IMAA's Marez speaks out on parallel systems
03-25-2005, 10:10 AM
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IMAA's Marez speaks out on parallel systems
Eloy Marez writes in High Flight, Spring 2005
“ON THE SAME SUBJECT, somewhat anyway, is the use of a backup battery system. I know it is commonly thought and done that the best (read: cheapest!) way is simply to plug another battery into an unused servo socket in the receiver. That is fine - but only a long as everything is fine! In the event of a discharged or defective cell in one of the packs, the good battery will attempt to charge it. That is the way battery charging is done my friend, a higher voltage is applied and charging current flows.
I have tested this and, using a professional quality ammeter, found that a good 4-cell NiCd battery will charge a defunct one at three amperes. Right three amps. This rate will deplete the good one very rapidly, enough so that it too will good [go] bad before the end of your flight if the first one fails soon after takeoff.
The Cermark Company to the rescue - it has recently introduced its new 'Power Backer’, which takes a secondary normally less capacity battery along for a ride and switches it in if the primary one goes low. It will then light a red LED so you can know that you landed on the backup battery – the important thing is that you were able to get back under full control.
The rest of the good news is that Cermark's unit priced at only $19.95 - about halt of all other similar devices, around.”
With all the modelers successfully employing the simple parallel pack/dual
switch system over the last decade, Mr. Marez wants to complicate the system
by adding more complexity. One has to wonder if he ever did a thorough
failure analysis comparing the two options for reliability. We won't get
into the probability of a pack failing in flight after a good preflight ESV
check or the reliability of a redundant path vs. single path, or the
charge/discharge characteristics of Ni-Cds . . .or the hundreds of flight
hours of giant scale models with no failures using the parallel pack/dual
switch system.
“ON THE SAME SUBJECT, somewhat anyway, is the use of a backup battery system. I know it is commonly thought and done that the best (read: cheapest!) way is simply to plug another battery into an unused servo socket in the receiver. That is fine - but only a long as everything is fine! In the event of a discharged or defective cell in one of the packs, the good battery will attempt to charge it. That is the way battery charging is done my friend, a higher voltage is applied and charging current flows.
I have tested this and, using a professional quality ammeter, found that a good 4-cell NiCd battery will charge a defunct one at three amperes. Right three amps. This rate will deplete the good one very rapidly, enough so that it too will good [go] bad before the end of your flight if the first one fails soon after takeoff.
The Cermark Company to the rescue - it has recently introduced its new 'Power Backer’, which takes a secondary normally less capacity battery along for a ride and switches it in if the primary one goes low. It will then light a red LED so you can know that you landed on the backup battery – the important thing is that you were able to get back under full control.
The rest of the good news is that Cermark's unit priced at only $19.95 - about halt of all other similar devices, around.”
With all the modelers successfully employing the simple parallel pack/dual
switch system over the last decade, Mr. Marez wants to complicate the system
by adding more complexity. One has to wonder if he ever did a thorough
failure analysis comparing the two options for reliability. We won't get
into the probability of a pack failing in flight after a good preflight ESV
check or the reliability of a redundant path vs. single path, or the
charge/discharge characteristics of Ni-Cds . . .or the hundreds of flight
hours of giant scale models with no failures using the parallel pack/dual
switch system.
03-25-2005, 10:14 AM
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RE: IMAA's Marez speaks out on parallel systems
I would think that 99.9% of battery failures in flight are open packs (i.e. vibration breaks the tabs) anyway so basically the backer device is useless for that scenario. I have never seen a shorted cell in flight, only during charging.
I have been using the simple setup and it has served me very well.
KISS prevails.
DP
I have been using the simple setup and it has served me very well.
KISS prevails.
DP
03-25-2005, 10:39 AM
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RE: IMAA's Marez speaks out on parallel systems
ORIGINAL: desertpig
I would think that 99.9% of battery failures in flight are open packs (i.e. vibration breaks the tabs) anyway so basically the backer device is useless for that scenario. I have never seen a shorted cell in flight, only during charging.
