ELEV-8 V3 - Flt 5 - Battery life test - battery ruined
Testing battery life and 'low battery' status. Flight time about 24 minutes
Okay - this may not have been a wise ideal. But I thought I'd get some sort of notice when the battery got below 10.5 V (./prefs.cpp: Prefs.LowVoltageAlarmThreshold = 1050;)
My firmware is right off the shelf (except for LED lighting modification) - as near as I can determine the buzzer should sound when the voltage drops below 10.5 Volts
The battery is a Gens B-30C-5300-3S1P - this is it's 5th use.
The charger is SKYRC e4 charger. One note about this charger - it never indicated full charge on this battery.
Voltage start (appears to be balanced):
All - 12.5 Volts
Cell 1 - 4.19 V
Cell 2 - 4.13 V
Cell 3 - 4.19 V
At end the battery seemed warm - it was 85 degrees F.
Voltage end:
All 9.02 Volts
Cell 1 - 3.47
Cell 2 - 2.07
Cell 3 - 3.47
Note that Cell 2 is 2.07 V - FAR below the 3.0 V maximum discharge for a LiPO cell.
The balance charger (SKYRC e4 charger) refuses to even attempt to charge the battery now.
I'm assuming that is a wise decision - the battery is probably shot.
Apparently LiPo batteries don't stay balanced as they discharge? Or could this be a faulty battery?
Okay - this may not have been a wise ideal. But I thought I'd get some sort of notice when the battery got below 10.5 V (./prefs.cpp: Prefs.LowVoltageAlarmThreshold = 1050;)
My firmware is right off the shelf (except for LED lighting modification) - as near as I can determine the buzzer should sound when the voltage drops below 10.5 Volts
The battery is a Gens B-30C-5300-3S1P - this is it's 5th use.
The charger is SKYRC e4 charger. One note about this charger - it never indicated full charge on this battery.
Voltage start (appears to be balanced):
All - 12.5 Volts
Cell 1 - 4.19 V
Cell 2 - 4.13 V
Cell 3 - 4.19 V
At end the battery seemed warm - it was 85 degrees F.
Voltage end:
All 9.02 Volts
Cell 1 - 3.47
Cell 2 - 2.07
Cell 3 - 3.47
Note that Cell 2 is 2.07 V - FAR below the 3.0 V maximum discharge for a LiPO cell.
The balance charger (SKYRC e4 charger) refuses to even attempt to charge the battery now.
I'm assuming that is a wise decision - the battery is probably shot.
Apparently LiPo batteries don't stay balanced as they discharge? Or could this be a faulty battery?
Comments
10.5 is a good setpoint for a 3S alarm. I really like these - https://www.amazon.com/Battery-Tester-Voltage-Buzzer-Alarm/dp/B005GJCJOA They allow for monitoring of individual cells. There's a button on top that lets you set the alarm voltage. I usually go with 3.4 V (it's per cell). They're also very loud.
Agreed. Get several.
I don't use LiPo packs without alarms. It's too easy to ruin cells without them.
It hadn't occurred to me to attach it while in flight. When I used it after this flight - it definitely produced a loud alarm.
Thanks for pointing these out - I'm going to get some and use them.
At this price I could have one for each battery and keep it on during storage.
I agree you should get several of these but the alarms use a small amount of power and should not be left on a battery in storage. The alarms would eventually drain the battery to the point where the alarm sounded (this would probably take a day or two (it's happened to me several times)). If you're not around to disconnect the alarm when it goes off, the alarm would eventually damage the battery by draining it too low.
Are you referring to the buzzer that is on the Flight Controller? I really can't be heard from 50' away.
The battery monitor is used in the code for checking for presence of the battery during throttle calibration as a safety feature, but I don't rely on it for any more than that. I believe we have made the battery monitor disabled by default (you can check your settings on the "system setup" tab in GroundStation) due to inaccuracy concerns. I always fly with the external voltage alarm that we include in the starter pack - and would recommend everyone does (but as Duane said, don't leave them on during storage) In addition to being much louder than the on-board buzzer (audible from ~100 ft during flight as opposed to ~20 ft), it monitors (and alarms based on) the cell voltage rather than pack voltage, which is a more "robust" method. I'm adding a high-priority internal task to improve & clarify our documentation & recommendations regarding battery monitoring.
Yellow Card #1 - as you seem to understand, not indicating full charge is abnormal
Yellow Card #2 (so sort of a Red Card) - Right after a full charge & balance, I would expect all cells to be in the 4.18 - 4.21 range, maybe 4.16 at the lowest.
That's not abnormal for a strenuous (in terms of speed or payload), but that's a tad bit warmer than I would expect if I was just hovering.
Red Card! As you suggested, that battery is toast. Some try to trickle-charge batteries if they are over-discharged in an effort to revive them (which i can't recommend in the first place), but based on what you've written this far, I think trickle-charging that cell is unlikely to resolve the issue long-term, besides being a very questionable action. LiPo battery cells won't stay perfectly balanced as they discharge, but should only vary but one or two tenths of a volt. It kind of looks like that battery had a defective cell even before your unintentional "stress test". As that's only the fifth flight with that battery, it would imply it's a manufacturing defect (unless you put significant stress on it in previous flights). So if this is the first time you have pushed the battery, we'll try to arrange for a replacement, either through us or the MFG. Your detailed observations and notes make troubleshooting much, much easier, so thank you for that! - it pays off to write everything down!
