Hi there, @ContactGT! The use of Cat5 is a common culprit for resistance in power, as it can often be too thin and usually must be spliced or doubled up. For this reason we do recommend 18 gauge or close to it for hardwiring. Here’s our wiring gauge article for reference.
The best way to obtain an optimal charge from existing wires, is to fine tune your battery usage. There are factors which can drain your battery quicker than a charge can be applied, or noticed. Feel free to check out our Community post for tips on limiting battery usage, or drain. I hope this helps! 