Death of a battery?

[Steve Evans]

Having sorted out the voltage logging I had three flights today. Two looked OK, one of which is shown below as representative.



The third had me wondering if dropping from a 15T to 14T pinion using the YGE internal gov was a mistake towards the end of the flight, but the reported battery voltage perhaps tells a different story.



It's taken a good charge this evening, each cell being at 3.78V, but after 2 years and 97 cycles maybe it's trying to tell me something?

Steve

[helidude71]

Hahaha, yep, 100 cycles is nice.
Maybe you should try some fresh packs.

Can you make a pic of your logger?
I would love to fit one on my X5.

[Steve Evans]

The top trace is from a pack with only 25 cycles on it. I have two older Turnigy 3300mAh 30C batteries and two newer 35C packs. I fear that running a 15T pinion may have put too much strain on it!

You'll find some pics of the logger HERE although the battery connection is now rather neater with a proper balance connector attached to the heli's nose.

Steve

[helidude71]

Nice! Is it specific for the CGY750?
Or will it work on a BeastX as well?

[Steve Evans]

It logs all S.Bus traffic at full frame rate (130Hz) and also samples head speed, ESC PWM, BEC and battery voltage at the same rate to a 4G uSD card. A huge amount of detail can be seen at that rate which Castle or Eagle Tree logging would simply miss. I designed and built this because to my knowledge nobody makes anything that even comes close in terms of speed, and nothing out there can log S.Bus traffic. Once I get the chance to play with S.Bus2 I may be able to pull telemetry data out of the CGY750 in flight.

Results are stored as a time-stamped (yes it has a battery backed clock too!) .CSV file suitable for loading straight into Excel. There's a USB connector on the heli to retrieve logs and connect to the built in command line interface. A typical 7 minute flight log is approx 3Mbytes. Nothing is CGY750 specific.

Steve

[helidude71]

Nice work Steve.
To my understanding S.Bus (II) is open. (That's why you can use it on all kind of FBL units.)
Any manufacturer can ask Robbe for info how to implement on their own products.
It's amazing nobody did it for logging purposes.

On my CC ICE 75 I have some kind of logging which is useful to tune the power system.
I miss it on my YGE.

[Steve Evans]

The logging on the ICE ESCs is too slow and/or brief to be of any real use I suspect. It's the transient stuff you need to capture, and you'll not see that logging once per second, and if you log any faster the log will be full before anything interesting happens. If I recall correctly the ICE log is about 21Kbytes in size, whereas I log nearly 3Mbytes per flight.

Being able to connect S.Bus 2 telemetry devices to the logger would be rather interesting as logging such information along with everything else I already capture would really add value.

The thing that makes S.Bus 2 potentially very interesting is that the 18MZ and associated goodies not only support telemetry, but the 18MZ also supports a servo connection supporting setting of S.Bus device parameters, such as gyro settings shown below:



Now, should the S.Bus 2 protocol actually be a superset of the S.Bus programming protocol then life gets interesting. There is a PC app which will allow you to save/restore CGY750 settings. What if this could be done in flight? Then you could map a spare channel on your radio to a CGY750 parameter that can only usually be programmed through the menus. I could potentially modify my logger to reprogram the CGY750 per condition on startup, or perhaps live, using mixing in the tx, or a spare trim/knob/lever. What if the CGY750 could be queried for current gyro information? Add that to a log and you'd be able to fine tune delays to eliminate bounce etc very precisely.

The S.Bus protocol uses a little under 3ms of each 7ms period to transfer channel data. The remaining 4ms the bus is idle for other interesting stuff to happen, such as telemetry.

Steve

[Mercuriell]

Very nice work look forwrd to seeing more nnthenwrokings of the cgy750!