I have been using the simple setup and it has served me very well.
KISS prevails.
DP
I would think that 99.9% of battery failures in flight are open packs (i.e. vibration breaks the tabs) anyway so basically the backer device is useless for that scenario. I have never seen a shorted cell in flight, only during charging.
I have been using the simple setup and it has served me very well.
KISS prevails.
DP
03-25-2005, 10:43 AM
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RE: IMAA's Marez speaks out on parallel systems
I happen to agree with Mr. Marez. The only way to reliably provide for backup is to isolate the packs.
Contrary to what Desertpig says the most prevalent mode of failure is a shorted cell, not open. I'm not saying that it never happens but rather packs do fail in the shorted cell mode more often than the open cell (broken tabs) mode.
Red, one could argue that adding the additional pack, without regard to the most prevalent mode of failure, increases the chance of experiencing the most prevalent mode of failure by a factor of two times.......in other words you've decresed the reliabilty of the system by adding components that could concievably cause an electrical contention if one or the other fails. That's not what you're looking for, is it?
When designing reliabilty into a system one must always consider all modes of failure and then assure that the most likely is covered. Simply plugging another pack, via a second switch is not covering the most prevalent failure mode.
I'm an EE and have much experience with designing redundancy into a system.
Contrary to what Desertpig says the most prevalent mode of failure is a shorted cell, not open. I'm not saying that it never happens but rather packs do fail in the shorted cell mode more often than the open cell (broken tabs) mode.
Red, one could argue that adding the additional pack, without regard to the most prevalent mode of failure, increases the chance of experiencing the most prevalent mode of failure by a factor of two times.......in other words you've decresed the reliabilty of the system by adding components that could concievably cause an electrical contention if one or the other fails. That's not what you're looking for, is it?
When designing reliabilty into a system one must always consider all modes of failure and then assure that the most likely is covered. Simply plugging another pack, via a second switch is not covering the most prevalent failure mode.
I'm an EE and have much experience with designing redundancy into a system.
03-25-2005, 11:03 AM
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RE: IMAA's Marez speaks out on parallel systems
From one that is also and EE and PE and has 30+ years in the design and application of battery systems . . . .
You need to understand the nature of cell shorts and how they occur in your "reliability analysis".
A short develops in a Ni-Cd or Ni-Mh when conductive particulate bridge the separator or the separator itself deteriorates to the point where it allows the positive and negative plates to touch. Rarely does the short occur all at once but rather building up a very small conductance path termed "soft shorts". In a charged cell the energy in the cell will blow away any short as it tries to develop. You've heard about "zapping" cells. The cell actually zaps itself before the short can develop. Only in cases of severe overcharge at high rates can the separator melt down to the point where the plates contact each other (hard short). In this case the energy in the cell then dumps and we have what is referred to as a hot steamer, the electrolyte boils, nylon in the separator melts down and is forced by the steam through the vent. On some occasions the vent is clogged by the molten nylon separator and becomes inoperative causing the cell to rapidly disassemble. So under normal circumstances a cell maintained at some state of charge is much less likely to short than a cell that is completely discharged. It should be noted however that the self discharge increases rapidly in cells where there is a short building (high resistance -soft short) due to separator deterioration and/or cadmium migration. One other shorting mechanism is a manufacturing defect where the positive or negative collector tab bridges the opposite plate. These usually fall out before the cells are shipped or assembled into batteries.
Bottom line: After a good ESV check, the probablity of a shorted cell occuring during any given flight session is nill. I challenge anyone to present evididence to the contrary. On the other hand, the probablility of a single point failure (ie. open circuit), be it the switch, connector, wire, solder joint, intercell tabs is the thing that the parallel/dual switch system addresses. This is only exceeded by the probability of someone forgetting to charge, or thinking he charged when the charger was plugged into a switched outlet or not functioning itself, and flying without an ESV check.
