Battery Maintenance ?

[R.Perry]

A friend had a battery failure the other day, it was on a Phantom 3 and needless to say it came crashing down. Fortunately it just scared the heck out of a few cows, but it didn't do so well.

I asked him if he monitored his battery status, and I got this "how do you do that".

Lets face it, most flight failures are due to battery failure. If a battery is beginning to show inconsistent cell voltage then it is time to replace it, and especially if you are flying a one battery drone.
This is what I use for my battery survey. One thing I am sure of is DJI doesn't keep accurate number of charges because all the below batteries have always been charged together. Also my voltages will read a little different than DJI because I go two digits to the right of the decimal.
Paying close attention to your batteries may save a lot of grief, and it is just good preventive maintenance. If I see a full 10th of a volt difference on the cells, I want a knew battery.

 

[R Martin]

A friend had a battery failure the other day, it was on a Phantom 3 and needless to say it came crashing down. Fortunately it just scared the heck out of a few cows, but it didn't do so well.

I asked him if he monitored his battery status, and I got this "how do you do that".

Lets face it, most flight failures are due to battery failure. If a battery is beginning to show inconsistent cell voltage then it is time to replace it, and especially if you are flying a one battery drone.
This is what I use for my battery survey. One thing I am sure of is DJI doesn't keep accurate number of charges because all the below batteries have always been charged together. Also my voltages will read a little different than DJI because I go two digits to the right of the decimal.
Paying close attention to your batteries may save a lot of grief, and it is just good preventive maintenance. If I see a full 10th of a volt difference on the cells, I want a knew battery.

Our program has a 0.01 V tolerance in deviation across all cells at 100%. Any deviation greater than that and the battery is removed from flight status. The disqualified batteries are great for pre-flights and getting everything ready to fly and you don't burn precious time in the air on a flight battery.

 

[BigAl07]

Well stated. When we have a single failure point and we have a component we CAN monitor it would be crazy not to do so. It only takes a few extra minutes to grab and document the data. Once it's "on paper" you can see a trend and hopefully avoid a failure. Sometimes they fail with no warning but in my experience the vast majority of the time the failure was preceded with a decline that is visible in the data.

 

[R.Perry]

Our program has a 0.01 V tolerance in deviation across all cells at 100%. Any deviation greater than that and the battery is removed from flight status. The disqualified batteries are great for pre-flights and getting everything ready to fly and you don't burn precious time in the air on a flight battery.

Wow, a .01 deviation would fail most of my batteries, even the new batteries on my P4. As you can see battery 7A as an example has a .04 between cell 2 & 3 and it has been that way for the last four surveys. If cell 2 continues to deteriorate the battery will be replaced, but for me it needs to be close to full 0.10, but that is just me. Maybe .05 to .08 might be more realistic for me. I also check battery temperature upon landing, and check motor temps after the first flight each day. It only takes a few seconds to check the temps.

As you can see I also check batteries at different charge status so I can see variations between fully charged and discharged. I try to never run my batteries below 25% and normally about 30%, yes it means less flight time, but batteries flown below 25% seem to get much hotter.
Cheers

 

[BigAl07]

I operate with 0.10 as my Fail Factor.

 

[Moosewax]

Wow, a .01 deviation would fail most of my batteries, even the new batteries on my P4. As you can see battery 7A as an example has a .04 between cell 2 & 3 and it has been that way for the last four surveys. If cell 2 continues to deteriorate the battery will be replaced, but for me it needs to be close to full 0.10, but that is just me. Maybe .05 to .08 might be more realistic for me. I also check battery temperature upon landing, and check motor temps after the first flight each day. It only takes a few seconds to check the temps.

As you can see I also check batteries at different charge status so I can see variations between fully charged and discharged. I try to never run my batteries below 25% and normally about 30%, yes it means less flight time, but batteries flown below 25% seem to get much hotter.
Cheers

Part of your extra heat from low voltage batteries is that as your voltage drops your amps go up to maintain the same amount of power.

 

[R Martin]

Wow, a .01 deviation would fail most of my batteries, even the new batteries on my P4. As you can see battery 7A as an example has a .04 between cell 2 & 3 and it has been that way for the last four surveys. If cell 2 continues to deteriorate the battery will be replaced, but for me it needs to be close to full 0.10, but that is just me. Maybe .05 to .08 might be more realistic for me. I also check battery temperature upon landing, and check motor temps after the first flight each day. It only takes a few seconds to check the temps.

