jag5100

I have a Cessna 182 4Ch which i bought from Parkflyers http://www.parkflyers.com/html/cessna_182.html

It has a 480 size brushed motor that works with the stock 8.4v ni-mh battery. I would like to know if somebody knows the voltage range the motor and the speed control can handel. I want to put in a 11.1 v Li Po battery since 7.4v reduces power. Will 11.4v burn the motor? If yes, If I fly below 75% throttle with 11.1 v, will the plane be ok?

I will really appreciate if you reply.

Thanks,

Jag

Fliprob17

Yes the 11.1 volt will burn up the motor. If you reduce the throttle, all you are doing is reducing the amp draw, not the actual battery voltage. You are still supplying the motor with 11.1 volts from the battery. The 2 cell pack would be the way to go. When fully charged, a LiPo hits 4.2 volts per cell. So a 2 cell LiPo will hit 8.4 volts when fully charged. Plus it is much lighter than the NiMh you are running and you will see a performance increase just do to the lower overall flying weight.

The question I would ask......Why not just convert to brushless? If you are going to spend the money on a LiPo anyway, just get a brushless motor and ESC as well. That way you would get the most out of the $$'s you would be spending.

4*60

My Feedback: (41)

I've been using 3 cell Lipo on speed 400 brushed and have quite a few flights. Some day I will burn them up and install brushless motors on them.

jdetray

Hi Jag -

There is considerable information on this topic here:
[link=http://www.rcgroups.com/forums/showthread.php?t=201680]Can motors on 3s LIPO [/link]

- Jeff

Fliprob17

Do you have the 7.2volt or 12volt version?

I know that some manuf. sell the SPEED 400, 480, 500 & 600 in a regular 7.2 volt version, and a 12volt version. The 12 volt can motors would obviously be fine on a 3 cell LiPo. Most of the RTF motors, like this Parkflyers one, are only rated at 7.2volts.

soarhead-RCU

Go down a inch in pitch and a inch in diameter on he prop and it will work OK I have found. I use 3s all the time on 7.2v 400s both DD and geared. The 6v motors have to be coddled a little though with the throttle stick and still suffer in lifespan. If its the 12v 480 you will have no problems. Lots of sailplane guys usued them will 10 cell nickel packs and had no problems so 3s lipos should be a breeze!!!
Good Luck
Bob

4*60

My Feedback: (41)

definitely NOT 12V

Sir Raleigh

I don't want to hijack the thread, but if I might ask a question along these same lines?

I have a plane that came stock with a brushed 480 motor and an eight cell, 9.6 volt NiMH battery.

Would the general consensus be that this is a 7.2 volt or 12 volt motor?

Or is there really no way to tell?

Fliprob17

I would venture a guess that it is the 7.2volt, seems to be the RTF standard. The only way to find out for sure is to contact the manuf. of the plane it came with and ask them. They generally are not labeled.

ozrcboy

jag5100 you will probably find the cessna flies quite well on the 2s LiPo. While the voltage is reduced, the number of amps a LiPo can produce is so much higher than NiMH/NiCd it usually more than compensates. As you probably know power = volts x amps so the amps you can produce are just as important as voltage.

Also, a 3s will work fine on just 400/480 can motors, but it will accelerate their deteroriation. However, it needs to be understood that electric brushed motors wear out - that's normal. Brushless motors tend to wear out very very slowly because there is no contact, but a brushed motor has wear on the brushes.

With a 480 motor costs $15AUD here you will get 30 flights or so on 3s no probs. I'm guessing in the states that motor probably costs around $5. Not big bucks.

Cheers,
Oz.

jag5100

Thanks. I looked in detailed about putting in a brushless motor. Then I will have to change the motor mount and ESC. Thats not a big problem. I will actually have to rebalance the plane since brushless motors weight different than my brushed motor. I know I will crash it if i rebalance it, lol.