You need to understand the nature of cell shorts and how they occur in your "reliability analysis".
A short develops in a Ni-Cd or Ni-Mh when conductive particulate bridge the separator or the separator itself deteriorates to the point where it allows the positive and negative plates to touch. Rarely does the short occur all at once but rather building up a very small conductance path termed "soft shorts". In a charged cell the energy in the cell will blow away any short as it tries to develop. You've heard about "zapping" cells. The cell actually zaps itself before the short can develop. Only in cases of severe overcharge at high rates can the separator melt down to the point where the plates contact each other (hard short). In this case the energy in the cell then dumps and we have what is referred to as a hot steamer, the electrolyte boils, nylon in the separator melts down and is forced by the steam through the vent. On some occasions the vent is clogged by the molten nylon separator and becomes inoperative causing the cell to rapidly disassemble. So under normal circumstances a cell maintained at some state of charge is much less likely to short than a cell that is completely discharged. It should be noted however that the self discharge increases rapidly in cells where there is a short building (high resistance -soft short) due to separator deterioration and/or cadmium migration. One other shorting mechanism is a manufacturing defect where the positive or negative collector tab bridges the opposite plate. These usually fall out before the cells are shipped or assembled into batteries.
Bottom line: After a good ESV check, the probablity of a shorted cell occuring during any given flight session is nill. I challenge anyone to present evididence to the contrary. On the other hand, the probablility of a single point failure (ie. open circuit), be it the switch, connector, wire, solder joint, intercell tabs is the thing that the parallel/dual switch system addresses. This is only exceeded by the probability of someone forgetting to charge, or thinking he charged when the charger was plugged into a switched outlet or not functioning itself, and flying without an ESV check.
03-25-2005, 11:17 AM
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RE: IMAA's Marez speaks out on parallel systems
I'm well aware of the mecahnism by which a cell shorts, Red. Given all that you've just written, may I ask exactly what is the point of adding the second battery if not to provide for an "inflight" failure?
Given that you advocate checking each battery with an ESV before flight, what's the supposed inflight failure mechanism you hope to avoid with the second battery?
Obvousely when both switches are in the ON position, the batteries will seek equilliberium and in essence become one source with additive capacities.
Given that you advocate checking each battery with an ESV before flight, what's the supposed inflight failure mechanism you hope to avoid with the second battery?
Obvousely when both switches are in the ON position, the batteries will seek equilliberium and in essence become one source with additive capacities.
03-25-2005, 11:21 AM
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RE: IMAA's Marez speaks out on parallel systems
ORIGINAL: exeter_acres
Interesting read......but to me it sounded like a paid Cermark ad
Interesting read......but to me it sounded like a paid Cermark ad
If using a SCHOTTKEY rectifier make sure you choose one with a forward voltage drop of .1v or less.......
03-25-2005, 11:43 AM
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RE: IMAA's Marez speaks out on parallel systems
If you use two 5 cell packs with any good high current (by high current I mean one which will easily handle the maximum current the battery is required to supply) diode in series with each battery pack, you will have a pretty good insurance of not having an electrical failure due to supply problems whether the failure mode is an open or shorted cell in one of the packs. If one pack fails, the diode isolates the bad battery from the rest of the system. In some 40 plus years of flying RC, my only in flight battery failure was a cell which shorted in flight.
03-25-2005, 12:07 PM
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RE: IMAA's Marez speaks out on parallel systems
ORIGINAL: branded
I happen to agree with Mr. Marez. The only way to reliably provide for backup is to isolate the packs.
Contrary to what Desertpig says the most prevalent mode of failure is a shorted cell, not open. I'm not saying that it never happens but rather packs do fail in the shorted cell mode more often than the open cell (broken tabs) mode.
Red, one could argue that adding the additional pack, without regard to the most prevalent mode of failure, increases the chance of experiencing the most prevalent mode of failure by a factor of two times.......in other words you've decresed the reliabilty of the system by adding components that could concievably cause an electrical contention if one or the other fails. That's not what you're looking for, is it?
