What do you set your LVA at?

[Scratch]

Just curious what you all set your low voltage alarms at. I'd love to see something like this:

Quad
DT750
2200 3S
1147 props
1530g (fully loaded, camera and battery)
8:40
3.4V

(Updated with better settings)

Is there any other variables I need?


Here's the deal, I'm assuming I'm way too high. I normally get an easy 8 minute flight time with both of my batteries, but I did "some" research, found a 3.6-3.8V for a setting. I figured I'd err on the side of caution so I went with 3.8.

Now, the beep is sounding at about 2-1/2 minutes!


If I set it to 3.6V, I get 5 minutes.

I'd love to see what the standard is, especially for my battery size.

 

[Dumpster Jedi]

Just curious what you all set your low voltage alarms at. I'd love to see something like this:

Quad
DT750
2200 3S
2:30
3.8V



Is there any other variables I need? Prop size maybe....


Here's the deal, I'm assuming I'm way too high. I normally get an easy 8 minute flight time with both of my batteries, but I did "some" research, found a 3.6-3.8V for a setting. I figured I'd err on the side of caution so I went with 3.8.

Now, the beep is sounding at about 2-1/2 minutes!

I'd love to see what the standard is, especially for my battery size.

I have yet to figure out how the LVA works on the KK2.1. If I set it to anything but zero, it just alarms constantly. 4.2 on the cells and LVA set to 3.8? On the ground, no throttle... alarm.

I run 3000mah 3S batteries and I'd prefer an alarm at 3.8 or so, generally where it is when I guesstimate it's time to swap batteries. I just can't get the damned alarm to work, so for now I have the LED hooked up and just use that as an arming indicator since the little red light on the board isn't easy to see.

 

[cranialrectosis]

I stop at 3.7. My 2200mah batteries on an 860gram knuckle I quad running the Altitude 1450s gives me 7-9 minutes of flight with moderate acro.

 

[Craftydan]

Scratch,

I calibrate it -- set it too high, fly until it beeps in hover or cruise (depending on what I'm flying), then land. let it sit for a moment (15-30s is usually enough) and check the voltage . . . above 3.70/cell? drop the setting a notch or two and fly again. Below 3.70/cell? bump it up a notch, swap the battery and fly.

Might take a pack or two to bracket in, but after that the setting stays pretty stable.

I've also found it changes dramatically between the motor setup and pack size -- my Tri is differnet than my quad (don't remember which way ATM, but it's a few tenths off), and if I cal it on my 2200's and fly a 1500, the 1500 will be swapped out with about 35-40% left on the pack, as opposed to 15-20% on the 2200s.

 

[Cyberdactyl]

What's cool about the relatively high frequency sound buzzer, is the clear doppler you hear when they go off and you're flying around fast.

 

[Craftydan]

DJ,

have you connected a wire between the battery lead (or balance plug) and the voltage reference pin? the KK2 needs an unregulated look at the battery through that pin to measure the voltage.

Once that's done, the set voltage is in tenths of a volt, so pretend there's a decimal place after the lowest number (11.1v => 111, 12.4v => 124).


*beware* -- don't hook that up to the ground pin right next to it (inside pin). it's safest just to snip off that pin. Otherwise you might accidentily connect unregulated battery to ground and short the battery through the kk2 board . . . and blow one expensive board as a fuse.

 

[Mustang7302]

Quad Copter
Turnigy SK3 1275KV Motors
8045 Props
650 Grams
LVA @ 10.2V (3.4V per Cell)
13-14 Minutes of Flight Time
Zippy Compact 2200mAh 3S 25C


Tri Copter (Bat Bone)
Turnigy D2822/14 1450KV Motors
8045 Props
730 Grams
LVA @ 10.2V (3.4V per Cell)
11-12 Minutes of Flight Time
Zippy Compact 2200mAh 3S 25C



Voltage sags under load. While fully charged each cell is at 4.2V, under load they will drop two to three tenths. The nominal voltage, where the cell is most stable is, around 3.7V and will linger around the longest during the course of the battery's consumption of its capacity. Once you start approaching the limit of capacity, the voltage will drop much more rapidly and could be as little as a minute from 3.7V to 3.2V.

I use the KK2.1's voltage monitor for my two copter currently by using a pair of wires which were soldered into the power harness from the battery; take special note of the polarity of the voltage sensor pins on the KK2.1 when hooking it up (positive is on the outside edge while every other set of pins on the board has its negative pin to the outside edge). Flying to 10.2V under load eases back to 10.6-10.7 after 30 seconds of disarming. The charge cycle after one of those flights puts 2200mAh of capacity back into my 2200mAh battery. There is the conservative 80% rule to consider, but it's your personal choice and calculated risks.

Weight also plays a huge factor in flight time. The heavier it is, the more load on the motors to over come gravity, the more current pulled, and the faster X amount of resource is depleted.

 

[Dumpster Jedi]

DJ,

have you connected a wire between the battery lead (or balance plug) and the voltage reference pin? the KK2 needs an unregulated look at the battery through that pin to measure the voltage.

