I have a custom solution too: 3*LiFePo4 26650 cells. They provide very much current at 9.6 Volts. I glued the cell holders to a 6*12 plate with MMA glue, added a switch and spliced the wires into a short PowerFunctions extension cable (but only the outer ones, so you could use one end to power the SBrick and the other end to control a motor with the same cable).
However, my solution is very bulky and heavy. I even tried the Lepin (now Xingbao) rechargeable battery boxes. They provide you a cable with a round connector (which you plug into the battery box) and an USB connector. These are cheap as dirt, but the electronics are very easily fried when you draw too much current (and a stalled L-Motor is too much already).
I would be very happy too, if Vengit would offer a high quality and compact rechargeable battery.
Disclaimer, i only own an sbrick, not a buwizz,and this post is about batteries, even if i talk about buwizz as an incentive to vengit to make a move
So here the main issue: in the challenge buwizz VS sbrick there is one big difference: ludicrous mode and full space required (battery box + sbrick is a lot bigger than a buwizz), both caused by the use of an internal 3s lipo battery from the buwizz receiver.
For all advanced lego user we know that lego battery boxes are an huge limitation, first of all for these characteristics:
- 9V max voltage
- 250mah current limiter (new AA battery boxes have a better one but sometime it's not enough)
- excessive weight, both AA and AAA battery boxes have and high weight from the alkaline/nimh batteries
- super expensive lipo version, with old current limiter and not technic friendly size, and still 7.4V
just for the sake of experimenting i modified an old broken 9V connector to use a 7.4V 180mah lipo battery
this battery comes at a price of 4€ each to the public (even if batches are always at discount on hobbywing and cost 4€ 5pcs), it was able to support a buggy motor and a servo motor for almost 10minutes of driving, even on rough terrain.
all this to suggest vengit one good move: a custom rechargeable battery box, that should be very compact, under the 50€ price-tag, with usb recharge and PF compatible port (the lego one is currently 140€, discontinued from the official lego and needs an external charger)
i know nothing about industrial production, but this is basically a power bank for lego, and could sell also to non-sbrick user due to the huge advantage that it provides and the reliability of the vengit mark. in addition to this it will also fill the gap between buwizz and sbrick where the latter is currently ahead only for the awesome support and easy control customization (lacking the all-in one solution and bonus power from buwizz)