When designing reliabilty into a system one must always consider all modes of failure and then assure that the most likely is covered. Simply plugging another pack, via a second switch is not covering the most prevalent failure mode.
I'm an EE and have much experience with designing redundancy into a system.
I happen to agree with Mr. Marez. The only way to reliably provide for backup is to isolate the packs.
Contrary to what Desertpig says the most prevalent mode of failure is a shorted cell, not open. I'm not saying that it never happens but rather packs do fail in the shorted cell mode more often than the open cell (broken tabs) mode.
Red, one could argue that adding the additional pack, without regard to the most prevalent mode of failure, increases the chance of experiencing the most prevalent mode of failure by a factor of two times.......in other words you've decresed the reliabilty of the system by adding components that could concievably cause an electrical contention if one or the other fails. That's not what you're looking for, is it?
When designing reliabilty into a system one must always consider all modes of failure and then assure that the most likely is covered. Simply plugging another pack, via a second switch is not covering the most prevalent failure mode.
I'm an EE and have much experience with designing redundancy into a system.
Branded -
If we're going to throw around titles, I'm an EE PhD, electrical and aeronautical engineering with a minor in mechanical. I have extensive experience in power system design, including battery subsystems. I have performed very sophisticated ESS and HALT tests on many types of battery cells. In the majority of "in use" failures cells increase in resistance or fail open - far more often than they short. You see this in reduced capacity or a slow degradation of the batteries ability to deliver current (i.e. hitting the wall) Without getting technical - Red's explanation above explains it perfectly. This holds true in the batteries used in full scale aircraft, automotive, cellular phones, back up power inverters, rechargeable consumer devices and just about everywhere else batteries are used. Perhaps there is something special about the cells in our flight packs? Doubt it.
In mechanical battery banks (i.e. assembled packs) the prevailing failure mode was an open pack (not an open cell) due to failure of the mechanical bond (i.e. weld) of the tabs or wiring.
While I agree I may have used a blanket statement above without offering any data - I have found no merit whatsoever in using a battery backer or sharing device as long as both packs are routinely checked, in the same capacity, and charged in a similar fashion using a gang charger. I have in fact seen them create more problems than they solve, hence my statement.
If you want to use different capacity batteries or different technologies, then maybe I can see using it.
I wasn't trying to start a p'ing match, just trying to offer up a biased opinion - how's that for piling it higher and deeper!
DP
03-25-2005, 12:16 PM
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RE: IMAA's Marez speaks out on parallel systems
ORIGINAL: branded
I'm well aware of the mecahnism by which a cell shorts, Red. Given all that you've just written, may I ask exactly what is the point of adding the second battery if not to provide for an "inflight" failure?
Given that you advocate checking each battery with an ESV before flight, what's the supposed inflight failure mechanism you hope to avoid with the second battery?
Obvousely when both switches are in the ON position, the batteries will seek equilliberium and in essence become one source with additive capacities.
I'm well aware of the mecahnism by which a cell shorts, Red. Given all that you've just written, may I ask exactly what is the point of adding the second battery if not to provide for an "inflight" failure?
Given that you advocate checking each battery with an ESV before flight, what's the supposed inflight failure mechanism you hope to avoid with the second battery?
Obvousely when both switches are in the ON position, the batteries will seek equilliberium and in essence become one source with additive capacities.
My purpose is not to convince those with alternative systems to change to a parallel pack/switch system, but only to present enough information to help others make an intelligent choice.
03-25-2005, 12:18 PM
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RE: IMAA's Marez speaks out on parallel systems
Are we a bit sensitive, Mr. Desert? You made a comment, I rebuked it in a way that wasn't inflammatory. Sorry you feel that way.
I'm impressed with your credentials but the fact is I've met many (and deal with on a daily basis) many supposed engineers that are not practicing engineers and have little or no practical experience. Not saying you fall into this category or not, just surprised that you would go off the way you did.
