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Old Sep 28, 2011, 02:00 AM
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cbxer55's Avatar
Somewhere in central Oklahoma
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I have the fortune of working in large hangars, working on real aircraft. Flew my SR eight times today, using four batteries, all flown until lvc was hit. All charged normally, as they have done since I bought this bird. I am averaging about 6 minutes on 500 mahs, charging using the selectra stock charger.
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Old Sep 28, 2011, 06:29 AM
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United States, TX, Houston
Joined Aug 2011
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I have a dollar store egg timer, that I set for 6 minutes. When it dings, down comes the 120. Sometimes not so graceful, other times I land with style. So far, the E-Flight batteries seam to be holding up well.
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Old Sep 28, 2011, 08:18 AM
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United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by A Rdnek View Post
The only concern that I have with Pilgrim's rig is the possibility of heat build up inside the glass case, if you ever start charging bigger (3 or 4 cell) batteries.
Ron
Good point - I'm only charging one 500mAh and up to four 160mAh batteries at a time right now but that will no doubt change. Maybe I should put a thermometer in the tank and see how much the temp changes during charging. Good for the fish, good for the batts lol
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Old Sep 28, 2011, 08:39 AM
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United States, IA, Grinnell
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Originally Posted by 1Pilgrim View Post
Good point - I'm only charging one 500mAh and up to four 160mAh batteries at a time right now but that will no doubt change. Maybe I should put a thermometer in the tank and see how much the temp changes during charging. Good for the fish, good for the batts lol
I don't think you would any significant temp rise with these small batteries and charger.
But I think you would with a large charger and battery. If you ever start using a 50 or 100 watt charger working close to its peak potential, the charger itself produces a lot of heat. But hopefully the battery does not.
Ron
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Old Sep 28, 2011, 09:27 AM
NotAnotherMomentLostToSei zures
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United States, MA, Malden
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Originally Posted by Blackanthem View Post
I have a dollar store egg timer, that I set for 6 minutes. When it dings, down comes the 120. Sometimes not so graceful, other times I land with style. So far, the E-Flight batteries seam to be holding up well.
EXCELLENT!! By staying with a low fly time, you will stay way within the 80% rule.

EFLight stock batt= 500mah
500mah X .8 = 400mah.

If your charger is capable of counting ma's put back into your batt and you don't exceed 400ma's put back, you are golden

I was testing an LVC devise on my 2S battery (750mah) the other day.
750 X .8 = 600mah. I ended up putting back 806ma's. Not good really but, it was within the correct voltages for each cell and total at the end of the flight! As you can see, I normally don't pay attention to the LVC, unless of course it kicks in for any reason that could mean trouble. Bad batt, binding, etc... Bottom line, that LVC devise will now sit on my bench collecting dust

Mike.
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Old Sep 28, 2011, 11:45 AM
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United States, WI, Sheboygan
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Quote:
Originally Posted by A Rdnek View Post
I don't think you would any significant temp rise with these small batteries and charger.
But I think you would with a large charger and battery. If you ever start using a 50 or 100 watt charger working close to its peak potential, the charger itself produces a lot of heat. But hopefully the battery does not.
Ron
Heat transfers from place to place in 3 ways, conduction, convection and radiation:

Conduction - most efficient. With the batts and chargers sitting on ceramic tile a good part of the heat should be conducted down and out through the floor, helping to keep temps down.

Convection - less efficient than conduction, more than radiation. This is where the tank volume could be an issue; in that case I can always get a bigger tank. Bigger fish, bigger batts, bigger tank .

Radiation - least efficient. Even though no visible light is emitted, some radiation does come from the batts and chargers. However, it passes through the glass walls and is also converted to heat by the nearby mesh/tile cover so its impact should be negligible.

Bottom line, it pays to be aware of temp buildup
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Old Sep 28, 2011, 11:53 AM
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United States, WI, Sheboygan
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Originally Posted by Chap1012 View Post
EXCELLENT!! By staying with a low fly time, you will stay way within the 80% rule.

