ISCO 4230 - 1.7.1 Calculating Current Draw

4230 Flow Meter
Section 1 Introduction
1-10
If you divide this figure by the average current of the flow meter,
say 15 mA, you will have:
4,000 ÷ 15 = 266.67 hours
Divide this number by twenty-four to get days:
266.67 hours ÷ 24 = 11.1 days
For considerations of safety, we suggest you subtract 10% from
this number (100% – 5% for 95% capacity and 5% for a reserve at
the end of discharge).
11.1 – 1.1 = 10 days
This is the battery expectancy for a nickel-cadmium battery with
a 15 mA continuous average drain, with a 10% derating factor.
You can use the same method to calculate for lead-acid batteries,
except the current will be 6,500 mA, and the period correspond-
ingly longer, in this case a little over 16 days. You can run the full
number of days calculated without derating if your batteries are
new and at 100% capacity, but you will leave yourself no safety
factor if you are in error on either of these assumptions.
Remember, if the battery fails, there will be a period of time
during which no measurements will be taken, (and no data
stored, if you are also using FLOWLINK® software).
Batteries lose capacity as they age. Capacity also drops off as
temperature falls. Low temperatures make less capacity
available due to the slowing of the chemical reactions, while high
temperatures accelerate the deterioration of battery plate sepa-
rators, particularly if they are aged. Nickel-cadmium batteries
show fairly rapid rates of self-discharge. A battery that is fully
charged and then placed in storage will lose some capacity each
day. In a week, this could easily be 5% or more.
When using lead-acid batteries, you must be careful to avoid
complete discharge, as this may cause cell reversal, which will
ruin the battery. Also, complete discharge in low temperature
ambients may cause the battery to freeze, which can deform the
plates or even crack the case. Always operate these batteries
with a reserve factor.
1.7.1 Calculating Current
Draw
Calculating current draw for a 4230 Flow Meter is somewhat
more difficult than calculating the battery capacity. You cannot
simply measure the idle current of the unit unless the printer
and report generator are turned off in the program. These func-
tions require power periodically, but not all the time. If the
figures given in the previous table are not satisfactory for your
application, you can use the following procedure (shown in
Figure 1-3) to measure the actual current draw.