Pond Skipper

Yes could hit the local electronics store for a 5A diode in series with the positive wire for a 0.7 volt drop down to 5.9 volts however diodes are unidirectional so when charging you will have to have a jumper plug for charging. 2S lipo when peaked at 8v+ perhaps can benefit if you use two diodes.

My 280mah nimh's peak out at 320mah with my smart charger and when in use with the Lil Speedy the 3 nano servo's could go 8 flights with still about 150mah left. I plan to use this pack in the 5ch 1/2A. The 250 1S for the Lil Speedy. Like most 350mah seems the way to go for 1/2A using 7 to 12g servo's

Mr Cox

Yes, one diode should be enough, that's what they use in the step down regulators...
The voltage drop over the diode is current dependent though, so a voltwatch will light up like a christmas tree and the receiver might not like it. The commercial one are only intended to be used with individual servos, I think, on these the voltage drops are not critical.

I'm using 400mAh NiMh in most of my 1/2A planes, they weigh around 1oz which is acceptable on a 10oz plane, I think. One has to check the batteries carefully though, they only give me about 2-3 good years and after that the performance goes down. This is only seen in their discharge properties, they don't deliver the specified mAh and they don't deliver high currents either. After 4-5 years they are pretty useless. Maybe I'm doing something wrong, but I don't have a trickle charger that goes down to 0.1C (40mA) for these.

MJD

My Feedback: (1)

I got spooked by NiMH batteries, some of the problems I had are of course my fault, but I had enough issues that I decided agaisnt them quickly as Rx packs.

Maybe I'd be smarter using the stoep up reg after all.. I just had "thoughts" about adding more electronics, and esp something new to me.

Mr Cox

I still think there can be some advantages to LiFe. I have a 700mAh pack which together with a regulator and extra capacitance (4.7mF) is slightly lighter than a corresponding NiMH battery (about 50g versus 55g, IIRC). You get a lower self-discharge rate and faster charging. The newer NiMH with a low self-discharge rate have a very high inner resistance so they are not well suited for RX packs but work great as TX packs.

If you can find a good HV receiver, there are for instance the Dymond D47 servos that are very precise and can take voltages up 9V. Then you could use a 2S Lipo directly and possibly save some weight too. The fire hazards are a little scary though, if one has to baby-sit the batteries during charging, plus give them a proper charge level before storage etc, one might as well turn over to electrics completely, as all the conveniences of glow would be gone...

aspeed

What do you mean electrics? Control line!! Just the glow plug battery, diesel? I think LiFe is fairly safe. At least the A123 brand.

MJD

My Feedback: (1)

I need to pay more attention to Dymond servos. I only have two D60's, which are excellent. I did not know about the voltage tolerance on the D47s - good info.

Mr Cox

When I see how people take worry about their Lipo batteries, it really seem like a lot of hassle...
LiFe should be much safer, but so are NiMh batteries too.

I flew a diesel today, a Cox Queen Bee with RJL head. The first comment from the others was how quiet it is in the air.

Pond Skipper

Well checked out the smart lipo 250mah I has some pluses / minuses
You can plug any size battery into the charge port up to 16v to extend field flying if desired for the day.
The black tab has to be remove to arm the device / easy to lose in the field can tie a thread to it to keep it onboard to the device. Or park it on only 1 prong.
So I plan to use a switch harness / on will close the circuit which turns it off / off which opens the circuit to allow it to turn on or to use the battery charge lead that comes with rc switches to link in a charged battery. This will make using the 250mah battery more using friendly externally without having to open up the plane to turn the thing on and off. The hand launch glider guys have been using this 11.1g set up since they came out at 250mah you should have no problem with 2 to 3ch setups getting 5 flights at the field with 1oz tanks.

Pond Skipper

On a side note you can charge direct to the battery with a smart charger if you have a micro plug as shown on the battery side. The Smart Lipo folks recomend disconecting the battery from the circuit board if you do not plan to use for more than two weeks.

MJD

My Feedback: (1)

OMGI didn't know about these!!

I think I just wet myself.

[later] nah, we're good.

