What rating controler?

[Dafydd_Cymru]

Hi ...I have 4 40w visionplus solar panels on my roof. A little while ago the battery was always flat having worked perfectly before. I get about 20.4v from the panels no load. With load, the terminals on the controller out give 11.2V From the controller the battery now does not charge but does with the engine going.
I assume my controller has gone as it is a recently new battery.

My question is the controller I have is 10A. Would it be ok to replace it with a 20A or 30A controller?
Many thanks in advance.

 

[Lenny HB]

You need a 20A one as on a very clear sunny day in June the output could peak above 10A. Also then means you could add another 100 watts if needed. Worth spending a bit more on a decent MPPT Regulator like a Votronic or Victron.

 

[andy63]

My question is the controller I have is 10A. Would it be ok to replace it with a 20A or 30A controller?

You could replace with a controller of higher current rating..especially if you think you may expand the system ...but imo 10amp controller is adequate for 160w of solar..
It sounds like your controller isnt outputting the required charging voltage but I'd be inclined to disconnect everything and re boot just to check .. and know the voltage and state of charge on your battery before connecting it up..
Andy.

 

[Dafydd_Cymru]

Many thanks! I did disconnect all. Then reconnected the load first then panels. No joy! That's why I think the thing is gone. I'll order a new 10A tonight....Joys of solar. 2nd one in 4 years.

 

[Dafydd_Cymru]

I may try it once more. I did not realise they recommend starting with a full battery. Mine was flat so the controller may not have set correct.

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[JockandRita]

I'll order a new 10A tonight.

I'd be inclined to order a 20A, and as Lenny HB suggested, a quality MPPT one at that.
I had a 10A controller, but soon became aware that it wasn't man enough for the additional 85w panel, which I have since seen both outputting 9.9A on my later controller display.

Cheers,

Jock.

 

[DBK]

I may try it once more. I did not realise they recommend starting with a full battery. Mine was flat so the controller may not have set correct.

If you battery was flat it may now be goosed, even if it is new. I would check this before buying another controller. Disconnect the solar then give the battery a good charge with a mains charger. Leave overnight then check the voltage. Anything under about 12.5 volts and it is probably shot.

 

[Hettie's Crew]

Why fit a 10A when the price difference is so small for a 20A. When I changed to an MPP I bought a 30A even though I only had 140w, thinking I would add more. We now have 300w and didn’t need to buy another controller

 

[Lenny HB]

Many thanks! I did disconnect all. Then reconnected the load first then panels. No joy! That's why I think the thing is gone. I'll order a new 10A tonight....Joys of solar. 2nd one in 4 years.

Many thanks! I did disconnect all. Then reconnected the load first then panels. No joy! That's why I think the thing is gone. I'll order a new 10A tonight....Joys of solar. 2nd one in 4 years.

A Votronic MPP 250 15A is less than a £120 might as well replace with a decent one as you have already had 2 fail.

 

[Dafydd_Cymru]

I have gone for a 40a replacement to add in the future. Curiosity, how do these things work. When I first connect the battery, do I need it fully charged for the controller to recognise that it is 12v?

I agree about getting a good one. I'll grab a cheap one for this trip then look around for a better one after I read up.

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[DBK]

I have gone for a 40a replacement to add in the future. Curiosity, how do these things work. When I first connect the battery, do I need it fully charged for the controller to recognise that it is 12v?

I agree about getting a good one. I'll grab a cheap one for this trip then look around for a better one after I read up.

Some controllers are both 12 and 24 volt, such as the Victron ones. They recognise which voltage they have been connected to and then provide appropriate charging voltages. In the case of the Victron ones they only need to be connected to the batteries once as they then remember the setting.

If the batteries are showing around 12 volts I am sure it will recognise what it should be doing - if it is dual 12/24 volts of course, if it isn't then it won't matter. But if the voltage is substantially less than 12 volts then the battery may be duff as I suggested above. Have you got a multimeter to check?

 

[Dafydd_Cymru]

Yes ...I got 11.1v....battery replacement won't hurt. Not that old but you never know. I seem to be replacing them every year. I might stick an extra one to ease the load.

 

[DBK]

Yes ...I got 11.1v....battery replacement won't hurt. Not that old but you never know. I seem to be replacing them every year. I might stick an extra one to ease the load.

