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Electric Stunt => Gettin all AMP'ed up! => Topic started by: REX1945 on August 17, 2015, 12:36:15 PM
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Folks,
The only electric airplane I have is an RC glider that uses a 3S pack with 35 Amp max draw.
I usually fly until the 3S pack is about 10.5 Volts total.
Recently, I forgot to unplug the pack after a short flight thinking I would go up
later in the day and it never happened.
Two days Later I removed the battery which had been powering the servos and Rx with a low
current draw 20ma or so...and the pack was discharged to 4.5 V total for 3 cells.
I thought that I had destroyed the batteries as the charger (Passport system) would not attempt charging.
After the battery sat on the bench for 2 days (disconnected), it registered a voltage of 8.5 Volts and took a full
charge to 12.55 V with all cells the same within .01 V. No bulging was observed and the battery seems ok.
How did I get away with it ?
Rex
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lucky maybe?
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If it were me I'd keep the battery for sport flying, but not next to a pile of oily rags.
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Hey Rex...... you thinking of putting down the 4strokes and going electric?
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Rex,
Do you have a separate battery for electronics other than motor? You might try it that way as the control remains live. If it is the only energy source, I probably would not fly it unless you can test it at flying discharge loads. In addition, you can get some useful information from some chargers that report internal resistance of individual cells. All that said, probably not useful for flying and likely ruined.
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It is unlikely that you have damaged the battery.
I have 4 lipos that were totally discharged. By that I mean that the voltage was driven below the level at which they would charge. All of these batteries are used a minimum of 3 times every week. Two of them have been in constant service for over 8 years.
When hooked up to the charger for recharge each battery threw off an error message indicating that the voltage was too low. I thought that they were ready for the garbage dump. Fortunately I called the tech folks at Thunder Power and they told me how to revive them.
Here is what you should do if you drive the battery charge so low that it will not accept a charge.
Set your charger battery type to NICAD and the amperage to 0.2 amps. Charge the battery until the voltage reads a MINIMUM of 13 volts. This takes a fair amount of time due to the extremely low amperage level so make sure you have a couple of hours available. Once the voltage reads 13 volts or higher stop the NICAD charge.
Switch the battery type back to LIPO and set the normal amperage level that allows you to do a normal BALANCE charge of 1C. Charge the battery. As long as the battery has not been destroyed it should recover.
Since no one with a working brain leaves a battery alone while it is on charge you can do a periodic check to see that the temp is OK and that there is no abnormal swelling of the battery. If either of things occur stop the charge immediately and toss the battery into a pail of salt water. Once any charge has been removed (this normally takes 4 - 7 days) toss the battery in the garbage as it is simply too dangerous to use.
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Eric, just checking that you wanted 13v for 3s, or was that for 4s. Good information, but would you risk a plane with it to start with, or use it for non-flight?
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I have run several batteries right to the point of exhaustion and beyond. If your charger supports it do it like Eric says. Otherwise get hold of an old Astro Flight 109 charger as it will charge anything at any rate. (Always use a balancer) Yes I would fly with the battery if it came right back to a full balanced charge. I would not get overly stressed about your batteries bursting into flame.
Kim
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In the interest of Science, I repeated Rex's experiment this very evening. Some of you may wonder how far an electric stunter will get on the second flight of a battery. The answer is just past the outside squares.
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Hey Rex...... you thinking of putting down the 4strokes and going electric?
Not really. The ratio of the 4s inventory to my remaining years to age 90 is about .6.
I have an OS .26, OS 52, and OS 90.
I have (1) Saito .30, (2) Saito .40, (2) Saito .56, (1) Saito .45, (2) Saito .65, and (1) Saito .72.
For the moment, I think I'll keep the electrics on RC gliders and sport planes.
I do have a Top Flite ARF Tutor that might be able to fly with an E-Flite .25, but I would have
to invest in a CL timer and the associated software as well as set of 4-6 batteries and, of course,
a more expanded prop collection. The big advantage would be that my ratio of flying time to
engine fiddling time would be much improved.
What voltage should I use to make the 25 replace an OS 40 2s or Saito 40 4s ?
Rex
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Fred:
I do not want to hijack Rex's thread but to answer your question.
