely to be able to recharge the battery to 100% SOC in a solar day even if adequate solar energy is available, but also the compromise voltage means the batteries will be held at voltage that is too high once the batteries are nearing fully charged. So, for example, if leaving the boat with minimal loads, a single stage charger will severely overcharge the batteries.

So always choose a PWM solar controller with three stage (bulk adsorption and float) charging.

There is no need to go to the greater expense of a good MPPT controller to obtain this feature.

A controller with single stage charging will only list one voltage set point in the specifications, so it is usually easy to tell even with the poor documentation that accompanies the cheaper chargers. If the controller only has single stage charging simply select another model. Your batteries will thank you .

 

[Thresher]

Thanks all. I only have a couple of lead acid leisure batteries and 100w solar panels so I think I will stick with my simple solar charger.