I am building a 1/2A student and would like to modify it for electric.  The wingspan is 24" and the plane is pretty light.  I know very little about electronics but I can't take model airplane fuel with me when I go on deployment so I am forced to learn.  I would like to use 35' lines and be able to have enough power to do the complete stunt pattern.  Ive done some reading around on the forum but alot of it doesn't make sense to me.


why cant I just have a motor and a battery with an on/off switch? 
what size motor/battery do I need?
what else do I need?

oh and for those wondering thats the first coat of paint before sanding. 

I also need one of those timer controllers, right?
where do I find them?


How does this setup look? 
Axi Brushless Outrunner 2212/20 Electric Motor - 57 grams - $54.90
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPRB9&P=0

7.4 volt - 800mAh 8C Li-Poly Pack - 43 grams - $12.00
http://www.commonsenserc.com/product_info.php?cPath=37_35&products_id=58

ElectriFly Silver Series 12 amp Brushless Electronic Speed Control - 14 grams - $34.99
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKSY3&P=7

AXI Model Motors Radial Motor Mount set - ? - $12.90
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPPZ9&P=M

Will Huban's Timer - 11 grams  - $16

Cellpro 4S Charger, 12V Power Supply Combo - $89.95
http://www.fmadirect.com/Detail.htm?item=2272&section=45

125 grams / 4.4 oz
$220.74 + Shipping

oops,
Almost forgot. Here is a link to two popular timers, the JMP-2 and ZTRON 3. Either one works great. I tend to prefer the JMP-2, but it isn't clear if it will be around for much longer. Also Will Hubin is making a timer. Here is a link to a thread on this forum.
http://stunthanger.com/smf/index.php?topic=7677.0

I was thinking about mounting the battery under the wing and cutting back the motor mount on the plane another .75" or so as the plane will be nose heavy as it is. 

I was under the impression that I would be able to use a car battery to charge the airplane up. like with my r/c car that I have.  (I am trying to keep the number of things down that I have to bring with me to the desert this December as I only get 20"x20" of space plus carry-ons )  as for apc props I don't like them as I have cut my hand badly using them.  I normally use only grish tornado props but they are getting harder to come by now that grish has passed away and props are no longer being produced.   With the above setup how much flight time do you think I would be able to get?  I would like to shoot for 4 to 6 minutes.   

Jeffery,
Remember about the APC props and electric-- you aren't flipping them, and you aren't adjusting the mixture  . I think they really are superior to most other props for electric. But if you want a different prop, that's ok.

You might be able to get 5 or 6 minutes a flight per battery. I'm getting 2 minutes on 1/3 of my 2s730MAHr battery. You have 3 cells, so already 50% more stored energy than I have. A larger slower turning prop is also probably more efficient than my smaller prop. I would feel comfortable at 4 minutes with my setup (and I think I can back-off a little on my initial throttle. So I am guessing that you will be ok at 6 minutes, although that is a lot of spinning around on a 1/2A!

I agree with Kim that a 12V battery will probably be fine for these small batteries. You aren't really having to put much energy back in, even if they are pretty depleted. I would put the lipo battery on top of the wing---less chance it will get damaged on the top. Also check out FMA for batteries. They are pretty reasonable in cost on their 750mAHr cells---but they are different in shape and maybe weight than the EVO, so make sure they would fit.

[edited to make clear it is the lipo to put on the wing, not the 12V lead battery!!]

not when you fly military 

The reason for a balancer is to adjust each cell in a multi cell pack (where the cells are in series) so that it has the same voltage (and basically the same amount of stored energy) as the others in the pack. Otherwise when you would charge though the power out connector, the higher cells would be overcharged (bad!), and the lower cells possibly undercharged. When you run the battery, the lower cells might get dangerously close to being past its "point of no return---also bad). Lipo batteries are much more sensitive to being under- and over-charged than the old Nicads and NiMH batteries, the main reason "balancing" has become mainstream.

