Upgrading existing solar set up - advice please on MPPT size (the start of many questions ...)

[MisterB]

Good afternoon. Like a lot of people i am trying to take advantage of the lockdown to catch up on a few projects on the Motorhome. Sat dish all tested and rteady for 'gluing' on, Sterling 50A B2B wiring started and a fridge fan installation being planned.

Next project will be to upgrade my solar that came with the MH. it has an 80w panel and a PWM controller. I would like to upgrade to around 150w and install an MPPT controller.

My first question is - if i get a 40A MMPT will it work more efficiently/better than a 60A or higher when connected to 150W of solar panel(s). The price difference isn't great but then again why spend extra money on something not needed other than bragging rights on who has the biggest. i have 2 x 110A lead acid batteries and i see no reason to change them. We usually drive for two or three hours per day when touring and probably only stay at one place for a couple of nights maximum without EHU, so i am sure the B2B will take care of most of our needs in terms of charging the batteries.

if you can see any major flaws in my 'plan' then please let me know, of course we all have our own way of doing things or how they should be done better, but i am keen to know if my thought process is on track.

Best wishes and keep safe.

 

[Manic]

I’ve got 2x100watt panels and have fitted a Votronic 250duo MPPT controller which seems to work very well.

 

[Lenny HB]

Some of the cheaper regulators are slightly better running at their max but not problem with decent quality ones.
You would only need a 60 A one if you were fitting a 1000 watts of panels, can't get that on most van roofs.

Look at what the maximum size panels you will ever fit to your van then choose a regulator to suit. I would go for either a Votronic or Victron.
I have a Votronic 350 MPP with 300 watts of panels.

 

[WESTY66]

Some of the cheaper regulators are slightly better running at their max but not problem with decent quality ones.
You would only need a 60 A one if you were fitting a 1000 watts of panels, can't get that on most van roofs.

Look at what the maximum size panels you will ever fit to your van then choose a regulator to suit. I would go for either a Votronic or Victron.
I have a Votronic 350 MPP with 300 watts of panels.

Hi Lenny, I am going to start my solar upgrade bit by bit, I have I believe a 100w solar on roof coupled up to the crappiest Pwm you have ever seen, so first thing I buy is going to be the Votronic MPP 350 Duo like yours (I am going to add another panel or two in a while) question is it says I can couple up to both leisure and starter is it just a straight forward pos & neg to starter batt and same to leisure? (I have two 110 Gels). Also will it cause problems when I have a B2B fitted later in the year?

Ady

 

[Jev88]

I have a quality PWM from another Funster I got with their panel when they upgraded.
It works physically better than several cheap MPPT controllers I have tried so I intend to invest in a Victron or EPever MPPT. I think 100watt panels typically max out at under 6watts from the controller built on the back (someone may correct me). So a Victron 15amp would suffice for 2x 100watt panels?
The knowledgeable chaos above will guide you.

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[MisterB]

I have a quality PWM from another Funster I got with their panel when they upgraded.
It works physically better than several cheap MPPT controllers I have tried so I intend to invest in a Victron or EPever MPPT. I think 100watt panels typically max out at under 6watts from the controller built on the back (someone may correct me). So a Victron 15amp would suffice for 2x 100watt panels?
The knowledgeable chaos above will guide you.

6 watts or 6 amps?

 

[Hettie's Crew]

Consider what you may do in the future, I only had a 140 watt poly panel but fitted a Votronic MPP350 duo digital rather than the 165 or the 250 because I thought I might add panels in the future. I later replaced the 140w poly with 120w and 180w mono panels (300w) with no need to change the controller.

 

[Lenny HB]

Hi Lenny, I am going to start my solar upgrade bit by bit, I have I believe a 100w solar on roof coupled up to the crappiest Pwm you have ever seen, so first thing I buy is going to be the Votronic MPP 350 Duo like yours (I am going to add another panel or two in a while) question is it says I can couple up to both leisure and starter is it just a straight forward pos & neg to starter batt and same to leisure? (I have two 110 Gels). Also will it cause problems when I have a B2B fitted later in the year?

Ady

There is a separate 1 Amp output you just need to run a cable from it to the starter battery positive.
I didn't use it as I had a CBE solar split charge relay lying around as that can give me up to 4 amps to the starter battery.

