Hi guys I was just wondering what brushless motor controller everyone uses. I noticed many of the controllers I have seen in builds have a braking feature. Do you just pulse it reverse twice to combat that or is there a an alternative motor controller that doesn't have that? Thanks in advance
http://www.hobbyking.com/hobbyking/..._w_Reverse_Upgrade_version_AR_Warehouse_.html http://www.hobbyking.com/hobbyking/...ogramming_Card_for_Car_ESC_AR_Warehouse_.html I use this ESC and the 60 amp one in bigger builds and the 30 amp one in smaller builds (4 cells for the 60,100amp 3 cells for the 45,30 amp) The program card will let you turn the brake off, and change many other settings too.
if you cant disable the brake it is generally viewed as too much of a PITA to use. (and in practice, they're a giant PITA). The HK ones you see in common use here can have the 'double tap' disabled via the programming. That said, if you plan to battle in a format where utilizing reverse is considered shameful, heinous or outright against the rules, the double tap requirement likely isn't much of an issue, because you wont be backing the props anywhere near as often or in such need of hurry as in fast-gun.
Alright thanks, also as for low voltage cut off. I assume you just check your batteries before starting, or do you have some other way to monitor it?
Yeah but I mean don't the escs shutdown when they hit the lvc? Or do you assume the fully charged battery will last long enough?
You don't need to assume, you take some measurements, get some numbers, and do some math. Loading lifepo4 in my current battlecruiser, i can pack in 40AH. Conservatively I mentally lop off 10% or so of that and assume i have about 36AH capacity. I know how much my drive and pump motors draw and can make an educated, though generally exceedingly conservative, assumption about how much time I have on the water total.
not dumb questions My general view is 'pack as much battery power in as possible' Locally (for me) sorties can run anywhere from 10 minutes to 30ish (rarer lately), and fast-gun rulesets allow for changing batteries between sorties. So if you expect that your maximum time required of your ship to be on the water without a battery change-out is 30 minutes, I would add 15 minutes to that and plan that I need at least 45minutes of run time. YMMV of course, and if you're building something weight sensitive like a DD you might cut the margins tighter and keep a closer eye on matters. If you're building a battleship you probably have weight to spare to heap in extra power above and beyond.
Ah alright thank you. I guess my big gun brooklyn just became more complicated, but I will make it all fit even if it kills me haha.
if I remember most of the big-gun stuff I've seen and read, your power consumption rate should be lower than in fast-gun. Not sure on their sortie times though. Definitely ping some active BG folk and ask if they can share their numbers with you.
Nick, From what i have seen from amp curves, you should probably hack off 25%. Check for the Amp Curve data online. Regards, Trey
are you referencing capacity loss from aging, cycling or simply not being able to realize rated capacity before dropping below minimum voltage?
Voltage loss. http://sustainableskies.org/wp-content/uploads/2010/10/typical-lifepo4-discharge-curve.jpg I am sure you have seen what happens to an over-discharged Lithium battery. on a 2.5 ah battery, it hits puff mode at about 2 ah, so 20% add 5% for safety til 25% for my recommendation. I also take advice from a master electrician who recommends only calculating for 60% (ah) use. (Meaning 40% left) Just my 2 cents. Trey
this is the curve for the cells I'm using. A bit more favorable, though no doubt after a few years it doesn't look quite so, and it definitely depends a bit on how low you consider acceptable. If you're fine going down to 3v/cell then you're close to 90%. But I like your number of 20-25% buffer better, it sits well with my paranoia of losing a ship for lack of power.
The life packs are much less prone to damage from over discharge than the lipos are, but it's still best to keep at least 10% charge as a minimum on them. They also have a great discharge curve.
Also the life batteries are far less prone to fire, puffing, or "blowing up" than the lipos are. That said, I have puffed a few lipos, but never blew one up. The only fire I ever had was due to a puncture in a lipo.
Oh I have those as well . Since I haven't tested the cutoffs, I don't want to find out they don't work 10 minutes into the second sortie as i am going on 5.
