xray328

My Feedback: (1)

I'm looking at these 4000 mAh lipos and just wondering if that translates into longer flight times or more power? Could you for instance use a 4000mAh lipo on a slow stick with a stock 300 motor? I know you need a heavy duty speed control but that aside would it work? I'm kinda tired of these 5 minute flights.

Charley

My Feedback: (2)

If you have the same voltage LiPo as your original battery, but have more mAH capacity, it will mean longer flights. Look at the mAH # as a fuel tank. The more mAH, the more milliamps in the tank. It won't go faster, it will go longer.

CR

MAKODS

Also consider this: a 3s1p 4000 Lipo is 11.1 volts which will quickly fry your stock 300 motor. You would need to use a 2s1p 4000 which is 7.4volts with that motor.

RickAvery

To throw another wrench into the gears, higher mah ratings usually mean higher weight thus more power expended to stay aloft. There is a break point for every model usually determined by AUW, wing loading, desired flight charicteristics etc... where higher capacity batteries, i.e. heavier, is a hinderance and not an asset. JMHO.
Rick

Time Pilot

I fly a 300 powered Slow Stick with a battery that weighs 5.6 oz. I don't know how much a 4000mah 7.2V LiPo weighs. Can't be much more, can it? You'd be able to fly for almost 80 minutes on a pack like that. I'd go for two smaller packs of 2000 instead....

Woody 51

2 x 2000Ma/H packs in parallel would probably end up weighing the same or more than a single 4000 Ma/H pack, so you probably wouldn't end up gaining anythingmuch by putting 2 together.

A Lipo pack will usually give you longer flight times than a similar MA/H Nickel Chem pack.

Time Pilot

I'd get two packs, fly one, then land. Swap packs, then fly again. 2.5-3 oz is a lot of weight that can be removed from the airframe by going to 2 packs and flying one at a time.

Flypaper 2

On my GWS Zero I get 1/2 hr flight time with a 2100 mah. batt. With a Himax 2025 motor.

Troglotech

The calculation for flight-time is based on the Wh (Watt-hour) rating of the battery (Ampere-hour x Voltage) divided by the weight of the battery(s). Obviously, the voltage has to be suitable for the ESC and motor that you are running. This calculation soon gives you the energy-density (and hence the flight times) of any given battery. This density, as a general rule goes: NiCd, NiMh, LiPo and finally Lion, in that order, although there are advances in LiPo and Lion that pushes each one ahead of the other at various times.

DarkWombat

Errr....Trog confused me slightly, but anyways just think of mAh as what it is: Milliamps Per Hour. It's a measurment of how much current can be drained from the pack for it to last an hour before it is drained. So, a 600mah pack will die after an hour if 600 milliamps of current is constantly flowing out of it for one hour, a 2000 mah pack will die in one hour if 2000 milliamps (aka 2 amps) is being drained from it, etc. As you can see, more milliamps means longer flight times, although as the others have said, it also means a heavier battery pack. I was looking at Polyquest LiPo packs and noticed that a 3C, 2200mah pack would weigh 4.83 ounces, but a 3C, 2600mah pack weighs almost an ounce more. It's better to get a lighter pack with a little less run time than a heavier pack with a bit more, because your motor will have to carry that extra weight and work harder anyways, and that means you'll probably get worse flight time with the 2600 mah pack.

Just my .02

ryanf420

trog, question?....What would be the reason for purchasing a l-ion batt with 3.6v per cell when Lipoly has 3.7v per cell, I thought that L-ion was on the market before Lipoly. but I still see some of the LHS here in Phoenix still keeping the L-ion batteries in stock..That is what caught my intrest about what the pros/cons are with these 2 different lithium batteries....Lipo cost the same as L-ion but have .1 more volts, are manufactured better to prevent fire, and lipos(to me anyways)seem to be a tad smaller?....trog, if you could clear this up for me that would be cool, or anyone else that may know.....Thanks

Ryan

gigelus2k3

There are no major differences between LiPo and LiIon cells, apart from the way the transfer membrane is designed.

LiIon were first on the market. They have the largest power density (Ah / m^3) among all solid-state rechargeable batteries, but, until very recently, were rated to much lower discharge rates than the old counterparts (NiCd and NiMH). Even today, the typical rating is less than 5-6C.

LiPo cells are newer and, due to their membrane construction, can take any shape (unlike the LiIon which must be cylindrical) so they tend to look smaller. The power density is a little smaller than LiIon, but their discharge rate is larger by a sizeable amount (10 to 15C are now commonplace)

The voltage rating is misleading. Unlike NiCd/NiMH/acid cells, the Li* ones have a pronounced voltage drop when the charge gets depleted. A fully charged cell will read 4.1 to 4.25V, while a fully depleted one (less than 1% capacity left) will read about 3V. This is a 30+ % voltage change and this fact can be used to estimate the cell charging status. Compare that to the Ni* cells.

3.6 or 3.7V rating is just an "averaged-out" one, don't base your reasoning on it.

To conclude, the motive you don't see more LiIon cells used in RC toys is that their discharge rate is lower than any other technology's. I do use home-built LiIon packs in my brushed SlowStick, but for a fast low-wing plane (Formosa or Corsair in my case), I have to use Lipo packs.

Hope this helps.

Serban