Taranis reading battery %

[wingsaway]

I was wondering if someone could suggest a better way to have the Taranis read my battery percentages to me while flying. I am using the FrSky FLVSS LiPo Voltage Sensor with smartport to my X8r and Taranis and I run two 4S 5000mAh batteries in parallel. The Frsky voltage meter is only on one 4S pack but they are in parallel.

I flew my hex and landed often to measure the voltage with an EOS sentry Lipo battery checker. I reordered the voltages and corresponding battery % upon landing. I then made custom voice files and programmed my Taranis to read the battery percentage at the measured voltage while I flew a new battery pack to test it out. I programmed the radio to:

A<x ---14.9v Cells -->a custom function reads "20%"
A<x ---15.1v Cells -->a custom function reads "25%"
A<x ---16.1v Cells -->a custom function reads "80%"
etc, etc

I originally had my values as A=x but I figured the voltage might skip the value and I could miss the warning so I changed it to a<x to be sure. When I'm flying my alarm goes off and reads 80% and I land and check and the battery is in the 90% or higher range. Should I change my programming to only look at "Cell" instead of "Cells" and then fly/measure the cell voltage to get new Cell values?

I also noticed that my FrSky FLVSS LiPo Voltage Sensor is not reading the voltages correctly off my battery. It will read the cells as 15.26v when it's really 15.38v, or 15.15 when it's really 15.26, etc, etc. So I can get my battery voltages from the FLVSS instead of my hand held lipo reader and adjust for this in the radio but it makes me nervous to relay on adjusted numbers from the FLVSS that may not be accurate in the first place. Any advice about how to go forward would be appreciated.

-Pete

[Kilrah]

You will never get anything close to an accurate indication that way. You've forgot that voltage fluctuates a lot under varying loads.

Sent via mobile

[wingsaway]

I've seen it done with APM and mission planner but it was used in planes where I assume the voltage drop was much lower. Is there any way to program the radio to factor in the load? Or should I be approaching this a different way? My Naza is able to do this and the red "battery warning" light doesn't come on until my battery is at 30%-with or without load.

My goal is to know the battery percent (ideally) during flight, or the battery voltage so I don't have to keep looking at my radio and I can know the status and fly longer or land if needed with batteries at 20-25%. This is especially important flying long missions where I cannot see the Naza Led to know, and a timer doesn't account for flight speeds, etc. Thanks

[rdeanchurch]

You would get a much better indication of percent used if you had a current sensor.
The 40A one sense voltage and current and OpenTx calculates mahr used.
I tried with just battery voltage sensor and there is a lot of voltage sag under heavy loads (as Kilrah says.)
Just turn on logs and run at high throttle and low throttle and watch the variations by examining the logged data.

[wingsaway]

Ah that's brilliant! The frysky current sensor I have only does 1-3s, didn't realize they had a higher lipo rated one that would work with the x8r reciever.

I assume you are talking about something like this:
http://www.alofthobbies.com/sp-40a.html

I'll have to make a harness coming off my two 4S batteries in parallel to this current sensor or just run it off one 4s battery and have my alerts set to the mAh rating of one 4s battery. Now that you say it, I think a current sensor is the way APM does battery %. Sounds like measuring current to get battery percent is the way to go. Then I can set a logical switch for current consumed and set a special function to play the percent at the level.

[rdeanchurch]

Exactly that one from Aloft is what I use.
You will want to use mahr (cnsp) for the % for the battery. It takes current and voltage and totals up the usage of the battery

[MikeB]

If you are using the SPort, you might also look at the 150A sensor. This uses 'clamp' technology so all you need to do is pass one of the power wires, after the parallel connection, through the hole in the middle of the sensor, no connectors required.

Mike.