I think it came with a 8x6 prop. soarhead-RCU wrote that if i go down an inch on pitch and prop size, probably 7x5 prop. Will it work good?

jag5100

I wrote to the Parkflyer manufacturer. This is what they said, "Dont use the 3 cell battery ! it will fry motor in less than 1 minute". However I did not ask them about going down in the prop size. Do you guys think 7x5 prop will make the plane alive with 3 cell li-po? Worth a shot?

ozrcboy

Hi Jag - just from personal experience, my best flying mate has flown a 3s in his PZ Supercub - he gets about 30 flights from a 480 motor before it needs to be replaced.

Always hard with conflicting opinions eh

Cheers,
Oz.

jag5100

Thanks all for your help. I will stick with 2 cell lipo.

Sir Raleigh

Thanks fliprob17,

It was just a question asked out of idle curiosity, so I'm not going to worry about it. I already have a brushless outrunner and ESC in the wings (pun intended) waiting to be installed when the brushed motor wears out.


Thanks again.

Fliprob17

Check out the "3 channel Art-tech" thread in the foamies section if you have not already. It is the same plane that ParkFlyers sells, just with a different box and stickers Just about everyone in there has converted the Cessna over to brushless at some point. Lots of good info. in there.

jdetray

Oz -

Batteries don't "produce amps." The current (amps) consumed by a power system is determined mainly by the motor and the prop, not the battery. The power system will attempt to draw whatever current it needs from the battery, regardless of the battery chemistry. You can make any power system draw more amps simply by increasing the size of the prop!

Lipos are popular mostly because they are so much lighter than the NiMH batteries they replace. You will often see a performance increase due to weight savings alone. But the power system won't necessarily draw more amps from a Lipo battery than it does from an NiMH.

- Jeff

Fliprob17

That is a funny little deal. I could have made that same comment "The question I would ask......Why not just convert to brushless? If you are going to spend the money on a LiPo anyway, just get a brushless motor and ESC as well. That way you would get the most out of the $$'s you would be spending."....... about 4 months ago, and it would have been taken completely different. Funny little stereotype that seems to follow you once you actually sell things. Seems that actual advice, is no longer just advice, but some misconstrued tangled web of trying to always sell something ..........even if "that time" you were not ......it is like this little hidden attachment on all your posts Being active in the forums, helping solve problems, hearing how people appreciated the help, and of course flying a whole ton actually motivated me to start the store.

RickAvery

I have found that if you're using the speed 400 motor as a direc drive i.e. in a flying wing or a pusher jet... you will burn it up in just a few flights with a 3cell Lipo. If however you're using it with a gear box with a 5 or 6:1 ratio, they can last quite a while as long as you're not over propped & are easy on the WOT action. Good luck.
Rick

jag5100

I agree. However i also tried a 9.6v Ni-mh 650mah battery on Cessna. The plane only worked for 1 min on that battery. the battery was producing a lot of volts. Do you think the battery is bad or it is 650mah thats why it won't last long?

ozrcboy

A fair point Jeff - I spose I short shifted with the message - I probably should have said: "In my experience motor/prop combos driven by NiMH/NiCd would draw more amps if only the battery could support it." But you are of course correct, prop size and the speed the prop is turning at determines how many amps are drawn provided the battery is not a bottleneck. In my experience with NiMH/NiCd it almost always is a bottleneck.

The planes I've seen use 2s into instead of a 7/8 cell NiMH/NiCd the difference in performance is not explained by weight alone - weight changes would affect acceleration, stall speed and climb rate, but it has no significant affect on top speed in level flight (which is all about how much thrust the engine can produce relative to how much drag the airframe induces at a certain speed). Further, in a static thrust test it is obvious just by holding the plane how much more thrust it has with 2s rather than 7/8 cell - well, at least that's what I think.

Cheers,
Oz.

jdetray

It's the low capacity of the battery. At only 650 mAh, it's not going to run a 480-powered plane for very long. If you were to put that power system on a wattmeter, you would see the voltage of that 650 mAh battery drop significantly. It might drop to 6 volts or less.

Basically, you're sucking all of the power out of the battery when you overload it like that.

- Jeff