As you can see I also check batteries at different charge status so I can see variations between fully charged and discharged. I try to never run my batteries below 25% and normally about 30%, yes it means less flight time, but batteries flown below 25% seem to get much hotter.
Cheers

I thought that I read (and I might have but was unable to locate the source from DJI) that the manufacturer recommends that a voltage drop outside of 0.01V was not good and that became my hard number to discontinue using the battery. Of the twelve batteries that I own (a mix of TB47s and TB48s) over the past three years, only one battery has strayed outside of that value. The more I fly, the larger my reserve gets. Again, not for everyone but it works for me and mine. I don't operate for-profit and I can afford to be more cautious than most.

 

[R.Perry]

Part of your extra heat from low voltage batteries is that as your voltage drops your amps go up to maintain the same amount of power.

I do understand that, and I also know heat is a major factor in battery premature failure.

 

[R.Perry]

I thought that I read (and I might have but was unable to locate the source from DJI) that the manufacturer recommends that a voltage drop outside of 0.01V was not good and that became my hard number to discontinue using the battery. Of the twelve batteries that I own (a mix of TB47s and TB48s) over the past three years, only one battery has strayed outside of that value. The more I fly, the larger my reserve gets. Again, not for everyone but it works for me and mine. I don't operate for-profit and I can afford to be more cautious than most.

I would like to see the article you seen. I have two brand new batteries for the P4, both show more than a 0.01 difference between cells. One is 0.03 the other 0.02 fully charged. We are only talking about one hundredth of a volt.
The other thing that confuses me is there doesn't seem to be any difference in flight time with any of my eight pair of batteries. I replaced two of my P4 batteries because they went over the 0.10 difference but still seemed to work well. I will see if I can get some data from a manufacturer.

 

[R.Perry]

Here is a good example, Cell two has a 0.13 voltage drop, and on Inspire two will trigger a battery error, and as you can see if it is during flight will tell you to return to home and land. The Inspire 2 will not take off with this much of a cell voltage difference. Meaning, this battery is probably done. What is funny is battery status shows 95% in both batteries.
I think what I'm trying to say, is this should never happen in flight, it should have been caught in preflight unless the cell discharged during flight and I find it hard to believe that prior to flight the cell showed a fully charged state.

 

[R Martin]

This is exactly why you should be monitoring voltage. The battery charge percentage is a poor indicator of battery health.

 

[R Martin]

I would like to see the article you seen. I have two brand new batteries for the P4, both show more than a 0.01 difference between cells. One is 0.03 the other 0.02 fully charged. We are only talking about one hundredth of a volt.
The other thing that confuses me is there doesn't seem to be any difference in flight time with any of my eight pair of batteries. I replaced two of my P4 batteries because they went over the 0.10 difference but still seemed to work well. I will see if I can get some data from a manufacturer.

I look at it differently. I am trying to get ahead of the problem before it manifest itself and becomes a real problem. As I said before, I am a government operator that is not for profit so I can afford to replace a component earlier than most would. When I play the safety card people here listen. Getting a battery with problematic numbers from a distributor should have warranted a return immediately on your part. There are enough reputable dealers available that would accommodate you. If the voltage across the cells is bad when you get it, how long will it be before they are completely out of tolerance and you need to spend another $180.00 for another battery?
Another way to look at this is this: We do not have the luxury of pulling over on the side of the road and calling triple A if something goes wrong. When something does go wrong in aviation its a big deal. People's lives are at stake, even if you do not carry passengers or a flight crew. Speaking for me, myself and I, I am not going to be featured on a news segment locally or nationally as "that guy" that screwed the pooch because of carelessness. Where my program is concerned, second best is not an option. It is just what I believe and it is what I practice.
My practices are mine. It is not a reflection on you or your practices. Each one of us has to decide for themselves how they are going to operate based upon their own personal situation. I understand when you are struggling to make a living and pinching pennies to get by till the next check all too well. I am extremely fortunate in that that does not spill over into my program because of my position and the support of a lot of good people higher up in the food chain from me.

