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ST16 vs SkyRC Voltage

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G'day All,
This is my first post to the forum and I am hoping someone can tell me what is going on. I am responsible for a fleet of three H520's that are primarily being tasked with 3D mapping duties. After having to replace a significant number of LiHV batteries I started to become a bit more vigilant on the performance of individual batteries.

What this has revealed is significant differences between what the ST16 controller is indicating is left in a battery and what the SkyRC charger is reading. Landing a battery at around 30% shows the batteries at pretty close to 15.0V on the ST16. Getting them back to base for charging approximately 45 minutes to an hour later will have the ST16 showing the same battery at 41% and 15.1-15.3V. Upon plugging the battery into the SkyRC charger immediately after cming out of the aircraft I am getting the indication the batteries are only at 9-12% and pretty much the same as the landed voltage readings from the ST16. This seems a large discrepancy between the two. I had noted that a LiHV battery charged to 80% reads at 100% in the ST16.

My main concern is that a battery landed at 30% on the ST16 is only at 9% according to the SkyRC charger. If it is flown to below the 30% mark what may be the implications? If the SkyRC is the right reading could I see a situation of an aircraft dropping out of the sky because it hasn't read its charge state correctly? Is it possible that Yuneec has not adapted its system to accurately read the true state of the LiHV batteries as opposed to a standard LiPO? Is my SkyRC unit the issue? To allow a safety margin I have mandated the batteries not be flown under 40% until further notice. I would like to think that a pilot can trust what they are being told by the battery in the aircraft at the time and not having to guess/compensate. I am not going to make any claims as to being a battery expert and therefore the observed discrepancies have me concerned enough to consult the brains trust. It may something very simple that I haven't picked up on. I hope that is so!!
Cheers
 
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Which Sky RC model is it? The Q200 is claimed to be factory calibrated, why not get/borrow a decent multimeter as a second opinion, at least that will reveal the culprit. But electronics can go bad.
 

h-elsner

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I guess the Sky RC charger will not corrctly comute the capacity from the voltage for LiHV batteries. 'Normal' LiPo and HV batteries hve different decharge curves.
Also there is always a problem to compute the capacity from voltage. This is only a far approximation. Each battery has its own individual decharge curve depending on age, chemistry and many other parameters.
There are different ways to approximate capacity.
I have compared the algorithm from ST10/ST16 software with a widely spread discharge table table from RC-Groups forum.
1589094935770.png

When you g00gle "lipo discharge curve" you will get a lot of results a a lot of different meanings. I would look more on the voltage than percentage.

br HE
 
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Which Sky RC model is it? The Q200 is claimed to be factory calibrated, why not get/borrow a decent multi-meter as a second opinion, at least that will reveal the culprit. But electronics can go bad.
Charger is a D100V2. I've no idea about factory calibration or not.
 
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I guess the Sky RC charger will not corrctly comute the capacity from the voltage for LiHV batteries. 'Normal' LiPo and HV batteries hve different decharge curves.
Also there is always a problem to compute the capacity from voltage. This is only a far approximation. Each battery has its own individual decharge curve depending on age, chemistry and many other parameters.
There are different ways to approximate capacity.
I have compared the algorithm from ST10/ST16 software with a widely spread discharge table table from RC-Groups forum.
View attachment 21780

When you g00gle "lipo discharge curve" you will get a lot of results a a lot of different meanings. I would look more on the voltage than percentage.

br HE
Thanks for your reply. The charger has a dedicated LiHV program which we have been using and my readings have been obtained from. I recognise that normal LiPO batts will be different to the LiHV units. My concern is that somewhere in the process I am getting an incorrect reading from either the ST16 or the SkyRC charger. It may be that I am not as battery wise as others which is making this whole thing seem strange. I had just assumed that what the ST16 it was telling me was correct.

If it helps people help me these have been my tables:
forum post.JPG forum post 2.JPG

The differences just seem to be too big and until I can get my head around what is going on I'm not overly comfortable with discharging the batteries too far which will obviously be detrimental to flight time.
 
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Charger is a D100V2. I've no idea about factory calibration or not.
No that one didn't. I've got one of those. Have you checked with a meter of the charger is accurately reading the voltage?
 
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No that one didn't. I've got one of those. Have you checked with a meter of the charger is accurately reading the voltage?
That will be next step mate. Have you ever checked to see if there is a difference with yours?
 
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That will be next step mate. Have you ever checked to see if there is a difference with yours?
Not really, I've got the little capacity checkers which are a bit hit and miss, I Will have to take a closer look.
 

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