Section 5 | Sample Battery Lifetime Calculations
©
2022
– Valeport Ltd
Page | 10
5.2. Calculations - Based on Batteries
The M
IDAS
ECM will function with a voltage supply of between 9 and 30V DC. The voltage output
of the 8x D cell battery pack will vary according to the type of cell fitted. The most likely cells to be
used will be standard alkaline type (1.5v each) or Lithium cells (3.6v each), giving a 12v nominal
output for alkaline cells, or 28.8v nominal for Lithium cells. The following calculations are based on
the same sampling scenarios as the memory calculations, using figures for a 12v alkaline battery
pack. Each example also gives a figure for a Lithium battery pack, calculated from a basic ratio of
alkaline to Lithium performance.
In all examples, it is taken that an 8 D cell alkaline battery pack will have a nominal capacity of
14Ah, and will be 75% efficient (total available charge, 10.5Ah), and that an 8x D cell Lithium pack
will have a nominal
capacity
of 17.5Ah, and will be 95% efficient (total available charge, 16.6Ah).
Continuous data sampling - 8Hz
•
At 12V, the instrument draws 140mA when sampling
-
Total charge available is 10500mAh
•
Number of hours available is therefore 10500mAh / 140mA = 75 hours
-
equivalent to just over 3 days
•
For Lithium cells, a similar calculation gives around 11 days
The instrument is effectively operating continuously when in Trip sampling mode, so similar
calculations will apply
Burst sampling - 4Hz
Sampling for 1 minute in every 10 minutes:
•
At 12V, instrument draws 140mA when sampling
-
plus 140mA for 5 seconds at the start of each burst
-
it draws 0.25mA when in sleep mode between bursts
•
In this scenario:
-
the instrument will draw 140mA for 65 seconds
-
then 0.25mA for 535 seconds. On average, it will draw:
(140 x 65) + (0.25 x 535)
(65 + 535)
= 15.39mA
•
Total charge available is 10500mAh.
•
Number of hours available is therefore 10500mAh / 15.39mA = 682 hours.
-
equivalent to approximately 28 days.
•
For Lithium cells, a similar calculation gives approximately 105 days.
The above examples are intended as guides only
Valeport accepts no responsibility for variation in actual performance
Note that performance of individual battery cells is not always consistent
