General Telemetry Settings

Harford

Active Member
I am increasingly making use of the telemetry capability of my DX9 with now 3 of my machines able to provide data - my interest at this stage is restricted to flight pack voltage.

However I am a little unsure of the minimum and maximum voltage values I should enter in the Flight Pack Voltage screen. If for example I am using a 3S lipo is this always going to be something like :
Volts Min - 11.1v _ie 3 x 3.7v
Volts Max - 12.6v - ie 3 x 4.2v
or am I completely missing the point ?
Also, what happens if the reading is outside these values - other than a warning from the Tx.

Many thanks for any enlightenment on what is probably another inept question.
 

Tony

Staff member
Those are good settings to start with. 12.6 is good since most chargers will stop the charge there. But the most important is that Min volt. This will tell you if you are about to crash. But, this is going to depend on a few things. First, are you using a flight pack and a receiver pack? If so, that is what I would put on the receiver pack. It will keep you informed of it's charge and once it hits 3.7 volts per cell, it will warn you and you have more than enough power to keep the servos going until you can land.

If that is only a main flight pack, then that low needs to be set lower, like 3.3 or 3.4 volts per cell. The main motor is going to draw down that voltage and if you have it going off at 3.7 vpc you will get a warning about a minute into your flight. Maybe 2 minutes lol. Hope this makes sense.
 

Harford

Active Member
Many thanks Tony,
In all cases at present, I am using a flight pack only. I know I am being a little conservative with the 3.7V but for some reason I had it in my mind that I risked over discharging the battery if I went much below this figure. Having read more about this subsequently, I understand a Lipo is fully discharged at 3.0v so that is a level to stay away from. Your suggestion of 3.3 or 3.4v makes perfect sense. Thank you again.
 

Tony

Staff member
It's my pleasure. Having it set where you had it will not affect anything but flight times. It will actually make the battery last longer. Studies show if you can keep a LiPo in the range of 40-60% constantly, it will last twice as long or more than one that is fully charged and drained. And somewhere around a 20-30% increase in life if you only charge to 4.0 volts per cell.
 

Harford

Active Member
It is only on the odd occasion I have discharged them below 3.7v but never below 3.6v. I have 3s 2200mAh lipos which are 8 years old which are still fine (used on a FB 450Pro). Around 7.5 minutes flight time - just gentle hovering around etc. Clearly I can be a little more adventuresome !
 

Tony

Staff member
Yes sir. 80% capacity is a good rule of thumb. Just charge up the pack, fly for your 7 minutes and then recharge the pack. If you put in less than 80%, then you can increase your flight time until you hit that number.
 

Smoggie

Well-Known Member
On my telemetry I typically use 3.4v to 3.45v per cell as the low voltage alarm. If you set it much higher then the alarm will go off every time you do any aggressive flying that puts high load on the battery.

I only use the low volt alarm a a last ditch warning, I use a timer as my first line of defence. Because battery voltage varies so much with load you can’t really use voltage alarm on its own, unless all you do in very gentle flying that doesn’t load up the battery.
 

Harford

Active Member
Thank you Smoggie. I fit into the very gentle flying category but using the timer also is good advice. I am familiar with the timer function as this is something I have been using for all machines prior to my introduction to telemetry.
 

murankar

Staff member
Plus setting a lower low voltage will accomidate for the motor load. My VControl telemetry warns me every 10% of comsumption. I land when the radio says 20%. In reality when unloaded the battery is at about 35%. So I have no need for a timmer, my radio still tracks the time but its only in the flight log.
 

Smoggie

Well-Known Member
I think the VControl might be clever enough to look at average voltage so not get so effected by very short term dips due to very high load? Plus of course it can do mAh consumed too
 

murankar

Staff member
I am not sure how the algorithm works. In program the pack in and it gives the output. What I have not done yet is set the alarm. I just stop flying when the radio says 20%.

It also has mah consumed, so it could very easily use that as a gauge.
 
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