As many other users have noted over the years, there seems to be any number of mAh ratings that manufactures place on the labels of their batteries. It is generally understood that a higher mAh rating will usually give a longer flight time. But, this must also take into consideration any additional weight that the battery adds to the overall A/C weight. Also, can we really trust the label on the battery? What if the maker decided to over-rate or even under-rate a battery. It is also a general rule that we should charge are batteries at no more than a 1C rating. So, if the battery is labeled at 7000 mAh and it is actually a 6000 mAh battery, we may decide to charge it at 7 amps instead of 6 amps. Is there any way that we can actually and meaningfully measure the mAh of a given battery?
Battery mAh ratings... anyway for us to test it?
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h-elsner
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Discharge a full loaded battery with a constant current drain and measure the time until the battery is empty. Monitor voltage during discharge. Full is usually 4.2V empty is 3.3V for a LiPo battery.
Then charge the battery and look what the charger measured. If it is nearly the same then you can be sure that you have approximated the capacity. Please note, capacity goes down depending on age of the battery.
br HE
Then charge the battery and look what the charger measured. If it is nearly the same then you can be sure that you have approximated the capacity. Please note, capacity goes down depending on age of the battery.
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That is a good question about actual "battery capacity".
Unfortunately I do nat have an official scientific answer. From my experience one way to determine the approx. "real" capacity (with a dedicated charger) would be to:
- start a charge from a 50 % storage voltage corresponding to the cell chemestry's values (i.e. 3.8 V/cell for LiPo, 3.85 V/cell for LiPoHV, etc., use 1/2 C charge current if in doubt)
- read out the number of "loaded" mAh during that charge from 50 % to 100 % (i.e. 4200 mAh would than "correspond" to 50% capacity gain)
- make a "real life condition flight" and plan to land at displayed 25 % battery remainder voltage (0% would indicate 3.0 to 3.3 V/cell for LiPo, 3.1 to 3.4 V/cell for LiPoHV)
(you may also "desktop"-discharge your flight battery by 75 %, but that is not very close to practical use)
- make a full charge from that 25 % (approx. 3.75 V/cell for LiPoHV) to 100 % (4.35 V/cell for LiPoHV).
- read out the number of "loaded" mAh during that charge from 25 % to 100 % (i.e. 6300 mAh would than "correspond" to 75 % capacity gain)
For my LiPoHV batteries these values apply:
4200 mAh for 50 % means 1 % = 84 mAh.
6300 mAh for 75 % also means 1 % = 84 mAh.
100 % would corresond theoretically to 8400 mAh. (ATTENTION: FULL DRAIN!)
My GiFi Power LiPoHV batteries are rated at 7900 mAh, what would result in a 94 % drain or 6 % remainder respectively, what would make sense.
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Thanks for the above results for possible solutions to my post. I did take some time today(it was a total rain day, no flying) to run a quick search of such topic on the 3drpilots site. I am also noting 2 links from the site. The 1st link is about a recent inquiry about how to determine battery health. Which then led me to the 2nd link for the Madhacker site. I have emailed the site to see if the devices stated there may work with other LiPo's and not just the Solo battery. No answer from them at this time.
Battery health--how to tell good from bad? | 3D Robotics Drone Forum
Madhacker.org – If it can be modified, it should.
It seems that the Solo battery does have 2 nifty devices that can be used to access info(if I understand them correctly) from the Solo battery. One is the BMSOne and the other is the 3DR Solo battery diagnostic tool. I'm not saying that any of these work with our battery types. But, they are an interesting read for what they can do and maybe some wizard techs on here may find a way to make something similar for our LiPo's.
Battery health--how to tell good from bad? | 3D Robotics Drone Forum
Madhacker.org – If it can be modified, it should.
It seems that the Solo battery does have 2 nifty devices that can be used to access info(if I understand them correctly) from the Solo battery. One is the BMSOne and the other is the 3DR Solo battery diagnostic tool. I'm not saying that any of these work with our battery types. But, they are an interesting read for what they can do and maybe some wizard techs on here may find a way to make something similar for our LiPo's.
h-elsner
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It is very difficult to deduce the capacity of a battery from voltage because we do not know the individual discharge characteristic for the battery and, if this would not be hard enough, this also changes with aging.
For me the only way to find out the current capacity of a battry to measure current and time for charge and discharge. If you don't have constant current for both you need to use a differential equation to compute capacity.
br HE
Reading the link tells me the 3dr batteries are “smart” batteries that have a BMS IC that monitors and controls the battery pack. DJI has the same thing in their products. I don’t need a chip telling me when I can’t use my battery anymore. Just google about a battery that the BMS chip has put into hibernation and you need to hack it back to life.
Smart batteries are the lazy person’s battery management scheme.
h-elsner
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As we don't have smart batteries for Yuneec drones, let us be smart users.
The easiest way to get an overview how battery behaves and to monitor aging of the battery is to save and check the voltage curve in telemetry recordings. Unfortunately most of the Yuneec drones do not report current and (tell me if I'm wrong) none of them report cell voltage. This would give additional helpful information. But, however, we have the voltage with and without load and values from idle, hover and full power state.
I look on two phases of the flight:
- how the voltage drops when arming.
- how the voltage drop when power is needed (ascent after start).
And of course the flight time until the battery warnings came.
Deep voltage drop indicates higher internal resistance or dead cell. From telemetry I can decide if I will use the battery, keep it under observation or retire it (for tests or as flshlight or so).
If one don't want to use the heavy battleship q500log2kml, you can also use a light fast boat like BatteryCheck tool.
br HE
The easiest way to get an overview how battery behaves and to monitor aging of the battery is to save and check the voltage curve in telemetry recordings. Unfortunately most of the Yuneec drones do not report current and (tell me if I'm wrong) none of them report cell voltage. This would give additional helpful information. But, however, we have the voltage with and without load and values from idle, hover and full power state.
I look on two phases of the flight:
- how the voltage drops when arming.
- how the voltage drop when power is needed (ascent after start).
And of course the flight time until the battery warnings came.
Deep voltage drop indicates higher internal resistance or dead cell. From telemetry I can decide if I will use the battery, keep it under observation or retire it (for tests or as flshlight or so).
If one don't want to use the heavy battleship q500log2kml, you can also use a light fast boat like BatteryCheck tool.
br HE
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That is the thing: I know that actual battery capacity is hard to determine. I took the mentionend values from practical experience documented in my meanwhile 518 lines long charging and storage report spreadsheet. 518 charges (full and storage) on 9 batteries over 2 years. So it is less a laboratory desk investigation than a practical field observation.
h-elsner
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A good documentation about battery usage, load cycles and so on, is the best help you can get regarding LiPo batteries.
h-elsner
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The SW is here:
The whole project is here (including source code):
github.com
br HE
The whole project is here (including source code):
GitHub - h-elsner/BatteryCheck: Post-flight battery quick check: Evaluate the condition of the flight battery on base of the voltage curve under real load.
Post-flight battery quick check: Evaluate the condition of the flight battery on base of the voltage curve under real load. - h-elsner/BatteryCheck
github.com
br HE
Excellent. Thank you my friend.The SW is here:
The whole project is here (including source code):
GitHub - h-elsner/BatteryCheck: Post-flight battery quick check: Evaluate the condition of the flight battery on base of the voltage curve under real load.
Post-flight battery quick check: Evaluate the condition of the flight battery on base of the voltage curve under real load. - h-elsner/BatteryCheck
br HE
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