Not cheap, but they are meant for people serious about size and weight. I think I'll take a look at the 450mAh unit, mainly because of the higher current rating and it's only 26g. I think it shouldn't be hard to get at that pin/charge port externally? Or is it less convenient than it looks..

They have a magnetic switch option on the 450 up.. but the weight doesn't seem to be listed.

Pond Skipper

Well I bought it for the Lil Speedy to shave some weight and up the speed a hair. The battery location for me is inside the wing bay area which in the field isn't a handy spot to be turning it off and on.. I did see the mag switch just not a lot of room in that plane for additional components. For most planes access to turn this device on and off shouldn't be a issue just in my case so the switch harness / charge plug idea seems like my best bet.

MJD

My Feedback: (1)

Gotcha. On the Toucan there is loads of room relative to these more minimalist 1/2A models, it is a squared out fuselage with radiused corners for smallish Lipo packs, and has enough depth for flat things under the aileron servo and enough room between the servo and firewall for a decent size fuel system. But overall it is a slick little devil with very little excess frontal area. I think the precisely molded wing makes up a large percentage of any performance points on the package. I was tinkering with the fuel cutoff just now but time for Zzzzzz.

OT bla bla: Had a great although mostly bouncy 2 hr flight in the Moth today, "buzzed" my wife and the neighbours in the village who we could see were all waving from a regulatory and turbulence friendly height (cliffs and valleys adjacent and 16mph winds and a huge storm front through a few hours earlier), then terrorized three airstrips owned by buddies before rocking and rolling our way back to home base.

Mr Cox

The price of Smart Lipo has been a little too high in order to just get one to play with, to me...

One thing to keep in mind though, is that the rating they give is for the battery, not the output. So with a 3.7V average on the battery boosted to 5V on the output, the current draw on the battery is at least 35% higher than at the output (disregarding the losses in electronics, not sure how large they are). So a 650mAh battery will at best provide 480mAh on the output. The weight is still better than the NiMh ones of coarse, but not as much as one might think at first...

Pond Skipper

Yea the .020 Lil Speedy has no room to spare.

The Skorch has a front hatch for the battery and depending on CG needs I may forgo 280mah 23.2g 4cell NiMh's for another 250mah Smart Lipo. If things are spot on I would consider going with the 26g 450mah Smart Lipo for more duration.

Good to hear you have been enjoying some air time in the Moth / general min safe altitude in a private plane flying VFR is 1k to stay on radio we have a nice ultralite field near by I have thought about buying a plane to store there. I use to cross country fly from LA to TX for a few years but these days its strictly RC.
I would not mind at all investing in some gear to fly in a quadcopter type inclosed two seater 4 gyro's 8 outrunners 8 three bladed props / sets of two counter rotating per station. I have a design that incorporates some wing surface area to allow lift at cruising speeds to help reduce amps. Think I would have to have to have a gas launched parachute system for the entire craft just in case.



Welp a doodle does help here is my wing ready for hardware I will not be using hinges rather monokote for zero hinge gap like the Lil Speedy the photo bottom right corner. That fly by at full throttle inspired me to build the next size up and the wing shape is spot on just bigger and twice as thick. I will only be lightly loaded with a 1/2 engine at 11oz RTF. There is another thin sheet of 1/64th matching the top sheet on the underside. Flared out as I will be using rubber bands to hold the wing on and protect incase of a hard tumble
4x29.5in / 88sq in wing is considered small by most yet the wing looks like a glider wing up against this 14in span 4.4oz scale Testors .049 Spitfire.
The flaps will help slow down this pylon type racer allowing 88sq. in rather than 150 to 200 squares typical of 1/2A planes.

Pond Skipper

Here is a single seat rendering reflexed tail undercamber wing for extra lift / operator on the cg no rudder as the counter rotating props handle yaw lifting body , simple manual operated retracts. I feel 80 at the props-90 kWh rated should do the job for 1.5hrs. / 107 hp if at full throttle lift at 60 hp. In tilt forward mode I would shoot for 70 mph ground speed at cruise and 130 at full bore for 45mins. Cross country X Games - Quad races over various land terrain, water and under bridges etc.

