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Battery voltage drop during flight

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I was out flying my I1 which had a battery with 12 charge cycles, i havent used the battery for like 4 months. The battery was fully charged about 12 hours before the flight
The outside temperature was +3 °C.

The battery percentage seemed to go down in a normal speed, but the voltage started at about 3.85 V or something like that and then in like the 30 first seconds went down gradually to 3.73 V.
Then the voltage seemed to stay at 3.73 V for the rest of the about 5 minute flight.

When i looked in the Go app for each individual cell voltage there was a difference of about 0.05 V between the different cells.

Is this voltage and the 30 seconds voltage drop considered normal?
Or was it the relative "cold" weather that messed up the voltage?
 
Do you have your battery set to self discharge? 3.85V sounds like storage voltage and not 100% charged voltage. You might want to put it back on the charger and let it charge to 100% again. I know you mentioned that it was fully charged prior to flying, but the voltage does not sound right.

Also, have you ever done the deep cycle on your battery? Charging to 100% - then taking it down to around 5% and charging back to 100% That process helps re-calibrate your batteries percentage of charge that it shows you. Over time they tend to lose some functional capacity.

Finally, if you are going to be flying in the cold, keep the batteries warm right up until your flight. There are a number of ways to do this - just ask if you need an idea.
 
I was out flying my I1 which had a battery with 12 charge cycles, i havent used the battery for like 4 months. The battery was fully charged about 12 hours before the flight
The outside temperature was +3 °C.

The battery percentage seemed to go down in a normal speed, but the voltage started at about 3.85 V or something like that and then in like the 30 first seconds went down gradually to 3.73 V.
Then the voltage seemed to stay at 3.73 V for the rest of the about 5 minute flight.

When i looked in the Go app for each individual cell voltage there was a difference of about 0.05 V between the different cells.

Is this voltage and the 30 seconds voltage drop considered normal?
Or was it the relative "cold" weather that messed up the voltage?
Yes - Pretty normal.

The nominal voltage of lithium cells is 3.7v - They will sit at this plateau during discharge for a while and then drop fairly rapidly after this until around 3.3v at which point they will drop like a stone.
This is all normal behavior and why I never trust 'Fuel gauges' or percentage displays. Fly by voltage and you will be safe.
 
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Well im not totally sure about the 3.85 V at startup, it could have been higher but in that case it must have dropped to 3.85 V very very fast, like in the first 10 seconds or something like that?
I have made the full charge and discharge down to 0 percent once a long time ago, but the battery has only 12 charge cycles according to GO app, or 16 according to Healthy drones, don't know which to trust?
Okay so the discharge rate is normal, that was good to hear.
I just wondered because I've read in a thread here on inspirepilots someone saying something about that the voltage should be not less than 3.75 V or something similar to that. But maybe that is without a load?


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Not an expert but with 1.5 yrs of Inspire experience, my opinion is;
- cell voltage variés a lot with load, most accurate check is on gnd, no load or hovering no wind
- 0.05 v variation on cells seems a lot, I'd definitely cycle the battery, I've read that the Inspire can favour a particular cell & this can confuse the Smarts in the battery
- I use the battery heater when temps get negative centigrade (3 doesn't seem so cold to cause problems) but u get the warning to make sure the battery is above 15 deg C so I hover at 5 ft, monitor the battery temp (it goes up pretty fast, 5 secs) but also check cell voltage variation. I stop and change batteries if the variation in hover is greater that +- 0.02v
 
Not an expert but with 1.5 yrs of Inspire experience, my opinion is;
- cell voltage variés a lot with load, most accurate check is on gnd, no load or hovering no wind
- 0.05 v variation on cells seems a lot, I'd definitely cycle the battery, I've read that the Inspire can favour a particular cell & this can confuse the Smarts in the battery
- I use the battery heater when temps get negative centigrade (3 doesn't seem so cold to cause problems) but u get the warning to make sure the battery is above 15 deg C so I hover at 5 ft, monitor the battery temp (it goes up pretty fast, 5 secs) but also check cell voltage variation. I stop and change batteries if the variation in hover is greater that +- 0.02v

Thanks, but is 0.05 V really that much? If i remember correct I've read that a difference of 0.2 V (not 0.02V) is where its considered abnormal? I might be wrong but i remember reading something about 0.2 V.
 