EFLight stock batt= 500mah
500mah X .8 = 400mah.

If your charger is capable of counting ma's put back into your batt and you don't exceed 400ma's put back, you are golden

I was testing an LVC devise on my 2S battery (750mah) the other day.
750 X .8 = 600mah. I ended up putting back 806ma's. Not good really but, it was within the correct voltages for each cell and total at the end of the flight! As you can see, I normally don't pay attention to the LVC, unless of course it kicks in for any reason that could mean trouble. Bad batt, binding, etc... Bottom line, that LVC devise will now sit on my bench collecting dust

Mike.
Thanks for posting these numbers again, Mike. All I have is a volt meter; is there a way to relate voltage drop to mAh? My batts consistently read 3.79V to 3.81V after a 5 minute flight.

I can't rely on the LVC at all because my eyesight is so bad and also because the heli is pointing away from me so little of the time. Fortunately my tx has a countdown timer; in a pinch I can also use the countdown timer on my cell phone.
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Old Sep 28, 2011, 11:57 AM
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Somewhere in central Oklahoma
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Quote:
Originally Posted by A Rdnek View Post
I don't think you would any significant temp rise with these small batteries and charger.
But I think you would with a large charger and battery. If you ever start using a 50 or 100 watt charger working close to its peak potential, the charger itself produces a lot of heat. But hopefully the battery does not.
Ron
I have one Esky charger for two, three and four cell packs. The dang thing has a fan built into it to keep it cool.

THe batteries do not get hot when charging, but the charger does get warm.
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Old Sep 28, 2011, 01:11 PM
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United States, WI, Sheboygan
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Originally Posted by cbxer55 View Post
I have one Esky charger for two, three and four cell packs. The dang thing has a fan built into it to keep it cool.THe batteries do not get hot when charging, but the charger does get warm.
So convection may be a bigger deal than I thought when it comes to keeping a charging station cool. Maybe I need think about ventilating my tank.

On the other hand, if I have a fire then the smoke and fumes will not be confined to the tank. What to do, what to do?

Okay, an ounce of prevention is worth a pound of cure. Most if not all of the fires I've read about were preventable through good safety practices. With proper battery management I should be able to prevent a fire in the first place.

In the unlikely event fire does break out at least the house won't burn down, and with working smoke detectors I can deal with the smoke. Conclusion: ventilating the tank seems to be the way to go.
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Old Sep 28, 2011, 03:59 PM
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USA, FL, Fort Myers
Joined Jun 2008
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Quote:
Originally Posted by 1Pilgrim View Post
Thanks for posting these numbers again, Mike. All I have is a volt meter; is there a way to relate voltage drop to mAh? My batts consistently read 3.79V to 3.81V after a 5 minute flight.

I can't rely on the LVC at all because my eyesight is so bad and also because the heli is pointing away from me so little of the time. Fortunately my tx has a countdown timer; in a pinch I can also use the countdown timer on my cell phone.


on the lvc when mine kicks in it basicly falls slowly out of the air .
also have developed the shakes ????
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Old Sep 28, 2011, 04:06 PM
NotAnotherMomentLostToSei zures
Chap1012's Avatar
United States, MA, Malden
Joined Mar 2008
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Quote:
Originally Posted by 1Pilgrim View Post
Thanks for posting these numbers again, Mike. All I have is a volt meter; is there a way to relate voltage drop to mAh? My batts consistently read 3.79V to 3.81V after a 5 minute flight.

I can't rely on the LVC at all because my eyesight is so bad and also because the heli is pointing away from me so little of the time. Fortunately my tx has a countdown timer; in a pinch I can also use the countdown timer on my cell phone.
Those numbers are pretty close to 31% and maybe 40% of the used capacity of 4.20v. If you keep the post flight voltage around 3.85v, that's about 50% capacity of the 4.20v pack. This would be better.

