Build a solar-powered lawnmower that you do not have to worry about being loaded or connected, just leave it out in the sun.
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I've had battery powered mowers previously and they're a real pain to keep in charge. You have to connect or remove the battery and this sucks.
This is a solution to the problem. Install the solar panels on the mower and leave it parked in the sun to charge it.
Here's how I did it!
Tools and materials needed:
- Soldering Iron
- Battery-powered lawnmower
- (2) 12 volt photovoltaic solar panels
- 4 general purpose rectifier diodes
- Double-sided tape
Step 1: Evaluate the current condition of the lawnmower
I had a DR Neuton Mower, but this Taurus appeared on Freecycle. It was a lot more DR world, so I decided it would be the donor machine.
The first thing I did was check the batteries. They were toast, so I had to build a new battery.
I got four spare batteries at my local electronic supply for $ 18.00 each. To keep them as a cohesive package, I applied a double-sided tape between each battery, just like the original configuration.
Step 2: How to connect it
A photovoltaic solar cell (PV) has a power output recognized in watts. When the sun shines, the potential of the photovoltaic cell is greater than that of the batteries, so the energy will flow from the photovoltaic cells to the batteries.
But what happens when the sun sets? So the batteries have more potential. This means that if no measures are taken to prevent it, the energy will flow from the batteries to the photovoltaic cells. This energy will be wasted when the heat emanates from the photovoltaic cells, ultimately by burning and discharging the batteries.
We can avoid it by installing diodes in the circuit. A diode is like a one-way non-return valve for electricity. Allows the solar panel to charge the battery, but it is impossible for the battery to heat the solar panel.
The circuit below shows the typical wiring for this type of application. This system uses four 6-volt batteries and is charged by two 12-volt solar panels. The general voltage of the system is 24 volts. When you align the batteries, their tension is added as you position more in the series. The panels are 12 volts, so you need to isolate them from each other. The diodes also perform this task.
Step 3: connect the batteries
Return to the battery pack. We treat these four batteries as two sets of two. Join them together as shown and test the tension to make sure they show 12 volts per pair. The OCV (open circuit voltage) could be in the order of 14 volts. It's normal. In fact, if it is less than 10 volts, you may have a faulty battery.
Finally, there will be an interconnection between the two sets. As shown in the diagram, we must touch this interconnection to connect our photovoltaic cells. Do it using a cable puller. Do not cut the wire, just open and separate the insulation.
Step 4: Install the Power Taps
Just like we did for the interconnection, open the positive power cable and install a diode. Make sure the band on the diode is closest to the red wire.
Step 5: Repeat the process
Do the same again on the negative side.
This time make sure the diode band is facing away from the black wire.
Step 6: Scavenge Some Parts
With this photovoltaic panel came a cigarette lighter socket. Yes, I said cigarette lighter. Read the owner's manual. That heat source is a cigar lighter.
We will not use it, but we have to give it a look.
First, cut the PV connector. Leave an inch of thread on it and strip the ends.
Put it aside and let's take a look at what's left.
Open the cigarette lighter plug. There is a circuit in there. What do you think I do?
Step 7: Continue with the wiring
Now we are ready to connect the supply taps to the PV sockets.
Slide the heat-shrink tube over the wire before welding the wire to the diode. Attach the wires to the diodes and weld them in place. Then, slide the heat-shrink tube over the solder joint and diode and reduce it downward to isolate the joint.
Make sure you get the right polarity! The peeled cable from the photovoltaic panel is positive. Make sure that this cable is connected to a diode pointing towards a positive battery terminal. I tried to clarify how to make this determination.
Step 8: Check your wiring!
At this point you should have two connectors connected by diodes to the batteries. Check them with a voltmeter; there should not be tension. Diodes are a one-way check valve for electricity from photovoltaic panels to batteries, not vice versa.
Step 9: Continue to check the wiring
At this point you are all wired and you can do some voltage checks to make sure you can proceed safely.
Step 10: Mount the photovoltaic panels
Now that the difficult part is out of reach, let's move on to easy things.
These panels have holes in the shape of a keyhole. Insert a screw into the hole and tighten a nut on it. This gives you a mounting pins.
Align the pin on the cover and drill the mounting holes for the photovoltaic panels. Then, cut the spacers to fit the contour of the motor cover. Do not forget, it's all plastic and things really fold up. It is quite lenient.
In this installation there were some reinforcements on the underside that had to be removed. The tin shears and an X-ACTO knife took care of the offensive plastic quickly enough.
Use the other half of the contour cutting spacer to shim the bottom of the support.
Step 11: Perform the wiring
Now that the photovoltaic panels are mounted, run the cables through the motor cover.
Step 12: Check the solar panel output
OCV (open circuit voltage) of these photovoltaic panels is of the order of 16-20 volts. If it is particularly clear, this is the reading you should get.
Step 13: The Final Hookup!
Connect the photovoltaic panels to the battery banks.
So, check the tensions. You should have two banks of 12 to 15 volts and the total voltage should be at least 24 volts.
Step 14: Here it is!
It works and works really well. I mowed my lawn every day for three days and the mower is fully loaded every time I turn it on. All I need now is a lawn.
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