Fitting solar from scratch

When your leisure battery is fully charged , the charge controller backs off the current to control the battery voltage and avoid killing the battery.

The only way you will ever see the full output of the controller is when the leisure battery is down at 12.8 volts or less. I have to turn on my fridge and turn off the solar cells for a few minutes to run down the battery a bit before seeing the full current when I turn the solar cells back on.

Low currents and 13.8 to 14.4 volts on the battery mean it has worked and the battery is fully charged...

 

This is probably a bad connection, most likely where the tinsel comes out of the panel and is terminated in a junction box or wires are soldered to it. Its usually possible to see evidence for that as the silver finish on the tinsel running to the connection point will appear grey or blackened through the glass or top plastic film.
If you want you can excavate the plastic layers on the back of the panel with a stnaley knife and uncover clean metal, solder on wires and seal with Sikaflex ( not silicone) . It was why I was given my otherwise £600 each panels. Time at sea with 5 panels in series had fizzed away the connections.

 

I need to replace the controller on our motorhome but not sure whether its worth fitting an MPPT controller or just spend a 1/4 of the price on a PWM one. Its only got a single 100W monocrystalline solar panel on the roof.
Is it worth the extra £50-60 for the MPPT? I could nearly fit another 100W panel up there for that price.

 

Leave the split charge system in. They'll both work together without a problem and it'll mean both batteries will charge while you're driving.

 

Unfortunately these panels are unable to charge a partially discharged battery. Once connected the panel voltage drops down to battery voltage and in direct sunlight (with the fridge switched on) the most I’ve seen is just over an amp from one panel and under an amp from the other with the battery voltage slowly dropping. Incidentally the battery is new, tests okay and charges fine from the split charge.

These were two brand new Eco-Worthy 100w monocrystalline panels, never exposed to salt water or even any rain but what they have been exposed to is lots of sun, high temperatures and partial shade. I’ve carefully inspected every inch of both panels and there are no signs of damage to the top surface or in the junction boxes.

Research suggests that semi-flexible panels stuck to a roof and exposed to high temperatures frequently fail within a year or two, and often less. If I bother to replace them, I’ll try to fit rigid panes with an air gap and I’ll definitely check both the open circuit voltage and short circuit current before fixing them.

 

This is what i'm playing with at the moment. Most 100w solar panels are too wide to fit the available space so i can either mount a huge 150w one on the front part of the roof which is 10ft above the ground and miles away from the cable entry point or find another narrow 100w monocrystalline panel and fit it on the opposite side of the roof to where the current one is. That might be a future upgrade so i'd like to fit a controller that will cope with the extra amps.

 

Personally if you are going to fit a new controller get an MPPT one and one that can handle another 100watt panel later on. So look at a 20 amp controller. Look up Will Prowse on you tube for an idea of what to buy

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I suppose that there must be a reason some panels like the Solbian SP100 panels I have on my bus are sold at £700 each for the same 100 watt rating.
Some of it will be scene tax, but some of it will be down to component sourcing from lower cost vendors, or at the extreme doing a Shenzen Scrap Heap Challenge to source the cells...

The £128 eco-worthy semi-rigid reviews on Amazon show there have been a few people who lose output from the panels after a short time.

 

Are the Solbian ones any good, how long have they lasted? I was thinking of installing one on my boat under the boom ... I know off topic. Can you stand on them and have you?

 

The Solbian panels were fitted on a seagoing boat, they did suffer corrosion damage, the boat was a low-freeboard catamaran, with the solar panels series connected giving 100 volts open circuit.
Which with salt water is asking for electrolysis - the series connector boxes equipped with Deutsch waterproof plugs also rotted where water got in.

I dont think anybody walked on them in that installation as the boat was quite small.
But they do have a very tough plastic covering, which is smooth, but it still has got a bit scratched over time.

I read of people even zipping them to biminis , where the wind will flex them.

So all I can say is that mine are still good after 18 months from restoration from corroded terminations and gluing on the bus roof at Techenders.

With regard to controllers, I began with the £20 or under PWM controller because I hadnt spent anything on the panels and was not sure they worked.
The charge controller wokred but it had horrible features like the positive connections are all joined together internally, the negatives are switched. This is OK for a standalone panel , battery and load. But not in a negative earth vehicle.
The result is if you short out the ouput of the controller, the leisure battery blows the PCB tracks before the fuse blows.

Now I know they work I have bought the Epever Tracer 20 amp version, mainly because it is a quality item at a reasonable price, and because it has the external data port for remote display and control.
I havent yet seen a proper sunny day with the sun high in the sky to get near full output - I have seen 40 volts into the controller but only a few amps on load around 36 volts.

 

I was looking at this Tracer MPPT 2210A one at £61.80 on ebay.
https://www.ebay.co.uk/itm/New-EPEV...hash=item3d9a035d4a:m:maeULwMNvRJWqorf61qou4A

 

Thanks Mike, we have a relatively high freeboard/dry yacht so spray less of an issue. I will have to add this to the list of things to do.

 

Nope. Its a big PWM.. Even the brand name is a laugh "Perfect Suitor" rather than Perfect Solar or some such..





Its not big and heavy , just 6 MOSFETs on a heatsink with some USB sockets slapped on it to make it seem better value.
You can get the same performance for 200W/20A from a cheaper unit.
This guy takes the cover off at around 08:00



That one weighs about a pound . The Epever tracer weighs 3.69 pounds, that weight is the magnetics for MPPT storing energy and transforming from 40V to 12V rather than simply pulsing the solar cells connection to the battery.

So if it is light weight it will charge batteries OK and cheaply but it wont be MPPT. Pay three times as much and you will get more charge on duller days than with a PWM.

With my original setup having 200W of "free" panels and a £20 controller was the cheapest solar power.

Now I have decided it works, I have coughed up the £65 for the Epever because I have never heard complaint about the charge controller just the panels..

 

To the average man selecting panels and controllers seems a nightmare. As well as the Solbian panels I took a look at some on Photonicuniverse ... they were significantly cheaper buggered if I can spot the difference. The rigid one I got from there, which is on my camper roof seems to be OK.

 

Heres what a panel looks like with corrosion damage..



Note the darker metal strip, beside the sticker, thats the positive corroding.

The PU sealant is filling holes left by the original termination box fixings.


Note there is NO WAY I would pay £700 for a solar panel. These were bought as the best possible for a commercial project, then chucked in the skip when damaged.


I would be looking at the second cheapest panel on the market and reading the customer reviews to help.

 

Is the weight really a good indicator? I have the votronic mpp165 it's a small unit and only weighs 225g but is MPPT and I thought the votronic kit has a good reputation. Maybe I need to take it apart to investigate

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There are a lot of cheap controllers out there. They have 6 MOSFETs as switches and a microcontroller and an LCD

My Sun Yoba in this style weighs 250g and it says MPPT ...




But its LIES!!

I will get a picture of inside this one



and the Epever later today ...




You need to be able to store all the energy in a magnetic field in a switchmode MPPT controller. Depending on the switching frequency the inductor storing energy may be 1000 or more times smaller than a 50HZ mains transformer doing the same job.. but it still needs a mass of ferrite which is heavy to store the energy, hence weight...