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Old 09-14-2012, 07:09 AM   #1
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Default Can I Change the Cutoff Voltage?

I just bought an Eflite 20 amp ESC for a 3 cell LiPo system but I am an eflight newbie. The instructions say I can change the ESC to either auto NiCad/NiMH or auto LiPo with a low voltage cutoff but it doesn't apparently let me adjust the cutoff voltage level. It also does not tell me what that voltage cutoff level is.

2 Questions:

  • What is the LVC set at?
  • Can that voltage cutoff level be changed?

(Can't find that info on the Eflite web site.)
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Old 09-14-2012, 08:49 AM   #2
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Originally Posted by bsrchas View Post
I just bought an Eflite 20 amp ESC for a 3 cell LiPo system
Which one? It looks like they have 2 20 amp esc's.
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Old 09-14-2012, 08:57 AM   #3
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The LVC is automatic set on that esc, no the LVC can not be changed. I dont belive E Flite has their own Programing card, it has to be done with the Transmitter sticks. IMHO E Flite ESC are not the best ESC out there
http://www.e-fliterc.com/ProdInfo/Fi...-Brushless.pdf

Do Yourself a BIG BIG Favor and use Turnigy Plush or Sentry ESC, they can be programed, they are IMHO Bullet Proof, never ever had one fail on me, and use a ESC thats 20% + bigger than what you need, if your motor says it needs a 20 amp esc, use a 30 amp esc, it will stay cooler and last longer, Turnigy ESC are the best ESC for the Money, you can buy better ESC , but you will spend a arm and a leg for them,

http://www.hobbyking.com/hobbyking/s...ontroller.html

http://www.hobbyking.com/hobbyking/s...ming_Card.html

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 09-14-2012, 09:53 AM   #4
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Originally Posted by xmech2k View Post
Which one? It looks like they have 2 20 amp esc's.
I have the 20 amp brushles (V2)

Originally Posted by CHELLIE View Post
The LVC is automatic set on that esc, no the LVC can not be changed. I dont belive E Flite has their own Programing card, it has to be done with the Transmitter sticks. IMHO E Flite ESC are not the best ESC out there
http://www.e-fliterc.com/ProdInfo/Fi...-Brushless.pdf

Do Yourself a BIG BIG Favor and use Turnigy Plush or Sentry ESC, they can be programed, they are IMHO Bullet Proof, never ever had one fail on me, and use a ESC thats 20% + bigger than what you need, if your motor says it needs a 20 amp esc, use a 30 amp esc, it will stay cooler and last longer, Turnigy ESC are the best ESC for the Money, you can buy better ESC , but you will spend a arm and a leg for them,

http://www.hobbyking.com/hobbyking/s...ontroller.html

http://www.hobbyking.com/hobbyking/s...ming_Card.html
Thanks. That's a big help. But if the Eflite LVC cant be changed, what voltage do they use for the LVC? they don't say in the instructions that came with the ESC or on their web site.

Also, thanks for the + 20% on choosing the ESC size. Motocalc says the max. amps I should pull is just under 16 so a 20 amp ESC seems to just make it.

The Turnigy link you provided says I can adjust the LVC to low, middle or high. Any idea what those voltages are?
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Old 09-14-2012, 10:13 AM   #5
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typically 'low'= 2.8v, 'medium' = 3.0v and 'high' = 3.2v

I always set mine to high and leave it there. Maybe if you were using old, tired LiPo's you might need medium setting to stop LVC acting too early.

As for over sizing your ESC by 20%.. Other than weight and cost there is no harm in that but i'd argue that it's not usually necessary. Check the spec of your ESC because most have a burst rating much higher then the label value. For instance my 60A ESC has a burst rating of 80A for 15 seconds. So personally I'm perfectly happy to have my peak amps measured on the ground with a fresh battery hit the ESC label maximum amp value, or even exceed it slightly. In flight you will most likely never see those amps anyway, and if you do it's only for a moment, which the ESC is designed to handle.

