RE: A123 as receiver pack - no fly voltage?
I've done a lot of testing on my A123 batteries on my 2.2 Ampere load tester. These batteries have a very FLAT discharge voltage. The voltage only drops about 1.5% from 90% charge to 10% charge. Once these A123 cells go below 2.9 or 3 VDC, you've got to land NOW, they will shut down very rapidly. You might not make it back in one piece. Its not a good idea to try to measure remaining amphour capacity with a volt meter because of this flat discharge characteristic. (I've got 45 years experience in electronic repair, trouble shooting, and testing with rechargeable battery powered equipment.) If you are flying a larger model with these A123 batteries, it's a simple process to recharge them inbetween flights if desired. These batteries can be recharged at currents up to 5 amperes or so, until their voltage increases to 3.6 volts per cell, or 7.2 VDC for a two cell pack. If your charger shows the number of MaHrs put back into the battery, you are all set. Just note how many ampere hours are put back in after a flight. Personal opinion, I NEVER use up more than 50% of the batteries AmpHour capacity during a typical flying day. The laws of Murphy apply here, you could have a servo pulling a little more power than expected, and ouch. I've found that balancing these cells after a days flying is quite satisfactory. I've put together a 6 channel DC voltmeter that measures voltages on all six of my cells simultaneously, with 0.5% accuracy. They do stay very well balanced, even without balancing them. FYI, absolutely never short one of these A123 batteries out. These batteries will win, and will burn up anything in their way. I accidentally shorted out a disassembled Dewalt DC9360 pack. (The Dewalt DC 9360 36 VDC packs use 10 A123 cells in series.) The resulting short burned a hole right through the side of one of the cells. It sounded like my 180 Ampere arc welder! That was two years ago, still flying the remaining 9 cells. I've got five A123 packs, all used on Electric models. Three are 6S2P packs, pulling 59 Amperes at full throttle. Two are 4S1P packs pulling about 35 Amps full throttle. None have shown any loss of performance after two years of flying, and about 10 hours of actual flying time on each pack. I've been charging them at 10 Amperes, (two cells are in parallel) the cells don't even get warm after a flight, and after a recharge.
Posted on: 3/21/2009 10:02 PM by Author "flyelectricmodel" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=8601977

RE: A123 4600 6.6v
These are a premade Hypersonic packs, 2s2p 4600.I do not want to cut into them or anything like that until I can make some contact with with someone about warranty.I did charge them at 1s 3.6v and it went up in vlts but only took 3mah and then the charger shut down saying charge complete.It was down to 2.11v in a minute or so.This is total pack voltage and not 1 cell. ?? Don't understand charge them at 3.6 Volts. These cells are to be charged to 3.6 VDC per cell, making your 2S2P charge voltage to be 7.2 VDC. If you are charging both series cells at 3.6 VDC, your charger will indead shut down real quick. Nominal voltage of two series A123 cells will be around 6.6 VDC, if they have been off of the charger for a few weeks or so.
Posted on: 3/16/2009 8:18 PM by Author "flyelectricmodel" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=8585205

RE: A123 4600 6.6v
What kind of problems? Word on the Internet is, A123 can be rather hard to get a hold of. I've been buying Dewalt 36 Volt batteries, and pulling the cells out of them. I believe the part number is DC9360, from ebay. www.battlepack.com also has these batteries for sale. Check with wattflyer/everydayflyer. This guy has a LOT of experience with the A123 batteries. I've got a few of these, a pair of 6S2P A123 packs that pull 57 amps full throttle, one 5S2P also pulls 57 amps full throttle, and two 4S1P packs that pull about 30 amps full throttle. All have been performing very well, this is the second year on them. Search for "a123" in www.wattflyer.com. You will find a lot of information there.
Posted on: 3/16/2009 11:55 AM by Author "flyelectricmodel" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=8583495

RE: M1 cell dimensions
If you are talking about the A123 26650 cells, I got mine from the Dewalt DC9360 battery packs. These cells weigh in at about 2.5 ounces each, measuring 1.05 inches diameter, and 2.62 inches long, including cardboard sleeve. Warning, DO NOT EVER SHORT THESE DANG THINGS! I did it once, it sounded like my 180 Amp arc welder, and burned a hole right through the side of the cell. Didn't hurt the remaining 9 cells, I'm still flying them two years later!
Posted on: 12/17/2008 10:04 PM by Author "flyelectricmodel" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=8256755