I only mentioned that I'm an EE because I do indeed design systems and components that are part of todays most complex military fighter aircraft. That's what I do for a living.
When applying reliabilty to a design, particularly one that will be airborne, one does not approach the problem by simply adding components beleiving that having two, three, or fifty of something automatically relates to an increase in reliabilty.
The point is that without looking at the most prevalent mode of failure adding components to system that do not address that particular, in the least, is a waste of time.....
Red seems to suggest that this scheme exists to prevent an open. Adding a switch in parallel with the primary would cover that base without the second battery. The only way to cover all possibilities is to isolate the batteries.
I'm impressed with your credentials but the fact is I've met many (and deal with on a daily basis) many supposed engineers that are not practicing engineers and have little or no practical experience. Not saying you fall into this category or not, just surprised that you would go off the way you did.
I only mentioned that I'm an EE because I do indeed design systems and components that are part of todays most complex military fighter aircraft. That's what I do for a living.
When applying reliabilty to a design, particularly one that will be airborne, one does not approach the problem by simply adding components beleiving that having two, three, or fifty of something automatically relates to an increase in reliabilty.
The point is that without looking at the most prevalent mode of failure adding components to system that do not address that particular, in the least, is a waste of time.....
Red seems to suggest that this scheme exists to prevent an open. Adding a switch in parallel with the primary would cover that base without the second battery. The only way to cover all possibilities is to isolate the batteries.
03-25-2005, 01:02 PM
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RE: IMAA's Marez speaks out on parallel systems
Branded,
Just another EE wading in. Looking at this from a typical users standpoint, assuming the modeler wants redundancy, dual harnesses and battery packs work. The average user is not going to be doing an exhaustive failure mode analysis.
It is easy to put in two complete switch harnesses and battery packs, everything plugs together. I use a voltwatch on all my airplanes. By having 2 switch harnesses I can cycle each pack individually and use the voltwatch to insure both are connected to the receiver buss. Charging is a snap. It's cheap insurance and easier to do than adding parallel switches or soldering Schottky diodes in series with the packs.
Just my 2 cents.
John
Just another EE wading in. Looking at this from a typical users standpoint, assuming the modeler wants redundancy, dual harnesses and battery packs work. The average user is not going to be doing an exhaustive failure mode analysis.
It is easy to put in two complete switch harnesses and battery packs, everything plugs together. I use a voltwatch on all my airplanes. By having 2 switch harnesses I can cycle each pack individually and use the voltwatch to insure both are connected to the receiver buss. Charging is a snap. It's cheap insurance and easier to do than adding parallel switches or soldering Schottky diodes in series with the packs.
Just my 2 cents.
John
03-25-2005, 02:17 PM
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RE: IMAA's Marez speaks out on parallel systems
I'm not an EE, but I did sleep at a Holiday Inn last night
. Anyway, if all you want is redundancy in the path from the battery to the receiver, buy a pack with two leads. Hangtime sells them as do other vendors. Then connect your two switches, etc, to the receiver. I don't know if another pack really buys you all that much. It's the mechanical stuff I worry about.
. Anyway, if all you want is redundancy in the path from the battery to the receiver, buy a pack with two leads. Hangtime sells them as do other vendors. Then connect your two switches, etc, to the receiver. I don't know if another pack really buys you all that much. It's the mechanical stuff I worry about.
03-25-2005, 02:22 PM
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RE: IMAA's Marez speaks out on parallel systems
What's the difference between what Cermark is offering now and what ElectroDynamics has been offering for awhile now in there Pow'R Back'R product?
I would have to agree with exeter_acres it sounds like a sales add.
As far as which way is the best way to go, no thought on that I'm just dumb high school and trade school graduate that just checks battery before 1st flight of day and every other flight after that.
I do get a laugh when you guys start huffing and puffing about what you do/did for a living.
Thank you for all of the useful information you post on this website and others.
Kris
I would have to agree with exeter_acres it sounds like a sales add.
