Ok, Ted (or anyone else for that matter), I've looked around the web and can't find an explanation for the 4S, 7S,2S terms used to describe batteries. I've checked Red's Battery Clinic and other such sites with no luck. As is obvious, I'm just starting to get interested in electrics. So what does this mean?
Is there a really good place on the web to try to cram all this information into my brain? For that matter is there anyplace that would make some sense out of electric motor sizes for electric airplanes? It can't be all that much of a dark science,can it?
You're not alone, Harlan. I forget what the designations mean too.
I "think" I saw a description of LiPo terminology on one of the commercial forums a few years ago, but I can't remember which one it was. It might have been the one that Anne Marie Cross owns, Wattflyer?
Designations are irrelevant. What does "Chevy Silverado" mean? If you had nothing else to go on but the name, and did not have the benefit of a nationwide advertising campaign and John Cougar Mellencamp, would you know if a Silverado was a compact car, a pickup truck, or a motorcycle?
How would you find out what it was, and if it were suitable for your purposes? You'd look up the specifications, kick the tires, ask questions... Eventually you'd learn that Silverado meant pickup truck, and that since you're looking for a midsize sedan, it's not what you want.
Works the same for electric motors and glow engines too. Until you learn to correlate marketing info with motor capabilities, it's a learning curve that involves looking at the specifications.
Unless there's been some back-room dealings going on that I am not aware of, Marc Vigod still owns Wattflyer.com.
I wonder what happened to Anne Marie Cross anyway. Haven't heard much since she and her husband left Great Planes/Hobbico. She popped up on RCGroups for a while. Last I knew she was running a race horse rescue operation on grants and donations, but that info is a few years old.
Thanks Jim, "fubar"and Rich. The simple answer is, therefore, 2S is two cells in series. I understand that! I also now understand 3P would be 3 cells in parallel. But now you've gone and done it. You've confused me with the 3S2P thing.
I think I'll go on a ultra serious hunt for more knowledge of electrics starting with batteries. That ought to give the motor manufacturers enough time to try to agree on a some standardized terms to halt the confusion .......... 'cuz I doubt that I'm the only dunce in the world.
Designations are irrelevant. What does "Chevy Silverado" mean? If you had nothing else to go on but the name, and did not have the benefit of a nationwide advertising campaign and John Cougar Mellencamp, would you know if a Silverado was a compact car, a pickup truck, or a motorcycle?
How would you find out what it was, and if it were suitable for your purposes? You'd look up the specifications, kick the tires, ask questions... Eventually you'd learn that Silverado meant pickup truck, and that since you're looking for a midsize sedan, it's not what you want.
Works the same for electric motors and glow engines too. Until you learn to correlate marketing info with motor capabilities, it's a learning curve that involves looking at the specifications.
Unless there's been some back-room dealings going on that I am not aware of, Marc Vigod still owns Wattflyer.com.
I wonder what happened to Anne Marie Cross anyway. Haven't heard much since she and her husband left Great Planes/Hobbico. She popped up on RCGroups for a while. Last I knew she was running a race horse rescue operation on grants and donations, but that info is a few years old.
--------------
What's the matter, constipated?
Since I'm wrong all the time, I'll leave trying to answer questions to you from now on.
But now you've gone and done it. You've confused me with
Not hard.
If you need more amps output than the normal pack can put out, you use something like the 3s2p.
You take a 3s (3 cell pack, all hooked in series, neg. to pos.)
You grab another pack, just like it, and hook that up to the first pack in parallel, (which of course means neg. to neg. and pos. to pos.) that gives you the 2p part of the name.
Now you have a pack that has the same voltage as a 3s pack, but because there are two packs side by side, they will put out enough amps (double the one 3s pack) to run that big honkin' motor without turning the battery into a fire bomb!
How do you charge a system like that, Jim? Do you unhook the parallel packs and charge them with separate chargers? With Nicads that wouldn't be a good idea.
Ed Cregger
P.S. I was kidding MK (I think it was MK - What's my name?). I ain't going nowhere. Not that anyone should care anyway.
I have never used a pack like that. I would think they would have to have a plug that you could take apart and charge it as a 6s, or use individual leads like on a balancing charger.
On the original LiPoly assembled packs, we just plugged them in and charged them, series, parallel, no problem. BUT there were problems, eventually the cell voltages (state of charge) drifted enough that a cell might be ruined by over voltage or under voltage conditions even though the pack as an assembly seemed to be ok
so most if not all of the newer packs come with two sets of leads attached, One set is the power leads.
the other set is attached so that there is a separate path for each individual cell. this set is used either for charging or balancing the pack (depending on your charging / balancing equipment)
MK, I respectfully disagree! (At least I think its respectfully.)
The guys who frequent this group have been extremely helpful to me over the past couple of years. Ed Cregger, in particular, has been very helpful. Does he get a little cranky at times? Sure! Me, too. Ed just wears it on his shirt where everyone can see it sometimes. But he's back to providing good information and opinions the next day, and that's what I come here for.
I don't (anymore) take every little nuance and jab as a personal affront. If that's your problem, you probably ought to spend more time reading a good book.
Here's the summary! I like these guys.
Harlan
Same old Ed, same old stick up his butt. Now I know why I quit coming here.
A piece of advice to newbies: If you are expecting useful and friendly advice, don't come here.
3S, 4S, etc. means SERIES. In other words, 3, 3.7V cells wired in series, giving you 11.1V, or 4 cells in series giving you 14.8V Now, if you see a "P" in the number, that means PARALLEL. When you wire packs in PARALLEL, you increase the milliamp hours or capacity.
So... a 3S2P (using 2200mAh packs) would be 11.1V and 4400mAh (because the
You use a charger that will handle the charge rate for the total mah of the pack. So if it's a 3S (11.1V) and two 2200mah packs in parallel, then you charge it at the rate for 4400mAh. A charge rate of 1C is 4.4amps.
Don't worry about a conversion chart! Just look for how much THRUST the motor will produce with a give voltage (lipo pack size) and prop. Some people believe in a WATTS formula but that's a red herring. Too many different variables effect watts.
Vision shows a Great Planes Stearman with link to video here
Wrong way round. Any fule can get lots of thrust with a large diameter low pitch propellor that will hover the model, but not fly it over stall speed. In fact I've seen a lot of 3D planes just like that.
watts per pound> 50 and pitch speed>2.5 times stall speed will get you into the air every time, unless it's an EDF..in which case you need at leasts 100W/lb, and 400W/lb is definitely much better...
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.