We had an old ride-on toy for the kids in the shed. My oldest son had great fun with it.
He got it from his niece a few years ago. By then, he could possibly be the fourth owner this car had to endure. And the car bears the scars somewhat. But none of that matters to my oldest son. He always had a ton of fun with it.

My youngest son is 16 months old now and ready to play with it for some time to come. I got the idea to upgrade it with some lights. Since i had most of the parts already, costs were kept to a minimum.

Step 1: What It Originally Looked Like.

I found a picture online of a similar car. This one still has the bonnet and the original stickering.

Step 2: Preparing

You want your car to be clean when you start this project. You can chose to remove some scratches or other damage before you proceed, but i opted not to. Kids may be rough sometimes and they don't care about some more scratches.

The car brand stickering has been on there for a few years... :)

Step 3: Adding LED-clips

I carefully proceeded with measuring out and drilling holes for the LED-clips. I used clips for 3mm LED's, but choose whatever you like.

Step 4: Add the LED's and Wiring

Here is how i wired the LED's. I mounted 4 LED's for each 'corner' of the car. The outer LED's will function as indicators, the other 3 per side will be the normal front and rear lights.

For power saving reasons, the LED's are placed in series with a resistor per side.

Note: the indicators are soldered in a combined ground configuration here. Later on, i found out this was not gonna work...

Step 5: Testing the LED-strips.

To make this car really cool, i ordered some LED-strips to give it some underglow effect. This is what testing those looked like.

As you can see on the second picture, the light from the strips shine through the sides of the car. This is ugly and needed a solution.
Placing some black tape on the inside of the bodywork fixed this problem simple and effective.

Step 6: High Beam and Brake Lights

Kids love pushing buttons. I made the front and rear LED's that extra bit cooler by adding pushbuttons making the lights go brighter. This is the really simple trick i came up with to realise this.

The LED's need a current-limiting resistor to funtion well on 12V. I did some measurements and found out that these LED's are happy with a resistance of 680 ohms. So these are permanetly inline.
The pushbutton has a 2 kilo ohms resistor soldered like in the picture. So when the button is pushed, the 2k resistor is bypassed and the voltage to the LED's rises, giving it the effect of high beam lights on the front and brake lights on the rear.

Step 7: Indicators

I bought a DIY 'flash light' print online which luckily had the correct rythm for this purpose.
In electronics, this circuit is known as a 'multivibrator'. It will continu to swich between the two lights until the power is taken away.
I combined the ground of the 4 LED's in the car and made a swich between left and right on the positive side.

Step 8: Indicating on the Rear Only...

After connecting, i found out only the rear LED's to be functioning. When i took off the rear's, the front LED's would light up. After some thinking, it came to me that different coloured LED's operate at a different forward voltage.

Not wanting to take it apart completely, I tried to split the front and rear indicators using a single resistor. This is enough to allow the voltage-drop between front and rear. Some experimenting learned that a single 100 ohm resistor does the trick perfectly. I soldered it inline on the combined ground wire between the front and rear of the car.

Step 9: What to Do With Power?

Until now, all the lights were powered by my large 12V power supply originating from a radio cabinet. Since this is a kid's toy, it must be battery powered obviously.
I used 18650 cells from a discarded laptop battery. Laptops most commonly have six of these, placed in series in three pairs. When the battery dies, it is common for just 1 pair to lose it's charge quite fast. So if you can get your hands on a laptop battery pack, using some caution will get you one or two pairs of these ideal powersources.

Fuse it or lose it!

Please add a fuse directly inline to the 18650 cells! It is a very common sight in DIY that people don't bother in adding a protection against short circuits in their builds.
These cells can deliver about 16 amp's of current when shorted, so this will melt your cables, of even catch fire! Don't be a silly DIY-er and place a simple fuse!

These cells will need protection. I bought some protection boards on ebay for a few dollars which are ideal. You can stick a micro-usb cord in there so your cellphone's charger can charge the 18650's. The board offers protection against under- and over charging, overcurrent and is really small and cheap.

Then, I used a step-up booster to kick up the voltage. The 18650 cells operate between 2.8V minimum and 4.2V maximum. We need 12V for all components to operate as desired.

The powerswitch is hidden under the buddyseat and soldered between the +out from the protection board and the +in to the step-up booster.
All lights are then powered from the booster, set at 12V.

Step 10: The Ugly Side.

These pictures show the wirework underneath the body. I tried to work it away as tidy as possible keeping in mind my kids may go investigate some day.
All the LED's have a fair amount of hotglue on them to prevent them from being pushed inside when hitting a obstacle. There is also hotglue used to fix the wires in place and to really keep the LED-strip from falling off.

A single LED-strip was used. There are contacts on the end where no wires are soldered in the factory, mainly designed so you can connect a chain of strips together.
I snipped the strip in half and soldered wires to this end. Now the car has some neat underglow.

Step 11: Switches and Buttons

Under the buddy, there is a simple on-off switch.

The rocker switch mounted under the steering wheel operates the indicators. It's a 3 positions, ON-OFF-ON switch so the indicators can be switched to the left, the right and completely off.
On the left side, there is a green LED soldered to the other side of the multivibrator-board. Without this LED, the indicators won't work. Mounting it there adds to the design. It's just like the lights on a dash of a normal car.

The pushbuttons are mounted to the right of the steering wheel. The black front button operates the high beam, the red back button switches the brake lights.