Time to actually think about flying....
- Thread starter Icedog
- Start date
Wow...thanks for taking the time to pass this on. My batteries have the BEC so I figured out that the battery port on the receiver wasn't going to be used so all the connections to the receiver have been sorted and I was able to at least confirm the throws on the control surfaces and they're all centered except for one aerliron which will need a bit of adjustment...or I suppose I could center and move the horn.
For batteries I have 2 3S 2200mah batteries and a smart charger I picked up on Amazon to get me started. AC adapter but no DC operation. Looks capable of charging up to 6S. It's programmable and has some memory for the batteries normally charged. When I got the batteries one was at 7.3 volts and the other 11 volts. I read somewhere that max charge should be 3 times the cell voltage-which I guess is 3.5 volts. Now the batteries are nominal 11.1 so I'm not sure exactly where to stop. Probably not "future resistant" but looks to be pretty decent for now. But this answers another question bouncing around and that is how many batteries are enough...I have 2 but looks like I might need 2 more. I don't know what the flight time is per battery yet (obviously throttle usage dependent) but I'm betting two isn't going to cut it unless I'm able to recharge on-site. Our field is pretty rudimentary and a lot of weekday flying is done off a local soccer pitch (with approval of Parks department) so more is probably better than less.
Sounds like the 6 channel Spektrum will hold me for a while. Very popular with the local club members as well so a pretty good knowledge base to fall back on. Hope to have that in another week or so.
For batteries I have 2 3S 2200mah batteries and a smart charger I picked up on Amazon to get me started. AC adapter but no DC operation. Looks capable of charging up to 6S. It's programmable and has some memory for the batteries normally charged. When I got the batteries one was at 7.3 volts and the other 11 volts. I read somewhere that max charge should be 3 times the cell voltage-which I guess is 3.5 volts. Now the batteries are nominal 11.1 so I'm not sure exactly where to stop. Probably not "future resistant" but looks to be pretty decent for now. But this answers another question bouncing around and that is how many batteries are enough...I have 2 but looks like I might need 2 more. I don't know what the flight time is per battery yet (obviously throttle usage dependent) but I'm betting two isn't going to cut it unless I'm able to recharge on-site. Our field is pretty rudimentary and a lot of weekday flying is done off a local soccer pitch (with approval of Parks department) so more is probably better than less.
Sounds like the 6 channel Spektrum will hold me for a while. Very popular with the local club members as well so a pretty good knowledge base to fall back on. Hope to have that in another week or so.
LOL Crashing in the sim is a LOT cheaper than crashing in real life. For the past 4 months, I've been practicing flying a collective pitch helicopter in the sims, and I've been crashing a LOT. And I mean "Oh, I got off the gr- dang. Ok, I'm off, and...No, don't go that w- dang. Ok, I'm up, and I'm flying...right into that tree. Dang!" crashing. On a real heli, I'd have probably already been in for about $3k in replacement parts. It's certainly paid off, because now when I get out there with my micro heli, I've been flying for almost 3 months and can do inverted hovers, tail first (backwards) flying, loops, and rolls, and I'm stepping up to where some of the guys who have been flying for years are trying to challenge me with stuff.
I'm not up to full on 3D flight like some of the really crazy good guys do, but with more practice, I'll be there. Give me a year and I'll be doing piro flips and tick tocks and inverted autorotation landings.
Ooooh, let's provide some education and basic safety for those batteries right now so that you don't burn down your house or have batteries explode. I know several people in different clubs who have had batteries explode on them, start fires that took out their garage or den, and I don't want that to happen to you.
Let's go over the basics:
1s, or 1 cell batteries, have a nominal charge of 3.7v. When charged up to "full" and ready to fly, that translates to (in theory) 4.20v. 2S batteries are 2 cell batteries, and they are basically doubled, so would be 7.4v - when charged, would be 8.40v. 3S start at 11.1v, and when charged fully, would be at 12.60v. To do the math, any lipo cell battery is 3.7v times the number of cells, which gives you the nominal voltage. Multiply that 4.20v times the number of cells, and you have what the fully charged rate is for the battery, so we could use that to go to 16.80v for a fully charged 4S, or even jump up to 25.2v for a fully charged 6S battery.