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Thanks, but is 0.05 V really that much? If i remember correct I've read that a difference of 0.2 V (not 0.02V) is where its considered abnormal? I might be wrong but i remember reading something about 0.2 V. I wonder if it wasn't something written by DJI themselves?
No, 50mV (0.05v) is absolutely fine. Greater than 200mV (0.2v) while flying would give cause for concern (and probably an error message in the app) but again not unflyable and should balance with a charge or two - if not......ditch it.
Repeated cell difference of over 200mV I would consider retiring the pack as it is usually an indication of a weak cell.
The only way to know how a pack is behaving is under load. Sitting on the deck just monitoring the potential difference accross unloaded cells is not telling you anything. Once a load is applied, depending on the health of the cell and the internal resistance will dictate how easily that pack/cell gives up its charge and what the voltage drop accross it's terminals will be.
An older tired pack will show more of a voltage drop under load and will take a longer time to rebound once that load is removed.
 
No, 50mV (0.05v) is absolutely fine. Greater than 200mV (0.2v) while flying would give cause for concern (and probably an error message in the app) but again not unflyable and should balance with a charge or two - if not......ditch it.
Repeated cell difference of over 200mV I would consider retiring the pack as it is usually an indication of a weak cell.
The only way to know how a pack is behaving is under load. Sitting on the deck just monitoring the potential difference accross unloaded cells is not telling you anything. Once a load is applied, depending on the health of the cell and the internal resistance will dictate how easily that pack/cell gives up its charge and what the voltage drop accross it's terminals will be.
An older tired pack will show more of a voltage drop under load and will take a longer time to rebound once that load is removed.

Thanks. So about the health of a battery, does it have to do mostly with the number of charge cycles, or how much does the age of the battery affect the battery health?

Lets say i have a battery which is 2 years old but only has a few charge cycles, would that battery probably be in good health?
And since it is smart batteries for the Inspire 1 that we are talking about the battery would have been stored with the right battery percentage etc.
 
Thanks. So about the health of a battery, does it have to do mostly with the number of charge cycles, or how much does the age of the battery affect the battery health?

Lets say i have a battery which is 2 years old but only has a few charge cycles, would that battery probably be in good health?
And since it is smart batteries for the Inspire 1 that we are talking about the battery would have been stored with the right battery percentage etc.
Both - a Lipo will degrade over time whether it is used or not. It is just the chemistry of the cells.
An absolutely perfectly stored Lipo (at 3.85v per cell and at around 6 degrees) will still lose between 2-5% of its capacity over a 12 month period.
Most people will not store their pack in optimum conditions and so expect a loss of between 8-12% per year.
DJI do not use particularly good quality cells in their packs so don't expect too much out of them.
If you get 200 uses out of one, you are doing well.
What we do know is that DJI are fairly aggressive in their estimation algorithms which take into account both age and number of cycles of the pack and adjust 'Life' accordingly.
You will get more out of a standard lipo with regards to pack life (assuming it's looked after) than any of the 'Smart' (Stupid) packs from DJI.
The only reason DJI came up with the 'Smart' technology was to try and weed out the idiot gene that some would abuse the pack and end up blowing themselves up or crashing their aircraft (some have still managed to do this).
 
Thanks, so i know that i should watch the Inspire 1 battery voltage when flying and not the percentage, so at which battery voltage should i be worried and land immediately?
 
Both - a Lipo will degrade over time whether it is used or not. It is just the chemistry of the cells.
An absolutely perfectly stored Lipo (at 3.85v per cell and at around 6 degrees) will still lose between 2-5% of its capacity over a 12 month period.
Most people will not store their pack in optimum conditions and so expect a loss of between 8-12% per year.
DJI do not use particularly good quality cells in their packs so don't expect too much out of them.
If you get 200 uses out of one, you are doing well.
What we do know is that DJI are fairly aggressive in their estimation algorithms which take into account both age and number of cycles of the pack and adjust 'Life' accordingly.
You will get more out of a standard lipo with regards to pack life (assuming it's looked after) than any of the 'Smart' (Stupid) packs from DJI.
The only reason DJI came up with the 'Smart' technology was to try and weed out the idiot gene that some would abuse the pack and end up blowing themselves up or crashing their aircraft (some have still managed to do this).
The one thing I wish they would do is have a way to discharge to storage. I don't like to leave mine charged until they discharge them self
 
