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Marez on Parallel Operation - One more time.

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Marez on Parallel Operation - One more time.

Old 07-18-2006, 08:11 AM
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Red Scholefield
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Default Marez on Parallel Operation - One more time.

OK, all off you people running packs in parallel, listen up.


High Flight Magazine
International Miniature Aircraft Association
Winter Issue 2005 Vol 26 No 4

Electronics Ala Mode by Eloy Marez
e-mail: [email protected]

PARALLEL BATTERIES, LAST TIME AROUND!

Some of you will remember I previously wrote here on the subject of the common practice of using two batteries to power the receiver and servos. I shared with you what you can expect to happen if one of the batteries developed a shorted cell, in that the good battery will attempt to recharge it.
My tests, using a calibrated commercial grade (Fluke) meter, gave a current reading of three amperes.

That is all - I did not have any further comments on the subject, pro or can. However, the matter was opened on one of the Internet forums. It was obvious that some had not read my original comments; others simply did not understand what they read.

My test can be duplicated by anyone with an ammeter and some batteries, one a fully charged 4 cell unit and one three cell, charged or otherwise. You may not read exactly three amps, since the series meter in this case is effectively a resistor, its value and effect differing from type to type. But in all cases, you will see a high current that will rapidly deplete the good battery.
I chose not to get engaged in the Internet forum controversy, but I did some further research on the subject, and while I did not, nor expected to find anything on this particular R/C application, I do have some expert opinions on the use of parallel batteries to share with you. Expert that is, if you will accept the word of the engineers, who work at the companies, who provide us with the high quality batteries already mentioned, and who produce their engineering, application and technical manuals.

First up to bat, Sanyo Electric, who should need no introduction and who we should believe if we believe anybody. In Sanyo's Engineering Manual, on parallel
batteries, you will find: "When a battery which has abnormally low voltage is used, caused by a short or other deviation, the high current which flows into the battery may generate heat, bum the lead wire, and eventually damage the device in which it is being used" This brings up further food for thought... which I had not considered, high current generates heat. That is how your wife brewed your coffee and made your II toast this morning. It is rare, but airplanes have been known to catch on fire in the air. Though we have always attributed the incident to being exhaust and fuel related, another possibility has just emerged. No, I didn't survey that either.

While this all started with NiCd batteries, I am sure NiMH's are also being used in this manner. On that subject, Sanyo, who uses the trade name "Twicell" for its NiMH's has this to say: "Do not connect two Twicell batteries in parallel as this may cause leakage - of battery fluid, heat generation, bursting or fire".

Some of the companies I will mention may not be known to you, but remember that a huge electronics world exists out there outside of R/C. Saft America, in its literature states: "If batteries (NiCd's - em) discharged in parallel, use a protective device to avoid back dischcharge from one battery to another". Power-Sonic Corporation comments: "If batteries (NiCd's) are discharged in parallel, use diodes to prevent back discharge from one battery to another".
GP Batteries, a major battery supplier, writes: "We do not recommend parallel charging or discharging. Parallel charging will produce irregular charging current and back discharge from one cell another". One of my (many) electronics textbooks, "Basic Electronics", by RCA's Bernard Grob, (Library of Congress No.76-141919) touches on the subject, though he refers to cells instead of batteries. You are reminded that cells are individual units, batteries are two or more cells connected in series. Mr. Grob writes: "Bad cells should not be connected in parallel with good cells, however, since cells in good condition will supply more current which may overload the bad cells. In addition, a cell with a lower voltage will act as a load resistance, draining excessive current from the cells that have higher output voltage".

There are others, but how many authoritative sources do we need? They all back up my original statement, that if one cell goes bad, further more serious problems will result. And I still maintain that those that are using them without serious consequence are doing so because of having chosen high quality batteries, and have been lucky. And I further maintain that a better method is one of the true battery backers available from Cermark, Electro-Dynamics, or Electronic Model Systems. The subject is closed, I promise!

* * * * * * * *

We know that there are many modelers doing this, myself included. How many of you flying parallel packs have ever encountered a problem using this system? How many have had a model saved using parallel packs as described at http://www.rcbatteryclinic.com/?
Old 07-18-2006, 08:25 AM
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Default RE: Marez on Parallel Operation - One more time.

Red:

I also read this in High Flight and said to myself "here we go again".

You convinced me several years ago and I have had nothing but complete success running parallel batteries through two switches.

The only problem, and it is documented as a problem, is trying to charge both batteries using a "dual output" battery charger.

It is not the fault of the battery configuration. It is a problem with the design of the charger.

How long will it take you to convince Good ol' Eloy?
Old 07-18-2006, 08:39 AM
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Red Scholefield
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Default RE: Marez on Parallel Operation - One more time.

