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Old Jan 26, 2015, 10:57 PM
The Curse of the Flying Scroll
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Lipo Ignition Batteries, No Good in Gassers ?

I heard somewhere once that lipos can't take the vibration of gassers. Since I have been using 3 of mine from a 40" electric's motor power to run the ignition in my 25cc gasser, the voltage droop has increased dramatically, even with only .5 amps out of the the 3S 1500 20C. 500mah discharge and they droop to about 11.8v now.

So, has it been proven that lipos can't take the vibration of a gasser ?
And then how about the Turnigy Nano Tech LifePo4 receiver batteries ? Does vibration crumble the electron highways in them also, as I think what is might be happening to the lipos ?
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Old Jan 27, 2015, 12:30 AM
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Keeping them charged is likely the main culprit.
Lipos have no issue with vibration that is known.

LiFePo4 should work great.

mw
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Old Jan 27, 2015, 12:37 AM
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Quote:
Originally Posted by Chophop View Post
I heard somewhere once that lipos can't take the vibration of gassers. Since I have been using 3 of mine from a 40" electric's motor power to run the ignition in my 25cc gasser, the voltage droop has increased dramatically, even with only .5 amps out of the the 3S 1500 20C. 500mah discharge and they droop to about 11.8v now.

So, has it been proven that lipos can't take the vibration of a gasser ?
And then how about the Turnigy Nano Tech LifePo4 receiver batteries ? Does vibration crumble the electron highways in them also, as I think what is might be happening to the lipos ?
If you're worried about vibration, consider those A123 cells. They have an aluminum case, and their internals are configured with copper sheets and copper rivets for connections. Yeah I tested that some 5 years ago by a really bad screw up on my part.
http://www.wattflyer.com/forums/showthread.php?t=58745

There are several places that will build up your A123 packs. Or, you can save 50% by building up your own.

http://www.wattflyer.com/forums/showthread.php?t=67896

A dead A123 cell won't open circuit like a LiPo. I've got one from a club member that was at 0.5 volts DC for over a year. It was "Jump Started" with my variable power supply, and tested. Still performs like a new battery while pulling 15 Amps. BUT, it won't hold a charge, its again at 0.5 volts DC after a month on the shelf.

RadicalRC will build up your A123 packs.
http://www.radicalrc.com/category/A123-Cells-Packs-199
Select this unit
A123 Life Nano Phosphate 2S 2500mah Receiver Pack

A123's will far outlast those Nih battery packs. I've got some that are 7 years old that still perform exactly identical to a brand new unit. And, they hold 95% of their charge for over a year, just sitting on your shelf. Store them at full charge, half charge, don't matter much. Just don't leave the receiver switch on for a week. Not good.

I used to buy A123's from Voltmanbatteries, but they've dropped selling them. I just purchased five A123's from this place, and got them the next day. Word of warning, you absolutely must use a Weller 100 Watt temperature regulated soldering iron to solder to these cells. they DO NOT come with solder tabs. And, no, a 100 watt soldering gun will not work. Period.
http://www.buya123batteries.com/ANR2...300475-306.htm
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Old Jan 27, 2015, 07:42 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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A buddy was killing his batts until he found this particular engine had a big problem drawing too much current. Someone told him to go for one of the ign. systems from HK . No trouble since with the lower current draw. He's using li-ion batts.

Gord.
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Old Jan 27, 2015, 07:53 AM
The Curse of the Flying Scroll
Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
9,162 Posts
I can visualize how vibration can crack and break the huge number of micro wires in these batteries. They are made of tiny hair like paths with ions attached to provide free electrons. I will before my next flight begin wrapping my batteries completely in foam and attach them so they can't vibrate.

Electric planes, no problem. Gassers, yes. My bet. Gasser RC airplanes would be a great thing for engineering students to learn vibration control with. Sure are a good source of it.
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Old Jan 27, 2015, 08:59 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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When I was into gassers, everything but the servos were wrapped in about 1 in. of foam. My car seats looked kinda naked.
Had no troubles with broken wires. Had to use slide switches on everything as toggle switches would vibrate apart in short order.

Gord.
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Old Jan 27, 2015, 12:55 PM
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Originally Posted by Chophop View Post
I can visualize how vibration can crack and break the huge number of micro wires in these batteries. They are made of tiny hair like paths with ions attached to provide free electrons. I will before my next flight begin wrapping my batteries completely in foam and attach them so they can't vibrate.

Electric planes, no problem. Gassers, yes. My bet. Gasser RC airplanes would be a great thing for engineering students to learn vibration control with. Sure are a good source of it.
Yeah,

Three years ago, I bought an accelerometer microchip, and connected it to one of my PicChip microcontrollers. That unit was calibrated to read plus/minus maximum of 25 G's.

Putting that accelerometer chip on the aileron servo of a club members giant scale 150 cc gasser, it pegged the reading at over 25 G's. It's a wonder our radio equipment works at all.

