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donjiskra
10-04-2005, 06:11 PM
I've ruined two expensive LiPo batteries now by inadvertenly discharging to a level where they can't be recharged.
Yes I know about Li-Saver and have used it but my problem was:

1- I left the pack hooked up to the ESC overnight ansd discovered the next day that the ESC still draws from the pack (to keep control of the servos in the event the motor is shut down by the Li-Saver.
So from then on I always disconnect the pack when not intending to fly.

2-I had tested a new plane using the pack LiPo that was on the shelf
I noticed that the motor power test was weak so I tried to recharge. The Triton charger, (a great unit!!!), went into "battery low" mode at 8.4 volts and would not complete the charge. Consequently another dead battery.
Battery is (was), a TP 2100 3s2p pack.

What I'm looking for is a device with a circuit that can be connected to the battery that will not allow the voltage to drop below the 3.7v safe low limit. The device/circuit would be used at all times, even just setting on the shelf.

I love LiPo's, but this is getting too expensive!!!!

Any help would be appreciated. I'll fabricate such a circuit if you can provide a schematic.

Thanks,
Don

rcers
10-04-2005, 06:26 PM
Don all batteries half a self discharge rate. On LiPoly that is mighty low.

I suspect you are doing the damage while flying. If you use a good ESC with LVC that is set for 3v/cell. Then you take home and charge them and wait till you fly again.

I have never lost a pack yet....

hoppy
10-04-2005, 06:34 PM
Some modelers have had success charging a overdischarged LiPo at a low rate like 1/5C till the voltage came up to 3.3V/cell using the NiCd charge mode. This is dangerous and the process must be monitored at all times so the pack is not overcharged!
When the pack is at the 3.3V/cell level, it can be put on the Triton and charged normally. This may or may not work and the pack may puff or catch fire as overdischarged batteries may be damaged. If it were mine, I'd do it outside and forever after consider that pack suspect. The longer the cells have been in an overdischarged mode, the greater the damage.

The manufacturers recommend storing LiPo's at 1/2 charge if they are not going to be used for several weeks or more and using a LVC limit 3V/cell or above. I fly and charge mine right after flying - since they have a very low self discharge rate, they do not have to be topped off prior to flying.

When charging, I do it in a BBQ grill away from any combustible materials.

GeraldRosebery
10-05-2005, 01:40 AM
I've ruined two expensive LiPo batteries now by inadvertenly discharging to a level where they can't be recharged.
Yes I know about Li-Saver and have used it but my problem was:

1- I left the pack hooked up to the ESC overnight ansd discovered the next day that the ESC still draws from the pack (to keep control of the servos in the event the motor is shut down by the Li-Saver.
So from then on I always disconnect the pack when not intending to fly.

2-I had tested a new plane using the pack LiPo that was on the shelf
I noticed that the motor power test was weak so I tried to recharge. The Triton charger, (a great unit!!!), went into "battery low" mode at 8.4 volts and would not complete the charge. Consequently another dead battery.
Battery is (was), a TP 2100 3s2p pack.

What I'm looking for is a device with a circuit that can be connected to the battery that will not allow the voltage to drop below the 3.7v safe low limit. The device/circuit would be used at all times, even just setting on the shelf.

I love LiPo's, but this is getting too expensive!!!!

Any help would be appreciated. I'll fabricate such a circuit if you can provide a schematic.

Thanks,
Don

There is work around for the "battery low" warning. Put the pack on a NiCd setting for 10 cells and say 1 amp. This will bring the voltage up and allow the Triton to later detect a 3S pack. After ten minutes on the NiCd setting, set the Triton back to the Lithium Ion setting and try again. If the pack can be saved this should get it charged.

Greg Covey
10-05-2005, 02:31 PM
The subject of this thread is the very reason for the existence of the Discharge Protection Module (DPM) at FMA Direct.

Currently, we have a DPM for the Skyvolt line which is now shipping. This same DPM will be repackaged in a much smaller design (like a 5-amp ESC) for the new Cellpro line that will be released in a few months.

The Skyvolt DPM is larger because the power wires run through it due to the proprietary connector. The Cellpro line uses industry standard Dean's Ultra (or smaller) connectors and routs the DPM from the taps connector to an in-line ESC connection.

The purpose of the DPM is to monitor each cell during discharge so the weakest cell, not pack voltage, is used to determine motor cut-off. The DPM also has a switch selectable delay period for a 30 or 60 second warning before the pack is considered depleted. This warning pulses the ESC throttle control to warn the pilot that it is time to land. No more dead stick landings!

hoppy
10-05-2005, 02:45 PM
The subject of this thread is the very reason for the existence of the Discharge Protection Module (DPM) at FMA Direct.


That gadget looks great but it won't prevent the problems he had, will it? ESC left plugged in and pack going dead on shelf?

Matt Kirsch
10-05-2005, 05:26 PM
Hang on here... 8.4 Volts is the fully-charged voltage for 2-cell LiPoly.

Make sure that second pack is actually a 3S. It sounds like either it's a 2S pack, or one of the cells is completely dead. Trying to force-charge a 2S pack to 9.0V by mistake is a recipe for a fire.

Regardless of whatever electronic doodad you have, make it a habit of disconnecting the battery from the ESC immediately after landing. Not only do you prevent the battery from draining, you prevent the motor from accidentally starting.

