RE: li-po for e-starter with stock motor
i havent finished building yet so i dont know what it is.
Posted on: 4/2/2004 1:27 PM by Author "urbnsol" in the forum "E-Flight Power Sources"
http://www.rcuniverse.com/forum/fb.asp?m=1683742

RE: Home made Lithium Ion battery charger
[quote]ORIGINAL: adam_one Before connecting the cells to the charger the max charging voltage has to be set by adjusting P1 (2k potentiometer). The max charging voltage must not exceed 4.2V per cell (Kokam), e.g. 8.4V for two serial connected cells. It is recommended using a digital voltmeter. The max charging current is set by choosing the value of Rx. Rx = 0.6 / max charging current For example, for a max charging current of 600mA, Rx should be 0.6 / 0.6 = 1ohm, while for a max charging current of 1.2A it should be 0.6 / 1.2 = 0.5ohm. The dissipated power on Rx at a charging current of 1.2A is: P = V x I = 0.6 x 1.2 = 0.72W [/quote] i dont have enough knowledge to evaluate a circuit, but i would only point out what was brought up on the other forum i posted earlier: having an adjustable output makes error more likely, also, pots can have a tendency to drift if they are not a high quality, linear taper one, which can be expensive, making it less attractive to build. another problem a couple of people ran into was using inexpensive multimeters to measure the voltage and current, leading to inaccurate reading, which as anyone who is thinking about building a charger for li-poly _should_ already be aware of, this can be EXTREMELY DANGEROUS. the lm317 is rated at 1.5A so anyone should be aware that is isnt the chip of choice for high current charging. the lm350 is rated at 3A and the lm1084 is rated at 5A. also in the other design, the regulators get rather warm so good heatsinks are a necessity to get the full potential from the charger. the 317-350 are bulletproof in that they are not supposed to be able to melt down, they have a built in protection circuit, and they will power down as they approach the rated thermal limit.
Posted on: 4/1/2004 9:05 PM by Author "urbnsol" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=1681858

RE: Home made Lithium Ion battery charger
i dont know what the chips are for, i havent gotten my packs yet, and im not getting single cells, im getting a kokam pack. as to charging, you can charge them series-parallel, but it isnt always recommended. also, the cells have to be the same ratings, ie all 700mah, or all 350mah, you cant mix and match cells, 350mah+700mah to make a 1050mah pack. THAT COULD BE DANGEROUS! i dont know exactly what would happen, but i wouldnt want to find out. if you had 4 350mah cells, you could make 2x2s packs and put them in parallel with an adapter board to fly, that would give you a 7.2v 1400mah arrangment li-poly and li-ion are the same basic chemistry so you can use the same charger, just dont exceed the charge rate of the pack, ie 1c=1xcapacity= no more than 750mah charge for a 750mah pack. can always charge at less than capacity, but not voltage, it just takes longer.
Posted on: 3/30/2004 8:19 AM by Author "urbnsol" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=1673109

RE: Home made Lithium Ion battery charger
there is a very complete discussion about making your own li-poly charger at: http://www.rcgroups.com/forums/showthread.php?s=&threadid=130567 the scott henion design is listed farther down in the thread, but i like the electron_head design better, its is simpler with fewer parts and less chance for error with the switches on the henion design, which of course is similar to the less expensive commercial designs with jumpers or switches. also, it is mentioned in the other board, but the lm317 is rated for 1.5A, the lm350 is rated at 3A, and the lm1084 at 5A with an even lower dropout voltage than the 317 or 350. just in case you want to charge those 2000/2100mah packs, or parallel a couple of smaller packs and still have the quicker charge times. im getting ready to build one of these myself with the optional charge complete indicator circuit. anyone who is thinking about building a charger should read the rcgroups thread and/or the scott henion page about safety and such, and while it is a bit long (270+ posts) there is a lot of good info on the rcgroups thread.
Posted on: 3/29/2004 9:52 PM by Author "urbnsol" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=1672242

