Battery Autonomy Test

Author:  Mohamed Ben Tato

Date: 20/07/2020 Machine nr: V2.01


The goal of this test is to verify the machine can operate on battery power for the minimum of 20 minutes, required by the MHRA-document.

In the current design no separate battery charger is used to charge the batteries. The 24V-nominal PSU is tuned to 26V and 2 lead-acid batteries in series are charged at this voltage. This reduces the number of electronic components needed, but means batteries are never fully charged.

This test verifies whether or not the batteries are charged enough by the PSU voltage without a proper charger.

Picture 1. RS® PRO 12 V 2.3 AH battery.


The machine uses two RS® PRO 12 V 2.3 AH batteries (see picture 1) .

The settings of the machine used in the setup:
RR= 35 BPM, PP= 30 cmH20 and I/E = 1:2.0 .

The fan is continuously on at 100%.

The machine is turned on normally, then unplugged from mains power and left to run. The PC controlling the machine remains plugged in and logs the actions of the machine.

Once the batteries are drained and the machine has stopped working, the running time can be reviewed from the log-files in the GUI.

The machine is then plugged in to charge the batteries overnight and the test is repeated the next day. This test was repeated twice.

Measurements and conclusion

After 3 charge and discharge cycles the two batteries were shown to support the Breathney machine on average for 2,5 hours.

This is well beyond the required 20 minutes goal.

It can be concluded no changes or additions are needed to the battery and charging system.