SBM-01 high precision battery monitor
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1. BATTERY MONITOR BASICS
1.1 Why should I monitor my battery?
Batteries are used in a wide variety of applications, mostly to store
energy for later use. But how do you know how much energy is stored in
your battery? No one can tell you that by just looking at it. Battery
technology is often underestimated, but some basic battery knowledge
and good monitoring is essential if you want a maximum life time of your
expensive batteries. The life time of batteries is dependent on many
aspects. Battery life time reduces by under-charging, over-charging, too
deep discharging, too fast discharging and too high ambient
temperature. By monitoring your battery with an advanced battery
monitor like the SBM-01, important feedback is given to the user so that
measures can be taken when necessary. This way, by extending battery
life time, the SBM-01 will quickly merit itself back.
1.2 How does the SBM-01 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 SBM-01 continuously measures the
present 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 cannot rely on an Amp-hours reading. When the same 100Ah
battery is discharged completely in two hours, it will give you only 56Ah.
As you can see the battery’s capacity is almost halved. This
phenomenon is called Peukert efficiency (see also chapter 2.2). When
the temperature of the battery is low too, its capacity is decreased even
more. This is why simple Amphour counters or Voltmeters are not able to
give you an accurate state-of-charge indication.
The SBM-01 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.
