9V Battery Adapter for Lego Powered Up/Control+ Hub

[2GodBDGlory]

While working on a project involving a PU hub today, I got frustrated with my hacked-together system for running it off some random 7.4V battery I had lying around, and came up with a simple idea that would make it easily possible to power the hub directly off of a standard 9V battery, specifically, one of my rechargeable lithium-ion ones. The idea is that this battery would give peak voltage (Actually 9V; there must be some kind of voltage converter inside the battery to get there) over most of the battery life; that it would save weight; and that it would allow for easy battery swapping and recharging.

The key thing here is that a 9V battery's output terminals are spaced such that all you need to run a Technic hub off of them is to hold the battery against them--no messing around with wires, springs, soldering, or contacts! With that idea, I modeled up this design for a 3D-printable part in Fusion 360, and had a very workable part on the second prototype! I think this is what I'll probably use to power my PU models going forward, and I thought it was an easy enough idea to replicate that I'd share it here.

You can think of it as the "poor man's" version of the impressive Phondly EnBo battery pack

Spoiler

 

It isn't as nice of a product, because it has lower battery life (I'd assume), and no external charge connection, but it can be easily produced by anybody with access to a 3D printer and a 9V battery (Very preferably a lithium-ion rechargeable one!), so I think it's an alternative that could be useful to quite a few people.

This is the battery I'm using here, so you have an idea of what I'm thinking (I can't really vouch for these ones, since I just bought them to replace some different ones I had)--basically they just output 9V in a 9V form factor, but have USB-C charging, which is quite convenient!
https://www.amazon.ca/dp/B08D925V8H?ref=ppx_yo2ov_dt_b_product_details&th=1

I have yet to give it extensive testing in a model, but in a basic test I ran a motor off the hub while shaking/whacking the hub for a while, and didn't experience any issues, so I expect the connection is good. Just make sure you don't jam the battery in backwards! It should only fit in one way, but if in doubt, there's + / - markings on it.

One last caveat! I designed it to fit in the clip-style hub, and I can't confirm whether or not it works on the screw-type one or not.

If anyone wants to try printing one, here's my Thingiverse upload for it:
https://www.thingiverse.com/thing:6434892

[msk6003]

5 hours ago, 2GodBDGlory said:

I can't confirm whether or not it works on the screw-type one or not.

Basically both use same battery component so it will work with screw type.

And how about using the extra space to route the charging port to the bottom with a USB-C extension cable?

[2GodBDGlory]

9 hours ago, msk6003 said:

Basically both use same battery component so it will work with screw type.

And how about using the extra space to route the charging port to the bottom with a USB-C extension cable?

Alright!

I had thought about using a cable like that, but there's not enough room for a straight USB-C port, so it would require a fairly unusual 90 degree USB-C extension cable, like this one here:
https://www.amazon.ca/Extension-UseBean-Aluminum-Extender-Nintendo/dp/B0836HS4LQ/ref=sr_1_5?crid=466J2XAW947F&keywords=90%2Bdegree%2Busb%2Bc%2Bextension%2Bcable&qid=1705341396&sprefix=usb-c%2B90%2Bdegree%2Bex%2Caps%2C178&sr=8-5&th=1

Not something most of us are likely to have lying around, but it wouldn't be too hard to modify the design to make it work with one, which would be quite convenient!

I'd only hope that the 0.6 foot cable they're advertising wouldn't be too awkward to fit in

[dustblue]

On 1/15/2024 at 10:34 AM, 2GodBDGlory said:

While working on a project involving a PU hub today, I got frustrated with my hacked-together system for running it off some random 7.4V battery I had lying around, and came up with a simple idea that would make it easily possible to power the hub directly off of a standard 9V battery, specifically, one of my rechargeable lithium-ion ones. The idea is that this battery would give peak voltage (Actually 9V; there must be some kind of voltage converter inside the battery to get there) over most of the battery life; that it would save weight; and that it would allow for easy battery swapping and recharging.

The key thing here is that a 9V battery's output terminals are spaced such that all you need to run a Technic hub off of them is to hold the battery against them--no messing around with wires, springs, soldering, or contacts! With that idea, I modeled up this design for a 3D-printable part in Fusion 360, and had a very workable part on the second prototype! I think this is what I'll probably use to power my PU models going forward, and I thought it was an easy enough idea to replicate that I'd share it here.

 

 

 

You can think of it as the "poor man's" version of the impressive Phondly EnBo battery pack

It isn't as nice of a product, because it has lower battery life (I'd assume), and no external charge connection, but it can be easily produced by anybody with access to a 3D printer and a 9V battery (Very preferably a lithium-ion rechargeable one!), so I think it's an alternative that could be useful to quite a few people.

This is the battery I'm using here, so you have an idea of what I'm thinking (I can't really vouch for these ones, since I just bought them to replace some different ones I had)--basically they just output 9V in a 9V form factor, but have USB-C charging, which is quite convenient!
https://www.amazon.ca/dp/B08D925V8H?ref=ppx_yo2ov_dt_b_product_details&th=1

I have yet to give it extensive testing in a model, but in a basic test I ran a motor off the hub while shaking/whacking the hub for a while, and didn't experience any issues, so I expect the connection is good. Just make sure you don't jam the battery in backwards! It should only fit in one way, but if in doubt, there's + / - markings on it.