I'm surprised he doesn't get a lot of flack from parallel users that are IMAA members. We can't be the only ones that read his column. But then maybe they realize that using parallel packs is the same to Eloy as a Muslim eating pork. Its a religious thing.
Old 07-18-2006, 09:05 PM
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Default RE: Marez on Parallel Operation - One more time.

I'm a little confused Red. Are you saying that Eloy is lying about what the battery makers state. Or, do you take the position that the battery manufacturers don't know what they are talking about?
Old 07-18-2006, 10:10 PM
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Default RE: Marez on Parallel Operation - One more time.

Just for the record; I have been using 4 cell parallel packs, without diodes or backers, for about 12 years without incident. In one case, I did have a cell short out in one of the packs, but the second pack saved me the aircraft.

I presently use the parallel circuit as sketched out on Red's website, in all 6 of my giant scaleys.

And yes Dick, while my Alpha 4 will charge parallel packs, lesser chargers using an internal common ground, will not. But that's the chargers fault, not the parallel pack circuit.

> Jim
Old 07-18-2006, 10:31 PM
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Default RE: Marez on Parallel Operation - One more time.

I also use the parallel system with Nicad and NiMh packs and have had no problems. I also respect Eloy's opinion on the subject. I don't care how others rig for redundancy. I've been OK with the parallel system.

I'm just confused. I've seen post from Red that infer that Eloy promotes products for payola, and has insinuated that Mr. Marez is nothing short of an imbecile.

With Red's above post. Does he think Eloy is lying about the manufacturer's statements, or does he disagree, (assuming Eloy is an honest man), with the manufacturer's statements.

And yes, you'd better know your charger. Chargers with low side current sensing will fool you by doing a sufficient job as long as the packs are reasonably well matched, (sometimes). When the packs aren't well matched they can wreak havoc.
Old 07-19-2006, 07:42 AM
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Default RE: Marez on Parallel Operation - One more time.

ORIGINAL: Flying Geezer

I also use the parallel system with Nicad and NiMh packs and have had no problems. I also respect Eloy's opinion on the subject. I don't care how others rig for redundancy. I've been OK with the parallel system.

I'm just confused. I've seen post from Red that infer that Eloy promotes products for payola, and has insinuated that Mr. Marez is nothing short of an imbecile.

With Red's above post. Does he think Eloy is lying about the manufacturer's statements, or does he disagree, (assuming Eloy is an honest man), with the manufacturer's statements.

And yes, you'd better know your charger. Chargers with low side current sensing will fool you by doing a sufficient job as long as the packs are reasonably well matched, (sometimes). When the packs aren't well matched they can wreak havoc.
The problem is that Mr Marez cuts-and-pastes ideas and facts to suit his needs for creating an article. A basic understanding of Ohm's Law & Kirchoff's Laws will go a long way.

Safe Flying!
Old 07-19-2006, 09:40 AM
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Red Scholefield
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Default RE: Marez on Parallel Operation - One more time.

ORIGINAL: Flying Geezer

I also use the parallel system with Nicad and NiMh packs and have had no problems. I also respect Eloy's opinion on the subject. I don't care how others rig for redundancy. I've been OK with the parallel system.

I'm just confused. I've seen post from Red that infer that Eloy promotes products for payola, and has insinuated that Mr. Marez is nothing short of an imbecile.

With Red's above post. Does he think Eloy is lying about the manufacturer's statements, or does he disagree, (assuming Eloy is an honest man), with the manufacturer's statements.

And yes, you'd better know your charger. Chargers with low side current sensing will fool you by doing a sufficient job as long as the packs are reasonably well matched, (sometimes). When the packs aren't well matched they can wreak havoc.
Is Mr. marez an imbecile? I would not call him that with all his electronic expertise. Unfortunately this expertise does not extend into battery technology to any depth. So find another word for someone that refuses to accept evidence when presented by hundreds of cases over a number of years.?

Is he lying about manufactures statements - Not exactly, he picks and chooses to support his flawed argument. We all know that manufacturers faced with constant litigation will go out of their way to warn against anything that could possibly be interpreted as being dangerous. If they say parallel discharge is OK, they they are faced with litigation when someone who doesn't kknow the difference between charging and discharging gets himself in trouble. Our R/C application is unique in that it is one of the few applications where parallel discharge can be accompanied by the proper series charge.
Old 07-19-2006, 09:38 PM
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Default RE: Marez on Parallel Operation - One more time.

The "litigation mitigation" theory coupled with the undocumented claim of hundereds (not exactly a big number) of cases of successful parallel operation, does not negate the evidence presented by Eloy Marez.

As stated in my earlier post, I use the parallel system in several planes, and have for years. It works for me. I'll bet Eloy's method will work, too. I just seems to me, that over the last couple of years, you have taken the arrogant position that your theory is the only right way, and Eloy's is totally wrong. "All the knowlege lies within no one man".