motor breakin
ive heard that i should break in my 350c motor but am not quite sure how i should go about it. ive heard to use a couple of c or d cells on the motor with no load or gear and let it run till the cells are dead. question is, cells in series or parallel, or just use 1 cell at a time? thanks for the help.
Posted on: 3/26/2004 11:05 PM by Author "urbnsol" in the forum "Brushed/Brushless motors, speed controls, gear drives"
http://www.rcuniverse.com/forum/fb.asp?m=1663811

li-po for e-starter with stock motor
posted in the radios/engines/batts forum before i realized there was an electrics specific version here. http://www.rcuniverse.com/forum/m_1663460/mpage_1/key_/anchor/tm.htm#1663460 thanks for the help.
Posted on: 3/26/2004 10:51 PM by Author "urbnsol" in the forum "E-Flight Power Sources"
http://www.rcuniverse.com/forum/fb.asp?m=1663767

li-po pack for e-starter with stock motor
ive been reading about these for a week or so and am trying to decide what pack i need to buy. i am planning on buying from fma everything i need, pack, charger, speed control for plane and maybe the safety guard, from fma. i was reading the app notes for the kokam packs and wasnt sure what i needed to get. ive got the 350c motor and stock prop for the estarter but was unsure of which pack to get. the recommended packs from gws are a 7.2-8.4v 500-730mah aaa nimh or 7.2-8.4v 270-400mah aa or 600mah aa nicad. so i was thinking about getting the 700mah 7.2v pack because it matched the specs of the recommended batteries, but after reading the notes i was thinking this may not be enough to run the plane. what kind of current will this motor draw? will this pack work well or would i be better to get the 1500mah 7.2v pack? would that be enough? according to the notes, a park flyer with a 280/300 motor will pull 8A so it recommends a kok340 3s1p pack, but for a 8-16oz park flyer with mabuchi brushed it say kok340/kok700/kok1500 2s1p but it doesnt say what kind of current draw i shoud be seeing. based on what ive read, i shouldnt exceed 2c for loads, which means if im drawing ~8A, i need a ~4A source, which means if i went with the 1500, id need 2s3p (7.2v/4500mah)? -quote from app notes #2_ Typical discharge curves up to 2C are shown in Exhibit 3. Although Kokam/FMA warrants performance to the 2C discharge rate, operating experience indicates that cells can be used at discharge rates above 2C if the user assumes all risk. ------ but im guessing that 8A would be a peak load, and i know that pack can take higher peak loads so a reasonable source would be 2-3A? so fire away. fill me in on the skinny and give me some suggestions.
Posted on: 3/26/2004 9:05 PM by Author "urbnsol" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=1663460

50mhz radios
i tried to get into this hobby a few years ago and i was given a jr max 4ch am radio by a friend who didnt want it anymore. i knew nothing about the tx at the time, but i am going to start flying soon and wanted to make sure the tx/rx was still ok to use so i called jr today to see about sending it in for a ckeckup and such. i think its going to be fine, but we'lll see. i am hoping to use this tx/rx for a trainer so i can delay some of the initial cash outlay, then get a new system for later planes. i am the type that does a lot of research before i buy something and i had been looking at radios (mostly jr, as i know that name from the research i did a couple years ago) for basic cost and info to give me things to think about before i really start looking to buy. so while i was talking to the tech on the phone today i asked about 50mhz radios because i didnt see any listings for them and figured it would be a special order type deal. he said the only ones they had in 50mhz was the 10x and something else, i cant remember the model number, but anyway i said ok then went to look up those parts for info and BAM!!! $$$$$$$$$$$$$$$$!!!!!!!! i am not looking to spend $1000 for a 10ch wizbang radio. while im sure it does lots of really cool stuff, thats not what i need. so i guess i need to look at some different brands. now for the question: can anybody recommend something in the 4-6ch range for a reasonable (<$250) price. dont anybody do lots of research, i can do that, just wanted to know if anybody knows of some right off hand, or better yet from personal experience. thanks for the help.
Posted on: 3/17/2004 11:58 PM by Author "urbnsol" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=1635942