What exactly is SmartGauge?

An explanation is often requested as to what exactly SmartGauge is, what it does, how it relates to the more usual voltmeters or amp hours counters and what type of operator/installation it is aimed at.


Is quite simply a "fuel gauge" for your batteries.

Unlike some amp hours counters, SmartGauge does not claim state of charge accuracy to some pointless high precision of decimal places. Does it really matter if the battery meter says the batteries are at 65% charge state or 65.1% charge state?

Also unlike amp hours counters, it will not run out of synchronisation with the batteries thus making any level of accuracy completely meaningless.

SmartGauge is aimed specifically at installations where:-

1. Many different operators use the system or.....

2. It is impractical to train all the operators in the many functions required to be set in amp hours counters or....

3. The operator simply cannot be bothered with the continual required intervention with the battery state of charge meter and the continual uncertainty as to whether it is telling the truth or whether it has run out of synchronisation yet again.

And for these installations SmartGauge is perfect. Simply install it and forget about it. No need to continually correct it or keep track of it. No need to learn to interpret the display.

If the operator just wants a meter that shows them the state of charge of the batteries, without any form of intervention from the operator then SmartGauge is exactly what they need.

Absolutely ideal for fleet vehicles, hire boats, emergency vehicles and any installation where the operator has got better things to do than spend months learning about batteries, installations and how to interpret the sometimes overly complicated displays on other types of battery monitors.

Installation time is comparable to that of a voltmeter i.e. minutes as opposed to hours or days for an amp hours counter.

Compare this with the other options.....


A voltmeter shows the voltage on the battery bank. That is all it shows. Unless the person looking at the voltmeter fully understands the technicalities of batteries and their charge characteristics, knows the actual charge or discharge current at the time the voltage reading is taken, knows the recent discharge and charge history of the batteries, knows the physical condition of the batteries and knows exactly how to relate all this information, then the battery voltage will tell the operator nothing about the state of charge of the batteries.

For example, 10.5 volts does not mean the batteries are flat. The batteries could be fully charged but with a very heavy load on them. Conversely, 12.8 volts does not mean the batteries are fully charged. They could be completely flat with a charger switched on.

A voltmeter can be a very useful piece of equipment. But it actually requires some very extensive knowledge on behalf of the operator and almost continual monitoring of the battery voltage in order to translate this information into an indiciation of state of charge.

If the operator posesses this knowledge and is prepared to sit and watch the voltmeter all day then they probably do not require a SmartGauge.

Amp hours counters

Amp hours counter operation has been covered elsewhere on this website. The comparison link gives a detailed look at their operation.

Amp hours counters make incredibly accurate measurements of voltage and charge/discharge currents, then calculate the resultant charge status from a combination of these measurements. Unfortunately there are certain battery parameters that are required in order to make these calculations but these parameters cannot be easily measured. The result is that amp hours counters only work for a very short period of time.

If the operator has considerable knowledge of Peukert's effect, battery charge and discharge characteristics, battery capacity versus age characteristics, the physical condition of the batteries etc, then amp hours counters can be a very accurate way to track the state of charge. But only in the very short term. For instance, it may be necessary to track the state of charge of a battery on, say, a racing car during a race. In this case, the condition of the battery will be very accurately known, the battery would be fully recharged and the amp hours counter reset to zero at the start of the race.

The counter will then very accurately track the state of charge of that battery and give an incredibly accurate indication of the remaining power during that one race. But in the longer term, without knowing the condition of the battery, and without repetetively resetting the amp hours counter, the meter will run further and further adrift, to such an extent that after about 10 to 20 discharge cycles, the meter may as well not be there because the readings will be so wildly inaccurate.

Unless the operator keeps a very careful eye on things, regularly monitors the meter, resets the amp hours, regularly checks Peukert's exponent is still functioning satisfactorily etc, then the meter can run further and further out of synchronisation with the actual battery state of charge. If the meter can run out of synchronisation with the batteries, then it makes no difference how accurate the manufacturer claims the meter readings to be. The meter can claim to display the charge status to 6 decimal places. But there is little point in this if it has drifted out of synchronisation by 200 amp hours.

In effect, these meters only give a decent state of charge indication when the operator already knows what the state of charge is because the operator has spent so much time monitoring the meter and batteries. If the operator has to know what the state of charge is in order to trust the meter, then what exactly is the point in having the meter?

All amp hours counters seem to do, as far as state of charge is concerned, is make the operator monitor the batteries themselves, then tell the meter what the state of charge is.

If the batteries, chargers and system etc are left to their own devices for a few weeks, the amp hours counter will be showing, literally, total rubbish without continual intervention from the operator.

If the operator loves to continually fiddle with the meter, resynchronise it's counters, check the batteries, measure, calculate and set Peukert's exponent then the operator probably will not require a SmartGauge.


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Page last updated 02/04/2008.
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