You need to work out why they are being discharged as you shouldn't be going through one a year as I am sure you know. Getting a second battery may just double the annual expense. If you don't have one a battery monitor is the one gadget I find invaluable. Without it I simply can't rely on knowing the state of the batteries. Even just a simple voltmeter would let you watch the voltage and if it gets down to anything close to 12 volts then start turning things off.

 

[HandyAndy]

Good job you went for a higher amp rated charge controller, your 4 panels would be producing a smidge over the limit had you bought another 10 amp one.
Please tell me you got an MPPT charge controller rather than a PWM one..

 

[Dafydd_Cymru]

Run this by you. If I measure the controller output voltage with the battery connected....is that measuring the battery voltage rather than controller output? I take it measuring controller output without a load would not work and damage the controller? So to test the controller I must need to measure output to the battery current?

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[Dafydd_Cymru]

Good job you went for a higher amp rated charge controller, your 4 panels would be producing a smidge over the limit had you bought another 10 amp one.
Please tell me you got an MPPT charge controller rather than a PWM one..

I thought that to...overkill 40A MTTT

 

[DBK]

Run this by you. If I measure the controller output voltage with the battery connected....is that measuring the battery voltage rather than controller output? I take it measuring controller output without a load would not work and damage the controller? So to test the controller I must need to measure output to the battery current?

If the sun has been shining for a while with the controller connected you should expect to see a voltage at the battery terminals of around 13.5 to 13.7 volts. Even with clouds you should see the same providing there is no load.

If you see substantially less my suspicion is the battery is failed. You could check by temporarily connecting the solar charger to the cab battery and check the voltage after an hour or so. Alternatively, as suggested earlier, disconnect the leisure battery and give it a good charge with a mains charger then let it rest for a few hours and recheck the voltage. Less than around 12.5 volts suggests a failed battery.

 

[HandyAndy]

If the battery is flat / in poor condition, disconnected from the controller, the battery will read battery voltage or less so maximum 12.6v
Connected to the controller on a good battery, with reasonable sunlight hours (cloudy or not) it should read above 12.6 if it's going to be actually charging. Ideally 13.2 or higher. Up to a max of about 14.6v.
Charge controller does need to be connected to a battery to sense what it's supposed to be doing.
Measuring before the charge controller will give you your solar input voltage, measuring the output of the controller will give you the output voltage going to the battery

 

[andy63]

your 4 panels would be producing a smidge over the limit had you bought another 10 amp one.

Where do you get that from?
He has 4x 40w panels i thought...
Even if brand new and capable of their max output its 2 amps per panel max... add 25% safety and a 10 amp controler is still fine..
The only valid point ive read about choosing a higher rated controller is if the price difference is negligible between the two ..or you would want to expand the system which I mentioned anyway..
Andy

 

[HandyAndy]

Where do you get that from?
He has 4x 40w panels i thought...
Even if brand new and capable of their max output its 2 amps per panel max... add 25% safety and a 10 amp controler is still fine..
The only valid point ive read about choosing a higher rated controller is if the price difference is negligible between the two ..or you would want to expand the system which I mentioned anyway..
Andy

Ohms law.
160w at 14.4v is 11.1 amps
160w at 12v is 13.3 amps.

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[Camping Gaza]

Don't forget, if you are connecting and disconnecting the controller, disconnect solar first, any load from the load terminals, then the battery, and reconnecting, battery first, any load, then solar otherwise it's possible to damage the controller, according to my manual.

Putting ohms law to one side and looking at real world practicality, you will not get what is stated from a solar panel. Most good ones will give you about 75 percent in optimal conditions, add losses due to wiring, panel heating and in the controller and it drops even more.

I have 300w on my roof and lucky to get much out of that unless I am at the equator in full sun, with clinically clean panels with no shadows and they actually track the sun.

Real world tests show about a 10 percent advantage (in optimum conditions) with a MPPT over a PWM controller, and at only 4x 40watt panels you should decide if the price difference is worth it.

A 10 amp controller will be fine, but I would get a 20 amp as you are buying new anyway, in case you want to upgrade your panels or add more. Buying a big brand controller is great if you are that type and have spare cash to burn, personally I have used cheap ebay controllers and found they do not last long, so a good middle price range seems to work well for me.

