Hello, 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.

 

Cannot tell which one is the voltmeter from your pictures.

Try hooking up voltmeter directly to the battery, then test if voltage still drops.
If not, you should run thicker wires to the fuse block and where voltmeter attaches to. No need to increase wires from the voltmeter.

You may also have a bad crimp or loose terminal which increases resistance.

 

Thanks for the reply, I have already tested that, and when the voltmeter is connected directly to the battery the voltage is not dropping, and yes, I forgot to mention, the voltmeter is the component that is between the switches(3 to the left and 3 to the right).

Will thicker wire solve it? I used 16 gauge wires for all the wires, 14 gauge for the battery to the plus and minus.
I also have 12 gauge wire, but I don't have the blade connectors for that size atm.
Is there any way to test if there's a bad crimp/loose terminal etc? Or generally test resistance somehow?
Thanks

 

I have made some projects like this and I have experienced what you are currently experiencing. The way I solved it was to run a dedicated positive line from the battery to the voltage meter, and then run the negative line from the voltage meter to a switch. You can add an additional switch to turn on the meter separately or you can interrupt that ground switch with the master switch, depending on what you want to do.

 

I thought about it, I'm not quite sure I understood you correctly, is it possible to somehow use the master switch the way I described it(gives power to the fuse block which means other components and to the voltmeter as well) without having that voltage drops?

 

A voltage drop of .1 volt is not significant. It is normal for voltage to drop when a load is put on the battery. It happens in AC voltage in your house too.

 

Let me clarify myself, yes voltage drop of .1 volt is normal, but there's a difference when I'm connecting my voltmeter directly to the battery or the way it is wired now.

When I power a few components together the voltage can even drop to 12.2v and below, while if the voltmeter would've been connected directly to the battery it would've drop by what it really should(nothing to around .1 volts).

Hope its clear enough, thanks

 

probably have a voltage drop at the switch or one of the many connections like fuse block or wire crimps that low of a voltage drop is normal though, you can measure voltage drop with a voltmeter by placing a load on the circuit, and start checking it with a voltmeter would probably do the ground side first from neg battery to neg voltmeter if there is no drop the meter would read 0, do the same for the positive side from battery positive to pos of voltmeter once you figure out witch side its on you can go more in depth and start checking every wire or switch and connection by just moving the leads.

 

Thanks! one more question, in case I don't find the problem, is it possible that its simply because of the wires or something? What I mean is, I'm using 16 gauge wires, is it possible that because of that there's nothing I can do besides replacing to higher gauge wires?

I currently run the main cables from the battery(the white ones) using 14 gauge wires, will changing those to 12 gauge might make a difference? Thanks!

Edit - Ok so I tested it, I don't really know if the problem is resistance or not, I tested all the wires etc and they were all perfect, but whenever I powered something up, the connection that comes "after" the component I turned on is getting less voltage, which I believe is more related to the wires than the connectors?

 

not sure what all your powering but I dont think the gauge of the wiring is the main issue but how it is wired could be an issue, all your grounds are just looped to the next one, same with power at the fuse block after the master switch its just 16 gauge wire looped from one fuse to another to power them all you can easily be overloading that wire if you turn on enough switches.
would probably consider rewiring the box and run 14 gauge to the master then use 14 gauge from master to a power distribution bolt, then you could attach all the other fuses to the bolt with 16 gauge so they all will have there own good power connection, and then do the same for the grounds by just running every switch to the negative cable stud you are ensuring that each one will have a good ground.
one other thing you may want to change would be to install a heavy duty master switch maybe even a battery disconnect switch in its place but it may be to large for what you want to do.

 

Before I decide to make some new cables, changing the design etc etc, I just measured the resistance from each end on both neg and pos, and the resistance was around 002-003 on 2k mode, on higher modes such as 200k etc it read around 005-007, I don't really know what it means, but do you think its the cause for the voltage dropping?

And in case I want to use a destribution bolt, is there anything special I need, or pretty much any bolt would do?

 

One more question, I have a battery charger that I'm using to charge the battery, is it ok to wire EC5 male from the battery outside, and then wire the car battery plus and minus to EC5 female and then connect the 2 EC5 cables to charge? Will it work?

 

I can't comment on the details, but......if your battery box is going into an enclosed space, as in an RV or........ it needs ventilation.

 

Yeah I know, my box is usually open, and even the box itself has some holes etc, so I think it should be fine

 

resistance checks really dont usually show up issues as it only takes 1 tiny strand of wire to be intact to have good resistance thats why a voltage drop test is done instead, as its checking for voltage drop with a circuit under a load where that bad connection would show up as a voltage reading but its tested the same way just with a voltmeter.
typical power distribution blocks are insulated but there generally bolted to metal so they have to be, looks like what your working with is plastic though, as long as it cant come into contact with ground a bolt should work, would probably just utilize what you have with the studs at each corner like you connected the ground cable to and move the master to one of them for a power distribution also.

 

Thanks for all the help!