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View Full Version : 3s1p a123 pack discharge capacity.


Mist-R Mosquito
02-17-2009, 05:32 PM
I've got two 3s1p 2400 mAh a123 packs, each in a B400, and I fly them to lvc but only put 1600 - 1800 mah back into each pack. One B400 has a Suppo 40 amp esc and the other has a Turnigy Plush 40. Low Voltage on esc's are programmed to low/NiMh which should result in no lvc (at least on Turnigy). I'm not sure about the suppo.

I've seen posts here and on other groups where pilots are getting a substantially greater percentage out of their packs capacity wise and putting back 2000 - 2200 mah. Does anyone have any ideas - I'd sure like to be able to access that extra capacity!

I'm using the Hobby City 4400kv outrunners with 13t pinions & Align 325 pro woodies.

I zip charge with a watts'up meter and a DB Terminator and balance the packs with an astro blinky. Source is either truck's battery or Black & Decker 8 amp 12v travel cooler power supply (this works really well if anyone's interested in a $13 tabletop zip charge source for 110v!).

Any help would be appreciated!

Thanks!

Gene

JustPlaneChris
02-18-2009, 01:47 PM
Gene, my recharges are usually in the 1800-1900mah range (Swift and Protos, 10S and 7S respectively). I don't usually fly them to the point of "dumping" in flight, since the discharge curve is pretty abrupt (time to auto!). It also makes them hard to recharge sometimes, since my charger complains about the voltage being too low.

I have lvc set to some ridiculous value in my Castle Phoenix and Jazz (1 volt per cell, I think) so I never really hit lvc. I'd guess your ESCs are still trying to protect your batteries and shutting you down before you really need to land. Really though, you are probably only missing 30 seconds to 1 minute of useable power with those last few mah. I wouldn't worry about it. :)

Mist-R Mosquito
02-18-2009, 02:29 PM
Thanks Chris! I see you all over the place. I was just in the a123 thread about the trex 600 on 12s a123 and came across your posts. I'm thinking about one of these with a cc 85hv, scorpion motor and funkey fuse for the summer. I could go 15s if it would improve flight time at 1800 headspeed. What's your take?

JustPlaneChris
02-18-2009, 04:26 PM
Oh man, I've spent so much time thinking about the 'perfect' A123 600mm machine my head just spins. :lol:

In theory, 15S would improve flight time since the amp draw would be lower than 12S. You do have to factor in the additional battery weight of course.

Then I read about T2o's 8S2P Kinetic conversion, and he's getting 10 minute flights at 1500rpm, and spiking 2300 watts through the system. That's 3 horsepower! :shock: Despite the low rpm, he reports stunning performance, probably in part because he's flybarless and can run 14 degrees of pitch without binding anything.

In short? Hell, I dunno. Ask me next week and I will have changed my mind again. :lol:

Mist-R Mosquito
02-19-2009, 10:58 AM
what do you think of the Raptor e620? I was looking around and came across a thread to space out the lower frames 5mm with a cut up knitting needle and allow a 10s brick pack (or 2) to slide right in. Then I was in the tool section at Sam's Club this morning and came across a commercial 12v wheeled battery charger for $90. It's got charge settings of 65/40/20/2 amps. Got me to thinking I could fly the Raptor on 9s2p and zip charge as 3s6p at 65 amps or 10.8 amps per 3s pack using powerpoles in a keyed configuration. This should give me recharge in about 10 minutes. I'm looking more for longer duration with a scale fuse than 3d power and I saw where people are getting 12 - 20 minutes of flight time on 10s2p.

JustPlaneChris
02-19-2009, 12:04 PM
Raptor is probably the most A123-friendly airframe out there, and they fly very well of course. Do check out T2o's E-Kinetic, though. Minimal mods required to go electric.

http://www.helifreak.com/showthread.php?t=91812

The Century Raven is an even better starting point (CCPM, driven tail, upgraded head/tail) and can be purchased brand new for $250 from RREModels.com, and it comes with good quality fiberglass blades even. I'm really thinking that's what I'd go for (right now) if I were to build up a 600mm electric.

Century helis are so often overlooked, yet they are good solid designs that fly extremely well. The Raven comes stock with stuff that is "upgrade" for other brands, like TT tail drive, thrust bearing tail grips, etc. The only drawback is the canopy reminds me of 1970's big collar polyester leisure suits, but the upcoming NX canopy will fix that. ;)

Mist-R Mosquito
02-19-2009, 02:29 PM
I'll check'em out. Just did a search on RR, RC Groups and here for e620's for sale and nada! Trex 600's everywhere no 620's. What's up with that?

Man I'm missing my 10s swift bad! B400's aren't bad but it ain't the same!

JustPlaneChris
02-19-2009, 04:39 PM
I have a theory why you seldom see eRaptors for sale, (and even less often see Century Ravens for sale) but always see Trex 600's. But in order to avoid fueling the rumor that I'm an "Align hater" I'll refrain from sharing my theory. ;)

Hey, if you're really missing your 10S Swift that badly, maybe we can make a deal for mine...

Mist-R Mosquito
02-19-2009, 04:42 PM
Gotcha! How do you think a swift would fly on 9s1p - for scale duration? (Then I could zip charge the pack as 3s3p with my 25 amp charger at 8.33 amps per pack.)

JustPlaneChris
02-19-2009, 04:57 PM
I believe this will answer your question better than words can. :) It's 9S A123, same motor as mine but with a 10T pinion (I think... I'd have to go back and check old emails).

RStBQYPE5sM

Mist-R Mosquito
02-20-2009, 06:00 PM
Chris - I was setting up a new gyro on my B400 and was hovering at eye level in normal mode when the heli seemed to hiccup. I set it down and checked it out and nothing was wrong so I spooled it back up. Brought it back to eye level and went to idle up and it was fine for a minute or so then lost some power. I set it back down and saw smoke coming from the heli. Esc is up front and I couldn't tell if the smoke was from the esc or the motor. The smoke stopped so I figured what the hell and spooled it back up. It hovered fine so I flew a couple more packs (3s a123's) - just hovering - and nothing seemed wrong.

Do you have any idea about this. I know I sustained some damage but I can't tell if it's the motor or the esc.

edit - over on RCG someone suggested it could be bearing oil. I oiled them pretty heavily yesterday and this is the first time I've spooled it up since. Sound plausible to you?

JustPlaneChris
02-20-2009, 07:15 PM
Hmm.... I can't imagine any part of that motor or heli getting hot enough to make bearing oil smoke up? Unless a bearing siezed, then that would definitely get hot enough. I'd check the motor for free operation first, then go from there.

Mist-R Mosquito
02-21-2009, 04:45 AM
Yeah - I'm dumbfounded. I can't figure out what could fry badly enough to let out smoke and still allow the heli to operate normally.

Mist-R Mosquito
02-21-2009, 02:32 PM
Three more flights and no ill effects :dontknow