Instruction Manual

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Step 3. Typically during step 2 the battery will track state of charge closely, but not exactly because
the self discharge will not be compensated precisely. Usually the recommended values will cause
the “battery % full” to read slightly lower than true, thus giving a conservative view of remaining
charge left in the batteries. However when the battery is again fully charged, the meter will
again reset to “100%” to resynchronize the battery with the meter, and then the meter will
continue as in step 2.
7.B: Deciding on programmed value for P14, P15, P32-P35.
P14, P15: Battery capacity. To keep track of “Battery % Full” you must program a non zero
value of “battery capacity”. When this is done, the meter will keep track of the battery % full
as described above in 7.A. If this number is programmed to 0, the meter will assume that no
battery is present, and no compensation for self discharge will occur, and the reset of “amp
hours” and “battery % full” will not take place as described in section 7.A. The main effect of
the “battery capacity” value is to determine the “scale” of the “battery % full” display. It changes the
rate at which the “battery % full” display declines as amp hours are removed from your batteries, as
described above in Step 2. Enter the value of your battery system capacity, in total amp hours. It is
often useful to enter a value that is lower than your actual battery capacity: from 50 to 75% of the
“nameplate” capacity. The reason is that you typically shouldn’t run your batteries right down to the
bottom of their charge. Also frequently in actual practice you will not get as much capacity as the
“nameplate” number suggests—as they are often overly optimistic. Refer to section 6.A under P14,
P15 for more information on the effect of this data.
P32, P33: Battery “charged” criteria. These are the voltage and current setpoints described above
in Step 1. Usually the “voltage setpoint” should be set to a voltage slightly lower
than the “bulk
charging voltage” of a solar or generator (or other) charging system. This would be typically about
14.3 volts for a 12V lead acid “liquid electrolyte” battery system. Multiply this number by 2 for a 24V
system, or 4 for a 48V system. If you have sealed type of batteries (which do not have watering
holes at the top) this voltage will usually be a little lower. You should consult the battery
manufacturer for proper charger
bulk voltage setting (that you set on your chargers) as it is
particularly important for sealed batteries to use a bulk voltage that is neither too high or too low.
Then set the “voltage setpoint” on the PentaMetric slightly below this point. A typical value for the
“current setpoint” can be found by dividing the system battery capacity (in Amp-hours) by 50 to find
the “amps” value to enter. A more stringent criterion can be imposed by reducing this “amps” value,
or it may be made less stringent by increasing it.
P34: Efficiency factor and P35: Self discharge current: Set the Efficiency factor to 94% and the
self discharge current to 0 if you are not sure what values to use. There is more information on
these in section 6.A under P34-P35, and also in the next paragraph.
Why not use the PentaMetric measurements of “battery efficiency” for these? Although you
must enter the value of “efficiency factor” (P34) and “self discharge current” (P35) that the
PentaMetric uses for keeping track of “Battery % Full”, they are also measured
by the PentaMetric,
as described in section 6.C.3: System “battery efficiency cycle” data. As described there (in
excruciating detail), the amount of “self discharge” loss is measured for each charge/discharge
cycle—and the result of this measurement is expressed in two forms: one as the “battery efficiency”
per cycle, and also, simultaneously as the “self discharge” current, in “amperes”. It is computed for
the last 1, 4 or 15 cycles. Note that although the answer is supplied in two forms, they are both
measuring the same thing. As we have not gained enough experience yet with these measurements
we don’t have yet advice that we can give with confidence that these numbers can be used and
directly entered into P34-P35. Also keep in mind that the calculation there for “self discharge”
includes strictly speaking more than just the “self discharge” current. It also includes in that
measurement the current loss at the “top of charge” due to gassing when the battery is less efficient
due to the conversion of some battery electrolyte to hydrogen and oxygen gas. Also, pointed out in
section 6.C.3,it should be noted that one single cycle can give misleading results if the temperature
varies from one cycle to another—as a rise in temperature can show misleadingly low efficiency, and
a drop in temperature can show misleadingly high efficiency. Taking a 4 or 15 cycle sequential
average, however, should eliminate that problem, as the temperature cannot rise or drop a great
amount over many cycles.