Battery Drained by Voltmeter?

[solar2012]

I recently built a solar charger for cell phones and other USB devices. The solar charger has a 12V lead acid battery; attached to this battery is a digital voltmeter that monitors the charge of the battery. I left the system hooked up for a day or two in the dark and noticed that the battery level was dropping. I am assuming this voltage drop is due to the voltmeter and not any other component, such as the charge controller or 12V outlet. I would like to know if a simple switch between the voltmeter and battery would solve this problem. This way I could flip the switch to the off position when the solar charger is not in sunlight. Any other solution would be appreciated.

[Sunking]

Charge controllers use power from the battery, secondary batteries have a self discharge characteristics, and volt meters take very little energy from the UUT assuming it is a newer digital unit.

[solar2012]

Thanks for clearing that up. It must be the charge controller that drained the battery. The battery drained way too fast to be just self discharge. Is there any way I could add an on/off switch to the charge controller? The instructions for the charge controller state that the battery should be hooked up first to avoid damaging the unit. I am afraid that once the swich is turned on, the battery would technically be the last component installed and the charge controller would be damaged. I may be overcomplicating this issue.

[inetdog]

Thanks for clearing that up. It must be the charge controller that drained the battery. The battery drained way too fast to be just self discharge. Is there any way I could add an on/off switch to the charge controller? The instructions for the charge controller state that the battery should be hooked up first to avoid damaging the unit. I am afraid that once the swich is turned on, the battery would technically be the last component installed and the charge controller would be damaged. I may be overcomplicating this issue.

The problem arises when voltage from the panel is going to the CC before it is connected to the battery. If you want to disconnect the CC from the battery, just switch off the panel connection first and reverse the order when turning back on.
You are not likely to damage most CCs, but they may not work properly until reset either. That might explain why it is draining your batteries.
Since your CC has a specific warning about that, I would not be as comfortable about it not being damaged.

[ImpactBattery]

If each component has any type of digital chips they will/can draw a parasitic drain…even the solar panel when in darkness. You can install a small switch right before the battery and run all the devices through the switch.

[Living Tribunal]

If each component has any type of digital chips they will/can draw a parasitic drain…even the solar panel when in darkness. You can install a small switch right before the battery and run all the devices through the switch.

I had a similar question and ran into this post. I'm putting together a basic solar battery bank. I bought an AGM battery and plan to attach a voltmeter to measure the voltage. I've explored the possibility of adding a disconnect switch between the battery and the voltmeter to prevent drain. Two basic questions:

1. Could someone recommend a cheap, basic switch that would work for this?
2. More general question: when I'm attaching things like a volt-meter to the battery is there a minimum AWG the wires have to be? I know if you buy a volt-meter they come with wires but I wasn't sure if those were suitable or if I had to replace them with something bigger.

Thanks in advance.

[Naptown]

You could also have an old sulphated battery that has a surface charge that bleeds off quickly.

[Mike90250]

If each component has any type of digital chips they will/can draw a parasitic drain…even the solar panel when in darkness. You can install a small switch right before the battery and run all the devices through the switch.

You can't blame only digital chips. Analog chips and plain old magnet wire meters also consume power. If something is giving you a reading, it is consuming power.