I have recovered 3S, 4S and 5S batteries using this method. As long as you get somewhere above 13 volts that is sufficient for the normal chargers we use to be able to run the recharge (somewhere near the 12-15% of capacity range seems to be just about OK). I have also used these recovered batteries in models with no problems. The only exception to that was one 4S battery which was slightly swollen up (not badly but swollen all the same). That one I relegated to ground test status.
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In the interest of Science, I repeated Rex's experiment this very evening. Some of you may wonder how far an electric stunter will get on the second flight of a battery. The answer is just past the outside squares.
Even when using a BICAS? :)
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In the interest of Science, I repeated Rex's experiment this very evening. Some of you may wonder how far an electric stunter will get on the second flight of a battery. The answer is just past the outside squares.
WHAT.......YOU TOOK OFF WITH A RED LIGHT????
I guess the system isn't foolproof......
How are you going to modify the electronics to avoid this??,
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WHAT.......YOU TOOK OFF WITH A RED LIGHT????
I guess the system isn't foolproof......
Paul,
You'll have to excuse Howard on this one; we got really confused about how traffic controls
work in Canada a couple of weeks ago....
Rex
Quote from forum : "...I learned some of the finer points of Canadian traffic rules and etiquette on the way home, but I still don't know what a flashing green arrow means. ...." H Rush.
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Check your IR if your charger has that feature.
MM
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If I am trying to revive a LiPo pack I will generally do something similar to what Eric stated, but slightly different:
If it is the example pack (3S) and its below the threshold to charge, simply unplug the balance lead, and charge through the main lead with the charger set for 2S at a 1C rate or lower.
If the voltage is as you stated, @6-8v at rest, it should start to charge the pack.
If it doesn't, then its lower voltage even, and you can set the charger to 1S and try charging again.
If that doesn't work, then I revert to the other NiXx charge regime that Eric mentions.
Basically, if the battery voltage is below the 2.8-3.0V/cell voltage, the charger sees the pack as a lower cell count pack and won't start charging it at the voltage it should be at. So you have to "trick" the charger into seeing the pack as a lower cell count pack.
Another alternative is to figure out which leads are + and - on the balance tap, and use a small two prong adapter to charge each cell one at a time, to raise the pack overall voltage. This is helpful if you have one really low cell for some reason, and you can identify it. Some chargers don't like to charge packs with larger variances in cell voltage, and for this situation, doing this works well, using a multi-meter to find the offending cells.
Hope this helps and is understandable.
I would still fly the sailplane with this pack. As long as the BEC is working, its not likely to effect the Rx voltage, in my opinion.
Regards,
Chris
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In the interest of Science, I repeated Rex's experiment this very evening. Some of you may wonder how far an electric stunter will get on the second flight of a battery. The answer is just past the outside squares.
One sample is not statistically significant, so I did it again today. It's Tim Wescott's fault. His TUT seems to prefer being programmed with a battery at less than full 6-cell voltage, so once again I programmed the TUT, then went flying without changing the battery, watching the bright red LED while I waited for the motor to start. I only made it through the inside squares. Wind was calm.
The previous sample came out OK. I put more than 2700 mAhr into that battery (it's rated for 2700) after the discharge. IR actually went down. I have since put several flights on it.
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Howard,
Wasn't sure if you guys ever figured out the flashing green arrow thing or not. If the left turn arrow is flashing at the intersection it means you have the right of way to turn left. Once it stops flashing, it means you can still turn left but do not have the right of way to oncoming traffic. You can advance into the intersection and wait for oncoming traffic to clear and then proceed with your turn.
Alan
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Latest battery depletion incident required putting 2948 mAhr into the 2700 mAhr battery. IR went down on this one, too.
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My guess is that the extra mah are simply expended while the charger is doing the final balancing operations. Interesting that the IR goes down. I've no idea as to why that should be.
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Howard - Keep up the fine work. I'm sure your research will some day benefit all electric stunt flyers. That said, it would not surprise me if a higher quality battery, such as Thunder Power, would carry additional mah than that advertised. Something like an additional 10% perhaps. You should borrow someone's Zippy battery next time you go out to fly and repeat your experiment. It would be interesting to see how many mah's the Zippy would take.
Alan - I do not believe it is the left turn flashing green light that has Rex and Howard perplexed. It is the right turn flashing green near my home, at 116 and 72, that warns those turning right, with the right turn signal flashing green, to beware of approaching traffic from the left. Next time I see Rex and Howard (Raider Round-Up?), I will draw a diagram to illustrate this peculiarity and why it is the way it is.
Cheers