As far as which way is the best way to go, no thought on that I'm just dumb high school and trade school graduate that just checks battery before 1st flight of day and every other flight after that.
I do get a laugh when you guys start huffing and puffing about what you do/did for a living.
Thank you for all of the useful information you post on this website and others.
Kris
03-25-2005, 02:50 PM
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RE: IMAA's Marez speaks out on parallel systems
OK some testing is in order.
Wiring harness incorporates same lengths you would expect in actual application, wire size #22 servo wire. Connectors Futaba J.
Pack A 617 mAh actual when discharged at C/5 to 3.6 volts
Pack B 612 mAh actual when discharged at C/5 to 3.6 volts
Charge A @ 500 mA to cut off. OCV after 15 min rest = 5.72 volts
Discharge B @ 500 mA to 3.6 volts.
Connect A in parallel with B and record current.
Current at start - 290 mA
Current after 8 minutes - 60 mA
Area under the curve = 17 mAh
Discharge B @ 500 mA to 3.6 volts after 24 minutes connected to A.
Capacity delivered 27 mAh
Pack A open circuit voltage after 15 minutes rest - 5. 23 volts
Pack B open circuit voltage after 15 minutes rest - 4.68 volts
Amount of energy drained from A in 24 minutes – 4.3%
All this if you FAIL to do an ESV check, and FAIL to charge one pack. You will be left with only 95% of the one packs capacity.
Wiring harness incorporates same lengths you would expect in actual application, wire size #22 servo wire. Connectors Futaba J.
Pack A 617 mAh actual when discharged at C/5 to 3.6 volts
Pack B 612 mAh actual when discharged at C/5 to 3.6 volts
Charge A @ 500 mA to cut off. OCV after 15 min rest = 5.72 volts
Discharge B @ 500 mA to 3.6 volts.
Connect A in parallel with B and record current.
Current at start - 290 mA
Current after 8 minutes - 60 mA
Area under the curve = 17 mAh
Discharge B @ 500 mA to 3.6 volts after 24 minutes connected to A.
Capacity delivered 27 mAh
Pack A open circuit voltage after 15 minutes rest - 5. 23 volts
Pack B open circuit voltage after 15 minutes rest - 4.68 volts
Amount of energy drained from A in 24 minutes – 4.3%
All this if you FAIL to do an ESV check, and FAIL to charge one pack. You will be left with only 95% of the one packs capacity.
03-25-2005, 04:28 PM
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RE: IMAA's Marez speaks out on parallel systems
,,,good one!!,,
ORIGINAL: SitNFly
I'm not an EE, but I did sleep at a Holiday Inn last night. Anyway, if all you want is redundancy in the path from the battery to the receiver, buy a pack with two leads. Hangtime sells them as do other vendors. Then connect your two switches, etc, to the receiver. I don't know if another pack really buys you all that much. It's the mechanical stuff I worry about.
I'm not an EE, but I did sleep at a Holiday Inn last night
. Anyway, if all you want is redundancy in the path from the battery to the receiver, buy a pack with two leads. Hangtime sells them as do other vendors. Then connect your two switches, etc, to the receiver. I don't know if another pack really buys you all that much. It's the mechanical stuff I worry about.
03-25-2005, 07:24 PM
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RE: IMAA's Marez speaks out on parallel systems
Red, why are we not concerned about incorporating this "redundant" capability in our transmitters? Same scenario applies....You could plug it in and have a bad charger...
Let's face it guys this is not a redundant system. In reality one bad pack will quickly diminish the second and your airplane is toast.
You must isolate the packs.
This is my last word on this subject because frankly there are too many individuals in these froums that wish to argue endlessley regardless of how absurd their position.
These topics are not a matter of opinion, they are electrical facts based on physics and the published reliabilty data supplied by manufactures concerning the ways their products most often fail.
Fact is the best recommendation that I've read thus far is the response that identifies the dual connector packs, which by the way I use.