I have a stock Eflight that I haven't flown and was not paying attention to the voltage. There are 13 (5 minute) easy "newb" flights on it and it reads: 3.75v. I don't like this number so, I'm throwing it in the charger and see how many ma's are put back in. This will give me a better "flight time" and it will certainly not be 5 minutes.

I will edit this post at the end of the charge/test: Results of charge

Stock Eflight battery: Charge time, 66:51 Minutes. Charging amps: .5A. ma's replaced in battery: 417 ma's. Resting voltage after 30 minutes; 4.16v (not great).....(remember the 80% rule; mah X .8 = ma's replaced [500mah X .8 = 400ma's]) I went past the 400ma's that was the ceiling by 17ma's. Now I know that the fly time must be cut down. But, how much? I will take one minute of fly time off until I can get the replaced ma's under 400 "for that batt." !!! I will now go 4 minutes fly time and just exercise it for now.

The safe bet is to keep the end (resting voltage) under or at 3.85v (about 50% capacity of that batt).

Now, what to do with this charged battery...? It is too windy

Mike.
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Last edited by Chap1012; Sep 28, 2011 at 06:37 PM. Reason: Results from charge
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Old Sep 28, 2011, 06:33 PM
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Virginia Beach
Joined Dec 2009
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Quote:
Originally Posted by 1Pilgrim View Post
So convection may be a bigger deal than I thought when it comes to keeping a charging station cool. Maybe I need think about ventilating my tank.

On the other hand, if I have a fire then the smoke and fumes will not be confined to the tank. What to do, what to do?

Okay, an ounce of prevention is worth a pound of cure. Most if not all of the fires I've read about were preventable through good safety practices. With proper battery management I should be able to prevent a fire in the first place.

In the unlikely event fire does break out at least the house won't burn down, and with working smoke detectors I can deal with the smoke. Conclusion: ventilating the tank seems to be the way to go.
Judging from my now extensive experience with burning a battery, i wouldn't worry about fanning the batts that you are now charging. If, however, you check the batteries as they are charging or when done, and they are too warm--that's when I'd worry about how hot they get. Maybe it's just me, but I think I'd be more worried about the glass cracking/breaking with a sudden hot burn. If it did, the burning battery could drop out and the smoke is definitely out.

Mike, do you think that would be a problem?
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Old Sep 28, 2011, 06:49 PM
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United States, MI, Livonia
Joined Apr 2009
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Originally Posted by rcphreak View Post
on the lvc when mine kicks in it basicly falls slowly out of the air .
also have developed the shakes ????
Same here even with my bad eyes I know when a 120SR LVC is on.. As it's on the ground someplace..
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Old Sep 28, 2011, 06:57 PM
NotAnotherMomentLostToSei zures
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United States, MA, Malden
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Originally Posted by Saxguy1000 View Post
Judging from my now extensive experience with burning a battery, i wouldn't worry about fanning the batts that you are now charging. If, however, you check the batteries as they are charging or when done, and they are too warm--that's when I'd worry about how hot they get. Maybe it's just me, but I think I'd be more worried about the glass cracking/breaking with a sudden hot burn. If it did, the burning battery could drop out and the smoke is definitely out.

Mike, do you think that would be a problem?
First, any charging lipo should NOT get hot or even warm (IF YOUR LIPO DOES GET WARM OR HOT DISCONNECT CHARGING PROCESS AT ONCE). They only get warm during discharge. As I said before ordinary glass is not a good insulator of/for heat. Glass will break under high heat and it doesn't have to be exposed to heat that long. Here are some lipo fires. I believe there are some with lipos in an aquarium. Very quick though.

http://video.google.com/videoplay?do...60570423705609

Mike.
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Old Sep 28, 2011, 08:02 PM
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Holy crud. Hear how that lipo whooshed? That was what happened to me. Fortunately--and maybe since I had already turned off the charge--it did not flame up as bad as that. The smoke was heavier, however.

I think I have lipo PTSD now. :0
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