LIPO voltages

[mediaguru]

I'm fairly new to the hobby, but have read extensively.

I'm running two 5000mAh Pulse batteries on my hexa. Pulse tells me not to go below 3.7 volts, but many go down much lower. I've been listening to them and as soon as my Taranis tells me 3.7, I land. Usually they're in the high 3.7's when they recover, like 3.75.

When I balance charge them the charger is only putting back about 2700mAh, or around 53%. Far from the 80% rule and more like 53%.

Does this seem normal? Can I go closer to 3.70 volts before landing and squeeze a few more minutes?

Some seem more concerned with the amount of mAh put back, and that's their 80%. So if that's the case I should be shooting for it putting back 4000, which is WAY different than 2700!

Thoughts?

 

[gtranquilla]

When looking at the battery voltages when the load is connected you will see a different/lower voltage than when the batteries are not connected to a load.
Under load you have to expect the voltage to drop a bit lower than 3.7 volts near the end of a flight.
The main thing is that the open circuit voltage must not go below 3.7 per cell - IMHO

 

[mediaguru]

When looking at the battery voltages when the load is connected you will see a different/lower voltage than when the batteries are not connected to a load.
Under load you have to expect the voltage to drop a bit lower than 3.7 volts near the end of a flight.
The main thing is that the open circuit voltage must not go below 3.7 per cell - IMHO

So when I'm landing it is often around 3.75 volts and after powering down the hexa it will often end up in the upper 3.7's to 3.8. So I could go longer?

What about only putting back in 2700? 80% of 5000 is 4000. It would seem I'm being overly conservative?

 

[Carapau]

Fly until you have used 80%, let the batteries recover a touch and I bet you will find that the resting voltage is somewhere around 7.5v ie once the batteries have cooled down. It's this resting voltage that is the important one rather than the in air voltage.

 

[mediaguru]

Fly until you have used 80%, let the batteries recover a touch and I bet you will find that the resting voltage is somewhere around 7.5v ie once the batteries have cooled down. It's this resting voltage that is the important one rather than the in air voltage.

I'm receiving telemetry in the form of total voltage, as well as the lowest per-cell voltage. Am I simply guessing as to when 80% is, or calculating 80% of the starting 4.2 volts per cell or 80% of 22.2 volts?

 

[gtranquilla]

As you are probably aware, the loaded voltage is always lower than the unloaded voltage.
Also after letting the landed rig sitting for awhile with power off - the battery voltage tends to recover to a slightly higher level.... which will give you misleading information if used incorrectly.

So when I'm landing it is often around 3.75 volts and after powering down the hexa it will often end up in the upper 3.7's to 3.8. So I could go longer?

What about only putting back in 2700? 80% of 5000 is 4000. It would seem I'm being overly conservative?

 

[mediaguru]

Yes I do get that. So I'm trying to figure the proper landing voltage for my rig. What you're saying is that you're looking for a 7.5 volt at rest voltage after the battery has recovered. That could mean an under load voltage may be 3.7 or less, or I'd have to just experiment with my setup is my guess. Trying to figure my number, as in I at exactly 3.70 volts on the telemetry I'm landed, then it goes back up to 3.75 shortly after the load is taken off etc.

As you are probably aware, the loaded voltage is always lower than the unloaded voltage.
Also after letting the landed rig sitting for awhile with power off - the battery voltage tends to recover to a slightly higher level.... which will give you misleading information if used incorrectly.

 

[fltundra]

Yes I do get that. So I'm trying to figure the proper landing voltage for my rig. What you're saying is that you're looking for a 7.5 volt at rest voltage after the battery has recovered. That could mean an under load voltage may be 3.7 or less, or I'd have to just experiment with my setup is my guess. Trying to figure my number, as in I at exactly 3.70 volts on the telemetry I'm landed, then it goes back up to 3.75 shortly after the load is taken off etc.

Get one of these...I have two, and you will always know where your at on MAH used.
Unisens-E http://translate.google.com/transla...inE&rls=org.mozilla:en-US:official&channel=sb

 

[mediaguru]

Get one of these...I have two, and you will always know were your at on MAH used.
Unisens-E http://translate.google.com/translate?hl=en&sl=de&u=http://www.sm-modellbau.de/shop/index.php%3FcPath%3D18&prev=/search%3Fq%3DUniSens-E%26client%3Dfirefox-a%26hs%3DinE%26rls%3Dorg.mozilla:en-USfficial%26channel%3Dsb

That's pretty cool. I have an FrSky voltage telemetry device and also a FrSky telemetry GPS, but the GPS has never worked.

 

[BenSkoning]

The really simple way is to set a volt monitor of a balance port any just set it to 3.6 volts per cell.
-Ben

 

[mediaguru]

My Taranis calls out the lowest per cell voltage to my from my TX currently. I should probably set it to 3.6 instead of 3.7, since as soon as 3.79 hits it says 3.7...

 

[fltundra]

My Taranis calls out the lowest per cell voltage to my from my TX currently. I should probably set it to 3.6 instead of 3.7, since as soon as 3.79 hits it says 3.7...

If I used voltage only, at 3.6 volts I'd be way past the 80% mark. Generally my lowest cell is at 3.68-3.70 when I hit max MAH at an 18 amp draw. So 3.6 for me would probably put me at around 10% capacity left, or lower.

 

[mediaguru]

If I used voltage only, at 3.6 volts I'd be way past the 80% mark. Generally my lowest cell is at 3.68-3.70 when I hit max MAH at an 18 amp draw. So 3.6 for me would probably put me at around 10% capacity left, or lower.

Right. Not 3.60, but as soon as it gets to 3.69 or 3.6X. I ran it down last night to 3.70 and after powering off the copter the voltages jumped back up to 3.75-3.8 area.

 

[fltundra]

That's pretty cool. I have an FrSky voltage telemetry device and also a FrSky telemetry GPS, but the GPS has never worked.

I use the Unisen-E with the Frsky lipo sensor. I like being able to compare my SuperX, Taranis, and Icharger logs, gives a nice picture of whats going on over time with my lipos.