who would be interested in NiMH battery packs for warps?

[billmi]

Originally posted by sniper1rfa
well, thy wont run the rev, not enough voltage (they NEED 18 volts, 12 volts will be all slow and stuff, and these are only 9).

The Revy only needs 12v, not 18 for optimal operation. It uses 18 as a source, because it's convenient to use a pair of 9v batteries. That voltage gets regulated down to 12v by the board. It can run an 9v, but then you have 9v Revy performance (which really might not be as bad as it sounds if you can provide more amperage than a standard 9v cell, but you'd have to try it to see).

See you on the field,
-Bill Mills

[sniper1rfa]

nope, not true (anymore). the only regulation the newer boards do is the 5V logic curcuits. "voltage" to the servo is controlled through PWM.

for those of you not in the new, PWM is Pulse Width Modulation. basically, its turning it on and off real fast, works by averages. for example, give the motor 18 volts, then run it for 2 ms, leave it off for 1ms, and repeat, and you average 12 volts (or at least, a simulation of it). there are several reasons why its better. the two most prominent reasons are that its easier to do, and voltage regs use a small amount of juice on their own (better battery life).

so, the modify my original statement, it will either be a 9V rev, or the servo will get 6V. either will work all right with a JMJ, but not neccessarily well. and since i have no way of knowing which it will do, my blanket statement is "no, it wont work."


thanks for the pics, RP!

[billmi]

Thanks for the correction.

If the newer boards are doing the motor speed control with PWM, do you know what's up with the 9v boards? It was my understanding that at least before they were the same board, in a different mount, if that's the case now they'd be driving the motor at less than 9v (average) due to the PWM.

It's also my understanding that PWM delivers better torque at lower speeds than truly lowering the voltage, and it certainly is easier to control through varying rates.

And BTW, that's a pretty decent price on the battery packs, considering you're including the charer.

See you on the field,
-Bill Mills

[sniper1rfa]

board is proably the same, programming is probably different. specifically, i doubt they are using any sort of limiter in the 9V ones. also, the low-batter indicator is programmed differently. otherwise, there would be no reason to use a different board. just a guess, though.

im not really doing the packs for the money. its more because its fun. were I to meet, for example, airsoft prices, i would be charging 60 per pack, not to speak of chargers. and i definately wouldnt have a starting price of 40 for custom packs. :-)

[Cyberious]

Warp battery

Interested. PM me with the info if you make them.

[SqueegeeKid]

I'm interested as well.

[billmi]

Originally posted by sniper1rfa
im not really doing the packs for the money. its more because its fun. were I to meet, for example, airsoft prices, i would be charging 60 per pack, not to speak of chargers. and i definately wouldnt have a starting price of 40 for custom packs. :-)

Yeah, those prices were looking reasonable compared to RC aircraft too.

Looks like the next wave is starting in rechargeable technology though - Lithium Polymer (not to be confused with Lithium Ion).

I don't know enough about that yet to know how practical it would be for these sort of apps.

See you on the field,
-Bill Mills

[sniper1rfa]

dont know much either, but i know Li-Ion isnt very good for any sort of power curcuit (great for logic curcuits, though), because each cell is 3.6 volts, minimizing the range of voltages possible.

you fly electrics? balsa models, or kits?

[billmi]

Welll, I think it would be better said that I crash electrics.

I built a .40 cub that was a gift to myself and my wife's grandfather. We worked on the airframe together, with him telling me stories about working on Stearman trainers, B24s, and B25s in WWII (he was on the crew that built Dolittle's modified 25s to strike Tokyo from an aircraft carrier.) Anyhow, I moved to FL before it was finished, and last year brought it out here and finished it, then learned cubs are notoriously hard to learn to fly.

So.... I saw plans in Model Airplane News for an electric L19 (renamed O-1 during the Vietnam Era) which is a similar high wing, but this design was a trainer with good dihedral. I photocopied and blew up the plans and built it mainly from leftover scrap for the cub.

It's already had a couple of crashes one that broke the wing in half, and both breaking apart the nose. In both cases they were about an hour's work to repair, it's a pretty sturdy design.

