What is the current thinking for a twin motor set up?
One big battery running both motors or two smaller batteries running
the motors separately as independent systems.
jack.
Shared battery. Don't want one to have a better charge or cut out before the other one. This is one of the big advantages of electric power twins. If needed you could parallel packs but not separate per side.
Shared is the route I have gone but started to second guess myself as I get closer to the end.
Jack.
I did "shared" in my CL-215 a few years ago but am gonna go with separate for the cl-415 and the Albatross just because of the batteries I have on hand. For instance ... I have a few 3S 3700'S (for the 415) as opposed to a 3S 7400. I also have a few 4S 4000's as opposed to a 4S 8000. ;) (for the Albatross)
So my opinion is that it'll really depend on your situation as far as what batteries you have. The point Ed made is valid but unless you run your packs down to (or close to) LVC that shouldn't be a problem imho. Of course others have a LOT more experience in twins than myself so take my advice with a grain of salt. ;D
Colin
Hi Colin, which Albatros? Twin seaplane?
Matlow
I would still run packs in parallel as the two motor/esc's would likely not pulse the power from the combined pack at identical times. This would lower the actual work load on the larger pack in my estimation.
Both ways work well.
I've used separate batteries in the Deuces Wild and the Twin Otter.
I've used single batteries in my Twin Star and Canadair Water Bomber, and last year's Bronco.
Never a problem.
Quote from: jabiggerstaff on February 01, 2014, 04:01:15 PM
Hi Colin, which Albatros? Twin seaplane?
Matlow
The one in my first post at http://temac.ca/smf/index.php/topic,4354.0.html (http://temac.ca/smf/index.php/topic,4354.0.html)
Colin
ONE big or packs in parallel is the only way to go!!!!!
Separate packs always lead to disaster at some point! You will always end up with a battery lower than the other when separated, then LVC and disaster!
Separate batteries does suffer from the LVC problem.
But if the motors are wing mounted and you can position the battery close to the motor you minimize the battery to motor/ESC wiring. If the main wing comes off in two sections, they a single battery will require more battery connectors. So in summary, separate batteries can save you weight (from the wiring) and give you more power (less wire and connector loss). An added benefit, if you carefully plan out the wiring, then loss of one of the batteries won't be catastrophic, i.e. you can still have radio & servo power and maybe even be able to fly with the thrust of one motor.
Marc
Quote from: MarcV on February 05, 2014, 10:18:29 PM
Separate batteries does suffer from the LVC problem.
But if the motors are wing mounted and you can position the battery close to the motor you minimize the battery to motor/ESC wiring. If the main wing comes off in two sections, they a single battery will require more battery connectors. So in summary, separate batteries can save you weight (from the wiring) and give you more power (less wire and connector loss). An added benefit, if you carefully plan out the wiring, then loss of one of the batteries won't be catastrophic, i.e. you can still have radio & servo power and maybe even be able to fly with the thrust of one motor.Marc
Just like full scale. Add more power to the remaining motor and opposite rudder to counteract the yaw from asymetric thurst (just like we do on take-off with high-torque singles).
Andy