Lego RC basics video tutorial series – Power Sources

This is the second episode of the Lego RC basics tutorial series, focusing on the different power sources available, how they compare to each other and what configuration I recommend to use.

The following power sources are presented in the video:

– 8881 Power Functions AA Battery Box –
– 88000 Power Functions AAA Battery Box –
– 8878 Power Functions Rechargeable Battery Box –
– BuWizz (3rd party power source & controller) –

I received a lot of questions about the different power sources and how they compare to each other, so I’m looking for an answer for two main topics. The tests and details can be seen in the video, but here are the questions and my conclusions:

– Q: What is the weight difference of the power sources? Does this weight difference has a visible effect on the performance of the vehicle where it is used?
– A: The weight difference seems to be significant (see data in the video), but in reality it does not have a big effect on the performance. Even with a lightweight and underpowered vehicle the difference is barely noticeable. It doesn’t really matter if you use the AA or AAA battery box, it might depend what you have already and what is the amount of available space in your model.

– Q: What happens if I use rechargeable batteries instead of alkaline ones? Is there a significant difference? What about the 8878 Rechargeable battery box, does it have any advantage for the price?
– A: The power (and speed) advantage of the alkaline batteries is only visible when they are brand new. Voltage quickly drops with use so their performance becomes comparable with the rechargeable batteries. Based on this I think it is more economical to use the rechargeable AA or AAA batteries and the corresponding battery boxes.
The 8878 Rechargeable Battery Box provides similar performance but for a much higher price (and you need to buy the proprietary charger as well), so I do not recommend buying it unless there’s a definite need to use the physical speed control on the battery box.

– Q: What about BuWizz? How does it compare to the others?
– A: BuWizz has 4 different speed modes. Interestingly normal mode supposed to be similar to the performance of the rechargeable battery boxes, but in reality their performance falls between the normal and fast mode. Fast and ludicrous mode provides a visible performance advantage but for a higher price point. Based on this BuWizz is recommended if performance is the most important factor and/or the space for the battery and the controller is limited, since it contains both in a small form factor.


  1. Hello, can you share the construction instructions for the car in the video?

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