Best regards,
Old 07-20-2006, 03:37 PM
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Default RE: Marez on Parallel Operation - One more time.

ORIGINAL: Flying Geezer

The "litigation mitigation" theory coupled with the undocumented claim of hundereds (not exactly a big number) of cases of successful parallel operation, does not negate the evidence presented by Eloy Marez.

As stated in my earlier post, I use the parallel system in several planes, and have for years. It works for me. I'll bet Eloy's method will work, too. I just seems to me, that over the last couple of years, you have taken the arrogant position that your theory is the only right way, and Eloy's is totally wrong. "All the knowlege lies within no one man".

Best regards,
Then why on earth would any sane modeler use a system condemned by someone he respects? The parallel system many experienced modelers have espoused has proven simple to implement and with demonstrated reliability over 15 years that is unequalled by addition of any number of gadgets, diodes, buffers, or other gimmickry recommended by Eloy.
Old 07-20-2006, 06:49 PM
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Default RE: Marez on Parallel Operation - One more time.

There are literally 100's, if not maybe over a 1,000, IMAC/giant Scale Aerobatic planes out there using dual pack parallel battery set ups with great success In fact it would be more the "norm" rather than the exception to do so.

My take is that Eloy has lost himself in his incomplete understanding of the subject and his idea that this is not a safe thing to do. He made up his mind first and then tries to justify his position. The exact opposite of science.

Any time I get questions on this I tell people to take 2 packs of the same cell count. Charge one fully. Discharge one fully. Plug them both into the same receiver (or even just use a "Y" to connect them). GO away for a few days. Come back and see if the low pack has been charged by the full pack (hint - No, it hasn't).

As to what happens if you get a hard short in the one pack. Well the same as if that was your only pack. You are dead meat probably. However, this is NOT the normal failure.

I run dual packs for two reasons:

1 - switches are crap. SO I use 2. Might as well use 2 packs then too.

2 - To get more capacity and to spread the load. Put in 2 packs and each pack will "see" half the load rather than one pack seeing the full load. Lessens the voltage depression seen under load.

Basically it comes down to what Red is saying. Eloy basically wants to ignore the vast amount of empirical evidence out there that shows that this is a safe and efficient way to power our receivers and servos because he has already made up his mind.
Old 07-20-2006, 09:57 PM
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Default RE: Marez on Parallel Operation - One more time.

As stated earlier Phaedrus, I use the same system you do for the same reasons you stated. I don't plan to change. My complaint is that many of you refuse to respect Eloy's right to his opinion.

Eloy Marez has contributed a great deal to this hobby for many years. It bothers me that he cannot express an opinion without unkind comments from those who disagree. I have not seen a post where anyone has attempted to duplicate Eloy's test, nor, have I seen a post refuting the manufacturers claims he cites. All I hear are unkind remarks about Eloy.
I haven't seen Eloy on the forum arguing about this. If I understand correctly, someone posted his article from High Flight Magazine, and then began to trash him.

I respect his right to his opinion, right or wrong. And, I would like to note that the gentleman were discussing has not trashed those who disagree.

What I have been reading is the kind of attitude that destroy's clubs and forums. The moderator on many forums would not allow this schoolyard behavior.

If any of you would like to trash me for respecting Eloy's right to his opinion, let 'er rip.

Old 07-21-2006, 06:04 AM
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Default RE: Marez on Parallel Operation - One more time.

Everyone is entitled to an opinion. Unfortunately, the opinion expressed pays little attention to all of the possibilities. First of all, it would seem to me that the most likely mode of failure is an "open" failure rather than a dead short of a single cell. Broken or poor solder/weld joint or a failed switch seems to me to be more likely than a dead short. A "soft" short of a cell resulting in a fast discharge is also quite possible. While four cells draining into three (or more likely 5 cells draining into 4 for most setups) might give you some problems, you would still likely have lots of juice to get back home. I seriously doubt that you would ever get enough current "inrush" to set fire to the system. A simple preflight voltage check should provide adequate warning of a funky cell in a pack. Especially for large planes, I think I would be more comfortable with two-pack redundancy. Currently, I don't fly anything where I have sufficient investment to warrant this type of system but if I ever venture into quarter scale or larger, I am pretty sure that parallel redundant battery packs would be part of the plan!

Ross
Old 07-21-2006, 07:41 AM
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Default RE: Marez on Parallel Operation - One more time.

I couldn't agree more, Ross.
Old 07-21-2006, 12:12 PM
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Default RE: Marez on Parallel Operation - One more time.


