Parkhawk batts

[RB]

What is the best batt for the PH? My wife saw an article in Discover magazine and had to have one. I have lots of airplane nicads but no nimh to speak of. I do have an FMA Supernova to charge the nimh.

Thanks
Ray

[Jerry Rose]

ParkHawks come with one 720 mah NiMh battery pack. I had several 720 NiMh packs with a different configuration, and tried flying it with them. They moved the CG aft of the correct CG point and made it harder to control the bird in pitch. The style of pack that Kinkade includes is best. (See attached picture.)

Since the battery is included, all you will need initially is a micro-receiver, and two micro-servos. Of course, flying around while a used pack is charging is better than being grounded, so more is better!

[niek]

Question:
What kind of connector is show on this photo?

[Jerry Rose]

That is a Deans Connector. And that is stock as it came from my PH dealer.

[niek]

Thanks.

Never seen before, not available her in europe..

[eflyer1234]

That connector is not too common here either. The Park Hawk comes with those in the kit, but is currently shipped without the connector attached. This has come about as many people are changing to the connector they use most.

In some cases, depending on connector choice, I can provide with your prefered connector when ordering the Park Hawk.

-Jeffrey

Jeffrey Goodman
JGRC
www.jgrc.biz

[Sparr]

that freaky connector looked wierd the first time i saw it, but the parkhawk is the SECOND 'plane' ive purchased with batteries using it. the worst part about new connectors is not knowing what they are called and therefore not being able to order a charging jack for them. recently i got my first of these and my first of another type and each time i had to cut the connector off of one of the batteries to turn into a charging jack (both were unisex).

[eflyer1234]

The correct name for the connector is the Dean's 2R.

This is a good connector for low amperage, 7 and under like the Park Hawk. I know several dealers including myself that carry these. A 2 pack sells for $2 plus $0.40 postage/handling.

-Jeffrey

JGRC
www.jgrc.biz

[frankenfoamy]

I was told the batteries are 780 mah NiHD. They are not Sanyo 720 mah. I tested both and I was surprised the non sanyos performed better. Like all NiHD, they like to be warm.

http://rcguy.tripod.com/

[Jerry Rose]

Originally posted by frankenfoamy
I was told the batteries are 780 mah NiHD. http://rcguy.tripod.com/

I think the idea that they are 780 mah batteries got started from a typo in the description of the ParkHawk at the NES website. Sal probably has the worlds largest model airplane offering, so once in a while that sort of thing can happen.

From what I've seen, the PH comes with a 720 mah NiMh pack. The supplied packs are either Sanyo or Varta based on the luck of the draw. Everyone knows about Sanyo, but the guys who received the Vartas seem to love them too. :D

[thopter]

I found this battery to absolutly amazing.
It put out 25% more power and weighs less then half a 9 cell 720mah NIMH
http://www.wildrc.com/htmlpages/3polymer.html
You'll have to get a special charger to use it and be careful not to over discharge it but I get 12 minute flights and at only 62 grams it climbs like crazy. I'm sold on lithium Polymer until fuel cells come out :D
I think next I'll try this one (RRC Lithium Polymner 1800 3 cell)
http://radicalrc.secure-mall.com/shop/index.php?shop=1&cat=21&cart=5698
This should give 20 minute or greater flights.
I also find that Lithium batteries hold there charge better over days and weeks on non-use.

[BillB]

I had been told that Lithium Polymer Battery max discharge rates are around 2C with a 5C pulse rate. That should only give a 2amp continuous and about 5amp pulse rate which doesn't seem like its enough juice. Is this correct information or can you push the battery beyond this rate and accept reduced life cycle? Does Higher voltage = less current.

I had read that the Parkhawk runs at about 7amp continuous max at 9.6 volts.

[thopter]

I've been told that too but the motor is spec'd at 5 amp under load and when I do the math I get 7-8 minute flights from a 8 cell NiMh and when I recharge it takes 450-500mA. That works out to an average of just over 4A. The battery I'm using is rated to run continuos at 4A and if increased slowly 5A. I've gotten many flights and the battery never gets very hot and I haven't seen any degradation yet. I am careful to always start out at only about 3/4 throttle but that plenty fast for it to climb rapidly. During flight I slowly or in short burst go to full throttle.

[BillB]

Its amazing that Li batteries work in this application...
I am sold.
I am going to try 6 Kokam Li-Polymer single cells at 1020 mAh, 2x3 in parallel. This should give me 2040 mAh @ over 11 volts and only 6x20.5gm = 123gm which is only 19gm more than the 8 cell NiMH. This should also give a 4 amp (2C) continuos with a 10 amp (5C) pulse rate. And mass cool amounts of air time.

