Author: Red Scholefield
Edition: Model Aviation - 2009/03
Page Numbers: 94,95,96
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The Battery Clinic — 2009/03

Ultracapacitors to revolutionize electric vehicles

“An electric car that goes 250 miles per charge at speeds up to 80 mph is expected on the market in about a year (now where have we heard this before?)

“Unlike current electric cars that take hours to recharge, the new ZENN car (Zero Emissions—No Noise) will recharge in less than 5 minutes. Key to the car’s success are the new ‘ultra capacitors’ that store the electrical power. They are made by ZENN’s partner, EEStor, Cedar Park TX. www.zenncars.com.” — Farm Show Magazine (Volume 32, Number 5)

What a breakthrough for electric-powered modeling, even full-scale electric flight. But now for a sanity check.

I did a bit of research and came up with some figures. The power required for a typical hybrid car going 60 mph is about 14 kilowatts (kW). Assuming that this is within the realm of reality, for a range of 240 miles it would consume 14 kW for four hours, or 56 kWh (kilowatt hours). To recharge in the quoted five minutes would require a source capable of delivering 56 kWh in 1/12 hour, or 56 × 12 = 672 kW; this assumes 100% charge efficiency.

Let’s say that the battery is a 240-volt system. This means we would need nearly a 3,000-amp service (roughly 15–20 times your normal residential service).

I typed “EEStor” into the Google search engine and found a bit of controversy about this revolutionary technology. The most significant point is that EEStor had not revealed even a prototype at that time. There is a great discussion; see the “Sources” listing for the web site address.

While on the subject of breakthrough batteries, it seems that the one that has already made its mark in our little world of electric-powered flight has attracted the attention of General Electric (GE). The company announced that it would invest $30 million in Li-ion battery manufacturer A123Systems. That makes GE the largest cash investor in A123Systems, with a 9% ownership. In addition to receiving capital from GE, A123Systems will get access to research and technology of GE Global Research to design battery-system components for automotive programs.

Also, the word on the street is that Panasonic might buy Sanyo for Panasonic’s battery technology and Sanyo’s solar-energy business. On the other side of the world, according to British modeling magazine RCM&E (Radio Control Models & Electronics), in September 2008 it became illegal to place Ni-Cd batteries on the market for RC use. I won’t risk even speculating on what this means to the modeling world in general.

Letters From Readers

The following is from Gary Zabriskie:

“I do wish to clarify one question about your November article; it is my understanding that while A123 (Enerland) is a LiFePO4 technology as other batteries sold are identified, the difference is that A123 uses a patented nano-phosphate technology rather than a more typical phosphate compound.

“As far as I know, only the genuine A123 batteries have this technology and they are also the only LiFePO4 chemistry battery capable of the extremely high continuous and burst discharge rates one might usually get only from a good quality Li-Poly battery.

“All other LiFePO4 technology batteries I’ve seen where the vendor actually advertises discharge rates, show those other brands to be capable of a substantially lower discharge capability rate than the A123 brand.”

Thanks for your note. You are right about the LiFePO4 technologies. There will be a number of vendors jumping on A123Systems’ coattails, claiming the same chemistry. The modelers will have to sort out the good from the not so good, as we have had to do with Li-Poly and even some of the nickel technologies. Unless the modeler has access to honest specifications, he or she will have to use the time-honored technique of going by the reputation a particular vendor establishes for the products it offers. This is difficult to address without a lot of test data other than on actual A123Systems products.

A123 Autopsy

On the subject of A123Systems technology, which many others and I have been using successfully for the past three years, I finally had a chance to dissect an A123 cell. A fellow club member had the misfortune of a nasty crash that drove the battery pack into the rear of an AXi motor, where the shaft penetrated the negative end of one cell—not pretty.

When the small amount of smoke cleared, I was given the battery for an autopsy. As I suspected, the construction is similar to that of Ni-Cd cells, where the plate is wound in spiral form with separator material between the plates. That is where the similarity stopped.

Looking at the negative end of the cell, three current-collector tabs were welded to the negative terminal. The positive end was identical. When unwound, the plates and separator material, a 0.5-mil-thick plastic-like material, were approximately 60 inches long by 3.25 inches wide.

