single a123 for ignition unit
11-12-2008, 04:16 PM
#27
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RE: single a123 for ignition unit
ORIGINAL: dick Hanson
Model ignitions are pretty low power requirement devices tho voltage on typical ignitions is 15000+ .
BUT it always takes more power to fire thru higher pressures.
This is why extremely high output ignitions were developed -for competition engines.
Most applications in passenger cars etc., neded high voltage with little amps - The gap plus the pressure is the condition which must be met.
ORIGINAL: liquid_TR
Well thats not really true, as the total coil turn ratio is probably around 1:4000 to actually turn 5V DC into AC and step it up to 20KV. (its actually made by first stepping up the 5V DC into a much higher potential AC by means of a small inverter in the ignition unit then stepping up that AC potential up to 20KV).
10KV can jump thru a couple of centimeters creating an arc discharge. there would be not much of a difference between using a 6V pack or 3.7V pack. both will create a suitable arc if they were stepped up directly without loss. The main reason the ignition unit wouldnt work below 3-2V DC is the inverter side electronics are actually cant work with such low voltages. If the transistors were chosen to work with those low voltages, we wouldnt have any problems using a single nicd cell. This is my theory. I actually never opened up a chinese ignition unit.
It takes MORE power to fire thru higher pressure in the combustion chamber.
10KV can jump thru a couple of centimeters creating an arc discharge. there would be not much of a difference between using a 6V pack or 3.7V pack. both will create a suitable arc if they were stepped up directly without loss. The main reason the ignition unit wouldnt work below 3-2V DC is the inverter side electronics are actually cant work with such low voltages. If the transistors were chosen to work with those low voltages, we wouldnt have any problems using a single nicd cell. This is my theory. I actually never opened up a chinese ignition unit.
BUT it always takes more power to fire thru higher pressures.
This is why extremely high output ignitions were developed -for competition engines.
Most applications in passenger cars etc., neded high voltage with little amps - The gap plus the pressure is the condition which must be met.
The actual voltage required to fire the spark depends on pressure, air/fuel mixture, plug, gap, and a few other requirements. Higher pressures = more air molecules must be ionized for the spark to jump => require higher energy levels.
When I posted the CH Ignitions link above I only looked at the table and didn't check their underlying premises or their test procedure. They ran their CH-RCEXL ignition on a controlled voltage, with the spark plug in open air, and triggered the hall sensor with a triggering device. Of course the plug will fire! The energy required to fire the plug depends greatly on the pressure at the plug gap! If they tested their theory with the plug in a pressure chamber I am certain the results would be different. As a corollary, the voltage required to fire the plug will also greatly decrease if the plug is put under a vacuum.
In fact many automobile distributor-less ignitions will fire when the piston reaches a certain point BTDC on both the compression and ignition strokes. The voltage across the plug under compression is much higher than during the exhaust stroke.
The ignition doesn't know or control the actual spark voltage. It merely charges the firing capacitor until the conditions-dependent critical voltage is reached, sending the spark to the plug. The ignition just pushes until it fires, and no further. In other words, if the output is capable of firing at 60kV, but the plug only needs 20kV to fire, all the overhead is excessive (unless it will charge FASTER to 20kV than a different system.
It is entirely possible to design an ignition system that will fire in a real-life situation (spark plug running the engine), but that will require a redesigned primary oscillator circuit. There may very well be an ignition system on the market that will work with a single A123 cell.
I hope I didn't mislead anybody with the CH Ignitions data I linked to regarding the voltage requirements of their CH-RCEXL system. They are a good company and very knowledgeable in these matters, but I applied their test data incorrectly, the fault is entirely my own.
11-12-2008, 04:52 PM
#28
RE: single a123 for ignition unit
ORIGINAL: BTerry
I had a big response typed up but RCU timed out. Oh well.
I had a big response typed up but RCU timed out. Oh well.
ORIGINAL: BTerry
The actual voltage required to fire the spark depends on pressure, air/fuel mixture, plug, gap, and a few other requirements. Higher pressures = more air molecules must be ionized for the spark to jump => require higher energy levels.
The actual voltage required to fire the spark depends on pressure, air/fuel mixture, plug, gap, and a few other requirements. Higher pressures = more air molecules must be ionized for the spark to jump => require higher energy levels.
11-12-2008, 05:31 PM
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RE: single a123 for ignition unit
ORIGINAL: captinjohn
RTK Sounds like the A123,s are going to work fine. Could anyone recomend any low cost chargers to use with the A123 cells? Are they the same cells that power many cord-less drills...ect on the market? Thanks capt,n
ORIGINAL: RTK
Well, I put twelve flights on my A123's with no regulator on an RCxel ignition v-2. So far so good.
The difference between nano and non nano 123 batteries, as I understand it simplistically, is the nano are capable of higher burst and discharge rates. Whether nano or non nano Li fe all should work for an ignition and are probably insignificant in difference when it come to a flight pack too. Not much difference between 30 amp or 60++ amp discharge rate when it come to my airplanes.
Well, I put twelve flights on my A123's with no regulator on an RCxel ignition v-2. So far so good.
