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I want to make a solar-powered vehicle that has battery backup.

I connected two PF switches to switch between  power sources.

It's a pretty simple mechanical solution - turning one switch on turns the other one off. If anyone has other ideas, I'm interested in hearing them.

One of the design goals is to keep it lightweight so it can be driven directly by the solar cell, so the fewer parts the better.

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5 hours ago, Didumos69 said:

Interesting. Curious how this will evolve.

Thanks - My original idea was to use the storage battery from the solar set, but it weighs more than twice the rechargeable battery box. I'm going to do some tests to see what kind of load it can move and maybe go back to that if it looks like it can handle the weight.

Ideally, I'd like to be able to have three modes - direct solar power to the motor, battery power to the motor, and solar power to the storage battery.

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The Sandcat from Pitch Black is a great example of a tough solar-powered vehicle. Maybe the Badger could take some inspiration...

latest?cb=20140528105153

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9 minutes ago, Maaboo35 said:

The Sandcat from Pitch Black is a great example of a tough solar-powered vehicle. Maybe the Badger could take some inspiration...

Ooh - a winch! That's an idea...

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I built a "wireframe" to hold the elements of the solar/battery power source and get the weight and some basic dimensions.

It weighs 489g and will move under solar input of a 250-Watt incandescent bulb. Next task is to load it up and see how much it can carry. That may set some limits on the power train, steering and differential. I'm planning some other functions, but they may end up being manual or pneumatic depending on how much I can eke out of the solar cell.

It's geared very low, but speed is not the goal.

Proto1-1.jpg

Proto1-2.jpg

 

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16 hours ago, howitzer said:

This should be interesting. I wasn't even aware that official Lego PV cells existed.

You can order them from the Education site. The set I got comes with a storage battery and meter, too (and some real wind vanes!). Or you can buy the cell separately. It can be connected directly to a PF motor.

I got one earlier this year and have been looking for an excuse to try it out. The storage/meter device is OK. It has a maximum storage of 100J, which can run out pretty quickly. And there is no way to regulate the output with the meter itself. You can switch directions, but not step the output. But you can run it through an IR switch and control the output with that.

 

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Second prototype chassis. This one is already disassembled for improvements, but for the sake of documentation:

Proto2-1.jpg

Proto2-2.jpg

I substituted the energy meter/storage battery for the rechargeable PF battery. The PF switch next to the energy meter switches between the solar cell driving a motor to the rear wheels or charging the storage battery. The storage battery output is then run to an IR switch with two small motors, one of which runs the rear wheels. The other one will power one or more functions. There's a gearbox in the middle (the blue handle) to select whether the rear wheels are driven by the solar cell or the storage battery. So it will have three modes - drive under direct solar power, drive under stored power, or recharge stored power with the solar cell. It is also possible to use stored power while recharging with the solar cell at the same time.

This is mainly to get weight and dimensions, but I tried out some functions that will probably make it into the final version. I used a linear actuator beneath the solar cell so it can be tilted to the optimum angle to the sun.

The survival technique of the Solar Badger is not to outrun or outfight other vehicles. But that doesn't mean it won't have some tricks up its sleeves!

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