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Topic: stepper motor - battery drain when unused? (Read 850 times) previous topic - next topic

baltazgt

Feb 17, 2011, 11:14 am Last Edit: Feb 17, 2011, 11:22 am by baltazgt Reason: 1
Quick question:
- how much quicker (if at all) will a 6AH lipo cell discharge if it is permanently connected to an idle stepper motor?

I bascially have two alternatively design scenarios:
A.  cell permanently disconnected from stepper motor and then plugged in when needed - which I presume will keep the battery life for longer.  I should say that the cell provides power to the stepper alone, a separate circuit provides power to the arduino which is controlling it.  
B.  cell permanently connected to stepper motor but without the stepper being used (because the separate circuit to control the stepper is off).

Is 'B' likely to lead to much quicker discharge of the cell - becasue all those coils in the stepper will increase its discharge rate, or will it not make much difference?

I have, of course, thought about just experimenting with this, but a 6AH cell left to discharge is going to be a lengthy experiment.  

thanks in advance.

ben

jraskell

Do you have a multimeter that can measure current?  If so, hook it up to your 'idle' circuit and measure how much current the stepper is drawing while idle.  This will tell you quite clearly whether leaving the battery connected will drain it much faster.  In fact, you can easily calculate approximately how long it would take to drain the battery, since you know it's a 6AH battery.

If you measure the circuit drawing 100mA while idle, then it will drain the battery in 6AH/.1A = 60 hours.
If you measure it drawing 1.3A, then it will drain the battery in 6AH/1.3A = 4.6 hours.
If it's only drawing 20mA, then it will drain the battery in 300 hours.

With your control circuit 'off' though, the stepper really shouldn't be drawing any current at all.

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