The difference between nano and non nano 123 batteries, as I understand it simplistically, is the nano are capable of higher burst and discharge rates. Whether nano or non nano Li fe all should work for an ignition and are probably insignificant in difference when it come to a flight pack too. Not much difference between 30 amp or 60++ amp discharge rate when it come to my airplanes.
11-13-2008, 12:38 AM
#30
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RE: single a123 for ignition unit
Well, for those interested in running on a single A123 with the under $5/- voltage step up unit, I can report that it works very well, big fat spark, engine starts easily and holds WOT without issues.I reckon with the 2300mah capacity you can fly all day and have some left. A quick charge thru the charge socket as its a single cell and I'm ready for flight again!
11-13-2008, 08:14 AM
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RE: single a123 for ignition unit
This is a good comment here......Are we creating a problem where none exists? These are stick and covering model planes, not F-22 Raptors.. On my RCExcell I use a simple 1200 MA. NiMH, top it before flying, and fly a usual day of five flights of 10-12 min. each.. The 50cc, and 46cc engines have never dropped a beat..
Can someone convince me to buy an expensive battery that's dangerous to charge in the plane, that may explode, or catch fire ..A battery that has to be charged , and stored, in a metal coffee can........This is progress?
11-13-2008, 09:39 AM
#32
RE: single a123 for ignition unit
A pair of 1100 ma A123 cells is neither expensive or a safety risk and far out perform heavier Nicad/NiMh. 10 12 bucks a pair and 3 ounces for the pack
and a dozen flights on a single cyl gasser
What could be better .
and a dozen flights on a single cyl gasser
What could be better .
11-13-2008, 09:50 AM
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RE: single a123 for ignition unit
I think you will find that the low voltage dropout level is not the ignition, it's the Hall sensor that quits working at low voltage.
11-13-2008, 10:02 AM
#34
RE: single a123 for ignition unit
ORIGINAL: eugene
This is a good comment here......Are we creating a problem where none exists? These are stick and covering model planes, not F-22 Raptors.. On my RCExcell I use a simple 1200 MA. NiMH, top it before flying, and fly a usual day of five flights of 10-12 min. each.. The 50cc, and 46cc engines have never dropped a beat..
Can someone convince me to buy an expensive battery that's dangerous to charge in the plane, that may explode, or catch fire ..A battery that has to be charged , and stored, in a metal coffee can........This is progress?
This is a good comment here......Are we creating a problem where none exists? These are stick and covering model planes, not F-22 Raptors.. On my RCExcell I use a simple 1200 MA. NiMH, top it before flying, and fly a usual day of five flights of 10-12 min. each.. The 50cc, and 46cc engines have never dropped a beat..
Can someone convince me to buy an expensive battery that's dangerous to charge in the plane, that may explode, or catch fire ..A battery that has to be charged , and stored, in a metal coffee can........This is progress?
LiPo have now been around for a long time. Precautions are well known at this time. Gasoline you pump into you car is flammable and you probably don't think twice. You could drown in the water that you drink too. You can choose what works for you. I have many LiPo samples many years old now. other than a few puffed cells I haven't had one burn up.
11-13-2008, 06:05 PM
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RE: single a123 for ignition unit
Before this turns into a flame thread, we are talking about A123's which are not Lipos and do not have the exploding traits of the lipos. I bought 5 packs of the 1100 mah's at Walmart for 7 dollars a pair, so they aren't expensive. I have no problem running the nicads but am always open to new ideas. That's what this hobby is all about, otherwise everyone at the field would be flying the same plane with the same motor same prop, same fuel and same radio.
11-13-2008, 06:54 PM
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RE: single a123 for ignition unit
I'm not Jim 
, but the Walmart near me had them in the power tool department. The are Black & Decker VPX tool batteries. They were on sale for $7 a pack. Each pack has two 1100mah A123 cells in it.
My buddy and I bought all they had.
Rick
, but the Walmart near me had them in the power tool department. The are Black & Decker VPX tool batteries. They were on sale for $7 a pack. Each pack has two 1100mah A123 cells in it.My buddy and I bought all they had.
Rick
11-13-2008, 07:14 PM
#38
RE: single a123 for ignition unit
ORIGINAL: 61ahs
I'm not Jim, but the Walmart near me had them in the power tool department. The are Black & Decker VPX tool batteries. They were on sale for $7 a pack. Each pack has two 1100mah A123 cells in it.
My buddy and I bought all they had.
Rick
I'm not Jim
, but the Walmart near me had them in the power tool department. The are Black & Decker VPX tool batteries. They were on sale for $7 a pack. Each pack has two 1100mah A123 cells in it.My buddy and I bought all they had.
Rick
These are now discontinued items in store
try on line ,but be preparred to spend 19.00(one pack) a pair
You will need a decent charger get Cell Pro 4 from FMA Direct. 50 bucks
11-14-2008, 07:59 PM
#39
RE: single a123 for ignition unit
Right now Menards has a small portable Black & Decker screwdriver (VPX1101) for 1/2 price right now. You get a nice charger, case and battery pac. $14.95...was about $30! I got one for my sone in Law. Capt,n P.S. I bet you can have them UPS one from any store that has them in stock. ADDED http://www.vpxsystem.com/
