@Brando
Maytech have a battery that seems similar, you may have to check the dimensions if using the original box.
The Turnigy batteries, plus buying a Hota D6 Pro to charge, at 6s and running in series is an easy option for a custom build.
The FD Assist Plus batteries and the Maytech are lithium ion, and in my experience not as good as lipo.
I also question the 12.6 ah of the FD batteries based on running them in series with a 12 ah lipo battery.
There are two types of people here, the builders and the constructors. The builders have time, equipment and skills creating their builds, and the constructors are like me and do simple designs that just do the job attaching random stuff off the shelf together that sometimes works.
I had a Assist plus and it wasn’t the best for my needs and was going to sell it to get a Max, but the electronics died, so I started my construction just replacing the electronics.
But a few builds failed and I improved it each time for more power, and my path to experimenting and likely more failed future builds has begun.