Crazyflie not charging

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asr
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Crazyflie not charging

Post by asr » Sun May 31, 2020 3:34 am

I setup my Crazyflie with the STEM ranging bundle last night, and tested out the flow deck v2 and multi-ranger functionality which worked nicely. However, after charging it up a few times (for about 40 minutes each time) and putting it in a hover, I noticed that the flight time was quite short. Doing a more thorough test today, I decided to charge it for 50 minutes (timed on my phone) and then put it in a pure hover to see how long it could hold this state before it landed due to a low battery status. To my surprise, it was only able to hold a hover for 1 minute and 35 seconds.

Looking more closely at what happens when I charge the Crazyflie, I noticed the following:
For the first few minutes, the status lights are as follows: M1 flashes red twice per second, M2 is lit solid blue and M3 flashes blue at a rate of about once per second (i.e. normal LED charging status lights as per the documentation). However, after a few minutes this changes, whereby M1 flashes at random intervals, M2 flickers (i.e. rapid flashing) randomly and M3 flashes at random intervals. I feel that when this weird transition happens to the LEDs the Crazyflie stops charging (can't be sure though). Has anyone else had a problem like this, and if so what did you do to fix the problem?

I did update the firmware after a few flights using the Crazyflie Client GUI, and I'm wondering if that might have botched a few things up. Any help would be greatly appreciated, very sad that it seems to be having charging issues so soon into its life.

EDIT: Here's a video of how the LEDs transition from a "normal" status to something that looks a bit off (the transition occurs at about 21 seconds remaining in the video):
https://imgur.com/a/BPNnu0q



tobias
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Location: Sweden

Re: Crazyflie not charging

Post by tobias » Mon Jun 01, 2020 9:35 am

That is the battery charge temp check that kicks in and limits the charging current as part of this issue. This temp check is needed for certification purposes. How hot was it in the room when you charged? The battery spec says charge temp 0-45 degrees but we are using the nRF51 inbuild temp sensor which should read the temp warmer then the battery temp actually is. Possibly we can raise it a bit but we will decrease the margin.

There are a couple of solutions, firs being charging in cooler temperature. Second, removing the battery and having it outside while charging. Third increasing the temp range in software here.

asr
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Re: Crazyflie not charging

Post by asr » Tue Jun 02, 2020 2:46 am

The room temperature was about 27 degrees Celsius, so not too hot. Yup, I have a big fan in my room which I turned on during two charge-up tests and it allowed me to charge from empty to full without the temp check problem occurring. Quite frustrating that this is happening though, since my room was in no way "hot".

I also timed how long it took to charge from empty to full during these two charge-up tests and it took 58 mins and 56 mins, which seems much longer than the advertised "up to 40min to charge" mentioned on https://www.bitcraze.io/support/f-a-q/ (although the flight times seem to be good, with about 7 mins and 10 seconds of hover time from full to empty (when red LED turns on)). Any ideas what could be causing such lengthy charge times, even when using active cooling?

tobias
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Re: Crazyflie not charging

Post by tobias » Wed Jun 03, 2020 10:52 am

We are now looking into increasing the temp range. Increasing it to 50 deg C looks ok according to our test and we are still within the battery spec. We still hit the limit though if we e.g. put it in direct sunlight. Also when having boards on top that heat the battery as well this limit will be easier to reach.

The charging can definitely be improved. One thing slowing it down is that the USB current is limited to 480-500mA and this has to be shared between both the charging and the running electronics. The electronics consume ~100mA so then only 380mA left for charging. Adding to that the multiranger which consumes around 70mA the charge current left is ~310mA. Improving this would mean lowering the electronics consumption or turning off the STM32 + decks completely as this can be done from the nRF51.

In you case I would just increase the temp limit and re flash the nRF51 as pointed to in my previous post.

asr
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Re: Crazyflie not charging

Post by asr » Sun Jun 07, 2020 6:56 am

Aha okay that makes sense, so since I have a flow deck and multi-ranger attached to my Crazyflie it's perfectly normal to have these long charge times? With a 240mAh battery and a 58 minute charge time this implies a charge rate of about 250mA, so if the general board electronics are using 100mA and the multi-ranger is using about 70mA, does this mean that the flow deck is using about 60mA?

I was able to get some time to do some more tests this weekend, and decided to remove the multi-ranger deck while charging the Crazyflie. Since the multi-ranger comes into direct contact with the battery, and is used to keep it in place, I'd hoped that the overheating issue during charging would have been solved. However, when charging this time, in a room at about 22 degrees Celsius, the "erratic LED flashing" problem occurred quite consistently at about 6 minutes into the first charging test, and about 4 minutes into the second charging test. For both tests, I let it charge for an hour in this state (i.e. I didn't use a fan to cool it), and after that it was able to get about 5 minutes and 10 seconds of hovering for the first charge, and 5 minutes and 15 seconds of hovering for the second charge. So this implies that the overheating issue is intermittent during the 1 hour charging period, since it was able to charge about 70-75% of the way in an hour. However, this is unfortunately quite far from what should have taken about 45 minutes to reach 100% charge (this is with the multi-ranger removed, but with the flow deck still attached and assuming it draws about 60mA during charging).

I also performed a final charging test by letting the battery sit outside the Crazyflie while charging, however this too resulted in overheating occurring at about the 4 minute mark. Similarly to the above two cases, I let it charge for an hour, but have not been able to test how long it's able to hover because the front right (M1) prop has just popped off 4 times in a row while hovering (but that's an issue for another topic/post).

I bought an extra battery with my Crazyflie, so I'm wondering if the temp check is done on the battery, or on the main Crazyflie board itself. If it's simply a battery issue I can swap it out for my replacement and see if I get better results.

EDIT: Here's a video of the LEDs showing the charging issue, with the battery sitting outside of the Crazyflie:
https://imgur.com/a/VHkLezz

tobias
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Location: Sweden

Re: Crazyflie not charging

Post by tobias » Mon Jun 08, 2020 11:38 am

End of last week I pushed an increased charging range which should fix this issue and your charging problem. The battery does not have a built in temp sensor instead we use the nRF51 inbuild one and the chip is located just below the battery. The problem is that the charging chip is also close by which heats up the PCB and the measurement gets biased with almost 15 deg C. This we corrected in the fix so now the charging shuts off when the battery is ~45 deg C.

If you have a stand alone charger that is part of the batter+charger bundle this will charge faster as it has ~500mA dedicated for one battery.

And the propeller issue is probably this.

asr
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Re: Crazyflie not charging

Post by asr » Sun Jun 14, 2020 5:39 pm

That's great to hear, so this isn't necessarily a faulty sensor on my Crazyflie? I'll flash the new firmware and give it a go in the next few days. And thanks for the link to the propeller issue, the image of the break is unfortunately looking very similar to what's happening to some of my propellers.

tobias
Bitcraze
Posts: 2013
Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: Crazyflie not charging

Post by tobias » Mon Jun 15, 2020 9:26 am

The new 2020.06 release has a fix for the charging now and it should work much better.

Regarding the bad propellers we will launch a replacement program in a not to far future.

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