[BillB]

I got my 1020 mAh Li-Polymer batteries in from FMA Direct and they look great, charge great with the MAHA Multi II charger. The only problem I am having now is how to attach them to the park hawk. I think the KOK880 battery would have been a better fit and less weight with a 1760 mAh capacity instead of 2040. The KOK880s are 10mm shorter which makes a better fit in the Park hawk.

[BillB]

I am using two paralell packs of 3 in series which should give me 3x3.7V @ 2040 maH. I am making two seperate packs each with its own connector for charging seperately. Kokam information recommends that you never charge these batteries in parallel. Charging in series is ok too. So I have a Y connector that connects the two 3 cell packs to the speed control.

I have attached a sketch of the heat shrink packaging I designed. Between each cell are two strips of double sided foam tape to creat an air gap. The heat shrink has the opening front and back to allow cooling air to flow around the batteries. The heat shrink also holds two thin peices of fiber board for attaching to the rubber bands that normally would hold the NiMH battery pack.

Here is a great link showing how to solder these unique batteries:
http://www.indoor.flyer.co.uk/terminals.htm

[BillB]

Here's a picture of one of my Kokam Li-Poly Battery packs with 3 1020 cells connected in series. You can see the Heat srink openings are front to back and the spacers to allow cooling air flow beteen cells. I am going to be switching to a Castle Creations Pixie-7p which is a programmable ESC that allows you to set a Low Voltage Cut-Off point for Li Batteries in series. It is the same price as the C-10 but has a slightly lower current capacity of 7A continuos and 10A surge.

[ls77]

Hi Billb, there has been a reversal on Kokams stance on parallel charging. You can charge in parallel now. I have been doing it for some time now. You must make sure that the two packs being charged are close in voltage levels before connecting them in parallel. They don't have ot be exact, within a few tenths of a volt is ok as they will naturally balance each other out to the exact voltage.

-Troy

[Jerry Rose]

Originally posted by BillB
Here it is!
The 2Ah Park Hawk with 6 Kokam 1020mAh Li-Polymers.....:D

In this configuration, where is your CG?

[BillB]

Good question.
You would think the CG would be the same as with the NiMh but not so.

The CG appears to be about 1/4" forward of where it would normally be since more of the battery is centered around the mounting point and in addition you have about 19gms more weight centered around the mounting point.

Not sure if this is a bad thing yet. It seems to fly well and climbs well but I haven't done any gliding yet or tested the limits of the battery since I have the Castle Pixie 7P ESC on order. The Voltage Cut-Off thing worries me.

[BillB]

I re-measured the CG and its more like 1/8" forward of normal when the tail is at 25 degrees and the wings are at about 20 degrees. Wing position seems to make a big difference in CG from the point of my measurements. And that brings up a good question.

What is the best point to measure the CG from on the Park Hawk?

[Jerry Rose]

A picture is worth 1000 words:

[BillB]

Yeah! Great Picture Jerry.
My CG is about 3/16" Forward of that center wing attach point. (Mine has the G10/O-Ring mounting)
But I can move the Batteries fore and aft slightly which changes the CG some. I am using two Mpi MX-50HP Micro Pro Servos (2x.32Oz) and a FMA 5 Dual Conversion Receiver (.31Oz).

That brings up a good topic of discussion... If you were able to change the battery location and the CG with a servo during flight could you cause more bird like landings? Or maybe even a slight hover before landing on some wide stance carbon-fiber stick like feet. And could you take off the same way?

I will send an update when I get my Pixie 7P in for a full report on how long a flight I can get using the Kokam's.

Its great hear you can charge these guys in parallel. That cuts my charge time in half. Awesome... I am really sold on these Kokam batterys. The best battery for medium discharge rate applications like the Park Hawk and they are kind to the environment.

[BillB]

Repost of my 2Ah Park Hawk. Was trying to change the image size and deleted the post....:D

[BillB]

The 2040mAh Park Hawk flys great except I am getting some ESC cut-out at full throttle. I think its due to the Batterys not putting out enough voltage at the full throttle current draw. Since I don't need to run at full throttle (3/4 throttle works great) this is not a problem. Just need to remember not to use full throttle for more than a few seconds. At full throttle the 2Ah Li-Poly Park Hawk climbs a lot faster than the standard NiMh 720mAh Park Hawk.