The mah that you see printed on a battery is like the capacity of the battery, or how long you can fly with it. A 2200mah battery will, in theory, let you fly longer than a 1000mah battery, because it's more than twice as large. (However, that 2200mah battery is also going to be larger and heavier than that 1000mah battery, so it's going to add drag to the plane, and it's not going to give you flight times that are twice as long).
So, now we have to look at how fast, or how much amperage, you can put into a battery to charge it. This is where it gets dangerous. Some manufacturers will print on their batteries that they have a max charge rate of 3C. I don't recommend ever charging at 3C on a battery; it can shorten the life of the battery, induce puffing on the battery, and could potentially cause it to explode in a literal fireball. Other people might tell you that they've charged high C rates with no problems; I'm going to tell you to ERR ON THE SIDE OF CAUTION. Seriously. It might take less time, but if it means a much lower risk of your house catching on fire, it's worth it.
So, to get back to what I mean by 1C or 2C or 3C charging - this is the amount of amperage you can use to charge your battery. Amperage is based on the milliamp hours for the battery itself; a 700 mah battery charging at 1C would be 0.7A, a 1000mah battery at 1C would be 1.0A, and a 2200mah battery charging at 1C would be 2.2A. This amperage amount rule is the same, regardless of whether it's a 1S, 2S, 3S, etc. battery. Now, you CAN charge it at a higher C rate, but it's dangerous. The best way I can paint a picture of this is that if you were to fill up a water balloon with water from your tap - put a lower flow of water in, you can fill it up and not have it burst, but as soon as you crank up the pressure to full on the faucet, the balloon fills too fast and it explodes all over, leaving you wet, right? Well, lipos charge in much the same way - except with too much energy, they explode with the burny burny fire stuff, not water.
Wattage plays in with this math equation: W/V=A. That is, Wattage, divided by Voltage, is the max Amperage output. So, a 50W charger, charging a 1S battery at the fully charged Voltage, would give us 11.90A as the max amperage we could potentially have. That's great, right? Not when we increase the voltage of the battery. A 2S battery would be 50W/8.4V, which equals roughly 5.95A max. 3S would be even more limiting - 3.97A. As we get to more cells, that decreases the max amperage quite a bit, to where that 50w charger isn't going to be enough to charge that battery. A 6S, 5000mah battery being charged on a 50w charger? Over two and a half hours, with 50w (5000mah/1.98A=2.53 hours, from 0 to 5000mah, IF the battery were ever actually that dead, which should NEVER get down to that level - if it does, don't try to charge it, recycle it).
So, try to charge your batteries at that 1C rate, and bring them down to a storage rate, which is 3.8v per cell. If you don't have a cell voltage tester, buy one; they're cheap, and they're a good way to get an idea of how long you can fly. I like this one here, because it has some extra features built in to it, and you can see the charge for each cell, which helps to tell you if you have a potential bad cell or unbalanced battery:
https://www.amazon.com/dp/B0178P8H9U/?tag=lstir-20
Lastly, ONLY EVER CHARGE A LIPO ON BALANCE CHARGE SETTING!!! If your battery is not balance charged and you have a cell with a significantly lower voltage than the others (say, two of your 3 cells are at 11.8v and one is at 11.3v) and you try to charge it up, it could cause the battery to "overcharge", and explode. Better to be safe than sorry!!!
Working yesterday so just getting to this...very, very helpful. I believe I charged my two batteries at 2 amps by charger default. I haven't attempted to program it yet. The first to about 12.5 volts the second to a little under 12. The charger is balanced so I think I'm OK there.
The manual (such as it is) talks about discharge rates. When and why would you discharge a battery? Can they take a set if not charged properly? My charger has a max charge power of 80 watts.
Suggestion to get a voltage tester is a good one...it's on the way.
The manual (such as it is) talks about discharge rates. When and why would you discharge a battery? Can they take a set if not charged properly? My charger has a max charge power of 80 watts.
Suggestion to get a voltage tester is a good one...it's on the way.
Actually, good question on discharging!
So, let's say you want to go out to fly tomorrow, right? Get out your charger, charge up the batteries, and then head to the field the next day, fly them until they're discharged appropriately (more about the level of discharge in a minute) and come home. Let's say, however, that you've got 3 batteries, and after the first flight, the wind picks up so you decide to go home. Or you end up having a case of "dumb thumbs" and the plane spirals in, ending your day prematurely.