<I would step down off my soap box but I am afraid I might fall and not be able to get up....and I forgot my Life Alert doohicky this morning...>

 

[R.Perry]

As for returning a new battery that has a .0.01 or 0.02 cell spread you will be returning a lot of batteries. You caused me to question DJI, and others about the cell voltage spread and all have said that is normal and doesn't constitute or warrant a return of the battery. In the perfect world all cells would remain equal, no perfect world here. On the Inspire I notice that one battery will discharge a little fast than its mate, as long as it isn't a significant difference I don't worry about it.
Of course if flying a one battery drone like the Phantom I am a little more discriminating.
One thing about government jobs, they can waste all the taxpayers money they wan't to.

 

[R Martin]

As for returning a new battery that has a .0.01 or 0.02 cell spread you will be returning a lot of batteries.

I have had one TB47 fall outside of tolerance in the three years I've been operating. I still use it to pre-flight and post-flight the aircraft so it is not a write-off.

Of course if flying a one battery drone like the Phantom I am a little more discriminating.

I currently fly an Inspire 1 so I am too.

One thing about government jobs, they can waste all the taxpayers money they wan't to.

One thing about government jobs is the amount of paperwork I have to go through on a yearly basis for the 3-4K operating budget I am running on. That, and a staff of one whereas the private sector would allow me a few more bodies. And maybe a raise every year or two if that wasn't too much to ask for.

 

[The Editor]

There is a lot of bad information on this thread.
A cell deviation of 20mV is of no consequence whatsoever.
In fact a cell difference of up to 200mV under load could be expected from even a balanced pack.
Over this figure could be regarded as 'abnormal/cause for concern' but retiring packs because of a deviation of 20,30,50 or even 100mV is reduculous.

This come from 30 plus years of flying everthing RC and using Lipo packs of differing size and configuration since they first appeared on the market.

 

[R.Perry]

There is a lot of bad information on this thread.
A cell deviation of 20mV is of no consequence whatsoever.
In fact a cell difference of up to 200mV under load could be expected from even a balanced pack.
Over this figure could be regarded as 'abnormal/cause for concern' but retiring packs because of a deviation of 20,30,50 or even 100mV is reduculous.

This come from 30 plus years of flying everting RC and using Lipo packs of differing size and configuration since they first appeared on the market.

We aren't talking about MV, and you are correct, I'm talking about 10th and hundredth of a volt spreads. You go over a tenth of a volt spread on the Inpire 2 and she won't fly.

 

[The Editor]

We aren't talking about MV, and you are correct, I'm talking about 10th and hundredth of a volt spreads. You go over a tenth of a volt spread on the Inpire 2 and she won't fly.

We aren't talking about MV, and you are correct, I'm talking about 10th and hundredth of a volt spreads. You go over a tenth of a volt spread on the Inpire 2 and she won't fly.

0.01v is 10mV. 0.02 is 20mV
A tenth of a volt is 1/10 which is 0.1v which is 100mV. So yes you are talking about mV.

 

[R.Perry]

Sorry my point was I like the KISS principal, a milli volt is 1/1000 of a volt. When I said we aren't dealing with MV I meant of most of the folks looking at their batteries they are only concerned about tenths or hundredths of a volt, not thousands of a volt because that is the way it is displayed. So if I was to say any more than a 100mv spread will cause a battery error I'm saying the same thing as saying anything over a tenth of a volt will create a battery error as you can see in the above example.

 

[R Martin]

There is a lot of bad information on this thread.
A cell deviation of 20mV is of no consequence whatsoever.
In fact a cell difference of up to 200mV under load could be expected from even a balanced pack.
Over this figure could be regarded as 'abnormal/cause for concern' but retiring packs because of a deviation of 20,30,50 or even 100mV is reduculous.

This come from 30 plus years of flying everthing RC and using Lipo packs of differing size and configuration since they first appeared on the market.

Agreed, but if the deviation generates a warning message in the flight control software, that is a good enough indication to me that its days are numbered. It wasn't an arbitrary decision on my part. The battery is still good for non-flight purposes and that is the only battery I have had a problem with since I began flying. The rest work flawlessly.

 

[R.Perry]

As noted above the 0.13 volt deviation caused a return to home warning. Once landed the drone won't allow flights until deviation is corrected ( batteries replaced)
Now here is another question, the Inspire has two batteries, if one fails, are both replaced or just the one? Is it wise to match a new battery with old?