LEGO has a mysterious new rechargeable battery, what can be the product?

I know, I know, I should be working on the reviews for the new Technic sets right now, but I stumbled upon something that I had to share with you. A quick disclaimer – this is not a rumor, or any insider information from LEGO, I found something that is available to the public and everything else is my own speculation and opinion. Now let the investigation begin!

So, in my video about the 42129 Mercedes Zetros you could see an interesting new Technic hub with screws instead of the snap-on lid:

Some of you speculated about a possible rechargeable battery box, others mentioned potential child safety reasons. There was also another video about the Off-Road Buggy that suddenly disappeared from The set is now back in most of the countries without apparent changes, but again one of the possible reasons was the hub change and again a rechargeable option came up.

This made me thinking – would it be possible to find a trace of a rechargeable battery online if LEGO is working on it? I’m not talking about leaks, but evidence published by LEGO themselves.

Here’s an interesting page on, but I understand if you are not a frequent visitor as it does not seem to be very exciting for the first sight. This is the battery documentation page in the legal section, as LEGO is legally obliged to share lots of different safety and test results about their different products with built-in batteries.

As you see there is a product number, and then lots of boring test result documents, mostly in Chinese and English. 8878 is the good old Power Functions rechargeable battery by the way.

Let’s scroll down, we have 9669 which is a Battery box for the Mindstorms Energy Meter, is for the Renewable Energy Add-on set, 9693 is the Mindstorms NXT rechargeable battery, and so on. As you see we have pretty old tech listed here as well, I guess LEGO has to keep the information up online even the product is discontinued.

There are 2 recent batteries that can be familiar, Rechargeable Battery No 2. which is the Spike Prime Hub’s battery. It appears multiple times as there are multiple products having it, 45601 is the Hub itself with the battery, 45610 is only the battery and 45678 is the whole Spike Prime box, which of course has the hub with the battery in it.

Rechargeable battery No 6. is very similar, we’re talking about the same battery here but in the new 51515 Mindstorms Robot inventor.

Now here’s the interesting part – there is an item called Rechargeable Battery No 4!

It is listed for 3 product numbers, but there’s no information about any of them yet online. Two of the numbers are close to the Spike Prime product numbers so it is probably a LEGO Education product (battery separately and with the main unit), but there’s one where the closest product number is the 45302 WeDo 2.0 Smart hub rechargeable battery. I don’t really think LEGO will release anything new for this product line, so this might be something maybe for the average consumers?

Now about the parameters! There’s not much in the documentation, but here’s the interesting part:

So it’s a Li-Po battery pack, the nominal voltage is 7.3V, but the capacity is only 600 mAh! That’s a pretty small capacity, for comparison the 8878 Power Functions rechargeable battery box had a capacity of 1050 mAh.

The weight of the battery is only 25g, compared to the 40g for the 8878’s battery, this means it’s a pretty small and lightweight battery. Here’s a photo of it from the documentation:

So here’s the big question – what will be the new product that uses this new rechargeable battery? I have a few theories, let’s see them!

Theory no 1.

The product will be a similar Education product to the 9778 LEGO Energy Display, that one also had a battery with a fairly low capacity as the unit does not consume a lot of energy.

Theory no 2.

The product will be a separate unit that can be connected wirelessly to the Spike Prime / Mindstorms / etc. hubs. It can be anything like a wireless speaker, a matrix display, etc.

Theory no 3.

It will be a rechargeable battery for the 88009 Powered Up hub. I don’t think this version has a too high chance, as the battery seems to be too small for that hub with a fairly low capacity.

Theory no 4.

As some of you suggested, it might be the power source for a potential light kit. We all remember the false hopes we felt when we saw the teaser for the LEGO CON the first time… but the related set numbers suggest some Education products, and I’m not sure TLG would start to release light kits there.

What do you think?

So, these were my observations and theories so far, now let’s hear what you think! What is the purpose of the battery, what can be the new product? Please let me know in the comments!


  1. Thanks for the research. Considering Theory 1 & 2 are unknown products and Theory 3 seems unlikely, I’d say that it will probably be part of a solution for lighting. The current battery hubs seem rather bulky for lighting only, so my bets are on the last one.

  2. Pingback: LEGO 45345 Spike Essential kit with small Technic hub, small angular motor & 3x3 LED matrix | RacingBrick

  3. As a time traveller from the future, it turns out that this battery is LEGO 45612 Technic™ Small Hub Battery, which is for the LEGO® Technic™ Small Hub, a small version of the 45601 Hub. It’s included in the 45345 SPIKE Essential set.

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