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25Feb/104

How much current does a receiver battery monitor draw?

For all the years I've been flying RC my method for making sure my batteries are charged is to put em on the charger overnight before I go flying the next morning. Touchwood this has served me well and I don't believe I've ever lost a plan to flat batteries. I've never monitored the state of my receiver batteries throughout the day though. How many flights are they good for? 5, 10, 15? For me, I never seem to get a full day of flying, maybe 5 or 6 flights at the most and the receiver packs hold up fine but it still left me wondering, how many electrons are left in the tank after those flights.
I saw some cheapy battery monitors on ebay and thought I'd try one out. The two I bought didn't actually state the current draw but identical looking versions were touting 5 mA. I was keen to put them to the test.

Close up

Test 1: Current draw of just the battery monitor. 10mA.

A 4.8 volt, 1100mA NiCd battery is connected directly to the battery monitor with a multimeter in line. The monitor shows a reading second from the top in the "Perfect" range.

Just the battery monitor

Test 2: A JR RS70 36Mhz synthesised receiver. 24.7mA.

JR Receiver current

Test 3: Futaba 36MHz crystal Receiver. 15.2mA.

Test 4: JR Rx & Voltage monitor. 40.1mA.

I expected a little lower at 10 + 24.7 = 34.7mA.

Test 5: JR Rx, Voltage Monitor & 1 micro servo. 45.2mA

Test 6: JR Rx, Voltage Monitor & 2 micro servos. 52.2mA

Test 7: JR Rx, Voltage Monitor & 3 micro servos. 57.8mA

Test 8: JR Rx, Voltage Monitor & 4 micro servos. 63mA


Comments (4) Trackbacks (1)
  1. So it would last at least 20 hours, and up to 40.

  2. Except that 63mA is current at rest. Those servos can me moving like crazy when the plane is flat out. I need to take a peak reading with all servos moving (and loaded) to figure out some sort of average current draw for maybe a 7-10minute flight.

  3. Ah yeh, I forgot the battery also runs the servos.

  4. The next step is to measure the voltage range that each light on the battery monitor represents.


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