There are products that exist that isolate the packs such as the Jomar and the Cermark. This is the only way to achieve a redundant supply to the input of the reciever.
Let's face it guys this is not a redundant system. In reality one bad pack will quickly diminish the second and your airplane is toast.
You must isolate the packs.
This is my last word on this subject because frankly there are too many individuals in these froums that wish to argue endlessley regardless of how absurd their position.
These topics are not a matter of opinion, they are electrical facts based on physics and the published reliabilty data supplied by manufactures concerning the ways their products most often fail.
Fact is the best recommendation that I've read thus far is the response that identifies the dual connector packs, which by the way I use.
There are products that exist that isolate the packs such as the Jomar and the Cermark. This is the only way to achieve a redundant supply to the input of the reciever.
03-25-2005, 07:55 PM
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RE: IMAA's Marez speaks out on parallel systems
Who does Eloy think he is, having an opinion of his own! In the future I think he should be required to check in with the REAL experts at RC UNIVERSE if he feels an opinion coming on.
We might also report him to the AMA and get his membership revoked.
We must boycott High Flight magazine, too. Or we could just pull his feeding tub.
We might also report him to the AMA and get his membership revoked.
We must boycott High Flight magazine, too. Or we could just pull his feeding tub.
03-25-2005, 09:23 PM
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RE: IMAA's Marez speaks out on parallel systems
ORIGINAL: branded
Red, why are we not concerned about incorporating this "redundant" capability in our transmitters? Same scenario applies....You could plug it in and have a bad charger...
1. Our transmitters see no where near the vibration environment seen by our flight packs. 2. Our transmitters have a voltmeter that tells us instantly if we have a shorted cell.
Let's face it guys this is not a redundant system. In reality one bad pack will quickly diminish the second and your airplane is toast.
You must isolate the packs.
This is my last word on this subject because frankly there are too many individuals in these froums that wish to argue endlessley regardless of how absurd their position.
PROMISE?
These topics are not a matter of opinion, they are electrical facts based on physics and the published reliabilty data supplied by manufactures concerning the ways their products most often fail.
Fact is the best recommendation that I've read thus far is the response that identifies the dual connector packs, which by the way I use.
There are products that exist that isolate the packs such as the Jomar and the Cermark. This is the only way to achieve a redundant supply to the input of the reciever.
Red, why are we not concerned about incorporating this "redundant" capability in our transmitters? Same scenario applies....You could plug it in and have a bad charger...
1. Our transmitters see no where near the vibration environment seen by our flight packs. 2. Our transmitters have a voltmeter that tells us instantly if we have a shorted cell.
Let's face it guys this is not a redundant system. In reality one bad pack will quickly diminish the second and your airplane is toast.
You must isolate the packs.
This is my last word on this subject because frankly there are too many individuals in these froums that wish to argue endlessley regardless of how absurd their position.
PROMISE?
These topics are not a matter of opinion, they are electrical facts based on physics and the published reliabilty data supplied by manufactures concerning the ways their products most often fail.
Fact is the best recommendation that I've read thus far is the response that identifies the dual connector packs, which by the way I use.
There are products that exist that isolate the packs such as the Jomar and the Cermark. This is the only way to achieve a redundant supply to the input of the reciever.
03-25-2005, 10:07 PM
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RE: IMAA's Marez speaks out on parallel systems
I see that branded is stirring the pot? I know that my opinion will go against the wave of opinions in this thread but Mr. Marez, as well as branded are absolutely correct.
There is no way of protecting yourself from onboard failures due to opens, as well as shorted cells (which do occur at a greater frequency than any other type of failure) unless you isolate the batteries either via diodes, or by other means.
Not to do so will just give you the illusion that you have a redundant power supply system.
JMO[
]
There is no way of protecting yourself from onboard failures due to opens, as well as shorted cells (which do occur at a greater frequency than any other type of failure) unless you isolate the batteries either via diodes, or by other means.
Not to do so will just give you the illusion that you have a redundant power supply system.
JMO[
]
