BMV 501 Battery Monitor

BATTERY MONITOR BASICS

Why should I monitor my battery?

Batteries are used to store energy for later use. But how do you know how much energy is stored in your battery? No one can tell by just looking at it. Battery technology is often oversimplified, but some basic battery knowledge and good monitoring is essential if you want to enjoy maximum life from your expensive batteries. The life time of batteries is dependent on many factors.

Battery life reduces by under-charging, over-charging, excessively deep discharge, too fast a discharge and too high an ambient temperature.

By monitoring your battery with an advanced battery monitor like the BMV-501, important feedback is given to the user so that remedial measures can be taken when necessary. This way, by extending battery life, the BMV-501 will quickly pay for itself.

How does the BMV-501 work?

The capacity of a battery is rated in Amphours (Ah). For example a battery that can deliver a current of 5Amps for a period of 20hours is rated at 100Ah (5 * 20 = 100). The BMV-501 continuously measures the nett current flow in or out of the battery so it can calculate the amount of energy removed from or added to the battery. But since battery age, discharge current and temperature all influence the battery’s capacity, you can’t rely simply on an Amp-hours reading. When the same 100Ah battery is discharged completely in two hours, it will give you only 56Ah.(because of the higher rate of discharge)

As you can see the battery’s capacity is almost halved. This phenomenon is called Peukert efficiency. Also, when the temperature of the battery is low, its capacity is decreased even more. This is why simple Amphour counters or Voltmeters give you far from an accurate state-of-charge indication.

The BMV-501 can display both Amphours removed (not compensated) and actual state-of-charge (compensated by Peukert efficiency, charge efficiency and temperature). Reading state-of-charge is the best way to read your battery. This parameter is given in percent, where 100.0% represents a fully charged battery and 0.0% a completely flat battery.
You can compare this with a fuel-gauge in a car.

The BMV-501 also makes an estimation of the time the battery can support the present load (time-to-go readout). This is actually the time left till the battery needs to be charged again. If the battery load is fluctuating heavily it’s best not to rely on this reading too much since it is a momentary readout and must be used as a guide only. We always encourage the use of the state-of-charge readout for accurate battery monitoring.

Besides the main function of the BMV-501, displaying the actual battery status, this monitor offers many other features. The readout of actual battery voltage, current and temperature, the ability to store historic data, the PC computer-link and the Super-lock function are just a few features of the BMV-501.