Once that's done, the set voltage is in tenths of a volt, so pretend there's a decimal place after the lowest number (11.1v => 111, 12.4v => 124).


*beware* -- don't hook that up to the ground pin right next to it (inside pin). it's safest just to snip off that pin. Otherwise you might accidentily connect unregulated battery to ground and short the battery through the kk2 board . . . and blow one expensive board as a fuse.

So is that connection reversed from the other pins (negatives being toward the outside edge), or am I just thinking backwards again? (And I wonder where my orientation issues come from)

 

[Craftydan]

Pretty much backwards to the convention . . . but on the original board, Rolf also didn't route a negitive wire to the plug to prevent a bone-headded battery short from plugging in a cable backwards.

. . . just one of their "improvements" to the design that lets them cheat Rolf out of royalties . . .

 

[DDSFlyer]

Quad Copter
Turnigy SK3 1275KV Motors
8045 Props
650 Grams
LVA @ 10.2V (3.4V per Cell)
13-14 Minutes of Flight Time
Zippy Compact 2200mAh 3S 25C


Tri Copter (Bat Bone)
Turnigy D2822/14 1450KV Motors
8045 Props
730 Grams
LVA @ 10.2V (3.4V per Cell)
11-12 Minutes of Flight Time
Zippy Compact 2200mAh 3S 25C



Voltage sags under load. While fully charged each cell is at 4.2V, under load they will drop two to three tenths. The nominal voltage, where the cell is most stable is, around 3.7V and will linger around the longest during the course of the battery's consumption of its capacity. Once you start approaching the limit of capacity, the voltage will drop much more rapidly and could be as little as a minute from 3.7V to 3.2V.

I use the KK2.1's voltage monitor for my two copter currently by using a pair of wires which were soldered into the power harness from the battery; take special note of the polarity of the voltage sensor pins on the KK2.1 when hooking it up (positive is on the outside edge while every other set of pins on the board has its negative pin to the outside edge). Flying to 10.2V under load eases back to 10.6-10.7 after 30 seconds of disarming. The charge cycle after one of those flights puts 2200mAh of capacity back into my 2200mAh battery. There is the conservative 80% rule to consider, but it's your personal choice and calculated risks.

Weight also plays a huge factor in flight time. The heavier it is, the more load on the motors to over come gravity, the more current pulled, and the faster X amount of resource is depleted.

Are you really putting 2200mAh charge back into a 2200mAh battery? Is it me or are you saying that it is discharging to the point of zero left in the tank? Sounds like you are of the Josh Bixler school of battery usage. But you did say it's of personal choice and calculated risk. I just go by the 80% rule and try and keep the batteries at 3.8v per cell and have more batteries to fly with.

 

[Craftydan]

Actually at 3.7v resting the cell is around 10-20% capacity, which is one of the reasons it's a magical number for lipos.

Down to there the voltage drop vs capacity is pretty linear (the right reactions dominate). After that the curve knees over and voltage drops rapidly (wrong reactions begin to take over). You've got another 10-20% to go before the bad reactions become strongly damaging (or drops the platform like a rock). Down to 3.7v resting won't cost you pack life much more than down to 3.8v resting. A little less than 3.7 and the lifespan will start to drop.

 

[xuzme720]

I dunno, Dan, puffy lipos are probably more aerodynamic due to less sharp corners...

 

[DDSFlyer]

And they are make for good fluffy cushions to land on...

 

[Mustang7302]

Are you really putting 2200mAh charge back into a 2200mAh battery? Is it me or are you saying that it is discharging to the point of zero left in the tank? Sounds like you are of the Josh Bixler school of battery usage. But you did say it's of personal choice and calculated risk. I just go by the 80% rule and try and keep the batteries at 3.8v per cell and have more batteries to fly with.

In the past I have run packs down to 3.2v per cell and back fed 110 - 115% of the battery's capacity on the charge cycle. I noticed that after a dozen or so cycles, the cells would start becoming out of balance by a tenth or two and would take way longer to balance charge. Never have I puffed a LiPo until I ran one without a LVA, wasn't watching a timer, and the craft couldn't maintain hover at more than 75% throttle.

In the scheme of LiPo safety, these practices are certainly frowned upon. Unless you're willing to accept the risk of hazards involved, stick to the 80% rule. I monitor my batteries after getting ran, let them cool to ambient before charging, and I always watch them as they charge.

 

[Cyberdactyl]

I got my first quad got stuck in a tree over night and I had to do the ultra slow charging to 9.0V, set on 'NiCad' so my charger would recognize it was a LiPo. It puffed slightly and still worked for a couple months afterwards with maybe 80% the duration of a new battery. At the time, I had only two batteries, so I was reluctant to throw it out. Now that I have several, I would trash it and not take any chances.

 

[Craftydan]

I dunno, Dan, puffy lipos are probably more aerodynamic due to less sharp corners...

And they are make for good fluffy cushions to land on...

hmmm . . . Perhaps that's why planes/multirotors fly better the more you repair them