RE: electric conversion question
Take a look at the Hacker A40 series of motors. These motors have a third ball bearing to support the "bell end" of the outrunner motor. I run mine at 45 Amps on 4 26650 A123 cells. The motor only gets slightly warm after a flight. Its in a acrobatic model with a 48 inch wingspan, weight of about 4 pounds. The model will almost fly straight up indefinitely. Flight times are around 5-6 minutes with a minute or two of reserve power. After a flight, the motor, CC 45 Amp ESC and battery pack are only about 10 degrees F above ambient temperature.
Posted on: 10/25/2008 2:59 PM by Author "flyelectricmodel" in the forum "Glow to Electric Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8083779

RE: Heat shrink over a battery pack - Need tips
Take a walk to your local grocery store, and look at the various plastic water bottles, tea bottles and the like. (These plastic bottles will shrink about 20% or so with a heat gun!) Find one just slightly larger than your battery pack, remove all labels, then cut the top and bottom off of it. Cut out a block of wood similar in size to your battery pack. Then shrink the plastic bottle around your block of wood to see if it will do the job. If so, cut another bottle and shrink it around your battery pack. These plastic water bottles are far tougher than the shrink tubing on the market. And, even if you throw away the water, it is quite inexpensive.
Posted on: 10/25/2008 2:47 PM by Author "flyelectricmodel" in the forum "Electric General Discussion"
http://www.rcuniverse.com/forum/fb.asp?m=8083747

A123 Cell Results 2008
I've got two different 6S2P A123 battery packs in two different models. The batteries drive a Hacker A50-12S and A50-16S motors. The motors are pulling about 57 Amps at full power. These models are outfitted with my design monitor that records total flying time for the year, and total ampere hours for the year, plus ampere hours for the current flight. The season of 2008 showed that each model had a motor running time of 10 hours and a few odd minutes, with the total ampere hours pulled from the battery over 210 Amp Hours each. These batteries were routinely discharged between 60 and 75% of capacity during a typical flight. No battery was ever totally discharged during a flight. The batteries were periodically checked with an AstroFlight A123 Little Blinky. The batteries are charged at 10 Amps total for the 6S2P packs. Its interesting to note that these A123 cells are very efficient during the charging process. Only about 4-5% Amp hours is lost between discharging and recharging these cells. These batteries were tested at the end of this flying season, and compared to their AmpHour and voltage under load at the beginning of the season. The batteries appear to have lost about one percent in Ampere Hour capacity, and actually INCREASED slightly in voltage (at 57 Amps) over the past flying season. (One percent in Ampere Hour capacity is measuring accuracy!) I'm getting to like these A123 cells more and more.
Posted on: 10/25/2008 2:31 PM by Author "flyelectricmodel" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=8083715

RE: Loss of control in flight using AR7000 & DX 7 UPDATE 5/5/07
Yes, I did have a complete loss of control on one of my three DX7 receivers. It happened on the ground in my front yard after several hours of "burn in time". Had this occurred in the air, it would have cost my model. My background is 45 years of electronic repair, so was very interested in what happened. The failure was traced to the DX7 receiver. The receiver was receiving a signal, but all four servos were dead. The failure was traced to a "Plated through hole" on the DX7 receiver, that caused loss of power from the battery center positive lead and all center positive leads of the servos. The plated through hole was not plated through. A quick solder job fixed it. A call to Spektrum resulted in "Never heard of that one before". The other two DX7 receivers were given a micro-ohm test, no problems were noted. All three receivers have had a number of flights with no problems. Also ran tests on one of the DX7 receivers on a variable DC supply that allowed dropping the 4.8 volts DC to lower levels. The DC was monitored by my Tektronix 2236 Oscilloscope. Repeated tests showed that the DC had to be dropped to 3.1 Volts DC before the DX7 re-booted itself. The "Patch Kit" Spektrum sells for about $6.00 covers this issue.
Posted on: 5/14/2007 8:25 PM by Author "flyelectricmodel" in the forum "JR Radio & Spektrum Radios"
http://www.rcuniverse.com/forum/fb.asp?m=5854835