Solar trailer build

[matthewslack]

Spring is just around the corner, and today is dry. I finally could resist no more, and so the first of my Sunpower 110W solar panels has finally made it out of its box, onto a heavyweight piece of plywood and into the wind and occasional sun. As the picture shows, for 'open' systems, adding solar input is quite simple. Just a panel, a suitable charge controller and plug in to your battery's charging port. You can connect to the output port as I have here, but better to go via the proper route to let the BMS do its stuff.

Is it worth it? That depends on how far, how fast, how off-grid you travel. Not much good on the crowded London streets, but on the open road for wild camping tours in Scotland I'm expecting it to be quite useful.

I use Anderson powerpoles for most of the connections, and standard solar MC4s to connect to the panel.

That plywood might make the odd local journey on the trailer, but my aim is something much lighter. It is a start!

 

[guerney]

That's great! So you're charging at about 4A? I've noted the parts (cheers!), in case I fancy having a go at this sort of thing sometime. Are you planning to add the other panels you mentioned, to this charging system? How many? Will the panels fit inside the trailer? Will you need a black belt in Origami, to make them fit inside trailer? Where do snarks be? Will you need a bigger net?

 

[matthewslack]

That's great! So you're charging at about 4A? I've noted the parts (cheers!), in case I fancy having a go at this sort of thing sometime. Are you planning to add the other panels you mentioned, to this charging system? How many? Will the panels fit inside the trailer? Will you need a black belt in Origami, to make them fit inside trailer? Where do snarks be? Will you need a bigger net?

In good sunshine, in northern UK, panel output will get up to 80% or so of the 'rated' 110W, and by the time it is 48 voltified by the charge controller, each panel will provide a max of about 2A. I'll start with a single panel, but the aim is to have 3.

I would like to end up with a mounting system allowing the three to be stacked when necessary for compactness, and fully extended when riding. One panel area is not an unreasonable trailer size in any situation, whereas 1.7m long by 1.15m wide is a bit of an inconvenience!

This roughly 300W of panel seems about the going rate for solo solar bikes.

Need a sensible balance between weight added and power/energy gained, as I live in hilly parts and my little motor has to get all the weight up them.

 

[cyclebuddy]

...and plug in to your battery's charging port.

Can you do that with Shimano batteries, just connect +/- volt to the charge port? I thought there'd be some kind of smarts like there is with Bosch to prevent you doing that?

 

[AndyBike]

Solar panels...
Scotland...
I think I've discovered a flaw in your plan ... lol

 

[matthewslack]

Can you do that with Shimano batteries, just connect +/- volt to the charge port? I thought there'd be some kind of smarts like there is with Bosch to prevent you doing that?

Yes, all sorts of problems there. I am on a two bike approach for that reason. I have careful plans to 'supplement' the Shimano battery rather than expect to charge it directly from solar, and I am building a TSDZ2 conversion onto an old mountain bike, which will have no solar issues, just 'where does the battery go?' and 'can I fix a trailer tow hitch to that?' kind of problems instead.

I have read online of successful parallelling of non-Shimano batteries with the Shimano one, adding a second BMS in parallel to the Shimano one, and also various expensive scenarios of bricking a battery by allowing current to flow backwards through the discharge port.

So lots of care, ideal diodes, datalogging, hacked chargers and above all only risking my oldest battery when anything potentially harmful is attempted for the first time.

It might be a long slow journey!

 

[Nealh]

I know sod all or very little about solar so a few Q.
Panels of a similar size/dimesions can have a different wattage rating Y or N !!!

For instance the one in Matthews pic is 150w and the one in the ebay link says 1000w and looks to be of a similar size. So is the ebay one advertising a bit false on the wattage ?
1000W Flexible Solar Panel Kit 18V Controller Dual USB Battery Charge Camping | eBay

Or are they like ratings for 18650/21700 lion cells and can have a different rating depending on the quality of the panels solar cells used.

 

[matthewslack]

I know sod all or very little about solar so a few Q.
Panels of a similar size/dimesions can have a different wattage rating Y or N !!!