MJD

My Feedback: (1)

Yes - I would not count on more than 300mAh available capacity from the 450mAh setup with losses also figured into the equation. But that is a good capacity for a 1/2A, and at 15-16g.

Pond Skipper

Yea should be interesting - a charged 3.7v lipo should be at around 4.2v so to push it to 5v isn't much I would speculate 85% of the battery capacity on tap for use which should be plenty for the lil speedy on 3 micro servos.

Mr Cox

Well, the point is that it would only be 4.2V in the beginning, and 3.7V on average, if you intend to use the full capacity of the battery.
The efficiency of the electronics is likely somewhere around 90% at best, and 3.7V/5V is 74%, giving a total factor of about 67% (at best). Not using the last 20% of the battery capacity, as recommended for Lipo for longevity, will give you about 53% in total compared to NiMh. So that is certainly something to account for...

Pond Skipper

Right I figure 85% for use and if used as high watt power source the rule of thumb is 20% / 65% available. In the case of servos will be drawing down the cell slowly.
I have noticed about 140 to 150 mah drain after 5 flights on three sub 5g micro servo's.
Note the 250mah cell charged with a smart charger will fill past 250mah as observed by my own smart charger - always puts more in than nominal ratings by all manufactures. I will try out this weekend and report the results. I have charged the battery with a 4 cell nimh using the charge in side of the circuit board, next will use the smart charger and see how much more the battery will charge at 1C need to snag a mini plug to go direct to battery.

Mr Cox

All chargers will charge "more" than the ratings written on NiMh, as it indicates how much you can get out of them. Cycling is the best way to check a battery, it is hard to find a charger that will go low enough in current for the smallest NiMh ones though.

Pond Skipper

At 1C which takes some time does a great job of exceeding nimh and lipo ratings of sub 350mah cells.
I will peak the night before a my flying day and then peak again at 1C the day of - lipo's will take a little more the second time but not much they are very stable and hold their charge well the nimh's however will provide reasonable amount of additional capacity by this secondary peak charge so making the practice worth the effort if you are using a pack that is borderline on capacity to fulfill required expectations . I have some nimh that came out a bit over a year ago on the market rated for 280mah touted as a high C energy battery for micro motors under 100w I'm able to exceed to tad over 370mah.

Mr Cox

Do they deliver that high mAh numbers during discharge too, or is it only the amount needed to charge them?

When batteries age, the delivered "juice" decreases down to very low values. I have some 5-7year old NiMh batteries that sort of act fine during charging, but will not deliver anything near their rating during a discharge anymore...

Pond Skipper

If you have the paitents always charge low C these do well for discharge use with elect motors:

Dynamite 7.2V 260mAh 1/2AAA NiMH 6C Flat DYNB0104 for Proboat Impulse 9 / Blackjack 9 -180 size flat can motors.

http://www.ebay.com/itm/361013475454...#ht_3108wt_970


for lipo these 180mah 20C are impressive for there size;
http://www.ebay.com/itm/390845556101...#ht_2472wt_725

As chemical types improve they still dry out so to speak the constant use changes the chemical make up and flattens them out. its the way it goes for all battery types having a finite amount of use pre engineered in the design the only factor that changes their duration is type of use, temp conditions during use and when stored and age when purchased. I have found when you buy new tech you have a better chances for longer useful life cycle rather if it was new old stock then you get what you pay for.

MJD

My Feedback: (1)

I weighed some small packs last night - the 450mAh smartLipo looks pretty good by comparison to all of them, even if you consider it is effectively about 300mAh. A 200mAh 2 cell LiFe is 15.7g.

Pond Skipper

I see the 450 has been phased out by the new 500mah perhaps???

Specs:
Capacity: 500mAh
Size: 46 x 25 x 14mm
Weight: 15.3g
Input Voltage: 6-16.8v
Output Voltage: 5v Stabilized
Maximum Output Current: 1 Amp
Switch: External Jumper


http://www.ebay.com/itm/New-Smart-Li...item1e8f9a138b