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Old 11-08-2011, 03:47 PM   #1
FlyingBrick50
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Default ESC reset

Hey Everyone

I have a question, after flying electric aircraft and you disconnect the battery and then reconnect the same battery (guys in my club say) it resets the ESC so LVC does not work (sees batt as 100% they say).
I argued that was not the case, that low voltage was low voltage and the programed ESC detects cell voltage everytime. 1OO% or 65% the LVC is the same as the first time it (the ESC) was set??? Flight time for sure is affected, not LVC
================================================== ==============
ONE ANSWER - Depends entirely on the BRAND of ESC.
Electrifly works that way. (IMO avoid that brand because of that)
Check it out and do the math. It's poor on a fresh lipo and horrible on a used lipo.

Some brands are set, or can be set to a something like AUTO @ 2.9/3/3.1v/cell. Exact voltages depends on the brand/model.
Still others to an absolute voltage of your choice (Castle with the USB Link). Castle will do AUTO also-no LINK required.

Some are set to an absolute volatage-no setting possible.
GWS is that way and the setting is so low I consider it lipo destructive. Absolute ESC dinosaur.

It pays to read the instruction BEFORE you buy these things.
No way to make a blanket statement about how they work.

--------------------------------------------------------------------------------

Jeff how are your escs set up?

Thanks
FB50

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Old 11-08-2011, 04:28 PM   #2
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I'd only add that if it is set to auto, and your pack is low on voltage, it may think it is a pack with one less cell, and allow you to take the battery down too low.

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Old 11-08-2011, 07:26 PM   #3
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Originally Posted by FlyingBrick50 View Post
Hey Everyone

I have a question, after flying electric aircraft and you disconnect the battery and then reconnect the same battery (guys in my club say) it resets the ESC so LVC does not work (sees batt as 100% they say).
I argued that was not the case, that low voltage was low voltage and the programed ESC detects cell voltage everytime. 1OO% or 65% the LVC is the same as the first time it (the ESC) was set??? Flight time for sure is affected, not LVC
I've got my various Castle Creations ESC's programmed to a fixed voltage of about 2.5 Volts per cell on the A123 packs. But I NEVER run the model to the point where the ESC LVC kicks in. Personal opinion, land after going through about 60% of the battery. That way, if you've got someone on the field with a dead glow engine model, or similar, you can stay in the air til the field is clear.

IMHO, flying to LVC on a LiPo (or A123 for that matter) especially with a battery pack of 6 series cells or more, is risking one cell dropping out first, going below its safe voltage level before the ESC LVC kicks in.

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Old 11-08-2011, 11:23 PM   #4
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Originally Posted by FlyingBrick50 View Post
Hey Everyone

I have a question, after flying electric aircraft and you disconnect the battery and then reconnect the same battery (guys in my club say) it resets the ESC so LVC does not work (sees batt as 100% they say).
I argued that was not the case, that low voltage was low voltage and the programed ESC detects cell voltage everytime. 1OO% or 65% the LVC is the same as the first time it (the ESC) was set??? Flight time for sure is affected, not LVC
================================================== ==============
ONE ANSWER - Depends entirely on the BRAND of ESC.
Electrifly works that way. (IMO avoid that brand because of that)
Check it out and do the math. It's poor on a fresh lipo and horrible on a used lipo.

Some brands are set, or can be set to a something like AUTO @ 2.9/3/3.1v/cell. Exact voltages depends on the brand/model.
Still others to an absolute voltage of your choice (Castle with the USB Link). Castle will do AUTO also-no LINK required.

Some are set to an absolute volatage-no setting possible.
GWS is that way and the setting is so low I consider it lipo destructive. Absolute ESC dinosaur.

It pays to read the instruction BEFORE you buy these things.
No way to make a blanket statement about how they work.

--------------------------------------------------------------------------------

Jeff how are your escs set up?

Thanks
FB50
The answer above is reasonable, but I will expand on it for you.