One last caveat! I designed it to fit in the clip-style hub, and I can't confirm whether or not it works on the screw-type one or not.

If anyone wants to try printing one, here's my Thingiverse upload for it:
https://www.thingiverse.com/thing:6434892

This is clever, one 9v battery is mush less fuss comparing to 6AA, you should sell it!

[JaBaCaDaBra]

1 hour ago, dustblue said:

This is clever, one 9v battery is mush less fuss comparing to 6AA, you should sell it!

And much less energy
Nice but useless idea, the battery won't last 10 minutes

[2GodBDGlory]

5 hours ago, dustblue said:

This is clever, one 9v battery is mush less fuss comparing to 6AA, you should sell it!

Thanks!

I don't think it's worth the trouble of selling it, when producing it is as easy as a single 3D-printed part. If people want a copy and don't have a 3D printer, I'd recommend either seeing if there's a publically available printer nearby (At a library, etc.), or looking into an online 3D printing service that could print/ship the part for you. I mean, I could print/ship units to people myself, but that's probably not very cost-effective.

3 hours ago, JaBaCaDaBra said:

And much less energy
Nice but useless idea, the battery won't last 10 minutes

To an extent that's true, but I've got a couple objections.

First, it is likely to have smaller capacity, but I think the difference is less than one would expect. After checking out my rechargeable AAs and AAAs, I found that I have some tiny, nasty, 600 mAh AA batteries, (Which are admittedly much smaller capacity than usual), and some Amazon Basics AAs at 2000 mAh. My AAAs, which are also something people would realistically use in some Lego models, are rated at 1000 mAh.

To compare to these, my lithium 9Vs are rated at 1300 mAh, which puts them at 65% of the capacity of the Amazon Basics batteries, while actually at higher capacity than the AAAs or those other lousy AAs. (And keep in mind that because the AAs/AAAs are attached in series, their amperage doesn't go up when you add multiple batteries; just their voltage). (Also, because this battery is higher voltage, at 9V rather than 7.2V, it's capacity in watt-hours is 11.7 kWh as opposed to 14.4 kWh for the AAs, which is a more impressive 81% of the capacity, if not the battery life)

So, it doesn't have as much life as good rechargeable AAs, but it's still fairly respectable.

Second, I'd just like to point out that not everything needs high battery life. I'm really not a fan of PU for general-purpose use, and will generally use PF wherever possible. Because of that, I tend to only use PU when I specifically need programmable servos, which don't run constantly, and so don't take that much battery. For example, in the MOC I'm currently working on, I have six PF motors running various functions, including high-load things like drive, as well as four PU motors, all of which are functioning intermittently as servos. Because of that, I expect that even a smaller battery life would be just fine for a model like that.

[dr_spock]

Nice work.  I think those 9V Li-Ion batteries should last enough for a truck trial run.  I was puling at most 1.24 Amps on my WIP truck with 2L motors using an EBL battery.  Those 9V Li-Ion batteries are not so expensive that you can't have a couple to swap out.  Beats having to recharge in the woods.

[gyenesvi]

That's a nice idea, I like the battery itself, great that it has regulated 9V output, thanks for the link! I was actually thinking about using such a battery with a PF connector / converter on it (GreenGecko workshop has it), to be used in small RC MOCs with PF electronics.

[2GodBDGlory]

Thanks! Just as a caution, when I started trying to use this design, I was finding connection between the hub and PyBricks to be spotty--I'm not sure what exactly the issue was, but it went away when I went back to AAs.

I have seen good success in the past running PF stuff off of rechargeable 9Vs like this, though, so that could be a good option for you, @gyenesvi

[Aurorasaurus]

On 1/21/2024 at 9:45 AM, gyenesvi said:

That's a nice idea, I like the battery itself, great that it has regulated 9V output, thanks for the link! I was actually thinking about using such a battery with a PF connector / converter on it (GreenGecko workshop has it), to be used in small RC MOCs with PF electronics.

Green geckos one is a bit expensive, if you have soldering equipment it wouldn't be too hard to make your own.

[gyenesvi]

3 hours ago, Aurorasaurus said:

Green geckos one is a bit expensive, if you have soldering equipment it wouldn't be too hard to make your own.

Indeed, I just referenced it to illustrate the idea :)

[dr_spock]

On 1/22/2024 at 6:23 AM, Aurorasaurus said:

Green geckos one is a bit expensive, if you have soldering equipment it wouldn't be too hard to make your own.

Soldering is not required if prewired 9V battery connectors and 3rd party PF connectors are used.  Put the wire in the correct pin and press hard.  Those components can be found on AliExpress.com.  Several could be made for the price of a Green geckos

If the 9V connector comes with pre-stripped wires, they can be cut off before putting in the PF connector to avoid short circuits.