Ebjerke, That is too bad! But understandable. I just purchased a new policy for my new P4 Pro, here in Watkins Glen, NY Friday for $63.00 per year. State Farm.
175 feet straight down slamming onto a frozen lake!
- Thread starter The Famous
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Except batteries get heated by operation. I've actually found the flight time is slightly longer when ambient is chilly.
I
I can already see your major error. You took off with 83% battery. This is a big no no especially if the battery had been sitting around for a week or two, even worse
Always take off with a full battery or this is what will happen
I can already see your major error. You took off with 83% battery. This is a big no no especially if the battery had been sitting around for a week or two, even worse
Always take off with a full battery or this is what will happen
Nothing to do with the heat in the batteries. I’ve flown in 41degrees C and my batteries get to around 60 degrees c and never an issue they are designed to hit the 70 degree c mark no problems
I agree that taking off with a partially discharged battery is a bad idea, if only because the SMART estimate of remaining capacity tends to be incorrect. I'm not sure that it explains the anomalous and sudden drop in voltage on one cell though - I've looked at a number of partial battery discharge curves and that is the first time that I've seen that behavior. Do you have any similar examples?
Yes it’s true that LiION can operate reliably at higher temperatures but the fact is optimum operating temp is 20 deg C. At 40 deg C we should expect a 20% reduction in cycle life, 40% at 45 deg C.
Looks like a bad battery to me. Was it an aftermarket battery? How many flights did it have on the battery?
The risk presents with packs that have entered auto discharge. Simply because the bleed resistors have slightly different values and may drain some cells at a higher rate and to a lower voltage.
I don’t think the issue is with the calculated remaining capacity, the BMS is likely tracking and reporting correctly. I often fly on oartiallybdischarged packs that haven’t entered auto discharge and the est remaining fight time and capacity seem to be accurate. The issue is more likely to be the uneven loading presented to individual cells during auto discharge. You start the flight with cells out of balance and the lowest cell will deplete at a higher rate in flight.
What is the days to dischargebsetting in the battery? How many days prior to flying was it charged? Was this the first flight since last charge?
My impression was that this battery had not started auto discharge - the OP mentioned charging within the week at least.
In any case - I've seen several flight logs where the flight was started at less than full charge and the estimated capacity was clearly wrong. The starting voltages were too low for the initial estimate, and the result was that the estimated capacity decreased non-linearly. However, the individual cell voltages still tracked each other fairly well. This is the first log I've seen with such a major deviation on one cell.
Agreed, this is looking like a bad battery.
My experience differs from yours however it is based on my actual use, not observations of others failures. I always charge within 24 hours of fight and any second flight on a previously fully charged pack is within the day of first flight. I can say from the depicted remaining flight times and available charge that I have never noticed an anomaly across a dozen DJI branded packs for P3 & P4.
The question is why does this happen to some users?
My personal experience is the same as yours - I occasionally launch with a partially charged battery just for flight tests and I've never seen a problem. I've also launched with a 70% battery after auto-discharge, and that flew fine too.
But personal experience is, by its nature, a limited dataset. My suspicion is that partially discharged batteries (either flown or auto-discharged) usually work fine. The events reported here that we get to examine and analyze are the less common behaviors, but I've never seen such a large cell deviation in such a short time.
Again we are in agreement, it’s the analysis of failures that may lead to knowledge of what the issues might be.
I have 3 packs that go significantly out of balance during the auto discharge. When they are retired I will measure the bleed resistor values for curiosity sake.
As to the significantly low cell in this case all I might add is that I have seen this on occasion with bare (absent smart electronics) LiPO packs. The DJI batteries do, from my experience, perform very well.
Cold could be a factor if an issue occurs shortly after takeoff, but after say 5 minutes of flight time, the battery would have warmed up during operation.
Battery showed OK, then suddenly one cell dropped in voltage.
What do the logs show the battery temp was?
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Omg, scary pictures, sorry for your loss. I have a battery that says cell#2 is damaged and to discharge to 5% and recharge,I’ve done that but it still has an issue.
After seeing this I probably won’t use it again, but that’s a $200 loss.
After seeing this I probably won’t use it again, but that’s a $200 loss.
If it's less than 6mos old, ask DJI for a warranty replacement. If it's over 6mo, keep it for ground test purposes, or charging phones or ipads with a USB charger adapter.
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You misunderstand my post - cold affects batteries by reducing their voltage. Assuming you start with a warm battery - like keeping it in your jacket - the cold will not affect your battery as much because in the course of operating it generates heat from internal resistance plus it is heated from the electronics inside the drone. I have actually found the battery life is a tad longer in cold weather - when I start with a "warm" battery.