If one of those scenarios occurs, you'll want to discharge those charged batteries. Why? Well, the best analogy I can give you is that they're like a balloon; a balloon, you'll blow up to almost bursting, tie it off, and it holds that air in. After a bit, that rubber is fighting back, and it can get weak at that stretched thin point of "almost bursting". A battery is much the same way - it's got all of this potential energy stored up inside that's going to get fed out to your plane's motor, discharging down to power your plane and make it fly. If you leave that battery charged up for a long time, it can swell up, or the cells can go bad, and you can end up with failures, sometimes catastrophic (i.e., a fireball, either in your house, car, plane, or hands).
So, how do you get rid of that problem? Take some of the energy out so that it's not at that "stretched thin" state. Doing that, you'll discharge the battery down to a safe, storage level, which is 3.8v per cell for a lipo battery. If you have bought into the more expensive Spektrum SMART batteries (I don't recommend them, as they're quite a bit more than most batteries on the market), there's a feature that they have where they will do a "trickle" discharge on their own, bringing them down to 3.8v storage charge, but most people just discharge them down on their own through their chargers. Most chargers only discharge at a slow, set speed, because they're having to discharge not only the potential stored energy, but heat as well, so it tends to come down a lot slower in order to keep the electronics cool and prevent it from burning up.
Now, all of this brings up one last thing to take into consideration, when it comes to batteries. Most ESCs have a low voltage cutoff in them, and will stop providing power to the motor at 3.3v per cell. Because of this, you don't want to fly your plane down to 3.3v; it's likely to come down and crash on you. There are ways to track this via something called telemetry, but it generally requires more expensive receivers and a voltage sensor to transmit the telemetry data. Most people will use a timer on their radio to count down an average time of flight left. I start with my first flight on a plane and set it to 5 minutes, max, and will fly long enough to get it trimmed out, make a touch n' go pass, and then come back in for a landing. Once that's done, I'll pull the battery and check the voltage for what's left on the battery, and adjust my flying time estimates more or less based upon that. I try to set my flying time to have about 3.8v per cell when I'm done for a couple of reasons:
1) If it's windy, or I'm flying more full throttle than gliding, I have a bit of cushion to work with. If I bring it down at 5 min. and I've been flying as fast as possible, and it comes down at 3.7v, at least I've not run the battery dead.
2) Let's say I'm flying at a flying field with several other guys, and one goes to come in for a landing while I'm getting ready on my final approach. I have battery left to go around a couple more times, let them clear, and am still not on my low voltage cutoff. Same reason in case they crash and have to clear the runway before I can come in!
3) If I come in at 3.8v, the battery's at storage charge, and I don't have to put the battery on the charger and get it to the 3.8v per cell.
Sorry for the very long delay in reacting/responding...here in New Mexico the weather is just starting to turn toward the flying so I'm un-mothballing everything. I'm discharging a battery as I write and the default setting (which I can't change)...discharges down to 9.1 volts for a 3S. Is that too low? The nominal charge level is 11.1 which sounds like the safe storage level you outlined. I can charge to 12.6 I just don't have the ability to program that in. Seems like this particular charger times out rather than volts out.
I did pick up the meter you suggested. It took of bit of experimentation to get the connection right the cells in the batteries I tested are right on in terms of voltage.
I did pick up the meter you suggested. It took of bit of experimentation to get the connection right the cells in the batteries I tested are right on in terms of voltage.
quorneng
Master member
Icedog
Are you sure the your charger is timing out? It should stop automatically when the cells each reach 4.20 V.
It is important that the charger cannot over charge a LiPo.
It is also important that a LiPo is 'balance charged' regularly to ensure each cell is brought up to full charge independently.
When LiPo first arrived it was the use of inappropriate chargers that gave them a bad name.
Are you sure the your charger is timing out? It should stop automatically when the cells each reach 4.20 V.
It is important that the charger cannot over charge a LiPo.
It is also important that a LiPo is 'balance charged' regularly to ensure each cell is brought up to full charge independently.
When LiPo first arrived it was the use of inappropriate chargers that gave them a bad name.
Yeah...I kept close eye on the first battery and it stops at 12.6 volts. The charger has a bunch of "programs" that I wasn't aware of till I started seriously reviewing the somewhat limited documentation and experimenting with the controls. It also has discharge (down to 9.4 volts) and storage (down to 11.4 volts) functions. Voltmeter check show the cells are all balanced before and after charging.
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