Back in the 1960's that was not the case. I had one radio that only lasted around 25 flights between radio servo failures. Actually wrote an article published in the defunct RCM magazine on how to keep vibration out of your servos.

http://www.wattflyer.com/forums/showthread.php?t=66525
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Old Jan 27, 2015, 01:09 PM
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United States, WA, Woodinville
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Originally Posted by vollrathd View Post
If you're worried about vibration, consider those A123 cells. They have an aluminum case, and their internals are configured with copper sheets and copper rivets for connections. Yeah I tested that some 5 years ago by a really bad screw up on my part.
http://www.wattflyer.com/forums/showthread.php?t=58745

There are several places that will build up your A123 packs. Or, you can save 50% by building up your own.

http://www.wattflyer.com/forums/showthread.php?t=67896

A dead A123 cell won't open circuit like a LiPo. I've got one from a club member that was at 0.5 volts DC for over a year. It was "Jump Started" with my variable power supply, and tested. Still performs like a new battery while pulling 15 Amps. BUT, it won't hold a charge, its again at 0.5 volts DC after a month on the shelf.

RadicalRC will build up your A123 packs.
http://www.radicalrc.com/category/A123-Cells-Packs-199
Select this unit
A123 Life Nano Phosphate 2S 2500mah Receiver Pack

A123's will far outlast those Nih battery packs. I've got some that are 7 years old that still perform exactly identical to a brand new unit. And, they hold 95% of their charge for over a year, just sitting on your shelf. Store them at full charge, half charge, don't matter much. Just don't leave the receiver switch on for a week. Not good.

I used to buy A123's from Voltmanbatteries, but they've dropped selling them. I just purchased five A123's from this place, and got them the next day. Word of warning, you absolutely must use a Weller 100 Watt temperature regulated soldering iron to solder to these cells. they DO NOT come with solder tabs. And, no, a 100 watt soldering gun will not work. Period.
http://www.buya123batteries.com/ANR2...300475-306.htm


I use a capacitive discharge spot welder to attach tabs to cells, it's easier and safer than soldering. Cost me about $100 to build, it's little more than about 1 Farad of capacitors, a variable 24V power supply and a big SCR that came from an old forklift motor drive.
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Old Jan 27, 2015, 01:26 PM
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I use a capacitive discharge spot welder to attach tabs to cells, it's easier and safer than soldering. Cost me about $100 to build, it's little more than about 1 Farad of capacitors, a variable 24V power supply and a big SCR that came from an old forklift motor drive.
I've often thought about making one like that. I've got a couple of 150,000 uF caps rated at 55 Volts DC and very high currrents. Also got a variable DC power supply, and high powered SCR's are readily available from places like Digikey.

http://www.digikey.com/product-detai...069-ND/1996052
http://www.digikey.com/product-detai...20GI-ND/359074


What thickness of copper strapping can your setup spot weld?
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Old Jan 27, 2015, 03:06 PM
The Curse of the Flying Scroll
Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
9,162 Posts
My ultralights vibration would destroy instruments quickly. I made vibration isolators with Dubro 514 foam and never replaced one again, several hundred flight hours. Got a bit over 350 hours in my CGS Hawk.
I'll order some and build a similar setup for a battery holder. Man it was handy to post this, I had not remembered the trick to that. Those EGT/CHT , Tach gauges were delicate needle pointer types. The airspeed, altimeter and vertical speed indicators were for full scale airplanes and help up to it but I isolated them anyway. The basic idea is to attach four corner squares and one center square of foam, epoxy one side to airframe, the top side is epoxied the plank the battery(s) sit on.
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Old Feb 03, 2015, 02:26 PM
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United States, WA, Woodinville
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Originally Posted by vollrathd View Post
I've often thought about making one like that. I've got a couple of 150,000 uF caps rated at 55 Volts DC and very high currrents. Also got a variable DC power supply, and high powered SCR's are readily available from places like Digikey.

http://www.digikey.com/product-detai...069-ND/1996052
http://www.digikey.com/product-detai...20GI-ND/359074


What thickness of copper strapping can your setup spot weld?

The strapping I use is nickel, I don't think it would work well to weld copper, that and aluminum are too conductive, both electrically and thermally and are thus difficult to spot weld.

Those capacitors you have should work fine at that voltage. I found a deal on a pile of 22,000uF 25V caps so that's what I used. I've seen an older commercial unit that used 160V but I figured the currents involved were already dangerous enough without using that high a voltage.

You can find big stud mount SCRs on ebay cheaply. They were used in large motor drives in the 70s and 80s before good MOSFETs and IGBTs came about. I think the one I have in mine is rated 1500V 120A continuous but so far it has tolerated the ~10kA (measured) pulses, just a few nanoseconds long.

For the probes I used pieces of solid 6AWG copper grounding wire sharpened to points. I found some 2/0 finely stranded wire for big car stereo amps for the leads.
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