Lego 42099 on 11.6V LI-ion battery

[zapbrannigan]

Me and my son were a bit underwhelmed by the power of the 42099 4x4 RC car. So I decided to make a ciruit to let the drive motors run on a 11.6 LI-ion battery (https://nl.aliexpress.com/item/1005005537002529.html?spm=a2g0o.productlist.main.11.1de7TjGLTjGLHh&algo_pvid=2fecfe3b-15c2-47f9-afcd-4d9e3348276d&algo_exp_id=2fecfe3b-15c2-47f9-afcd-4d9e3348276d-5&pdp_npi=4%40dis!EUR!20.04!9.02!!!150.64!!%402101df8a16967479545852168e44b7!12000034252477538!sea!BE!130665062!&curPageLogUid=GvE8RuYxrOtn).

You need an L293D motor driver chip and some resistors diodes and capacitors and a cheap dual comparator. You also need a LDO regulator to 5v to power the L293D and the comparators. I bought some lego wedo cables and sockets on aliexpress: https://nl.aliexpress.com/w/wholesale-wedo-cable.html?spm=a2g0o.home.search.0

Information about the cables can be found here: https://www.philohome.com/wedo2reverse/connect.htm

You need to connect pin 1 & 2 coming from the hub to the circuit, the other pins can just be connected as they are (they are needed for motor-hub communication). The output pins of the L293D go to pin 1 & 2 going to the motor. You can see the other connections to the L293D in the circuit diagram.

The L293D can drive the two motors, but you only need to make the circuit once. For the second motor, just connect pin 1 & 2 coming from the hub with a big resistor (1MOhm) and connect the outputs of the L293D to pin 1 & 2 going to the motor.

It works really wel, the car has a lot more power with the 11.6V battery and is much easier to charge (the AA batteries only run the servo motor so they last longer). I'll proably add a LDO regulator to 8V to also run the hub on the LI-ion battery (and get rid of the AA batteries altogether).

It was a lot of soldering work on a prototype board, maybe I'll make a PCB.

Edited October 8, 2023 by zapbrannigan
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