GT40 Pint Battery Mod
This is just an accompanying article to the YouTube review posted on my channel, which I’ll include below:
If you’re looking into this mod, and want to grab some extra vents for the controller box, in the event that you want to eventually reverse the installation, these are the vents I recommend:
https://www.badgerwheel.com/shop-online/spare-vents
Once again, it’s important to note that ANY mod of a Onewheel likely will void its warranty with Future Motion, and carries some kind of risk. Tampering with hardware of this kind, around voltages of this level, is ingerently dangerous, and should be treated as such. DIY modifying, and DIY work/projects with vehicles of this nature require care, patience, and a degree of knowledge. Make sure you are comfortable and able to follow basic safety protocols when working with electronics. This includes having a safe area to work, and plans in place in the event of catastrophic failures and accidents.
In addition to the review, I’ll include a video disassembly of the outer parts of the unit, and how to access the internal BMS. One of the review units I have is currently not functioning, and that is because I was doing charge testing in ways that were advised against by the manufacturer.
They advise that users shouldn’t hot swap, or hot plug/unplug the mod from a live (on) board. This can damage the mod’s internal BMS, or the internals of the Onewheel. So, in an effort to see what would happen, I switched on a bench power supply and set it to 63.5 volts, had it running with a current of about 3 amps, and just plugged it into the GT40. A little light flicker, and a small pop/click sound later, and the unit was dead. Obviously, it was my fault, and so the unit needs a new BMS/PMS.
That brings me to the opening of the unit, in the video below:
This is interesting to see for a couple of reasons. As I mentioned in the video, the internals are much simpler than I had thought. The PMS/BMS is very small, and seems easy enough to replace. Fixing this unit won’t be too difficult as soon as a replacement PCB is received.
I was indeed surprised to find that the BMS/PMS was not hooked up to each cell for balancing. This struck me as odd, but not entirely an issue. As I’ve observed in other batteries made from new A grade cells from the same batch of manufacture, the cells didn’t incur any significant drift in this application to warrant the extra space and heat of a balancing circuit for a 1p configuration. In practice, the current draw and charge current are so low that the cells aren’t stressed as they would normally be if they were used on their own. And so, the total deliverable energy of the pack remains consistent as it ages through the cycle life of the cells.
Interesting to think about, at least.
In my testing, I didn’t find there to be able noticeable drift from this battery that would lead to issues with its delivered capacity. My unit has been cycled a total of 24 times as of this writing. 3 cycles were full top-to-bottom charges and discharges, and the rest were partial uses until the setup was empty. I just tallied these all up, and then arrived at that number of cycles. In those cycles, I was able to achieve an empty voltage of the GT40 mod’s battery, of 41.8v resting, which is about 2.8(ish) volts per cell. It charges up to 63.2 volts resting still, which is also within normal range.
I don’t have any complaints about the unit, and it has remained on my Onewheel Pint Regular. It rides well, and it’s a nice mod that performs as it’s promised to.