If you are going to use the AES output to the fridge, it is best to fit a switch or relay inline to disconnect if you are on EHU. The fridge isn't very clever and if it detects 12v even when on EHU it switches to 12v. I fitted a 230v relay that disconnects the AES feed when on EHU.

 

[Jev88]

6 watts or 6 amps?

Sorry typo! 6 Amps. Info should be available for your individual panel. Like this..... 5.04amp on this panel.

 

[Off da Grid]

Don’t over do it with the controller unless your going to fit more panels in the future.
I’ve got the Votronic mppt 350 duo for my 255watt panel works a treat.
One note to consider you should allow 10 to 20% more capacity on the controller than your panels can max out to allow for ideal solar conditions.
In perfect conditions not likely in the U.K. a cold solar panel in winter perfectly lined up to the sun could potentially output more than its rated capacity. Which is measured at 25° C, the hotter the panel the less efficient it becomes.
Solar is more efficient when cold. I’ve seen more than 10amps from my setup at 9:00am in the summer.

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[WESTY66]

There is a separate 1 Amp output you just need to run a cable from it to the starter battery positive.
I didn't use it as I had a CBE solar split charge relay lying around as that can give me up to 4 amps to the starter battery.

If you are going to use the AES output to the fridge, it is best to fit a switch or relay inline to disconnect if you are on EHU. The fridge isn't very clever and if it detects 12v even when on EHU it switches to 12v. I fitted a 230v relay that disconnects the AES feed when on EHU.

Lenny HB, when you post stuff to help me with my electrics, all I see is

 

[Crazylegs]

We fitted one of these kits to our old van.

12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

12V solar panel solar charging kits for motorhome caravan boat campervan yacht marine off-grid

www.photonicuniverse.com

Always keep our two leisure and starting batteries topped up, the trouble and strife can dry her hair (via an inverter) so when we got a different van this winter we did the same again.

 

[Lenny HB]

Lenny HB, when you post stuff to help me with my electrics, all I see is

View attachment 378978

You need to go to Specsavers then.

 

[Madcaravanner]

Just got this - which recommends 30amp controller to charge 300 A/Hr of batteries
Arrived this morning from UK by Post Office 48hr free delivery

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=402144577086

 

[Lenny HB]

Just got this - which recommends 30amp controller to charge 300 A/Hr of batteries
Arrived this morning from UK by Post Office 48hr free delivery

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=402144577086

No way is that going to be an MPPT controller at than price. A decent 30 amp regulator is nearer £200.
I paid £165 for my 25 amp Votronic, you get what you pay for with solar regulators.

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[Jev88]

No way is that going to be an MPPT controller at than price. A decent 30 amp regulator is nearer £200.
I paid £165 for my 25 amp Votronic, you get what you pay for with solar regulators.

I almost hate to agree with you ?.
EPever and Victron cost a lot more but cheaper ones just don't seem to perform. But then most users aren't capable of testing properly. Measuring actual Ampage supplied is a bit tricky without knowledge.

 

[Allanm]

Just got this - which recommends 30amp controller to charge 300 A/Hr of batteries
Arrived this morning from UK by Post Office 48hr free delivery

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=402144577086

I had one of those a few years ago before I got my head round what I really needed. It’s not an MPPT controller, the seller says it works like one, but it doesn’t.
It was rubbish and I sent it back saying to the seller it was misdescribed. I got a refund straight away.

 

[autorouter]

Don’t over do it with the controller unless your going to fit more panels in the future.
I’ve got the Votronic mppt 350 duo for my 255watt panel works a treat.
One note to consider you should allow 10 to 20% more capacity on the controller than your panels can max out to allow for ideal solar conditions.
In perfect conditions not likely in the U.K. a cold solar panel in winter perfectly lined up to the sun could potentially output more than its rated capacity. Which is measured at 25° C, the hotter the panel the less efficient it becomes.
Solar is more efficient when cold. I’ve seen more than 10amps from my setup at 9:00am in the summer.

Be careful of the difference between panel amps and battery amps. A solar controller amps rating is the output amps to the batteries, not the input amps from the panel.

When the panel voltage is 18V and the battery voltage is 13V there's not a huge difference. However some large panels are 28V or 36V, so the difference is significant.