Hello. I'm considering buying an SBrick(or possibly a buwizz) for use with some buggy motors but all the videos I've seen recommending using two one for each motor so they don't drain the battery super fast. since two or possibly even one buwizz is not really affordable for me I was wondering if a potential work around could be to connect a single SBrick to two or possibly even more battery packs. would it work? or would the brick only get power from the one. I can see based off of pictures the power connects underneath the brick so would it just default to the top reciever brick or could one or more batteries provide extra running time?

If you want to power it from two batteries at once, you will have to be somewhat unorthodox. Because the wires used to attach to the SBrick have the 9V connection on the bottom, you would have to couple the wires together using old 9V plates or wires. That said, I have no idea whether this is safe; I think it would be in parallel, so I doubt you would have over 9V, but maybe there are other issues. There are other users on here with much more electrical know-how.

In my Buggy I use 1 battery box, 1 Sbrick, 2 Buggy motors for drive and 1 servo for steering.
It works fine for, say, 20 to 30 minutes with rechargeable batteries.

Placing 2 battery boxes in parallel is possible, but you have to put them in the same position and connect them both to the SBrick or put 1 cable in the other box.
The only benefit you have is a slightly longer driving time, but your car will have to move more mass.
If you are using 1 battery box, make the design so that you can easily change the battery box.

If you really want more driving time, you can use 2 battery boxes and 2 SBricks. Connect 1 Buggy motor to each Sbrick.

Battery boxes have polarity switches. If polarity aligns you get double the power at the same voltage; if it does not you have a short.