Here are before and after pics:

http://www.corin.com/bill/rc/L19/birddog.jpg

http://www.corin.com/bill/rc/L19/first_flight.jpg

There have been a few references to Lithium Polymer in battery articles in Backyard Flyer magazine over the last year, but with not a lot of detail since it's a new tech. Sky Hooks and Rigging has some very light compact batteries. One of the plusses is that the cells can put out significantly higher voltage per cell, so weight wise they are more efficient (less weight spent on the containers of multiple cells to reach desired voltage) and as much as I've learned so far they're looking well suited to the amperage output needs of electric motors. Considering the E-Mag runs on NiMHs fine, which have typically poorer amperage peak output than NiCDs. I know of one helicopter design (read as weight critical) that runs 3 minutes on a NiCD pack, and a NiMH pack can't deliver the amperage needed to get airborne. The designer is expecting to release a Lithium Polymer pack and charger this spring, and from their tests they are talking about a 11 or more minutes of flight time.

See you on the field,
-Bill Mills

[shartley]

ouch.

[sniper1rfa]

11 minutes over NiCad? wow, that would make an AA of this chemistry like 4-5000 mAh. either that, or the pack have fewer and larger batteries. impressive.

i fly electrics with my grandfather. we have ammassed a ton of them. 3 pure sailplanes (a segita and two gentle ladies), 4 powered sailplanes(two lasers and two others), and 3 powered planes (a cub and two cessna scale models). very fun to fly. If you wanna get better, see if you can grab a Stick Trainer of some sorts. they can take a beating.

NiMH are fine for anything but serious drain aplications. the AAA's i use in my packs are good for 8 amps. I suspect a chopper needs a little more than that, since eventhe gas ones have trouble getting off the ground.

[billmi]

Well, the crashes on the L19 were all pilot error... Not having actually taken the time to find an instructor - first flight was a bit windier of a day than I should have flown, and I gave too much elevator on takeoff, stalled and rolled right - into the ground.

Second flight - wasn't intentional - calm day, but evening, and no time before sundown to get to the flying field - I figured I'd do some taxi runs up and down the street (as I'd done in initial set-up testing.) Good plan, since the tailwheel is fixed, taxiing is a bit to learn - it has to have enough groundspeed and throttle for the rudder to get that wheel to drag left or right. Anyhow, I have too much throttle, and got airborne - found it's nice and stable, but on my street there's not room to turn around in the air (too many trees.) I ditched in a bush, but there was a tree in the middle of it :-P So now, I'm waiting for a good calm day to coincide with me actually having time to get to the flying field...

Back to topic, on the Lithium Polymer batteries - I did a little web hunting today, and found a company selling them - their site says they are a Gel based Lithium Ion battery, but instead of metal, their casing is mylar saving on weight and bulk - which I would expect would make them more fragile, yet substantially lighter for the MAh delivered. With E-Mag's already having a battery housing of aluminum, perhaps a smaller housing could hold a Li Polymer battery with the same or more muscle as the current NiMH packs.

Be it NiMH or Li Polymer, I'm interested in eventually setting up a pack curved to a radius close to an HPA tank to fit in a pocket on a tank cover.

See you on the field,
-Bill

[sniper1rfa]

interesting. any info on charging or anything? that my current problem, i cant find decent chargers, and custom ones are too damned expensive.

curved? that would be hard, though i could make one that is flexible to a certain degree (enough to bend to a tank). the thing i would be worried about is fatiguing the connections and snapping them. even like 22 guage wire would go without suppost of some kind.

fly in the morning, like 7-9 AM. after the dew, and before the wind. thats one nice thing about electrics, there are no time constraints. The AMA (american model association) restricts gas flight to 9 AM- 5PM.

[hostage]

heh i was thinking about talking to you, I have a crap load of the charges that I got at a steal from rat shack, 9.6v. Mb we can do a trade.
-Doron

[sniper1rfa]

i have a supply of them cheap now.

actually thinking of starting to build them now. well see where that leads.