The Bogart Trimetric battery monitor uses current and voltage readings to track the power in and out of a battery. A precision resistive shunt is installed between the negative terminal of the battery and all the loads. All current going into the battery (charging) and all current leaving the battery (discharging) is measured. Electronic circuitry and a microcontroller record battery voltage and battery current.
Because the Trimetric keeps track of current leaving or entering the battery, a very good approximation of the state of charge of the battery can be determined and displayed.
Less Expensive Battery Monitor
A battery monitor could be as simple as a voltmeter and an ammeter, permanently installed so the user can keep tabs on the battery at any time. If the user has an understanding of the properties of deep-cycle batteries, a great deal of information can be observed and recorded.
The battery voltage is displayed on the voltmeter. The ammeter is connected such that all the current going in and out of the battery passes through the meter. Observing the ammeter will tell the user ‘how heavy’ the load is that is powered by the battery or how much current the charging system is providing.
State of Charge Related to Battery Voltage with No Load
Voltages shown are for a 12-volt battery system at 25 degrees C (77 degrees F) . These voltages are for batteries that have been at rest for 3 hours or more and not being charged. It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity with a hydrometer, but in some battery installations, this is difficult or impossible.
|Approximate State of Charge||12 Volt lead acid battery||Volts per Cell|