Hi All.. I started this project with an idea after I bought some flexible solar panels and I had this dream for some time of creating some kind of solar powered vehicle.. I wanted to create something that could actually power itself from the sun, not only charge the battery while parked but actually power the motor from the sun while its running.. the goal being to have an unlimited range. Well I actually achieved this. Read on to find out how you can live this dream!
Ive edited this instructable to now include a pic of the most recent prototype. The flexible solar panel is no longer high up but mounted just behind the seat to give a much more streamlined and easier ride :)
Step 1: Parts Checklist
So, what are you going to need to build a solar ebike, trike, go cart or drift bike..
The final build will really depend on what parts you have available and also in order to have a solar roof or some kind of lightweight flexible solar power you'll need somewhere to put the panel or panels.
Either a roof, or a bike trailer or similar.. If you have a go cart frame you might want to use that..
I had a chinese onewheel clone, which is a self balancing fat one wheel skateboard (see pic).
This product was very limited in its uses.. the power wasn't enough to safely balance it in many situations and it wasn't a practical transport option.
But it does have a decent 48v lithium battery, and a good fat hub motor which is perfect for this project.
What youll need..
- Hub motor (bike hub motor for front wheel or whatever works best for you.
- Old bike parts (I got the front of a bike from the local recycle center for $5)
- Some metal tubing for framing.. (I used part of a car roof rack bought for $2)
- Battery 24, 36 or 48 or even 60v lithium is best but whatever you have handy or can source.
- Ebike controller.. (more on that later, cheap to buy online) will need to match your battery voltage.
- Ebike kit which includes an electric throttle either twist or thumb and electric brake lever.
- Flexible solar panel (100w at least which will provide about 6 amps at 17v)
- MPPT solar controller
- DC to DC Boost converter (ups the solar voltage from 17 to about 75 volts)
- Time and coffee :)
Step 2: Work Out Your Bike/cart Frame
I originally wanted to make a solar recumbent electric bike but realised that the cost was huge for a standard recumbent bike. Then I realised that a drift bike would be a much cheaper way to create a practical sit down vehicle.
So I loosely modeled my design around a typical drift bike with a normal bike front wheel for steering and a low rider seat position. I worked out how to mount my wheel using its existing aluminium housing..
Find someone who has access to a welder and work out a suitable frame that works with the bike parts your going to use. Work out the correct seat position so that your feet can rest on the foot pegs on the front wheel and still be able to turn easily.
There is an option to use a drift bike front wheel with pedals and a free wheel system to give you pedal assistance for those bigger hills :)
Step 3: Setting Up the Motor and Controller..
Im using a generic ebike controller with my motor and throwing out the original self balancing circuit (as that is not required and a lot of power was wasted in the self balancing circuit which we don't need for this project).
There are many controller sizes from about 250 watts up to 2000 watts or more.
For this project we need to find the ideal balance between power and efficiency.
In New Zealand the legal limit for an ebike motor is 300 watts.. any bigger and you need to register it as a moped.. which is easy but means having a number plate and so on.
Also you need to match your controller with the motor.
The motor I had is about 500w max at a guess. So I opted for a 450w 9 mosfet controller which is capable of peak outputs around 800w or so during acceleration but only uses about 100 to 150 watts at cruising speed.. and is enough power (just) to get up a hill unassisted. This also means the average wattage during normal use will be under 300 watts but with a little extra power available when needed.
I wanted my solar roof to be as small as possible and also deliver enough power.. so thats also why i've chosen a ebike controller that averages about 1.8 amps at 48v (about 100 watts at cruising speed on the open road.)
Watts = volts x amps so my 100 watt solar panel will deliver enough power to keep the battery charged and drive the motor at cruising speed on the flat.
Its pretty straightforward to set up the motor.. just follow the instructions that came with the controller you purchase..
i'm using parts which came direct from china via aliexpress website.
The controller I bought fitted perfectly in the aluminium frame so that was easy.
Connect the two large power cables to positive and negative on the battery, and connect a switch to the positive if you want to have an external power switch. I used a 20 amp 12v switch which did the trick.
