Dual Battery Voltmeters and Isolator

[Fishop]

Probably a silly question.  When installing a voltmeter to each of my two batteries, I would have to install it before the isolator wouldnt I? Ie between the battery and the isolator??

Would that cause any significant drain on the batteries over time?  Or should I install them with an additional switch to prevent that from happening.

 

Thanks

[zmk1962]

Hi @Fishop... in my view the only silly question is the one that's not asked !

Where you install the voltmeter (VM) really depends on what you want to achieve.

If you want to be able to monitor each battery stand alone even when the battery is offline from the circuit then yes you need to install a separate VM for each battery before the isolator switch. As you say this will create some minor drain on the battery to run the LCD display and you can get around that by installing a switch in the VM circuit to isolate the VM.  

I have a VM in my Landcruiser, its always on and shows battery voltage even when the keys are out of the ignition.  When I travel overseas - sometimes the Landcruiser is not used for more than a month and I have not seen any significant voltage drop over that period - the LCD VMs have a very low current draw. But then again, even with an occasional month layup my Landcruiser is used a lot more than my boat, the boat has many months of layup and it's probable that any constant draw on the battery would show up over that period.

I have one VM in my boat circuit and three batteries. I have installed the VM after the isolator switch. With the isolator switch off, everything is off including the VM. With this set up I can cycle through the switch and check the voltage of battery 1, 2, 3 or any combination of batteries and I do this before a trip offshore -  10V or less and its clear there is a problem, probably a dropped a plate. When I start the motor I can also check the voltage of my charging circuit (I see the VM display range from 13V-14.6V depending on RPM and that is a healthy indicator I am charging the battery(s) that are online via the isolator switch). 

The downside of this set up, I cannot monitor the offline battery(s) at the same time. For me this was not a major consideration.

So it depends on what you want to achieve.

Hope this helps.

Cheers

Zoran

 

[raging]

I’ve put on Bluetooth voltage meters on my batteries, so they are out of the way & I just check via my phone.

they draw 1ma which is bugger all.

[Fishop]

8 hours ago, zmk1962 said:

Hi @Fishop... in my view the only silly question is the one that's not asked !

Where you install the voltmeter (VM) really depends on what you want to achieve.

If you want to be able to monitor each battery stand alone even when the battery is offline from the circuit then yes you need to install a separate VM for each battery before the isolator switch. As you say this will create some minor drain on the battery to run the LCD display and you can get around that by installing a switch in the VM circuit to isolate the VM.  

I have a VM in my Landcruiser, its always on and shows battery voltage even when the keys are out of the ignition.  When I travel overseas - sometimes the Landcruiser is not used for more than a month and I have not seen any significant voltage drop over that period - the LCD VMs have a very low current draw. But then again, even with an occasional month layup my Landcruiser is used a lot more than my boat, the boat has many months of layup and it's probable that any constant draw on the battery would show up over that period.

I have one VM in my boat circuit and three batteries. I have installed the VM after the isolator switch. With the isolator switch off, everything is off including the VM. With this set up I can cycle through the switch and check the voltage of battery 1, 2, 3 or any combination of batteries and I do this before a trip offshore -  10V or less and its clear there is a problem, probably a dropped a plate. When I start the motor I can also check the voltage of my charging circuit (I see the VM display range from 13V-14.6V depending on RPM and that is a healthy indicator I am charging the battery(s) that are online via the isolator switch). 

The downside of this set up, I cannot monitor the offline battery(s) at the same time. For me this was not a major consideration.

So it depends on what you want to achieve.

Hope this helps.

Cheers

Zoran

 

Thanks Zoran,

 

Yes I am looking at the digital ones with a switch built in and a usb charger as well (as my cigarette plug doesnt work) for charging phones.

Still undecided on whether or not to put it before or after the isolator.  Having the switch I can just switch it off i suppose.  I guess I dont really need it until I need the boat, at which point I would turn the isolator on and my battery voltages would show up. 

 

Thanks for your help

Edited September 27, 2018 by Fishop

[Fishop]

7 hours ago, raging said:

I’ve put on Bluetooth voltage meters on my batteries, so they are out of the way & I just check via my phone.

they draw 1ma which is bugger all.

Nice that sounds like the go.  No additional wires to worry about