I recently bought a 12v deep cycle battery 75 AH and I made a battery box following these tutorials: https://www.youtube.com/watch?v=cAErwLnsSIY and https://www.youtube.com/watch?v=torSEtjPZ2I (no need to watch it ofc, just to understand the basic idea).
A small description how it wires as well: The battery is wired to the first fuse in the fuse block, which is wired to the "master switch", this switch gives power to the rest of the fuses which are wired to other components, and also gives power to the voltmeter for measurement of course.
The problem is that whenever I'm using other components such as leds etc the voltage in the voltmeter is dropping(not the actual battery voltage, but the voltage the voltmeter is reading) and I'm not sure how to change that.
for example, when turning the master switch, the voltmeter is reading 12.5v, then I'm turning on the leds and the voltage is dropping to 12.4v in the voltmeter and so on.
I can wire the voltmeter directly to the battery, but I don't want it to be powered all the time. I'm not 100% sure how it works, but I tried wiring the switch to the voltmeter, and from the voltmeter to the fuse block, but it still doesn't work. Any ideas?
Here are some pictures of the battery box, not great quality, and the wires are currently very messy until I'll fix everything: https://imgur.com/a/uJLqyKF
Thanks, hope I made myself clear enough.