Is connecting negatives safe

Other Hardware General Electronics
1

I'm a aware you can use different power sources with each other by connecting grounds. I'm wondering, of I do this with a 48v power supply and a sensitive device on a 3v power supply, the 48v shouldn't affect the 3v device if only grounds are connected, right?

2

Correct.

3

If you have to ask that question maybe you should not be so vague. How about telling us EXACTLY what the heck you are talking about so we can decide if there is more to this than a simple common ground.
What runs on 48V ? and What runs on 3V? and Why are you connecting them together ? It is possible there are other options we have not suggested because we know absolutely nothing about your project.

4

The 48v is connected to two platinum leads in tap water to induce electrolysis. The 3v powers this sparker which creates an explosion. I know that the speaker will break if denied a path to arc or if input exceeds 6v. This is why I wanted to know

5

There is no reason why the sparker and the electrolysis supply cannot share a common ground.

6

CantSayIHave:
The 48v is connected to two platinum leads in tap water to induce electrolysis. The 3v powers this sparker which creates an explosion. I know that the speaker will break if denied a path to arc or if input exceeds 6v. This is why I wanted to know

48V!

Why do you use such a high voltage? I run electrolysis machines with power supplies that are switchable between 6 and 12 volts. The six volt setting produces the stoichiometric ratio of 2 volumes of hydrogen to one volume of oxygen gas. When set to 12 volts the ratio is closer to 3H:O and the oxygen smells strongly of ozone.

7

I assumed a higher voltage would split molecules faster, so I chained 4 12v batteries. Am I wrong? Should I be increasing current instead?

8

Yes.

The rate is proportional to the number of transferred electrons, which depends on current. Eventually your electrodes will be the limiting factor.

9

I assumed a higher voltage would split molecules faster, so I chained 4 12v batteries. Am I wrong? Should I be increasing current instead?

Yes.

The rate is proportional to the number of transferred electrons, which depends on current. Eventually your electrodes will be the limiting factor.

I think you need to try SERIES PARALLEL
2 batteries in series in parallel with 2 batteries in series (cut the voltage in half and double the current)