The one thing I wish they would do is have a way to discharge to storage. I don't like to leave mine charged until they discharge them self
Can thoroughly recommended one of these which will do what you are after.
Alex (who builds them to order) is a good guy and builds a quality product.
Phantom Angel
 
I don't recommend people ever drain their batteries down to 3.33v, just to re charge it, why make the battery suffer?
sure you think it calibrates it, nonsense, after a flight, the battery has lifted a drone into the air for a long time, it is drained enough,
it is warm ok, is this proof enough for you that the drone batteries are discharged.
then when you charge it, lipos naturally balance during a charge, even in normal charging, not balancing.
anyway, you do what you want with your lipos, hell,charge them up to 4.3v and leave it for days, I don't care.
lol
 
I don't recommend people ever drain their batteries down to 3.33v, just to re charge it, why make the battery suffer?
sure you think it calibrates it, nonsense, after a flight, the battery has lifted a drone into the air for a long time, it is drained enough,
it is warm ok, is this proof enough for you that the drone batteries are discharged.
then when you charge it, lipos naturally balance during a charge, even in normal charging, not balancing.
anyway, you do what you want with your lipos, hell,charge them up to 4.3v and leave it for days, I don't care.
lol
This thread is from 2017 btw and yes you do need to calibrate the old BMS chips on the Inspire 1 series.
Back then they were not intelligent enough to compensate for loss of capacity and increased internal resistance.
 
Hello everyone.

I have an Inspire 1 v1 that I hardly use anymore but I keep the batteries in good shape. Charge them full and discharge them to storage every 4 weeks and deep cycle them every 2 months. I use the Smart Power Charger from Lyhn Phan and the Phantom Angel from Alex.

A couple of days ago I flew it for a job and all three batteries (even though they were freshly fully charged) droped their cell voltage to around 3.5v turning the number yellow and then red within seconds of taking off. I never got those drops before.

So yesterday I deep cycled all 10 of them and fully charged them. Today I flew them and 2 of them (the newest with 19 and 26 charges) droped from 4.31v to 3.85v during the first 30 seconds of flight. Another two from 4.21v to 3.60v, one had a low voltage protection and droped to 3.45v, one had a cell broken, two had "Battery connection to center board failed".

I knew that at least 4 had a warning issue at some point a while ago, so I werent surprised with those (even though I had flown them down to 3.33v with no issues), but the "Battery connection to center board failed" issue is completely new to me. I started to think that it might be a issue with the connector on the drone that is not connecting correctly.

In the images you can see the time of the flight and it is short.

So I am afraid the batteries are dying (they were bought between 2015 and 2017). Any advise will be greatly appreciated.

Best,

JF
 

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Battery Connection to Center Board Failed is as you thought, a connection problem from the main power board to the rest of the aircraft.

Personally I would do a complete disassembly of the aircraft and unplug and replug every connector. You shouldn't have to mess with the motors or ESCs, just the main wiring to the main module in the front and the main power board connectors.

Also, you might want to discharge the batteries, open then up, disconnect the balance connector for a good hour and a half, plug it back in and then do a full charge.

All of that and I bet if the batteries are good you will be in good shape. If not, then start looking for broken solder joints on the main battery lugs that go to the power board from the battery on the aircraft. If something is really wrong with it, just buy a new main power board and swap it in if all else fails. They are not that expensive.
 
Battery Connection to Center Board Failed is as you thought, a connection problem from the main power board to the rest of the aircraft.

Personally I would do a complete disassembly of the aircraft and unplug and replug every connector. You shouldn't have to mess with the motors or ESCs, just the main wiring to the main module in the front and the main power board connectors.

Also, you might want to discharge the batteries, open then up, disconnect the balance connector for a good hour and a half, plug it back in and then do a full charge.

All of that and I bet if the batteries are good you will be in good shape. If not, then start looking for broken solder joints on the main battery lugs that go to the power board from the battery on the aircraft. If something is really wrong with it, just buy a new main power board and swap it in if all else fails. They are not that expensive.
I will disassemble as much as I can. I am always worry to damage something in the process. I will do a "under load" discharge making the batteries to shut down on flight, then charge them and see if anything pops up. If so, I will disconnect the balance connector as suggested.

Thank you Brian.
 

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