What I originally did, since my charger didn't have the balance built in, was to buy a "Blinky" balance (and adapter connector) from AstroFlight 
http://www.astroflight.com/store/store-type-tem.html?item=products:af-106&sid=0001AdfOCPV6EQgQ8c2X2M9

You need the adapter ($5 more or so) for the particular Lipo manufacturer in order to plug in. Here is what I bought.
http://www.astroflight.com/store/store-type-tem.html?item=products:af-549&sid=0001AdfOCPV6EQgQ8c6g6B8

What you do is to plug in the balance connector that comes on most Lipo's (but not all) these days. The Blinky led lights start to flash, if they flash randomly, then all cells are basically at the same voltage. If one light stays on, then that cell is higher voltage than the other cells. The light being on means that cell is being discharged to lower its voltage (basically to drain the cell) to the level of the other cells. And it goes on until you get the random pattern of flashes again. The drain is small, so it can take some time to get things in balance. Now this also works when you are charging the pack through the main power connector.

The other option (other than not having one at all) is to buy a charger that balances the pack while charging. I have a second charger, the FMA CellPro 4s (charges up to 4s packs). That one works by charging the pack directly though the balancing connector. That way it can selectively charge the lower voltage cell more than the higher voltage. Again you probably need an adapter--unless you have FMA lipos. The adapters aren't that expensive. An advantage of these type chargers is that since each cell is being individually charged, that some manufacturers allow you to charge faster than 1C because there is no danger of any one cell being overcharged --especially at a high rate which is probably extra bad!

Finally I mention that my small 2s Thunnderpower Pro Lites don't have the balancing connector. My guess is that they are older packs. I prefer a balancing connector, but I went for the lightest pack. I don't know if Thunderpower eventually plans to add the balancing connector. Anyway because of that, they (TP)  say to never charge these packs at a rate higher than 1C---so my 730mAHr cells should never be charged faster than .73 Amps--so it would take a little over an hour to charge an low pack to full charge (note I didn't say "empty" pack---that could destroy the pack).

Jeffrey,

A cell balancer evens out the voltage of a multiple cell battery pack so that each cell has exactly the same voltage when fully charged. (VERY IMPORTANT!!) It does this by applying resistance to the cells that are "ahead" of the others until they catch up. Without the balancer one (or more) of the cells in your pack could have a low/incorrect voltage and thus the total voltage for the pack would be less than what was expected. The charger will then try to increase the voltage to the pack to bring it up to the correct total amount and in doing so it will overcharge the properly performing cells. The opposite scenario can also occur where one of the cells has too much voltage and the charger will cut off charging too early as it will see the correct amount of total voltage. Now if you take that battery and use it, it may discharge too low too early causing a problem for the battery (voltage too low to recharge) or for your plane (stops putting out enough power to complete the flight). LiPo cells do not tolerate overcharging or allowing the cells to get below a minimum voltage.

Yes you must use a balancer for multiple cell (LiPo & A123) batteries for three resons.

1. To achieve the best performance from the battery.
2. To prolong the life of the battery.
3. To help prevent your house or car from burning to the ground.

As to which to purchase that will depend on how many cells you will ever be charging at once and your budget. There are Chargers, Balancers and Integrated Charging Systems. I am going to suggest that you purchase an integrated charging system such as the Thunder Power TP-535, TP-610 or TP-1010C combined with one of the TP balancers. The reason I reccommend this combination is that the charger, balancer and battery are in a closed loop and the charger and balancer can "talk" to each other to provide a greater level of charge information and warnings as well as being the safest method available.

http://thunderpowerrc.com/html/cba-chargers.html

For a balancer I reccommend the Thunder Power TP-205V or the 210V

http://thunderpowerrc.com/html/cba-balancers.html

Personally I use two of the 1010C chargers, an Astro 109 charger, 2 of the 210V balancers and one 205V balancer. Having extra balancers on hand allows you to balance a battery to a state that will permit charging without tying up your charging system. Extra chargers allow you to discharge batteries for pre-use conditioning or to correct a stubborn cell imbalance.

A note on batteries: Good batteries will reward you with better power to weight, longer life and better support. LiPo's are expensive regardless of which type you purchase. Using a top line battery is not an extravagance. You will have fewer problems and more success. I highly reccommend using Thunder Power batteries as they are simply the best batteries available on the market. (And you even get TP balance taps thrown in without asking :-)   )

Whatever setup you use you should familiarize yourself with the product safety sheet and charging instructions for the type of cell you are using.

Hope this helps.

Kim.