I've yet to have an ESC fail. Only time I'd worry is if the ESC didn't have good cooling.

Steve
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Old 09-14-2012, 03:08 PM   #6
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Originally Posted by JetPlaneFlyer View Post
typically 'low'= 2.8v, 'medium' = 3.0v and 'high' = 3.2v

I always set mine to high and leave it there. Maybe if you were using old, tired LiPo's you might need medium setting to stop LVC acting too early.

As for over sizing your ESC by 20%.. Other than weight and cost there is no harm in that but i'd argue that it's not usually necessary. Check the spec of your ESC because most have a burst rating much higher then the label value. For instance my 60A ESC has a burst rating of 80A for 15 seconds. So personally I'm perfectly happy to have my peak amps measured on the ground with a fresh battery hit the ESC label maximum amp value, or even exceed it slightly. In flight you will most likely never see those amps anyway, and if you do it's only for a moment, which the ESC is designed to handle.

I've yet to have an ESC fail. Only time I'd worry is if the ESC didn't have good cooling.

Steve
I was gonna ask the question about how to size an esc. Now I don't have to , Thanks. Theoretically your way seems simple and exact. Some of the el-cheapos though I wonder if it's wise to "oversize"

ps. One particular plane I have is the Sensei and I wanted to use 11x5.5 prop , but was a bit scared to use it because it drawed 26 amps and the esc is a 30 amp. Maybe I shall be ok?
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Old 09-14-2012, 04:04 PM   #7
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Originally Posted by nidly View Post
...I have is the Sensei and I wanted to use 11x5.5 prop , but was a bit scared to use it because it drawed 26 amps and the esc is a 30 amp. Maybe I shall be ok?
that's fine..
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Old 09-14-2012, 05:56 PM   #8
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OK. Do I assume then from the above responses that all ESC's use 3.0 volts as the LVC?
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Old 09-14-2012, 06:03 PM   #9
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Originally Posted by bsrchas View Post
OK. Do I assume then from the above responses that all ESC's use 3.0 volts as the LVC?
That's typical for the default value, but I wouldn't be sure they are all the same.

You shouldn't be flying to LVC anyway, it's just a last ditch safety net. Much better to use a timer and adjust flight time to give 3.7v per cell measured after you take the battery out.
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Old 09-14-2012, 07:02 PM   #10
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Originally Posted by bsrchas View Post
OK. Do I assume then from the above responses that all ESC's use 3.0 volts as the LVC?
Most of them are adjustable. All of mine however are cheap and use 67% of plug-in voltage or just a fixed value of < 9 volts.
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Old 09-14-2012, 08:40 PM   #11
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Good info. Thanks to all who replied.

As mentioned above, I'm an eflight newbie. As an engineer, it doesn't make sense to have and LVC set at such a low voltage as to potentially damage the battery. Rather than the complication of timing flights, measuring the voltage after landing, adjusting your time as a result, and then retesting the voltage, it seems to make sense that ESC manufactures would allow you to select an LVC that is higher to eliminate all the flight timing and voltage measuring.

When flying with glow fuel, I never timed flights because, if I flew too long, I would just have to land dead stick. I never watched a clock. I just guessed at the time.

Now, with eflight and a 3.0 volt LVC, it appears that if the "tank runs out", I not only need to dead stick a landing, but I could also be damaging the battery. I guess I would like to set a higher LVC above 3.0, such as 3.2 to 3.5 so that the "tank runs out" before I could damage a battery.

Can that be done with some ESC's so that a voltage could be selected by the actual value rather than just low, medium, high?
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Old 09-14-2012, 09:00 PM   #12
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Originally Posted by bsrchas View Post
When flying with glow fuel, I never timed flights because, if I flew too long, I would just have to land dead stick. I never watched a clock. I just guessed at the time.