ORIGINAL: Ross Kean

Everyone is entitled to an opinion. Unfortunately, the opinion expressed pays little attention to all of the possibilities. First of all, it would seem to me that the most likely mode of failure is an "open" failure rather than a dead short of a single cell. Broken or poor solder/weld joint or a failed switch seems to me to be more likely than a dead short. A "soft" short of a cell resulting in a fast discharge is also quite possible. While four cells draining into three (or more likely 5 cells draining into 4 for most setups) might give you some problems, you would still likely have lots of juice to get back home. I seriously doubt that you would ever get enough current "inrush" to set fire to the system. A simple preflight voltage check should provide adequate warning of a funky cell in a pack. Especially for large planes, I think I would be more comfortable with two-pack redundancy. Currently, I don't fly anything where I have sufficient investment to warrant this type of system but if I ever venture into quarter scale or larger, I am pretty sure that parallel redundant battery packs would be part of the plan!

Ross
Redundancy is not the only advantage. It lets you use a couple of standard 600 mAh packs where you might want more capacity than just one will provide. The only investment is simply another switch harness if you already have the standard packs.
Old 07-21-2006, 12:23 PM
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Default RE: Marez on Parallel Operation - One more time.


ORIGINAL: Flying Geezer

I couldn't agree more, Ross.
You agreeing to everyone is entitled to his opinion - no argument from anyone on this. . . . or are you agreeing with the technical aspects Ross has covered. Seems kind of disrespectful to Mr. Marez's opinion. When there are diametrically opposing technical views usually only one is right and the other is as a minium, suspect. And in this case should a poll be taken do you want to bet who the loser would be?
Old 07-21-2006, 02:21 PM
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Default RE: Marez on Parallel Operation - One more time.

Let me be as clear as posssible. I agree with everthing in Mr. Kean's post. I agree that everyone has the right to his opinion. I agree with every technical aspect of his post.
I don't know why you would call me disrespectful to Eloy Marez, I have been defending his right to an opinion without being trashed. I even agree that there are probably some merits to the system he recommends. I wonder if you are reading my posts with an open mind, or, have such a personal thing for Mr. Marez that you can't let it go.

POLLS? Polls are for politicians. Usually the polls are fairly accurate in a presidential election, but look at the presidents we get. A poll indicates what most people think, not what they know. Run yourself a poll on NiCad memory and see what you get.

Scientific facts are based on in-depth, documented, experiments. Scientific theory is determined the same way. When I was a kid in school the "magnetic theory" was alignment of the molecules in ferrous metal. Then, the electronic microscope was invented and we got a new theory. Not a fact, but a theory.

Run a poll if you are a candidate for "King of the battery hill". Leave me out for I am not a candidate, and Mr. Marez has not yet announced his candidacy.

Best regards,
Old 07-22-2006, 05:20 PM
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Default RE: Marez on Parallel Operation - One more time.

ORIGINAL: Flying Geezer

I have not seen a post where anyone has attempted to duplicate Eloy's test.

If any of you would like to trash me for respecting Eloy's right to his opinion, let 'er rip.

Geezer, not to trash but to educate.

Here is a test even more simple than Eloy's.

Connect two packs via a wattmeter, one pack discharged completely (open circuit voltage 4.56 volts) and one fresh off charge at at 5.42 volts.

Initial current from the source battery to the load battery 520 mA, after 15 minutes (typical flight time) this was down to 60mA with 75 mAh being transferd.

Now connect a 3 cell pack (simulating a pack with a shorted cell). Initial current 1.68 amps - after 15 minutes current had dropped to 800 mA with 227 mAh transfered. Consider now that if the short had just occured (you are not in the habit of doing an ESV check prior to flight?) then the 1.68 amps would probably have cleared the short and you would be back to senario above.

Any questions?
Old 07-22-2006, 08:11 PM
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Default RE: Marez on Parallel Operation - One more time.

quote:

ORIGINAL: Flying Geezer

I have not seen a post where anyone has attempted to duplicate Eloy's test.

If any of you would like to trash me for respecting Eloy's right to his opinion, let 'er rip.
************************************************** **************************

Still haven't!

The point of all my posts have not been related to technology, rather manners, decorum, attitude. However, Go back to the beginning and re-read them. I'm not helping you at all, so let it rest.

Best regards,
Old 07-22-2006, 11:40 PM
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Default RE: Marez on Parallel Operation - One more time.


ORIGINAL: Flying Geezer

quote:

ORIGINAL: Flying Geezer

I have not seen a post where anyone has attempted to duplicate Eloy's test.

************************************************** **************************

Still haven't!
Red's examples above are certainly within the same test parameters and sorely duplicates Eloy's example... Battery packs mono-mono charged/depleted and a second test same parameters with four/three cells. Real world test data suggesting it’s of little to no consequence.

I have performed these tests with similar results to Red’s. I am also aware of several noted Engineer/Modelers whom strive to stay abreast of these things; they realized again similar results with empirical testing and believe it’s a non-issue too.

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