-- Some ESCs are set for motor cut off at a specific voltage per cell, regardless of the starting voltage.
If the ESC has an Low Voltage Cut off (LVC) that is set to a specific voltage per cell, let's say 3.0 volts per cell, then the cut off when using a 3 cell Lipo will occur at 9v, as long as the battery that was plugged in had a voltage above 9 volts. So you could plug in a fully charged 3 cell Lipo (12.6v), and the LVC would occur at 9v. You could also plug in a partially discharged 3 cell Lipo, and the LVC would still occur at 9v, as long as the battery was above 9v when you plugged it in. If the battery was below 9v when you plugged it in, the ESC might detect it as a 2 cell Lipo, and the LVC would then occur at 6v.

-- Some ESCs are set for motor cut off at a certain percent of the starting voltage. When you plug a battery into an ESC that has the percentage type LVC, the motor cut off voltage depends entirely on what the battery voltage was to begin with. For instance, some ESCs are set to cut off at 60% of the starting voltage. When you start with a fully charged 3 cell Lipo (12.6V), the cut cut off occurs at about 7.5v (2.5v per cell). Not good, but it shouldn't ruin a battery if all cells are equal. If you plug in that same battery when it has been discharged some, let's say to 11v, then the LVC won't occur until the battery has reached 6.6v (2.2v per cell), and that can definitely damage a battery.

-- Some ESCs are set for motor cut off at a specific voltage, period. With this type of ESC, the LVC might be set at 9v, and the cut off will occur at 9v if you start with a fully charged 3 cell battery, a partially discharged 3 cell battery, or even if you start with a fully charged 4 cell battery. These ESCs do not "auto detect" the number of battery cells, so you cannot set a "per cell" cut off. However, this type of ESC usually comes with the LVC set at a 60 to 70 percent cut off, and can be manually set at a specific voltage cut off (usually 6v, 9v, 12v, 15v, etc.).

-- Most ESCs can be set for a sudden motor shut down, or a gradual motor shut down when LVC occurs. I recommend setting them for a gradual motor shut down, as this gives you time to land the plane before all power is lost. Note: If you ever have a motor quit suddenly, try moving the throttle to the off position, then back on to about 1/4 throttle. The motor usually restarts, and you may have enough power left to get the plane safely on the ground.


You can see that it is very important to understand what type of LVC your speed control has. We try to make this very clear in our store listings, as well as the instruction sheets included with the ESCs.

Most of our ESCs have the specific voltage per cell type of LVC, and they auto detect the number of cells. All of the Emax ESCs have this, as well as the Power Up 20A and 32A, and the new HURC line of ESCs up to 40 amp. The HURC ESCs above 40 amp will come with the LVC set to 60% of starting voltage, but can be manually set to a specific voltage (3rd type above). The Power Up 40A and 70A come with the LVC set at 72% of starting voltage, which works out to 3.0 volts per cell when starting with a fully charged Lipo battery.

Just one last comment. I'm a member of a flying club, and a lot of our members fly electric planes and helis. Very few of them ever run a battery down to the point where the LVC shuts off (or slows down) the motor, so they don't pay much attention to what the ESC LVC is set at. However, you may save a battery, or even a plane, if you undertand the way the LVC of the ESC functions. I watched one of our members launch an expensive 3D plane vertically out of his hand, and he had inadvertently put in a mostly discharged 3 cell battery. The plane climbed about 15 feet, and the motor shut off. The nose of the plane flipped down and the plane smashed into the ground nose first. The result was a broken cowl, broken prop, and bent motor shaft. This may have been prevented if the LVC was set to a gradual motor shutdown, or if he had checked the battery voltage before flying. Little hint there

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Old 11-08-2011, 11:41 PM   #5
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Thank you for that expanded explanation Jeff. The OP apparently didn't believe my information in his previous post on this same topic. How can the 'guys at the club' possibly be wrong?

Like I said, it pays huge dividends in the sport to actually READ the instruction/spec sheet that comes with your electronics.

fly
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Old 11-21-2011, 11:18 AM   #6
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Most of our ESCs have the specific voltage per cell type of LVC, and they auto detect the number of cells. All of the Emax ESCs have this, as well as the Power Up 20A and 32A, and the new HURC line of ESCs up to 40 amp. The HURC ESCs above 40 amp will come with the LVC set to 60% of starting voltage, but can be manually set to a specific voltage (3rd type above). The Power Up 40A and 70A come with the LVC set at 72% of starting voltage, which works out to 3.0 volts per cell when starting with a fully charged Lipo battery.


Thanks Jeff

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