On the other end of the scale, you can get cheap gauges off eBay that plug into cigarette lighter ports, and will tell you the voltage of wherever the power is coming from. Victron, Redarc, Enerdrive and several other companies make some amazing products. Some will read the power going in, power going out and then tell you how much longer your situation will run for.

These days, you can get some pretty fancy little gauges. You can read more about that here – Are you damaging your 12V batteries? Alternatives I don’t like letting my secondary, or deep cycle batteries get below 12.1 volts, to maintain a healthy battery for a long time.

When stopped, it should sit around 12.6 to 12.8 volts full. Your cranking battery should get up to around the 14.2 – 14.4 volts while driving, if you have a vehicle that doesn’t have a smart alternator. Most deep cycle batteries top out at around the 14.3 to 14.5 volts, but it is manufacturer dependent, so look this up. These are obviously worlds apart, but particularly with a lithium battery we’d never go back to a battery monitor that wasn’t a shunt setup. We’ll be replacing it with a Renogy DCDC, shunt and battery monitor.ĮDIT 2 – We’ve been running a Renogy Battery Monitor and shunt for more than a year now, and love it. To be fair, I’m pretty sure the display wasn’t 100% when it was first installed, and the canopy does get quite warm. There are alarms that can be set for different voltages, which beeps very annoyingly if they go outside of the limits, and it just uses a basic toggle switch to swap between modes.ĮDIT – After nearly 5 years of use the Projecta Dual Battery Monitor is starting to lose its display, making it hard to read.įor now I’ve just swapped it to one display which makes the text larger and more legible, but I suspect it will die soon. There are a couple of options when it comes to the display you can have it only showing one battery, or showing both. Wire them up correctly though, or you’ll end up with your battery voltage displaying the wrong battery first. You hook the wires up to each battery, and it will display the voltages of each battery. They are pretty simple, and they work well. The Projecta dual battery monitor in our Land Cruiser I’ve just had another one installed in the back of the Dmax Canopy, to keep an eye on both batteries. We had one installed in our 80 Series Land Cruiser for several years, and really rated it. If you’ve got a second battery in your 4WD, and you want to keep an eye on the voltage theProjecta Dual Battery Monitor is a common option

Dual battery monitor gauge