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Old Nov 12, 2004, 03:45 PM
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Auto-detect cell count cautions

Jeti “Lithium Support” ESCs use cell auto-detect to determine low voltage cut-off. If you fly multiple flights on one charge, it will go through the auto-detect routine each time the motor battery is reconnected or the receiver is switched on – both with and without BEC. The result could be a cell count one lower than it should be – I’ve done this on a bench test. The Jeti LVC is 2.56 volts/cell, so a one cell error makes for a really low LVC. The Li-Saver solves this problem. If you connect the Li-Saver battery sense wire to the battery side of the battery/ESC connector, it will hold the starting cell count regardless of battery reconnects or receiver turn ons. http://www.flydma.com

Another auto-detect caution. If you forget when you last charged a LiPo and put a fully charged pack on an Astroflight 109, it may auto-detect a cell count one higher than it should. If your charger has the 1.3 or 1.4 firmware, closely monitor the charger for the first three minutes as the cell count is locked in at phase 2. An upgrade chip is available from Astroflight for $10.00.
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Old Nov 12, 2004, 04:06 PM
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Glad to see Astroflight 109 locks in the lipo cell count after 3 minutes. The old firmware was an accident waiting to happen.

Ed
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Old Nov 12, 2004, 06:42 PM
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The 1.08 Beta software for the Castle Creation ESC have an auto cell count feature which I like ,however they warn you to make sure that it detects the correct cell count. The motor is chirped twice for 2 cell and 3time for 3 cells.
I am sure that if you disconnected and reconnecet a partically discharge pack it could be detected as 2 cells and the LVC wold be set to low.They do warn you to use a fully charged pack.
If you forget to extend your transmitter antenna you are likely to crash.If you are careless then you are going to have more bad luck.

Charles
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Last edited by everydayflyer; Nov 12, 2004 at 07:49 PM.
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Old Nov 13, 2004, 02:32 AM
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Charles,
Because I do fly multiple short flights on a charge, I have decided that future ESCs will be Castle Creation. I made that choice because I understood that CC stored cell count in nonvolatile memory, so my turn offs and ons would not affect cell count. Does the 1.08 beta software change this, or is the new auto-detect just an option?
Bill
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Old Nov 13, 2004, 06:22 AM
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As far as charging goes, "auto detect" (or any other voltage selection method) is not needed when LiPos are charged in parallel.

The voltage is always 4.2

- RD
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Old Nov 13, 2004, 10:48 AM
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Quote:
Originally Posted by ebill3
Charles,
Because I do fly multiple short flights on a charge, I have decided that future ESCs will be Castle Creation. I made that choice because I understood that CC stored cell count in nonvolatile memory, so my turn offs and ons would not affect cell count. Does the 1.08 beta software change this, or is the new auto-detect just an option?
Bill

Auto cell count is just an option which I happen to like and use on some aircraft due to the fact that I switch between 2 and 3 cell packs depending on the wind and my frame of mind.

CC ESC can be programmed for many (standard)voltage cutoff points and if you use their USB port programmer you can set custom cutoff points.These values are stored in a nonvolatile memory just as you stated.
One another note that t is also one of the main reasons I fly HiTech Prism and Eclipse ETransmitters.
http://www.castlecreations.com/products.html
I have 11 of their brushlss units from 10-45 Amps. and have always been very happy with them.
Charles
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Old Nov 13, 2004, 11:31 AM
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Charles
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Old Nov 14, 2004, 07:14 AM
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I understood that the jeti esc (li-po advance model) only "read" the battery voltage each time it was connected to the the pack - dont believe it actually "re-senses" the voltage just by turning off the receiver as stated??
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Old Nov 14, 2004, 07:28 AM
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[QUOTE=ebill3]Jeti “Lithium Support” ESCs use cell auto-detect to determine low voltage cut-off. If you fly multiple flights on one charge, it will go through the auto-detect routine each time the motor battery is reconnected or the receiver is switched on – both with and without BEC. The result could be a cell count one lower than it should be – I’ve done this on a bench test. The Jeti LVC is 2.56 volts/cell, so a one cell error makes for a really low LVC. The Li-Saver solves this problem. If you connect the Li-Saver battery sense wire to the battery side of the battery/ESC connector, it will hold the starting cell count regardless of battery reconnects or receiver turn ons. http://www.flydma.com
snipQUOTE]
I just installed Li-Savers in both my helis today, and I sure hope you are right, as the instructions which came with them says:-"If a mostly discharged battery is plugged in, the Li-Saver may interpret it as a pack with one fewer cells than it actually has. Hence the calculate cutoff voltage may be lower than three volts per cell. Always plug in a charged or mostly charged pack for proper cutoff."

What is the "battery sense wire"?? Mine came with just two power wires, so presumably you would need a double set of connectors.. battery-->Li-Saver-->ESC.

Is that correct?

(Mind you, having a 7.4v 2S 1800mAh pack is a pretty good excuse to spend a lot of time with my heli!)
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Old Nov 14, 2004, 07:58 AM
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[QUOTE=Tonystott]
Quote:
Originally Posted by ebill3
What is the "battery sense wire"?? Mine came with just two power wires, so presumably you would need a double set of connectors.. battery-->Li-Saver-->ESC.

Is that correct?

(Mind you, having a 7.4v 2S 1800mAh pack is a pretty good excuse to spend a lot of time with my heli!)
Correct a y connector ,one set of leads to battery other to ESC. You can unplug(disconnect) the ESC while leaving the pack connected thus maintaing the correct cell count.
I have used the Li-Saver and it works great. Now I am able to use my older brushed ESC with LiPoly packs without the fear of over discharging them.
New life for old electrics withou having to purchase new ESC just for LiPo compatibility.

Charles
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Old Nov 14, 2004, 01:12 PM
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I understood that the jeti esc (li-po advance model) only "read" the battery voltage each time it was connected to the the pack - dont believe it actually "re-senses" the voltage just by turning off the receiver as stated??

I have checked this on two models - one with BEC and one without BEC. The test was done by actually bench running the motors, shutting down, running, shut down, etc. The motor pack was left connected. With a voltmeter in line, the motor would contimue to run well below the Jeti 2.56 vols per cell LVC.

As to battery sense wires, we must be talking about different devices. The Li-Saver I am referring to has two JR type connectors to be connected between the receiver and the ESC, AND a third pair of wires that are to be connected to the motor battery. In order to work as I described in the original post, those battery sense wires must be connected to the battery side of the ESC/motor battery connector. See photo at:http://flydma.com/lithium/lithium.asp?path1=lithium
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Old Nov 14, 2004, 01:29 PM
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That is the same Li-Saver which I use. Instead of connecting battery sesory wire to battery side of ESC I used(made) a y connector harness so that i could unplug the ESC from the power source without disconnecting the Li-Saver.This also makes it much easier to mover from one aircraft / ESC to another one.

Charles

Charles
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Old Nov 14, 2004, 02:02 PM
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Ah, yes. I failed to menmtion that I break the battery sense leads with a small Deans connector set so that I can remove the motor battery and leave the Li-Saver in the airplane.
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