In the case of battery monitors that essentially present a voltage reading, monitoring temperature in real time can more accurately depict voltage, and therefore, state of charge. We know from Ohms Law that as resistance changes (mathematically) both voltage and current will change. As batteries heat and cool due to both ambient temperature variations and electro-chemical reactions in each cell of the battery, their internal electrical resistances also vary. There is a direct correlation between temperature, current (amperage), and voltage. Why does temperature matter? Monitoring battery temperature and building that data into a micro-processor that is sending out a voltage reading is useful for those seeking extreme accuracy. Some of the vendors did not offer any guidance for calibration, presumably because calibration is limited, if at all possible. Victron, for example, offers an optional temperature sender to provide that data input to their monitors. Several of the vendors in our group have given these matters considerable attention and make recommendations to periodically synchronize or calibrate the monitor with the batteries being monitored. (See accompanying How We Tested on right for details on the testing.)īattery chemistry and internal construction, age, temperature, and rate of discharge and recharge efficiency all play into the degree of accuracy we can expect from a battery monitor. This is something our testers had to take into account as well when they established a protocol. But when it comes to determining state of charge or hours of use remaining, there are many factors that can introduce some margin of error. These devices are quite good at monitoring amperage and voltage and keeping track of these values down to 0.1 volts in either case. Its important for readers to understand the limitations of any battery monitoring system. It appears that the other vendors really have not tested their products with that battery chemistry in mind. Of our test units, the Victron monitors were the only ones to even mention lithium iron technology and make a recommendation for adjusting the units profiling to fit lithium technology and discharge/recharge regimens.
#BOAT BATTERY MONITOR SYSTEM GENERATOR#
Among these vendors, we looked at offerings ranging from a simple, red warning-light voltage monitor (Scad) that automatically shuts down heavy electrical loads before a dead battery occurs or turns on a generator to get a battery charger up and running when needed, to very sophisticated adjustment and profile settings (Victron) that can work well with lithium iron phosphate (LiFePO4) battery technologies. What We Testedįor this report, Practical Sailor studied and compared monitoring systems from five different suppliers: Blue Sea Systems, CruzPro, Scad Technologies, Victron Energy, and Xantrex. Many boat owners today can easily have several thousand dollars invested in batteries by keeping close track of their batteries state of charge. The bottom line here is that keeping track of your batteries states of charge is especially important for maximizing battery-cycle life. On the other hand, many cruisers now expect to have such amenities as air-conditioning and refrigeration on board-features once considered luxuries-which has increased their appetite for amps significantly, in spite of product vendors considerable efforts to design in lower power consumption. The net result is systems that dramatically reduce the amount of power we need to keep things illuminated. For example, LED lighting systems have finally evolved so that they not only use very few amps to provide high-quality interior light, but they also actually meet international standards, as is the case with running lights. The need for accurate monitoring is especially important when you consider that over the last decade, we have seen some important improvements in battery technology as well as other areas of onboard electrical systems. Certainly, for many cruising sailors, battery banks are among their most important onboard resources, and knowing when you might be running low on electrical fuel is as important as keeping track of potable water and diesel fuel. It has been 16 years since Practical Sailor looked at battery monitors, so we thought it was high time to take a look at the latest offerings in this area. But just how accurate are the monitors we use to gauge our batteries states of charge?
#BOAT BATTERY MONITOR SYSTEM FULL#
These tests demonstrated that a sealed batterys capacity will be reduced over time, if its never brought back up to a full state of charge. Two recent tests graphically demonstrated the importance of monitoring state of charge in a boats batteries: Tracking Batteries, in the May 2015 issue and AGM Battery Test Update, in the August 2015 issue.
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