Good battery care for me outstrips MPPT vs PWM for me based on my consumption vs my charge rate, as I also have a 40 amp B2B charger, and keeping all your batteries charged with a maintenance charge from a decent controller is more important IMHO

 

[andy63]

Ohms law.
160w at 14.4v is 11.1 amps
160w at 12v is 13.3 amps.

Check out the spe

Ohms law.
160w at 14.4v is 11.1 amps
160w at 12v is 13.3 amps.

But the current rating for the panel and its power rating are based on the panel stated voltage which is around 20v..
Check out the current rating of any 40w rigid panel.. it's usually 1.9 odd amps
When i said 2amps per panel i was been generous..
If you have ever seen 160w of solar producing 10 amps tell me where you got them from..
Andy.

 

[HandyAndy]

Fair enough, only had the info in the op to go on, didn't google the panel specs

 

[Lenny HB]

Check out the spe

But the current rating for the panel and its power rating are based on the panel stated voltage which is around 20v..
Check out the current rating of any 40w rigid panel.. it's usually 1.9 odd amps
When i said 2amps per panel i was been generous..
If you have ever seen 160w of solar producing 10 amps tell me where you got them from..
Andy.

20v is the open circuit voltage you need to base your calculation on the on load voltage which is around 17v. Which give 9.4 amps but you some times get a bit more under ideal conditions so 10a would have been very marginal.

 

[Lenny HB]

I have gone for a 40a replacement to add in the future. Curiosity, how do these things work. When I first connect the battery, do I need it fully charged for the controller to recognise that it is 12v?

I agree about getting a good one. I'll grab a cheap one for this trip then look around for a better one after I read up.

Did you get a decent MPPT regulator?

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[Dafydd_Cymru]

Did you get a decent MPPT regulator?

Decent is such an ambiguous word! MPPT yes but a budget one. I'll use this while I look for a better one. The one I bought is probably as naff as the one that has gone but it will give me time to research them.

 

[Dafydd_Cymru]

If the battery is flat / in poor condition, disconnected from the controller, the battery will read battery voltage or less so maximum 12.6v
Connected to the controller on a good battery, with reasonable sunlight hours (cloudy or not) it should read above 12.6 if it's going to be actually charging. Ideally 13.2 or higher. Up to a max of about 14.6v.
Charge controller does need to be connected to a battery to sense what it's supposed to be doing.
Measuring before the charge controller will give you your solar input voltage, measuring the output of the controller will give you the output voltage going to the battery

Unconnected the solar panels give 20.4v
with battery load, the output of the controller is giving 11.1v So I am starting to suspect the battery now.
I may bring it home to charge tonight and test it again. Trouble is the kids watching tv at night while away can totally flatten the battery every night.

 

[Lenny HB]

Decent is such an ambiguous word! MPPT yes but a budget one. I'll use this while I look for a better one. The one I bought is probably as naff as the one that has gone but it will give me time to research them.

Problem with the cheap ones is they say MPPT but they are not, it is quite surprising the amount of extra charge you get out of a good one. We rely on solar for 90% of our charging so a good regulator is important to us.

 

[Dafydd_Cymru]

Problem with the cheap ones is they say MPPT but they are not, it is quite surprising the amount of extra charge you get out of a good one. We rely on solar for 90% of our charging so a good regulator is important to us.

May I ask what yours is to read up on it? Reading your trips... I am impressed!

 

[andy63]

20v is the open circuit voltage you need to base your calculation on the on load voltage which is around 17v. Which give 9.4 amps but you some times get a bit more under ideal conditions so 10a would have been very marginal.

I was making a point about panel power ratings...
but yes i hear what youer saying even though I'm of the opinion that your scenario is largely theoretical and extremely unlikely and is still within the specs of the controller.... which would have to be a good quality mppt controller to achieve what you proposed, an therefore likely to cope..
I dont believe that the max current for each panel could be exceeded using a pwm controller which is what I was basing my comments on..
But either way id still be happy with a 10amp controller on 160w of solar based on everything ive seen on my solar installations.. unless i had plans to extend it...
Andy

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