PS While it's quite dry and probably mostly information you know, I recommend anyone working with LiPos read through Lithium-Ion Polymer Safety Instructions. Disclaimer: I wrote it.
If would be nice to get a warranty replacement - but not all that important - sometimes eating something is the best reinforcement.
Thanks for posting the LiPo info - always helpful (considering how fundamentally hazardous these batteries are).
One thing I've been meaning to creates is a "flight log" page - so that I remember to record the details from each flight and keep it as a log book.
Any suggestions for this?
Looking back over my notes - it seems that the battery had trouble charging -
So here's the battery data I have from the first 4 flights:
Flight 1 - about 10 mins
Full charge
Battery stats - end of flight
11.3 all
3.78
3.73
3.78
Flight 2 - about 17 minutes
Battery full charge 12.6v
End of flight
11.3v -- 3.75 avg cell
Flight 3 - about 15 minutes
Battery 12.6, 4.2, 4.14, 4.21
End battery - 11.3, 3.79, 3.76, 3.79
Flight 4 -
no data - had a flip - I wonder if I had overrun the battery on this flight - might be a better explanation for the flip crash...
Flight 5 - (copied from above) - 24 min flight time
Voltage start (appears to be balanced):
All - 12.5 Volts
Cell 1 - 4.19 V
Cell 2 - 4.13 V
Cell 3 - 4.19 V
At end the battery seemed warm - it was 85 degrees F.
Voltage end:
All 9.02 Volts
Cell 1 - 3.47
Cell 2 - 2.07
Cell 3 - 3.47
Having one cell that far below 3.0v while the others are above it looks really suspicious - the cells should have relatively matched curves, so I'd expect them to be within 0.1v of each other at worst when discharged, and within 0.02v when fully charged.
The external battery monitor is the way to go. I also have a timer on my transmitter that monitors "throttle on" time, so I have a pretty good idea of when it's getting low.
Regarding a Flight Log;
For those looking for a digital solution, there are a number of applications available for this purpose, including DroneLogbook and Hover; the Drone Girl has a nice post about some of the options here.
For a packaged analog solution, two options to consider are the Drone Operator's Logbook or the UAS Pilot Log.
Admittedly, I have not used any of these solutions (though now that I know they exist, I'll probably check some of them out - If I do, I'll be sure to report back).
Finally, you could create your own logbook, which is the route I've taken previously. In my case, I've been using a digital spreadsheet, but you could also make your own booklet or any other solution that works for you. Here's the information I log (I create a new spreadsheet row every time I change date/time, location, payload, or battery):
-Location (Description)
-Location (UTM Coordinates)
-Appx Windspeed
-Density Altitude
-Total Flight Time (my transmitter gives me this)
-Which Battery I Used
-What voltage level the external Low Voltage Alarm was set to.
-Initial Battery Voltage (would be better if I recorded voltage of each cell)
-Final Battery Voltage
-Battery Useage (mAh put back into battery during charging, as read out by my charger)
-% of Battery Capacity (calculated from Battery Usage & Battery Capacity)
-Battery, ESC, & Motor Temperature immediatly after flight (as meaasured w/ infared thermometer, I only do this when initially testing new components or payloads to make sure they are not over-stressing the system)
-Aircraft
-Additional Payload (if any)
-AUW (all-up weight
-Notes (could be on performance, rigor of flying, etc)
There's probably stuff I'm missing, so If anyone has other ideas or suggestions, please share!
I just read and downloaded what you are describing here,
Now I wish I'd found it when I started working with those batteries. This goes back when I bought a flatpack style one and its charger, all the way to the 18350s we use now.
Here's one:
https://rogershobbycenter.com/lipoguide/
It's a lot of information - frankly I find Kyle's summary more helpful - it's something I'm going to print out and post next to my charger.
On that subject - while I'm satisfied the charger that comes with the kit (SKYRC e4 charger) --
Can someone suggest a more sophisticated charger? Searching online turns up a lot of trash - and no clear ideas.
My only complaint is that it is one port, so you can only charge one pack at a time . With a little planning (I keep my packs at 3.8 V per cell for storage) it's not a big deal. Besides that, it does everything, to include datalogging on a PC.
In terms of brands, I recommend Venom, HiTec, and Tenergy. In my experience, all three companies sell quality products (you will pay more for brand name, but I think it's worth it for battery-related items).
I personally use a HiTech X1 AC charger and love it, but I think it's discontinued. I'd first decide on what the max charge rate you want (for a high-quality charger, 5 amp min), whether you want it to accept AC & DC or just DC (& therefore require external power "brick") (I recommend the former), and if you want to charge multiple batteries simultaneously with one charger. Once you've decided on those three things, look through the above websites for a charger that matches those specs, and then shop around for the best price.
Battery start
12.5
4.17, 4.11, 4.19
Finish (meter alarms - when I tested - it wasn't connected during the flight)
--- the charger still charged this battery - but the 'sag' of the #2 cell is evident
10.3
3.58,3.15,3.60