If you matching a controller with a motor from another supplier then you'll need to follow this flow chart to find the right combination of motor phase wires, they are usually green blue and yellow and can be in 6 different combinations.
Be careful when testing, only use a little throttle.. if the wheel doesn't spin smoothly then try the next combination until you get a nice smooth rotation with minimal amps...
Once you have the battery, controller and motor plugged in and working together with the throttle connected and its running then you'll need to connect the brake lever and connect your brake cable from the controller to the lever and test that its cutting the power to the motor when you squeeze it.
Next your ready to set up the solar charging.
Step 4: Solar Set Up.
I went back to the recycling depot and found this clothes rack that is the perfect size (1m x 0.5m) for my 100 watt solar panel which easily fits on top and connects using zip ties.
Then the power from the panel goes to the solar controller converts the power into usable watts to keep the battery full and power the motor.
I found these microphone plug and sockets in the photo and used these to design a simple plug and play system for the solar. So that the solar charger plugs into the same cable that usually supplies power from the wall charger that came with the battery). So if needed I can still plug in the original wall charger to charge the bike at night time for example.
My lithium battery pack is a 48v 5 amp hour with built in BMS (battery charging circuit).
The solar panel puts out about 18v at 6 amps which isn't enough volts to charge a 48v battery.
The solar charger works best when the input voltage is higher than the output (48v for this battery pack) so ive also added a DC to DC boost circuit that converts the power from the solar panel from 18v to about 80v, and then the 80v DC goes to the solar converter and charges the 48 volt battery pack. Because its an MPPT controller it converts the excess volts into amps and gives a good level of efficiency.
Another option would be to use 3 smaller solar panels in series (to get around 50v).
If the pack is already full then the excess solar power goes into running the load (which is the motor) and then you have unlimited sun powered transportation!
The clothes rack fits nicely on the back of the bike without getting in the way of the seat. Next I used a lot of zip ties to tie all the cables and wires down and also make the clothes rack more rigid and stable.
The clothes rack is removable so that it can just be used as a ebike for distances around 20kms (the range of the battery) and when I want to go further I just clip on the solar roof, plug it in and drive off..
Even with the bike switched off the battery is still getting charged while the solar is connected.. so its always topping up the battery every time you stop riding or when your parked up.
Step 5: Completed Bike
I gave the bike a fresh coat of paint to smarten it up and now she looks real nice.
I hope others will take from this the idea of self sustaining transport and build similar vehicles using whatever you have handy.
Flexible solar panels have become quite cheap just in the last year or so.. they are now as powerful as traditional heavy panels and way more versatile.
One of these panels will cost you around $150 USD including shipping direct from china..
Approximate cost of this entire project is under $1000.
Who would have imagined you could build a practical electric vehicle that powers itself from the sun from under $1000!
Well you can :) That's much cheaper than a new prebuilt electric bike, and it never needs plugging in! (as long as there is sunshine).
I look forward to seeing what others can come up with. I have seen on youtube various electric solar vehicles, but most of them only increase the range a bit. My challenge was to find the right combination or weight, power and solar to have virtually unlimited range. And I did it :)
This chopper ebike is so much fun to ride.. top speed is about 30 km/h which is plenty for my needs and also keeps it road legal as a electric assisted bicycle.
I will add links to the parts I used later on... all parts came from china direct and are easily available.
Ebike kits usually include a controller, hub motor, brake levels, throttle, pedal assist (if you want that too).. and sometimes a battery also, but batteries are harder to get sent these days by express shipping, so try and source a suitable battery in your home country or build your own. Plenty of instructables on DIY ebike batteries.
Step 6: Updates...
Back again. The DC to DC Boost converter arrived from the courier so today hooked it up and it worked exactly as planned in my head. So that was nice. So now the power from the solar panel goes through the step up boost converter circuit and then to the solar charger which then goes to the charging port on the BMS (Battery management system).