Greg Covey
10-05-2005, 06:18 PM
hoppy,

Always so negative...must be the E-Zone personna. ;)

The DPM itself will not drain your pack for about 3-4 weeks. It also has an optional LED/Speaker module to warn you that you have left the pack plugged in after an hour and also when the initial warning occurs for pack depletion.

N3CLI
10-05-2005, 07:33 PM
Greg

Fred certainly does his homework as usual, and has done so over the many years since Ace.

When is your new transmitter being launched?

Will it have the open gimble Chidgey sticks?

Waiting for one on 6 meters.

Fred AMA68196:)

Fred Marks
10-05-2005, 10:12 PM
Dear Fred,

Together, we make Fred squared! Thank you for your kindness.

Don, this need not happen to you ever again unless you have the experience of the old-time Beech Bonanza pilot. When Beech first came out with the retract gear Bonanza, a lot of old time Cessna, Piper, etc pilots made a lot of wheels up landings, so a warning horn was installed. If you lowered flaps and/or throttled back below a certain level, a horn that could wake the dead sounded. Nonetheless, a guy was on final with the gear up. The tower operator kept screaming at him that his gear was up. The pilot comes back with "Say again, please, I can't hear you for this d--n horn! "

To make it easier, please go to www.fmadirect.com (http://www.fmadirect.com) and look for:

SV6S-SPKR https://www.fmadirect.com/images/products/2057_small.jpg (https://www.fmadirect.com/site/Detail.htm?item=2057&section=38) LED/Speaker Module (https://www.fmadirect.com/site/detail.htm?item=2057&section=38)
Accessory for SV6S-DPM, provides status information, comes with cable. You can do the search for the PN and it will take you right there.

donjiskra
10-05-2005, 11:31 PM
Gentlemen,
Appreciate your posts!!!
I am apprehensive of doing the NiCD charge method, sounds pretty risky!!!
Appreciate the FMA latest technology & innovation. Cool!!!
The DPM technology is awesome,the designers should get the Nobel Prize.

I did not see a 3S1P battery listed at the FMA site.

Also, I presented the discharge problem to an electronics tech. guy who said I needed a relay that would turn off at the required voltage.
Sounds simple, eh? I would only use this device when the battery is out of the plane and on shelf.

My ESC's have LVC so problem there. Ive learned NOT to leave the battery connectd when NOT flying.

Fred: loved the warning siren anecdote!! THANKS

Your support and comments are much appreciated.

Don

Fred Marks
10-06-2005, 12:39 AM
Don,

You must never use anything, relay or solid state, that cuts voltage completely as doing so could lose an airplane for you. The idea of an alert module is to warn and remind you to disconnect the battery. At my age, one thing I have found to be a certainty: if I absolutley, positively have to remember to disconnect something, it will be forgotten! If something screams at me "hey dummy, you forgot to disconnect" it, by George I may remember! I do remember that I could hear a Supernove alert anywhere in Gaithersburg!

We have 3s1P packs for a bunch of capacities. Look under

(https://www.fmadirect.com/site/fma.htm?body=Store)

hoppy
10-06-2005, 01:43 AM
I would only use this device when the battery is out of the plane and on shelf.
Don

I'm not sure what it is you want to disconnect. The battery pack has no connections that need to be, or that even can be disconnected. Are you thinking about the Lipo on the shelf that was under voltage? Was that pack new? Used? Fully discharged when put on the shelf? Fully charged? Lipo's, if sound, will hold a charge for a long, long, long time. There have been occasions when new packs have loss voltage. So tell us more about what it is you want to disconnect on the battery when it is on the shelf.

By the way, an ESC set for 3V/cell will protect your pack 99+% of the time if the pack is not overdischarged, and preferably if you stop flying when the power starts to fade and befor the LVC kicks in.

donjiskra
10-06-2005, 02:02 AM
I understand your comments completely.
Reckon my thinking is for a device/circuit the could be wired into the battery leads.
Evidently an ESC that has LVC will shut down the motor so why not have a similar circuit that could be used in the battery leads.
I repeat this is not for use in flight, only for protecting a battery from discharging.
Hope this helps?
Don

Fred Marks
10-06-2005, 03:35 AM
I understand your comments completely.
Reckon my thinking is for a device/circuit the could be wired into the battery leads.
Evidently an ESC that has LVC will shut down the motor so why not have a similar circuit that could be used in the battery leads.
I repeat this is not for use in flight, only for protecting a battery from discharging.
Hope this helps?
Don

Don,

I get as nervous as a long - tailed cat in a room full of rockers when any device is put in line that could, under any circumstances, cut power to the radio. I think old Henry Ford had it right when he said "Things that are left off do not cause trouble!" We could adapt the SV6S unit to send a cut-off to a relay or FET switch instead of the screamer, but I sure would lose sleep over it. Sometimes I toss and turn for 20 or 30 seconds now!

donjiskra
10-06-2005, 03:48 AM
Hey Fred,
You must be more fun than that "barrel of monkeys" possesing a great sense of logic is to be admired!!!

I would not want to have such a device/circuit working a radio. That would certainly be asking for disaster. I only want it for non-flight shelf sitting.

Keep 'em coming Fred. You are an inspiration!
Don