Instruction Manual

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slowly. Eventually, as the battery begins to approach full charge the voltage will rise to the “bulk
voltage” setting of the charger. (This charger could be an inverter charger or solar charge controller.)
The voltage is prevented from exceeding this “bulk voltage” by the charger to prevent the battery
from gassing excessively. Further charging takes place while this voltage is maintained, however,
and as this occurs the current (amps) will gradually decline indicating that the batteries are becoming
more and more charged—typically requiring several hours for lead acid batteries. The battery can be
assumed to be well charged when the “amps” value declines to a sufficiently low value. The
PentaMetric determines that the batteries are well charged when the (filtered) voltage (AD3) exceeds
the “Charged setpoint voltage” (P32), (usually set just below the “bulk” charge control setting,) and
when the (filtered) amps (AD7) becomes less than the “Charged setpoint current” (P33).
Recommended values for “charged setpoint volts and amps” (P32 and P33) will be discussed
below. When the PentaMetric senses that the batteries are “charged” the following happens:
1. The “days since charged” display(AD24) will reset to 0
Then, as soon as the battery begins to discharge again i.e when the filtered amps (AD10) become
negative:
2. The “amp-hours” (AD13) measuring the battery will be reset to 0.
3. The “battery % full” (AD22) will reset to 100%
Step 2.Starting from this point of “100% charged”, as the battery is subsequently discharged
(amps are negative) the PentaMetric measures the charge that is removed (“amp hours” or
“amps times the time elapsed”) This will cause the “amp hours from full” (AD13) to become
more negative starting from 0. At the same time the “battery % full” will decrease
proportionally from 100%, to keep track of how full the battery is. The “Battery % full” tracks the
charge removed—at a rate determined by the “amp hour capacity” that is programmed in P14. So,
for example, if the “amp hour capacity” is programmed to 1000 amp hours, then if 100 amp hours are
removed from the battery, (for example, by having a 20 amp load for 5 hours) the “Battery % full” will
display 90%, and when 200 amp hours are removed “Battery % full” will read 80%, etc. Finally when
1000 or more amp hours are removed it will show 0%. Conversely whenever the battery is “charged”
(amps are positive) the numbers will go the opposite way. However all this is subject to the
following compensation for battery self discharge:
Compensating for battery self discharge: An ideal battery would allow you to extract during
discharge the same number of amp hours that were delivered into it while charging. Real
batteries, however, have a self discharge current that causes some loss of charge even when
there is no load on the batteries. To take this into account the PentaMetric allows two different
methods for compensating for this. It is not intended that both methods be used simultaneously
(although the meter does allow this if desired). Ordinarily just one of these methods should be
selected;
Method 1: “Using a charge efficiency factor: This is the more “traditional” method used by
the TriMetric battery monitor, and the method used by some other similar monitors. This counts
the amp-hours discharged (in AD13 or AD14) exactly, at 100% rate, but when adding amp-
hours back (charging) they are counted at a lesser value, for example only 94% of actual
charge. This requires that to make the “battery % full” display go back up to 100% charged,
slightly more charge (6% more in this case) must be put back compared to what was
discharged. This is the effect produced by the “efficiency factor” setting (Program mode P34)
which is set at the factory to a recommended value of 94%, however you may program this to
any value you wish from 60 to 100%. To disable this function you should set it to 100%.
Method 2: Using a constant self discharge current: This method has not been used to our
knowledge, however it is probably closer to the way which “self discharge” actually occurs in a
battery. This method is to assume a constant amount of leakage (in amperes) and constantly
subtract that amount from the amp-hour total at all times. This is the “self discharge current”
(Program mode P35) which is set at the factory to 0. However you may set it to any value from
0.00 amps to 9.99 amps. The actual self discharge can vary with type of battery, temperature
and age of the batteries; however it is approximated here as a constant current. A typical lead
acid battery can have a “self discharge” that is 1% of capacity per day. For a 1000A-hr battery
bank this would be 10 amp hours/day, which is 10/24= 0.40 amps.