M300 Batteries... Looking for Community Input

For all you lidar lovers who fly the DJI M300, I have a question…

Scenario: You are on a multi-battery mission. The M300 returns home at the appointed time, lands and you spring into action! You grab your fresh set of batteries (each pair is considered ONE unit, they are not mismatched), go to the M300, carefully remove one old battery and install the new battery, repeat… But now your drone won’t take off!! Why? Well, you “fresh” batteries happen to have a voltage mismatch (damn self discharge feature). My left battery was at 91%, the right battery was at 89%… the voltage difference was too much for software, therefore, I can not fly. (remember, your time is limited when the R2A is running on the ground, at the first sign of distress, perform R2A shut down so you don’t corrupt the data you have)

Booooooooo.

So what are the options? This is where I am looking for community feedback…

  1. We could turn on the self-heat but the batteries are already warm and we are nowhere close to freezing. A hot battery working hard is a bad idea.
  2. We could place the batts in the charger (but I’m in the field and I did not bring my charger, nor do I currently have the facilities for mobile recharging)…
  3. Could I bleed off the full battery with a dead battery on the other side? Would it eventually bring down the full one, closer to the it’s twin? I know it won’t fly, but how else does one match batteries in the field? :thinking:

What would you do?

As it turns out, I had to return to base, recharge/grab new batteries, return to field and refly. The concern is that one day we will be in the middle of nowhere with this problem.

Cheers!

I always charge batteries the night before a mission so that they are as close to equal as possible. If you let them sit, you are more likely to encounter this behavior. Not much you can do besides run the higher battery down until the % and voltages match. Just keep the aircraft powered with only the higher battery installed until the voltage is closer to the other one.

For this reason amongst others I like to think of every RTH as though it could be the end of the mission, and therefore make sure to fly home with the same behavior every time no matter what. That way if you need to end the capture you’re not chancing having an improper final high velocity calibration.

FYI: The max time you want to have the R2A sitting on the ground is 5 minutes. I usually cut it before then and just start a new capture if I know that I’m going to have to wait any longer than a normal battery swap. After all it only takes about 3-5% of your battery to do your convergence maneuvers and be back to capturing your mission.

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from our in-the-field experience, we always take a charging station and portable generator…cuz you never know when you may need to charge batteries…even though you may think you have enough to fly your mission. This way, you have a backup scenario to avoid leaving your project site, only to return again. Time is money so being fully prepared always C.Y.B.!!!

as long as we keep max time of the R2A on the ground (recording) at 2 minutes or less, we’ve never had an issue. couple times around the 2 minute mark we’ve experienced processing issues.

We haven’t encountered this issue yet but I do pretend each segment is our last even if I intend to do a battery swap.

I’m nervous to just continue past the battery swap as I have had corrupt data more than once after a hot swap.

This is a totally suitable practice, however you shouldn’t be afraid of battery swaps and continuing to run your R2A. As long as you adhere to standard procedures you should have no issues whatsoever. We have had luck with doing missions as long as 6-10 battery swaps that still output great data.

That being said, there is no issue at all with stopping after each flight and then starting a new mission. All the .las or .laz files can be uploaded to a single project anyway and they will all align perfectly as long as you use the same base station RINEX file, or at the very least set the base station up in the exact same position and use the exact same values when prompted for them in PCMaster.

Lat.
Long.
Ellipsoidal Height.

We ran into similar issue. To solve, we have installed a stickers on each battery (1 Green / 1 Red) that are numbered in pairs. 1 / 1, 2 / 2, 3 / 3, 4 / 4. We always charge all batteries the night before. When I come in the next morning I turn the charger off for 10 minutes then turn it back on just to top off any batteries that may have discharged overnight. They are put in the battery case with Green sticker up to indicate they are fully charged then we always keep them paired together. In the winter we keep the batteries in the heated cab of the truck to help with cold weather discharging. Once we fly those batteries out then we put them back in the case Red sticker up to indicate discharged. We also alternate the battery pairs we start out with to distribute the usage. No more battery issues.

Leads down, Charged. Leads up, burnt.

Pairing batteries is good practice, but actually isn’t necessary with TB60s