Install Volt Meter to Battery Switch

[Lake-Effect]

Originally Posted by sailorchic34

While using the battery switch common terminal will get you the active battery voltage. It will not show you the resting battery voltage. Really its the resting battery voltage that gives you a better look at SOC. Reading the voltage on an active battery bank does not give a true indication of the SOC battery voltage. It always shows a voltage less then the true SOC

I use a [SPDT] on/off/on switch with a digital voltmeter, wired to the A and B sides of the battery switch. This allows me to read the active battery and the resting battery. Plus I can turn off the LED display at night or at the dock too.

Seconding this.This is the most common method, and the most flexible, for voltage measurement.

Originally Posted by Andina Marie

HOLD THE PHONE EVERYONE. He said he has a 24 volt system.

I took the OP to mean he had two 24v banks, each with two 12v batteries in series. Regardless of the actual bank voltage, the technique of measuring each bank's voltage is the same. Now, if he had 24v banks and wanted to measure individual 12 battery voltage... that would be something different.

[Sailorman375]

Yes 24 volt system with two banks, each with 2 12 volt batteries. It would be nice to be able to measure each battery I guess, but that would entail a bunch more wiring I would think.

[FlyingCloud1937]

you said that in a blonde sort of way.

Originally Posted by sailorchic34

Nope, I'm saying adding a separate small DPDT switch. The meter connects to the center common lug on the DPDT switch (not the guest battery switch). Each outer lug on the DPDT goes to the separate battery lugs on the battery switch. So #1 goes to one side of the DPDT switch and #2 goes to the other side of the DPDT switch.

Its opposite of what everyone else said. I'm saying it works better with an extra small switch, that allows you to read each battery bank separate. Using the main guest switch does not really allow you to check the resting state of the battery. Only the in use state. The resting state is what gives a much better reading of SOC

BTW, I only have a voltmeter for checking SOC. It works fine enough on my simply boat

Darn blonde moments. I meant using a SPDT switch..

[FlyingCloud1937]

bingo to you both,

that's why some people should never touch a wire on their boat, no matter how much professional consulting they had.

he said he had a 24 v sys, not a 12 v sys

Originally Posted by Sailorman375

I've got a 24 volt system with two banks consisting of 2 each 12 volt batteries. Can I install a volt meter at the battery switch and if so do I just wire the positive to each positive pole and the negative to a common negative? In other words, I'm trying to use one volt meter and switch between banks to check voltage.

It's easy for even good pros to mis-understand what a boat owner says he has.

lloyd

Originally Posted by Andina Marie

HOLD THE PHONE EVERYONE. He said he has a 24 volt system. I'm hoping he meant a 12 volt system with 2 batteries as suggested by the switch question. A small single pole 2 position switch with center off would allow reading either battery without having to manipulate the battery switch, and allow disconnecting when not in use. Fairly good quality meters are available at reasonable prices, it may be much simpler to add a second meter.

Avoid typical marine dash board analog meters (with a non digital display). I've seen errors as much as 15% in some. And digital doesn't equate to accuracy, the price of some Harbor Freight digital meters is extremely attractive but they can be equally inaccurate.

Originally Posted by Maine Sail

Bingo! I would add that you can also install a "self returning" switch so when you let go it returns to center, not 1 or 2, and turns off the volt meter. For owners who are forgetful these self returning switches work well to avoid parasitic draw especially if the boat is mooring sailed..

[daddle]

You will want a fuse on each positive meter wire. Near the battery switch.

[Wotname]

Originally Posted by Andina Marie

HOLD THE PHONE EVERYONE. He said he has a 24 volt system. .........

Originally Posted by FlyingCloud1937

bingo to you both,

that's why some people should never touch a wire on their boat, no matter how much professional consulting they had.

he said he had a 24 v sys, not a 12 v sys



It's easy for even good pros to mis-understand what a boat owner says he has.

lloyd

Err... would someone like to tell this pro (i.e. Wotname) what difference it makes whether the system is 12V or 24V when it comes to wiring up a voltmeter. Last time I checked, the methodologies of voltmeter wiring is not voltage dependant - at least not for ELVs.

Clearly the OP has a 24V system consisting of 2 banks. Each bank has two 12V batteries (obviously connected in series).

He has a voltmeter that he would like to connect up to his 1/2/Both switch and he clearly has little electrical knowledge (no criticism intended, just a fact to note). I think it is safe to assume he has a 24V voltmeter. The simple solution (especially given his lack of electrical expertise) is for him to connect it in the manner he asked about - direct to the 1/2/Both switch.

While I agree that Sailorchic's (& others) method is superior, it is might be asking too much of him to go the extra distance.

And of course, Daddle is correct, at least the positive lead of the voltmeter should be fused. This fuse should be as close to the source connection as possible and be rated to protect the voltmeter wiring. I suggest 0.5 amps. The source will either be the 1/2/Both switch or the battery terminals depending on which method he selects.

[Sailorman375]

Well.... After reading all this. I will go with the SPDT switch and yes I have a volt meter with the proper range. The idea was to be able to monitor SOC and batteries are a fair distance from my panel (where I want the meter to reside). I don't use the batteries except when away from the dock (live aboard). I use an Iota power supply and by pass the battery banks when connected to shore power. I admit my knowledge is limited, but I think I can handle this one at this point. Thanks for all the input.

[Astral Blue]

Originally Posted by sailorchic34

While using the battery switch common terminal will get you the active battery voltage. It will not show you the resting battery voltage. Really its the resting battery voltage that gives you a better look at SOC. Reading the voltage on an active battery bank does not give a true indication of the SOC battery voltage. It always shows a voltage less then the true SOC

I use a DPDT on/off/on switch with a digital voltmeter, wired to the A and B sides of the battery switch. This allows me to read the active battery and the resting battery. Plus I can turn off the LED display at night or at the dock too.

I completely agree with this position. A volt meter is useful to determine whether your battery is receiving charge from the alternator or another charging source. However, it goes far from showing your state of charge. In fact, a volt meter will provide almost no useful information at any given point, especially if you have other batteries connect in parallel or if you have any source(s) of current draw.

If you are concerned with charge remaining and charge state, I would highly recommend a battery monitoring system. Xantrax makes an excellent unit. These units actually have a processor that continuously runs a series of complex algorithms to determine charge state and charge remaining. Therefore, you don't even need to wait for voltage at rest readings to give you a guess. You can have accurate information consistently.

Hope this helps.

[Wotname]

Originally Posted by Sailorman375

Well.... After reading all this. I will go with the SPDT switch and yes I have a volt meter with the proper range. The idea was to be able to monitor SOC and batteries are a fair distance from my panel (where I want the meter to reside). I don't use the batteries except when away from the dock (live aboard). I use an Iota power supply and by pass the battery banks when connected to shore power. I admit my knowledge is limited, but I think I can handle this one at this point. Thanks for all the input.

Sounds good, don't forget you will need two fuses with this method, one near each positive battery terminal. Try to get yourself a SPDT in either an ON-OFF-ON configuration (i.e. with OFF centre position) or even better, an (ON)-OFF-(ON). This is a centre off switch with a momentary function to either side.