For instance the one in Matthews pic is 150w and the one in the ebay link says 1000w and looks to be of a similar size. So is the ebay one advertising a bit false on the wattage ?
1000W Flexible Solar Panel Kit 18V Controller Dual USB Battery Charge Camping | eBay

Or are they like ratings for 18650/21700 lion cells and can have a different rating depending on the quality of the panels solar cells used.

Mine is 110W, they do make a very nice 170W but I could not source them in the UK at a sensible price. They ought to be 1.5 times the 110W, since they are exactly 1.5 times the number of cells, but I could not get below 2.25 times as much. I could have had them from Grin at 300USD back in December, but worried about the transport from Canada.

The lightweight semiflexible panels, which are the only sensible choice for bike applications, share with batteries 'you get what you pay for'. Cheap will disappoint, quality will last ten years plus without much loss of output. Cheap ones fail because the cells break, not necessarily visible to the eye.

So, must be Sunpower cells, look them up for why, and I found genuine Sunpower panels in the UK for close enough to the same price as Sunpower cells assembled by another company, so I paid the bit extra.

That listing is a nonsense: not even a typo of 100W, the panel is so small probably barely 20. Work on 150 to 200W peak per square metre of panel area. Anything seriously outside that is nonsense.

The panel power is what's called peak output, formally written Wp, and is output in standard lab conditions. Real world in the UK, expect 80% of that in good sunshine when facing the sun, and in the overcast sky here today, I am averaging about 10%.

For low cost solar, including these panels, Bimble Solar.

 

[Nealh]

Thanks for confirming, I did wonder if the photo cell quality differed. Hence asking.

The outlay for moving or wild off grid power isn't cheap so the alternative for simple home off grid use just simply wouldn't recoup any outlay costs.

 

[guerney]

Would the noise of a wind turbine like this scare off snark? 11kg doesn't include the mast - not a lot of detail in the advert, and it'll likely be highly impractical transport and setup-wise for hunting expeditions in the deep Scottish windy winter wilds. I'd need planning permission for use on my roof, a mate was refused such recently for his commercial property.

hongmei1 Wind turbine 400W 3 Phase Mini Horizontal Wind Generator For Boat Use With CE Certificated Wind energy into electricity (Color : Free Controller, Specification : 5 Blades) : Amazon.co.uk: Garden & Outdoors

Great prices on your favourite Home brands, and free delivery on eligible orders.

www.amazon.co.uk

The one shown near the beginning of this video looks quite similar:

 

[matthewslack]

Thanks for confirming, I did wonder if the photo cell quality differed. Hence asking.

The outlay for moving or wild off grid power isn't cheap so the alternative for simple home off grid use just simply wouldn't recoup any outlay costs.

Yes the costs and benefits have to make sense to each potential user.

It is a very different story costwise for fixed systems as the normal glass topped panels are much cheaper, and do not have the same issues with cell breakage. A new 100W glass panel is about £50, but a secondhand 250W panel is also about £50. Compared with my Sunpower panel, that's one tenth of the cost per W!

The other biking comparison is with having a bigger or second battery.

If you want to ride twice as far as your battery can take you (I know you are a special case as you have many batteries!), then you can buy another battery.

Or (on a decent day admittedly) you could tow one of these panels and get about 50 or 60W from it, which is half of what a gently ridden ebike needs, which means your range is doubled.

The costs are similar.

 

[guerney]

This wind generator looks easy to lug around on a bike trailer based getaway, to somewhere dark and windy. 600W peak is hard to believe:

GOTOTOP Wind Turbine 600W 12V Wind Turbine Generator Red Lantern Vertical Wind Generator 5 Leaves Wind Turbine Kit (Red) – Davici Furniture

davicifurniture.com

 

[matthewslack]

This wind generator looks easy to lug around on a bike trailer based getaway, to somewhere dark and windy. 600W peak is hard to believe:

GOTOTOP Wind Turbine 600W 12V Wind Turbine Generator Red Lantern Vertical Wind Generator 5 Leaves Wind Turbine Kit (Red) – Davici Furniture

davicifurniture.com

Small wind turbines are not much use, especially little vertical axis ones like that. Conventional horizontal axis ones on a hill, yes. On a roof, pointless. Not enough wind speed, too much turbulence.

