jfetter
Posts: 321
Joined: 11/25/2003
From: MIRAMAR, FL, USA
Status: offline
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quote:
ORIGINAL: reincarnate
Hey jfetter... Can you give me an idea of what it's going to cost to run a plane this size with electric? Motor, ESC, Batteries? I'm going gas or glow (jury' still out), but I've always wondered what a big electric would cost to set up. Also what kind of flight times do you get with your set up? Just curious for the future.
OK, my answer is by no means gospel, I have my own system and I beleive in only A-grade components plus I am a monster with batteries. People at the field clutch their heart when I open my field battery case with 10 FlightPower EVO 6S2P 5000 MAh packs ($395 a pop) because they just see the initial expense. When I started out, I would fly 2 packs and field charge them in between flights, it can be done but there is some down time. Every battery pack should take an hour to charge (LiPo's) because you always charge them at 1C, or 1 times the capacity. So for my 5000 MAh packs, I charge them at 5 amps (really 5000 MAh, their exact capacity in an hour). People have a hard time with this (I don't know why, it's quite simple) but if you always remember that, you'll see that flying for 15 minutes and then dropping in pack 2 and flying for another 15 minutes means you'll land and pack 1 will still have 45 minutes to charge.
Now the logical thought would be to add 2 more LiPo packs, even if the nearly $800 doesn't bother you, you can calculate that flying all 4 packs for 15 minutes, you would land and pack 1 would still have 15 minutes to charge. Also, you now have more than 1 pack charging at a time, so you have to bump up the number of chargers you have (not too bad, the AstroFlight 109 is still one of the best chargers and only $129). But that comes at a cost as well because charging 2 x 5000 packs at 1C requires a 12-volt draw of nearly 11.5 amps, too much for your small lead acid starter batteries (I had 3 in parallel and I'd drain them before 2 packs were charged, not actually drained but too low to keep the sustained 13.8 volts the chargers need to not error out). This means a heafty car or marine battery or a 12-volt source like a 20 amp DC converter.
If you add in allowing the packs to cool to ambient temperature before charging (always best practice), you quickly come to the conclusion that flying a lot with electric really boils down to how many batteries you bring with you. You can charge at the field sure but if you really, really like to fly and stay in the air as much as possible, it's hard to have a charging system that can keep up with less than 3 chargers running simultaniously and 6 flight packs. This system works, I did it for a long time but finally I decided that I would just buy more packs. The difference was that I would try and buy packs that would be ideal in most planes by themselves or the right size to run in series with the larger 2-meter planes I knew I would end up with. I chose 6S but 5S would have been a great choice as well. Most .60 - .90 sized planes require a 5S to fly well but really a 6S to have a kick. Likewise most 2 meter or larger warbirds require 8S to 10S, so if I use 2 of my 6S packs in series for a 12S pack, I get kick to spare (though this comes at a cost because I have to oversize my motor and speed controller so they don't fry, which really translates to more money).
OK, what's it all mean? It's just different than glo/gas, no harder, just new things to learn. Once you get in to electric it all starts to make sense, you'll go from smaller foamies, perhaps indoor helis to .40/.60 planes, perhaps even more to the larger stuff, I guess it depends on your ability to rationalize spending money up front for batteries that are really comparable to buying your glo fuel a few years in advance. I crash and destroy 2 of my 6S 5000 packs and I am out the plane, electronics plus $800 in "fuel". I wont get the chance to get my moneys worth from those 2 packs, that can be hard to accept for some. Truth is if the LiPo gets 300 charge cycles (about what the manufacturers say it should), I will be flying for a fuel cost of $1.25 per flight (1 pack) or $2.50 (when I use 2 in series), not really out of line with glo though more than gas. But if you factor in my plane balances the same before and after the flight, my motor needs no tuning, it runs the same hot, cold, humid, dry and there is no cleanup, you might find that preferable as I do.
Here's the cost of my e-flight components for my Fliton Inspire 60 for an example of startup cost;
Axi 4130/16 outrunner motor - $189
Jeti 75 amp Spin ESC - $199
FlightPower EVO 5000 MAh LiPo - $375 (I get 12 minutes of "strong" flying)
This combination equates to about 145 watts/lb. a retio that says unlimited vertical and the ability to easily hover (150watts/lb is the goal if that is your desired flying style). You don't need a glo engine or a throttle servo so the cost of the electric motor is a wash, if you buy 2 batteries, then the difference is $950 over glo (ESC (speed controller) plus 2 battery packs). This $1,000 does not cover LiPo chargers, 12-volt converters for field charging, WhattMeter and Spin controllers for tuning, etc. Bottom line is you will need to spend more than $1,500 if you have no components over the cost of the regular glo version. If you are talking about the Sundowner which will use 2 of these LiPo packs in series and require a 100 amp speed controller and larger motor, the numbers are even higher. For me it's not an issue because I have been flying larger electrics for close to 4 years, I have a substantial invenstment in LiPo's so that is not a charge I see (I do recognise the investment though and the time to keep them all balanced and charged properly). I guess in the end it comes down to what you like, it's a hobby after all, it's supposed to make you happy while you have fun...
(sorry for the essay!)
Jack
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RE: H9 Sundowner - 