I was unable to discern much difference in the plates—only that they were different thicknesses: the positive side was about 7 mil and the negative side about 2.5 mil. The can (aluminum) was 14 mil thick. The cell was relatively free of liquid, but I used the proper protection for eyes and hands during the teardown. (Notice the gloves in the photo.)

I was unable to disassemble the vent system, but it appears to be some sort of fusible plug to relieve pressure from overheating, which these cells were, as evidenced by the burn marks left by the interconnecting tabs.

Individual charge and discharge of the intact remaining three cells indicated one to deliver full capacity after the ordeal, while the other two delivered less than half—even at a 2.3-amp discharge. This indicates that whatever high discharge they experienced had taken its toll.

What should the AMA do about perceived safety issues with poor-quality products?

A letter was forwarded to me in which the sender was concerned about the quality of some RC products that are being sold and questioned the AMA’s role in protecting its members from such products.

My response to a particular incident with a charger was:

"Your concern over 'Cheap Li-Poly Dangers' is probably justified to some degree as I have personally seen some disasters waiting to happen, not so much from the cells themselves but from the assembly techniques or more frequently how the users apply them.

"The case you state where the battery burst into flame a couple of minutes after being disconnected points to a weak point in the way the connections (internal to the pack) are made by some manufacturers or assemblers. The act of disconnecting the pack could easily account for the incident you report.

"Any stress on marginal connections or insulation techniques on the PC board or whatever was used for the cell interconnections could have caused a short on one or more cells which would result in what your friend encountered.

"While this is not applicable to all Chinese products, the low-end ones have had a reputation for questionable quality. It is a given. We all know that and should consider it whenever we are buying components for critical applications.

"When I see servos selling for $3.50 I have to wonder what sane person would risk an airplane to use them. The same for cheap low-ball priced batteries.

"While the AMA is concerned with safety I don't see what they could do, with the resources available, about marginal RC products short of banning them all together, and you know that would never fly with modelers that are notorious for cheaping it out at every opportunity. Along the same line I have been tracking incidents for some time and in the majority of cases I can usually pinpoint the cause of the incident and it is seldom the 'quality' of the product.

"I really don't see any more of a safety issue with today's shoddy products than we saw in the early days when people were building their own receivers and transmitters with very little expertise in electronics, or the skills associated. Somehow we survived.

"Again you fault a new and unproven NiMH pack made in China for a crash of a 35 pound, 1/4-scale model. Without examining the way the pack was installed and isolated from the high vibration level encountered in models of this size I would be very reluctant to attribute the crash to the pack opening when the crash itself could have caused the pack to open.

"Was any kind of careful post-crash examination made to determine why the pack was opened? Was anyone present with the expertise to make such a determination?

"Secondly, anyone flying a demonstration with a quarter-scale model in an air show for nursing home residents with an unproven pack is certainly another topic for discussion. This should be something that has been run out at the club field where there is less risk should a crash happen."

The AMA is unable to function as a "watchdog" of the industry. It would be nice, but it would require more money to staff a department for this job.

Also, how would we enforce it? We can't make a company change anything unless it is breaking some law. Shabby items will cull themselves out when modelers try them and are disappointed.

Unfortunately, items that can lead to an accident are everywhere, from an engine that quits at the wrong time, to a model that has a structural failure in flight, to a radio system that is less than reliable. Nothing is 100%, even for the best of companies.

What size wire do I need?

I'm frequently asked this question. The "Sources" list contains a web address that will lead you to a chart that answers that question well.

CBA II Upgrade

West Mountain Radio is offering a free software upgrade for its CBA II battery analyzer that the user can download from the company’s web site. I have found nothing that compares with this computer-controlled discharge module for keeping track of how battery packs are performing.

FMA Direct Takes Another Big Step

I'm expecting the new Cellpro Multi4 charger any day for evaluation. If it lives up to the other FMA Direct charger offerings, it will be worth the wait; it addresses all the chemistries we use and includes charge-balancing function for lithium systems.

All that is available for $79.95. You can get the details at the FMA Direct web site. — MM

Sources:

The Battery Clinic 12219 NW 9th Ln. Newberry FL 32669

Transcribed from original scans by AI. Minor OCR errors may remain.