Replies to This Discussion

ModeratorPermalink Reply by John Church on May 24, 2011 at 4:20pm

Hi,
I don't have battery monitoring hooked up yet- it is next on my list (should have been first). But, I see you mention the "Current" test. Do you want to use the "Battery" test instead to get what you're looking for? (Again, I haven't done this yet, and maybe it's not what you're after, but I thought I'd ask.)

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Permalink Reply by Simon on May 24, 2011 at 4:37pm

Thanks for the Reply John, 

 

I will double check that tonight. I am pretty sure it shows the same thing. 

 

The HK GCS also displays the same thing. Current works but voltage doesnt.

 

Regards

 

Simon

 

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Permalink Reply by Bob Anderson on May 25, 2011 at 11:52am

How are you getting HK GCS to display Amps?  It is my understanding that the MAVlink protocol does not at present have a message that includes battery current, so HK GCS has no way to get that information from APM 2.12

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Permalink Reply by Simon on May 25, 2011 at 3:27pm

It works, I have not changed the code, in monitor mode 4 and APM 2.12 the mah graph decreases in proportion to the current used

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Permalink Reply by Bob Anderson on May 25, 2011 at 6:02pm

OK ... but I don't think it should be working.  I have hooked up current sensing and APM Terminal reports battery voltage, current, and mAh correctly.  But when I switch to telemetry, HK_GCS reports amps = 0 and the mAh is constant.

 

I have communicated with HappyKillmore, and he confirms that that feature does not work yet because MAVlink does not report battery_current and HK does not parse the MAVlink packet that reports mAh.

 

So, another mystery.  I'm scratching my head.

 

Have you measured (with a DVM) the voltages that are appearing on AN0 and AN1 ?

 

The fact that  test] battery reports about 18 volts on AN0, AN1, AN2, and AN3 says that it not wired the way you think it is.

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Permalink Reply by Simon on May 25, 2011 at 6:29pm

Thanks for the reply Bob,

I will make a little YouTube video of the MAH going down from 2500 when you power up the motor. The servos and APM etc dont draw enough current for the AttoPilot sensor to pick it up.

I haven't used it much (its still new to me) but it looked like it was working.

I am pretty sure I have the correct setup - I have a lead from the battery (+) to the AN0 and I have soldered in a 3.9K resistor in. Total resistance is 13.9K between ground and the AN0 pin. the current is from the AttoPilot current sensor and goes to AN1 with out any resistor soldered in.

Thanks for your help!

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Permalink Reply by Bob Anderson on May 25, 2011 at 9:51pm

Yup.  You're correct.  It is working.  I had a constant that was a little off, so my current sensor was reporting only a few ma --- not enough to see the mAh change.

 

With the constant corrected and with a more substantial current drain, the mAh widget shows the drain nicely.  I tested with both 1.2.96 and 1.2.98

 

I was suggesting that you use a DVM to measure the actual voltages present at AN0, AN1, etc.

 

I might be suspicious of a open circuit somewhere --- floating ground --- and so on.

 

I believe that you were reporting slow voltage buildup.  I find it takes about 10 seconds to stabilize.  There is a filter of the form:  rdg = 0.9 * old_rdg + 0.1 * new_rdg that slows the response.  If you see much longer than that, then suspect a wiring problem.

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Permalink Reply by Simon on May 25, 2011 at 7:20am

Hi John,

I have the APM in battery monitor mode 3 and this is what I get:

 

test] battery
Volts: 1:18.21, 2:18.00, 3:17.79, 4:17.61
test]

 

If I have it in monitor mode 4 (current and voltage) This is what I get:

 

ArduPilotMega] test

Test Mode

test] current

Hit Enter to exit.

V: 10.8929, A: 0.0000, mAh: 0.0000
V: 11.6246, A: 0.0000, mAh: 0.0000
V: 12.2831, A: 0.0000, mAh: 0.0000
V: 12.8757, A: 0.0000, mAh: 0.0000
V: 13.4091, A: 0.0000, mAh: 0.0000
V: 13.8891, A: 0.0000, mAh: 0.0000
V: 14.3211, A: 0.0000, mAh: 0.0000
V: 14.7100, A: 0.0000, mAh: 0.0000
V: 15.0599, A: 0.0000, mAh: 0.0000
V: 15.3749, A: 0.0000, mAh: 0.0000
V: 15.6583, A: 0.0000, mAh: 0.0000
V: 15.9134, A: 0.0000, mAh: 0.0000
V: 16.1430, A: 0.0000, mAh: 0.0000
V: 16.3479, A: 0.0000, mAh: 0.0000
V: 16.5340, A: 0.0000, mAh: 0.0000
V: 16.7016, A: 0.0000, mAh: 0.0000
V: 16.8523, A: 0.0000, mAh: 0.0000
V: 16.9880, A: 0.0000, mAh: 0.0000
V: 17.1102, A: 0.0000, mAh: 0.0000
V: 17.2201, A: 0.0000, mAh: 0.0000
V: 17.3190, A: 0.0000, mAh: 0.0000
V: 17.4081, A: 0.0000, mAh: 0.0000
V: 17.4882, A: 0.0000, mAh: 0.0000
V: 17.5603, A: 0.0000, mAh: 0.0000
V: 17.6252, A: 0.0000, mAh: 0.0000
V: 17.6836, A: 0.0000, mAh: 0.0000

V: 17.7362, A: 0.0000, mAh: 0.0000
test]
test]

 

The current works ok, its just not drawing much when I am testing.

 

One thing I notice is the voltage is getting larger until ut reaches 18v.

 

Thanks

 

Simon

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DeveloperPermalink Reply by Doug Weibel on May 25, 2011 at 11:25am

We have some (somewhat slow) filtering on the voltage and it starts at a "low voltage" value for a 3 cell lipo.

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Permalink Reply by Simon on May 25, 2011 at 3:24pm

Thanks Doug, That makes sence.

 

However I can not get it to read the voltage, it always goes to 18v no matter what voltage I connect.

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Permalink Reply by Bob Anderson on May 25, 2011 at 11:59am

With the standard code, the current sense output is supposed to be connected to AN1.  Have you done that?

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Permalink Reply by Simon on May 25, 2011 at 3:29pm

yeah, current on AN1 and voltage on AN0. The voltage is direct from the battery, not the current sensing board. I cannot get it to read anything else other that 18v, it doesn’t matter if I have it plugged in or not.

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