 

[matthewslack]

A little bit of afternoon sunshine pushed power up to around 60W, and 100 minutes worth of measurement shows 43Wh gained, so an average of 25.8W. Overcast is consistently 10 watts or so.

 

[matthewslack]

Blue sky, 110Wp panel pointing directly at the sun, 95W output this morning. Low ish temperature helps, but even so, quite a bit higher than I was expecting. This might work quite well!

Evening update:

Dull first thing, then perfect blue sky day for 6 hours, from 11am to 5pm, although the hill got in the way towards the end. Total of 560Wh, with 484 of that in those 6 sunny hours, so 80W average in the sun and 70W average all day.

That is with manual tracking i.e. moving the panel to face the sun every hour or so. Maximum instantaneous power I noticed was 98W. This is 20% higher than I expected to see, so a good benchmark test.

Two or even three panels in the summer is going to quite an experience!

 

[guerney]

A little bit of afternoon sunshine pushed power up to around 60W, and 100 minutes worth of measurement shows 43Wh gained, so an average of 25.8W. Overcast is consistently 10 watts or so.

View attachment 45910

That's a very interesting looking beadboard! So you've got an Arduino, programmed it - is that a memory board addon card at the top with sd card for recording readings? Programmed in Python? Did you have to write a program from scratch or was there something suitable floating about on the interwebs? Do you have a circuit diagram? No worries if you've put this together without one and you don't have one to hand.

 

[matthewslack]

That's a very interesting looking beadboard! So you've got an Arduino, programmed it - is that a memory board addon card at the top with sd card for recording readings? Programmed in Python? Did you have to write a program from scratch or was there something suitable floating about on the interwebs? Do you have a circuit diagram? No worries if you've put this together without one and you don't have one to hand.

Arduino nano, which has an avr328p processor. I've been messing about with avr since 1999, well before I heard of arduino.

This one is quite basic code except that I use a timer interrupt rather than the arduino time related functions to get precision timing.

There is code out there for all the add on boards, and good tutorials for how to use them, and that is where I start with each project because it is really quick to get going.

This one has the micro SD board on the spi port, tiny ssd1306 oled display on the i2c port, two LEM LTC6 current sensors, three resistor potential dividers for voltage measurement and a TL431 voltage reference on 6 of the ADC channels.

The LEMs were available rather than chosen, very good and hall effect so isolated from the circuit unlike a shunt, really easy to use, but consume about 30mA each, so in future I'll move to a different way of measuring current.

The code samples all 6 ADCs at 125Hz, calculates power each time from each related pair of V and A sensors, accumulates Ah and Wh, and reports to serial port and logs to SD card at 1 second intervals.

The code is too messy to publish just now, and I'm still working on what goes on the tiny display. It's good enough for this stage of the project.

There are two channels, YELlow and PURple, for solar and battery, and the sum of them is what the motor is using. There will be a larger display in the future, driven by the serial (USB) output.

 

[jimriley]

Solar panels...
Scotland...
I think I've discovered a flaw in your plan ... lol

A better idea might be a large roof with a gutter, the rain water then driving a turbine, suitably geared. The added benefit is you would stay dry.

 

[sjpt]

I remember little water turbines in burns were quite common when we went on holiday in the Highlands in the 60's. Three or so little wooden blades with used tin cans at the end. I think they generated enough power for a weak light bulb or two. (no LED bulbs then)

 

[matthewslack]

The underpinnings are taking shape. The base rectangle is an old Burley Solo, with a spare towbar put in backwards and joined to the original for extra length. The framing for the panels is reclaimed 25mm aluminium square section tubing from an old aviary, joining plates are new 2mm and 1.5mm aluminium sheet 6082T variety, all riveted except the four leg ends are bolted to the Burley brackets. Blue pipe to deflect any unintended interactions.

There will be weight on a platform or box underneath which will need to be sufficient to counter aerodynamic tendencies, and low c of g to avoid rollover.

1670mm long by 1160mm wide, for three 110Wp Sunpower modules, which will be secured by double sided outdoor mounting tape and bolts in the provided grommets.

More bolts and bracing to add, and the towbar may get a little longer.