Initial tests are favorable. With Boost set to maximum out voltage (around 80v) by turning the screw pot clockwise we get about 85 watts from the 100w solar panel.. This fluctuates from 70 to about 90 watts. The solar converter displays on its readout about 55v at 1.5 amps which is volts x amps = 82.5 watts which is accurate.
With some more tweaking and adjustments of the volt and amp pots (screw dials) on the Boost converter may be able to get closer to 90 Watts. The Boost converters efficiency is around 90% (95% max in ideal conditions) so were losing at least 10% of the panels power so we would hope to get close to 90 watts.
A useful tool to use is a ebike simulator or calculator. I like to use this one:
Just input the size of your motor, controller maximum amps, battery size in amp hours, drag coefficient (is your bike sit up, recumbent, semi recumbent etc).. and then it will give you an estimate of power to weight ratios and maximum distance etc. I choose a grade of 0% for my simulation to find out how much watts im using on the flat cruising at 100% throttle. It gives me 69 watts at 1.5 amps which is encouraging because if im getting about 75 watts (average) from the solar panel at 1.5 amps and then take into account regenerative braking and some hill climbs then we should average out about the same amount of watts coming into the battery as is coming out to power the motor.
Which will equate to approximately an unlimited range on a bright sunny day when the sun is high.
In lower light conditions, cloudy or low angled sun then we may get 30 to 50 watts and will lose some battery charge.
So in ideal conditions we should see no battery drain will driving on relatively flat ground.
Over this weekend I will be testing this by going on an overnight camping trip using local bike tracks and rural roads to travel well beyond the normal range of the battery pack. I will take a tent and a few supplies and see how the bike performs over longer distance with good sun and some extra luggage. Will update with results in a few days!
I will be using a free app called Urban Biker:
This gives a GPS map for the route, records average speed, power usage, distance etc.
My ebike controller display will also give me distance travelled, battery voltage etc so I will be able to monitor in real time the battery voltage.
I also promised a list of the parts ive used so here below are the links to all the parts I used.
I ordered these parts from:
It is a portal for parts direct from the manufacturer to your door so they cut out all the middle men.
Ive done a lot of research into this plus they also test and use many of the products they sell.
These parts im listing are recommended and pre tested for this kind of project.
Going to techdirect saves you hours and days of searching for the best products from the most reliable suppliers. They take out all the guess work by only dealing with 5 star recommended sellers and products they have bought and tested themselves.
So here is a list of parts:
Lithium battery 48v 4ah
The battery doesn't have to be big, because were using the sun remember!
With this battery size you'd expect to get around 20 to 30 kms at night or very low light conditions from a full charge.
The battery is the most expensive part of an ebike kit. You could also build your own battery pack using one of the instructables from this site! You don't have to go with 48v.. 36v or even 24v would be ok. Just make sure your controller matches the battery (ie both 48v for example). Even a cheap lead acid battery (2 to 4 in series) might do the trick if you live where there is good strong sunlight.
If you go with a system that is 24 to 36v then you wont need to step up the voltage as high using a booster.
You may even be able to not use a booster if you choose say 3 smaller solar panels and hook them up in series to give a voltage or around 60v or more.
Flexible Solar panel or number of smaller panels in series.
This is the panel im using. Its the best price on the net ive found anywhere. Delivery is under 2 weeks worldwide to most locations. Free shipping via EMS is a great deal. They can be flexed up to 30% but to lie it flat on a horizontal plane will give the most watts for any time of day.
You could also try some of the smaller flexible panels (say 2 or 3 of the 50 watt ones) if that configuration works better with your design. You could also have extra panels that fold out while parked to speed up charging time.
There are many options so use your imagination! :)
Here are two x 50watts option:
Or you could buy a complete solar kit, however be aware if you choose a solar controller that does 24v maximum then you'll also need to use a 24v battery and 24v controller. Heres an example:
Im using a trusted MPPT controller from a company I know personally who are a supplier from china.
There are a lot of fake MPPT controllers on the internet so make sure your buying a real one.
I don't get any commission for telling you about these controllers if you buy one. I just know they are best for this situation.
