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Old Nov 02, 2002, 08:33 PM
Electron Abuser
Allen, Texas (North Dallas)
Joined Oct 2002
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Matching of cells with Apex internal resistance meter.

Anybody got experience utilizing the new Apex battery internal resistance measurement instrument at:

http://www.apexhk.com/

They claim it's easier to measure the internal resistance of batteries utilizing their special internal resistance meter than normal cell matching with typical Competition Electronics Turbo Matcher.

I utilize an older Victor Hi IQ matcher tester to do packs and am always looking for a shortcut because it takes a while. I run hi amperage on CP1700 - CP 2400 cells in F5J at 100 amps. Internal resistance after zapping does matter to me and I would like an quicker way to match paks.

Steve Nue: Do you have any comments?



Heres their catalog Spec:

APEX BATTERY INTERNAL RESISTANCE METER

Features:

Designed for checking the resistance and voltage of rechargeable batteries such as Lead Cells, Nicad, Ni-MH and Li-ion batteries.
Provide immediate performance data of batteries required for matching instead of spending hours using batteries matching machine. A group of matched batteries will often need to be rematched after used for about 3 times.
Measuring the resistance of sockets, connectors, MOSEFT inside speed controller, silicon wire and motor coil. Provide reference for estimating the best performance.
Using AC Four terminal method, provides accurate result with the resistance of the lead and the probe contact resistance cancel out.
Digital LC display the readings of the battery status.
Reverse polarity protected.

Specification:

Measurement current frequency: 1kHz +/- 10%.
Power source: 9V battery X 2 or DC jack input 9V-15V 0.2 A.
Input: 1-30 cells, DC 50V Max.
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Old Nov 12, 2002, 11:02 PM
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The only way to match packs is to fully test each cell you have. Like the Victor does. The only way to speed it up is to get more testers. Not by any means cost effective for the hobbyist. Without matching for runtime you would very quickly kill packs, and never get the full potential from the good cells.

Greg
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Old Nov 13, 2002, 12:24 AM
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Joined Jul 2001
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I have to agree with gkamysz on this one. The primary characteristic that needs matching is capacity. Internal resistance is important too, but is not an indication of identical capacity. The better the capacity match, the closer you can come to completely discharging the pack without flipping a cell. For the other listed tasks, it looks just fine.

Regards,
Q
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Old Nov 13, 2002, 12:28 PM
Electron Abuser
Allen, Texas (North Dallas)
Joined Oct 2002
335 Posts
Yes, Yes... I quite agree for normal cell matching that capacitance is the key issue. However in the application of abuse that I deal with, 90-120 amps of current on CP1700 cells for F5J LMR gliders, F5B and F5D pylon, internal resistance is the critical factor. I have noticed over the years that different cells in the pack operate at different temperatures. I measure that with a Radio Shack infrared thermometer on the test bench and after flights. Cell temperatures randomly fluctuate 20-30 degrees F. This is not due to cell location in the pack, (although there is a difference there) but I believe this is due to the different internal resistance of the cells. Cell temperatures are well over 215 degrees F sometimes, depending on the length of the run, whether its 20 seconds or less/more.

My situation is that all of the packs I fly are Zapped by industrial strength zappers, usually 60,000 70,000 ufd or so at 70 or so volts. The internal resistance of the 1700's are such that they will sometimes burn up at these currents if they are not zapped well.

So a key issue is to really get at the internal resistance measurement that some of the cell matchers actually measure, such as the Competition Electronics Turbomatcher. The problem is that the matching currents are generally very much lower than I fly and it's hard to determine the correlation at low currents and high currents. Resistance should be measureable, but thats the real issue. I probably could match by cell temperature at flight current load amps, but am looking for a simplier way. If the measurement meter works, it would simplify and shorten the cell match process tremendously because I fly anywhere from 7 to 27 cell packs. I have lots of packs, and they really need to be torn apart after a half a season to be rematched. This is the way I used to do in the serious RC car racing competition. It's just a lot of work for airplane packs due to the number of cells.

But make no mistake. This is mission critical in some events like F5J LMR sailplane competition. These airplanes are almost a 1000 sq. inches wing at 100-110 oz. of weight and after a 20 second motor run are in the stratosphere.

I was at the Phoenix worlds competition several weeks ago, and depending on my packs, could outclimb some other airplanes that were 30 oz. lighter in the 20 second motor run unlimited class. (I fly an Escape vs the Graphite) Hacker B50S LMR Carbon, 14 cells CP 1700 and CAM 18-10 prop. About 98 amps static. However when I put another new pack that was Zapped by another company's Zapper besides Diversity, I got killed in the climb. To put it in persepective, all 10 competitors launch at the same time in F5J competition. It's obvious who has the Hoss motor batter combination. Generally, all do at this level of competition.

Just looking for a quick way to match. Steve Neu suggested it's a black art. I'm willing to become a Vodoo doctor to give it a try. After all, it's fun to tinker as well. Just need to keep the armor plating around the test area.
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Old Nov 13, 2002, 01:10 PM
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Joined Jan 2001
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I agree

And you need to run cells several cycles to make sure they are stable. Capacity, IR, Voltage Average are all factors. This equipment could be used to pick out the lowest IR cells before matching though, looks interesting


Quote:
Originally posted by gkamysz
The only way to match packs is to fully test each cell you have. Like the Victor does. The only way to speed it up is to get more testers. Not by any means cost effective for the hobbyist. Without matching for runtime you would very quickly kill packs, and never get the full potential from the good cells.

Greg
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Old Nov 13, 2002, 01:42 PM
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Allen, Texas (North Dallas)
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Yes, I agree about the cycling.
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Old Nov 13, 2002, 08:05 PM
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If you want the lower possible IR that's fine but if the cell is 90% the capacity of the best it doesn't matter how low the IR is. I think your best bet would be to select cells based on IR then cycle those. Either way, to get the type of packs you seem to be looking for you are talking 1000's of cells. Better off just to call up Orion or GM and offer them $20 per cell for the best they have, You'll still be in ahead in $$ and have plenty of time to spare.

Greg
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Old Nov 13, 2002, 10:56 PM
Electron Abuser
Allen, Texas (North Dallas)
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Going to Orion or else is always not a bad idea, however its been my experiance that packs cell capacities are not always stable, and need to be broken apart, and rematched every so often. This is especially true at the high abuse currents that we run. I know that some cells get off after awhile, and its really important to be able to rematch paks. In fact, the best packs sometimes are assembled after the original match. I also have a lot of all types of cells as well, and orion doesnt do all types. And then there's always the tinker factor. I just love that part.
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Old Nov 13, 2002, 11:02 PM
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Allen, Texas (North Dallas)
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By the way, in F5J we only utilize about 40% of the capacity of the cell for the one climbout. We dont run the cells down to cuttoff. The reason is to get max performance. We simply have to have the highest current available by any cell for the Rocket like climbout. The extra weight is more than offset by the lower internal resistance or abilty to deliver max current in 20 seconds for unlimited, or 30 seconds for 7 cell. Glide performance isnt an issue within reason.
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Old Nov 14, 2002, 12:25 AM
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I realize that some of the events don't empty the pack. I don't know why the AMA events are set up this way but they are. FAI events require that you drain the pack to be competitive.

Hey John, How much do you think a new matched and zapped 500AR(real 500AR) pack is worth? ;-)

Greg
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