Now, with eflight and a 3.0 volt LVC, it appears that if the "tank runs out", I not only need to dead stick a landing, but I could also be damaging the battery. I guess I would like to set a higher LVC above 3.0, such as 3.2 to 3.5 so that the "tank runs out" before I could damage a battery.

Can that be done with some ESC's so that a voltage could be selected by the actual value rather than just low, medium, high?
Yup
Include the Castle Creations ICE series with those ESCs that allows manual setting of the LVC voltage. You will need the uBEC programming card to do this through your computer. The CC ESCs allow custom setting of the exact voltage you select for LVC.

As for me, I just time my flights so as to NEVER use more than about 70% of the battery. Your $$$$ batteries will last longer, and if you need to go around on a landing approach, you've got something left for emergencies.

I've been using those 2300 Mah A123 cells, and going to LVC on them is not a good idea. These cells put out full power till they are just about completely discharged. Then they quit. Cold. I've flown right to left on our field at full power, turned around, and found my self dead stick. They quit that fast. (I've set up my CC ESC's for a soft LVC, not the "shut off the motor" LVC.)

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Old 09-14-2012, 10:39 PM   #13
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Originally Posted by bsrchas View Post
As an engineer, it doesn't make sense to have and LVC set at such a low voltage as to potentially damage the battery. Rather than the complication of timing flights, measuring the voltage after landing, adjusting your time as a result, and then retesting the voltage, it seems to make sense that ESC manufactures would allow you to select an LVC that is higher to eliminate all the flight timing and voltage measuring.
I'm an engineer too and I see it rather differently.
First I'd much rather take the (highly debatable) risk of slightly shortening the life of a battery, compared to the very real risk of writing-off an entire plane. Having your motor quite just when you demand full throttle (as will occur with LVC) will catch you out sooner rather than later, especially if you enjoy doing low level aerobatics.

Comparison with i.c. doesn't really stand up, flight time is rarely a problem with i.c. planes because they are usually fuelled for very long flight duration, so you rarely if ever hit empty. Electric is different as durations are generally shorter with much less margin for error.

Most Tx's have timers built in and it only takes two or three flights to work out your optimum flight time by checking battery voltage, that's really not such a big deal in my book and just becaomes part of the routine for setting up a new plane.

There are other ways to do it. You can use a radio with telemetry and set a warning buzzer on the Tx to go off when the battery hits whatever voltage you see fit (I use 13.7v on my DX8 for a 4s pack), so no timer necessary and no chance of hitting LVC, in fact you can safely disable LVC.
If you don't have telemetry then you can buy those cheap LiPo voltage checkers that plug into the balance plug and have a alarm which you can program to go off when any cell drops below a user programmed voltage. They are only a few $ and the alarm is easily heard on the ground, no flight box should be without one.
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Old 09-15-2012, 12:34 AM   #14
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Originally Posted by JetPlaneFlyer View Post
I'm an engineer too and I see it rather differently.
First I'd much rather take the (highly debatable) risk of slightly shortening the life of a battery, compared to the very real risk of writing-off an entire plane. Having your motor quite just when you demand full throttle (as will occur with LVC) will catch you out sooner rather than later, especially if you enjoy doing low level aerobatics.

Comparison with i.c. doesn't really stand up, flight time is rarely a problem with i.c. planes because they are usually fuelled for very long flight duration, so you rarely if ever hit empty. Electric is different as durations are generally shorter with much less margin for error.

Most Tx's have timers built in and it only takes two or three flights to work out your optimum flight time by checking battery voltage, that's really not such a big deal in my book and just becaomes part of the routine for setting up a new plane.

There are other ways to do it. You can use a radio with telemetry and set a warning buzzer on the Tx to go off when the battery hits whatever voltage you see fit (I use 13.7v on my DX8 for a 4s pack), so no timer necessary and no chance of hitting LVC, in fact you can safely disable LVC.
If you don't have telemetry then you can buy those cheap LiPo voltage checkers that plug into the balance plug and have a alarm which you can program to go off when any cell drops below a user programmed voltage. They are only a few $ and the alarm is easily heard on the ground, no flight box should be without one.
Nice thing about those ESC's that have the capability of a "Soft" cut off on LVC. These soft cut offs keep the battery above the LVC point by reducing maximum power to the motor, rather than just shutting it off.