A standard PWM controller will not convert the extra volts into amps so you absolutely need a MPPT controller for this kind of project because as you drive about under trees and different light conditions the volts and amps from your panels will vary a lot and so you need a controller that can adjust quickly and deliver the maximum watts under changing conditions. PWM controllers cant do this and need to be matched exactly with your panel voltage to get the best efficiency. MPPT controllers do this automatically. For more info on PWM vs MPPT just google it :)
This is the controller im using. Its a true MPPT and has great reviews and 5 year gaurantee which is great for a chinese brand. Very well made and sturdy but smaller than many also so good for a bike project.
These controllers will do 12, 24, 36 or 48v so thats why i choose this as I already had a 48v battery so it made sense to find a solar controller that can do 48v.
Electric brake lever.
Electric bike throttle.
Here's a link to a bunch or different throttles depending on if you want to use a thumb style, full twist or half twist and also if you want a battery indicator or switch on your throttle. Ive chosen the wuxing brand because they are well made and cheap. The first throttle I bought was a generic chinese and it broke on the first day. It was crap, so now I only use brands I know are striong and long lasting but still a good price.
This link above is for various controllers from 36v to 48v, and 350w up to 1000w so you have many options depending on how much solar you are using and if you are going to have PAS (pedal assistance).
Check out these controllers and contact the seller directly if you have any questions. When you select the size you want and purchase you can also leave a request in the comments for any customisation you want, like higher maximum current or no PAS (which I did) if your not using pedals
This kit comes with an excellent digital display which gives you battery voltage, speed, distance and so on.
Another option to save you time is to buy a complete ebike kit with front wheel hub motor, battery, controller, display, brake and throttle and PAS sensors. This kit example will give you everything you need except for solar panel, Boost converter and solar controller. This is the best deal ive found for a complete ebike kit anywhere on the net.
DC DC Boost converter.
Fat wheel (go cart size) 500w hub motor.
This is the motor I used for my project. If you want to use a rear motor and have pedals on front wheel then this is a good option. Will work with a range of voltages from 24v up to 60v.
Here's a few other options for small chunky hub motors suitable for the back.
Two hub motors could also be used on the back as a trike for more stability. Both hub motors can be run from one controller to give an even power ratio. Both motors would need to be the same power and brand.
OK, that's all for now. Have fun and I look forward to seeing your solar vehicle projects!
Step 7: Second Update
Ok so I ditched the flimsy roof frame (clothes rack) and got a nice strong frame welded for the roof and also attached rubber around the frame to stop rattling and attached the solar panel with zip ties. Also put the DC Booster and solar controller into a waterproof box (with ventilation holes in sides) and added an extra circuit breaker for safety. So have a circuit breaker on the panel and also on the battery.
Great news. After some tweaking of the trim pots on the DC Booster I am now getting about 115 Watts (50 volts x 2.2 amps) so the booster is working great, I'm getting maximum Watts from this panel. So now motor load Watts is about the same as solar Watts coming in which means perpetual solar transport :-)
Full long distance road test to come soon :-)
Step 8: Third Update
Final roof frame complete and bucket seat from a drift bike installed. Also put front wheel on from a drift bike so now have pedal assistance for those bigger hills :)
Road tests have gone very well. Estimate that I need another smaller solar panel about 50 watts to give it unlimited range on a sunny day.. currently getting about 80% of the power needed from the sun so the range is pretty good.
Still haven't tested its range yet. But driving about doing errands it performs really well.. a 5 km drive only lose a couple of volts and it recharges back to full within 20 mins.. so for normal use around town the battery stays at 3/4 full. Since installing the solar I haven't even come close to running out of power.
Actually at 2/3 power (60%) about 18km/hr in bright sun I've achieved unity (power coming in from solar greater or same as power to run motor) with unlimited range which is pretty awesome. I don't know of any other solar bike/trike that has achieved this.
It's all about balancing the to weight ratio and getting maximum amps from the solar.
Ive done a few minor additions to strengthen the frame and added a bike stand.
lots of fun to ride :)
First Prize in the
Solar Contest 2016
awakekiwi made it!