The ins and outs of monitoring your 12V system health.

Continuously monitoring your 12V system’s health ensures optimum performance and service life for auxiliary batteries.

The list of gadgets we can bolt on or wire up to our 4WDs these days is pretty much endless.

When considering fitting any new accessory to our rigs, we need to ask ourselves how high of a priority such an upgrade might be, and whether, in fact, we need fit it at all.

A quality dual battery system, for most 4WDers, definitely lands fairly high on the priority list. Weekend users hoping to run a fridge and phone charger on the odd overnight camping trip will be happy to set up a basic dual battery system and let it chug along in the background.

Those with more demanding power requirements will be better served by doing their homework prior to setting up their 12V systems, and continually monitoring them to ensure optimal performance and service life of auxiliary batteries.

Some level of battery monitoring provides peace of mind, especially when auxiliary batteries are relied upon for safety and to run essential gear. If you know nothing about the battery condition via monitoring, then the only way to find it out is the hard way – when it goes flat!

There are various ways that batteries can be monitored from simplistic voltage and current readings, right through to using these measurements to calculate against battery chemistry and size characteristics.

Voltage measurement is the entry-level battery monitoring solution. Whether a hardwired gauge or wireless solution is employed, it will essentially tell the user the instantaneous voltage of the battery at any given time.

Voltage can give you a line in the sand from which you can see if things are behaving as they should. If the voltage is higher than the normal rest voltage observed, then you know the battery is charging. If the voltage is lower than normal rest voltage, it is under load or in a discharged state.

Learning what is normal for the particular installation is the best way to understand its behaviour and limitations and to know whether something is wrong.

As voltage is influenced by charge/discharge and rest periods, picking something that is abnormal is your indicator that something is going wrong.

There are rules of thumb around battery voltages indicating a state of charge – but better yet the battery data sheet will provide further detail.

Different battery types, sizes, temperatures, charge and discharge rates will all alter the outcome. Some voltage gauges even feature an alert to let you know when voltage is not in good shape. Couple measurements of voltage and current and we start to see some more useful information.

Current flowing into or out of the battery will influence its voltage, and the amount of current flowing impacts the level of voltage change. The internal resistance of the battery (dictated by its type and condition) is another of the key factors that determines the voltage change due to this current flow.

What this means is that you can have a better understanding of the battery condition given the current flow information. If the voltage is low, despite a very high current flow into it, you know the battery is deeply discharged and will take quite some time to charge.

If the voltage is high and the current flow into the battery is low, you know the battery is nearly full. Faults can even be found here, if the battery voltage is high and so is the current flow into it, there may be a fault with the battery and the energy could be getting turned into heat.

Conversely, if the voltage is low and so is the current flow, there may be a charging system fault, whereas if charging from solar alone, you may just not have enough sunlight.

All this data about voltage and current can certainly prove a bit daunting when you just want a cold beer…

Bring on technology to do the hard work! Advanced battery monitoring is often integrated into complete battery management systems. More accurate, meaningful and easily digestible information is provided on all aspects of the charger, load and battery.

Furthermore, higher accuracy current measuring components, that are measuring fractions of an amp right up to hundreds of amps, can be employed.

Shunt type current sensors can provide greater resolution and range than inductive sensors (used in simpler gauges) and are wired in series with the circuit being measured, usually in the battery negative lead.

Battery construction and size impact the efficiency of battery charging and effect of discharge currents on state of charge, all of which can be considered and calculated if you have the information input to the system and monitored in real time.

To work out all of the above around the campfire does not appeal to most! Advanced monitors can do all of these calculations and deliver the information in a way that is easy to understand at a glance, similar to how a vehicle trip meter provides quick data on fuel consumption.

Decide what level of detail and information you require by checking out the RF wireless battery monitors by Hummingbird at or REDARC’s range of 52mm monitoring gauges and battery management systems at

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