The Castle Creations ICE series of ESC's is one mfg that has this capability. This soft cut off is not very effective on my A123 cells though. Once these cells drop down to near LVC, they simply quit.

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Old 09-15-2012, 02:02 AM   #15
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Both the timer AND an accurate LVC are good things. Many of us use both at zero cost. They are both "moving targets" though.

The timer is a moving target because it doesn't take into account the flying style (how much throttle is used) It's just an average and in short average flights it can be very accurate. In longer UN-average flights it can be off bunches. It also assumes a fully charged battery.

The accurate LVC is a moving target because it doesn't take into account the differential in voltage between loaded and unloaded voltage. Again an "average" flight will be accurate , but flights that are at the two opposite ends of "average" for current can throw this figure off quite a bit.

I use a timer on all flights and if I happen to be aggressive or very windy I can simply land a few minutes early. If I am mild then I can fly past timer beep. I also use the LVC too and very rarely hit it. It's there "just in case" I forgot to charge battery or forgot how fast I flew.

I haven't used telemetry , but it would be a sure bet. Also there's a time that is throttle dependent that I'd like to try out too. It shall be very accurate I think. Not all TX will have this option.
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Old 09-15-2012, 02:24 AM   #16
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Originally Posted by JetPlaneFlyer View Post
So personally I'm perfectly happy to have my peak amps measured on the ground with a fresh battery hit the ESC label maximum amp value, or even exceed it slightly. In flight you will most likely never see those amps anyway, and if you do it's only for a moment, which the ESC is designed to handle.

I've yet to have an ESC fail. Only time I'd worry is if the ESC didn't have good cooling.

Steve
I'm game to try this , what esc do you usually use? Do you use good ones or some real cheapos? ALL mine are cheapos , but I'd like to trust the labels. Most of my stuff is Hobbico or Flyzone or HobbyKing.

Only problem is I know all my currents on the ground , but it's always with a half full pack. I'd need to estimate or re-test them all hot off the charger to get an accurate MAX current.
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Old 09-15-2012, 10:00 AM   #17
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Originally Posted by kyleservicetech View Post
Nice thing about those ESC's that have the capability of a "Soft" cut off on LVC. These soft cut offs keep the battery above the LVC point by reducing maximum power to the motor, rather than just shutting it off.

The Castle Creations ICE series of ESC's is one mfg that has this capability. This soft cut off is not very effective on my A123 cells though. Once these cells drop down to near LVC, they simply quit.
yeah, i always use 'soft' cut off, but even soft can be dangerous if you are doing something like hovering at quite low altitude.. Even with cut-off set soft the power reduces very quickly as the battery voltage falls away.
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Old 09-15-2012, 10:06 AM   #18
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Originally Posted by nidly View Post
I'm game to try this , what esc do you usually use? Do you use good ones or some real cheapos? ALL mine are cheapos , but I'd like to trust the labels. Most of my stuff is Hobbico or Flyzone or HobbyKing.

Only problem is I know all my currents on the ground , but it's always with a half full pack. I'd need to estimate or re-test them all hot off the charger to get an accurate MAX current.
My personal favourite for bang for buck is the ZTW range of ESC's, or the relabelled ZTW sold under the names 'Black Mantis' and 'Mystery'. If buying Mystery ESC's it's the ones with the blue heatsink that are ZTW. here's the cheapest place i know of to get them: http://dx.com/s/mystery+programmable

HobbyWing / Turnigy Plush (same ESC) are also great ESC's but a bit bigger and heavier than the ZTW.

The likes of Castle Creations Ice are fantastic but in a different price bracket.
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