OK! Having experimented with these you likely need to return that controller. Most of those don't let you adjust the output voltage outside of either 12V or 24V. The second one you linked the MPT-7210A is the most commonly used one and does work. It's slow, but it does work fine.
The better one, cheaper but it does not have a case so you have to get a box to put it in is the DROK 15A boost converter
I could not find this on your local amazon but that's what you're looking for. Actually HERE is the link to it on their web store. Maybe you can order it via a different amazon or get it directly from them. Even with buying a case it likely will be half the cost of the MPT-7210A and if your source battery will handle it (I'd think so) you can hypercharge at 6A instead of the normal 3A!

Of note I'm building one of these too but I bought two 5000mah Lipos instead of one large one but I am running them in series (so 12s effective) to raise the voltage for more efficient charging.