NoMercy

Will a 7.2v 350 mah 6 cell battery work ok with my Slow Stick. Or are there ones that are much better. The kind they have at my hobby shop is that for 22 dollars.

NoMercy

I would really appriciate it if one of you could tell me the best battery I could get here... http://h1070999.hobbyshopnow.com/

flyinrog

My Feedback: (1)

I used a 7.2 volt 270 mh..in my stick FD, and I got them for like $12 from microrcflyer.com because they had the wrong connector on them...would run for close to 10 minutes, all I had to do was file/dremel the tab off of the connector.......Rog

sierra gold

Assuming you have the GWS 300S in your Slow Stick, then I think the majority opinion would be to use a 7 cell Nicad or an 8 cell Nimh.

I would recommend anything over 700 mah and personally use an 8 cell 1100mah Nimh with much success.

Sierra Gold

Derek_TX

My Feedback: (1)

THis site offers great prices on battery packs:

Battery Space


Two 9.6V 1000mAh Hi-MH Long Battery Packs for Watt-Age
Sale Price $28.95

cwat212

2nd the site above.

I bought the 8.4V 1000Mah NiMH for $25. great price

SalvageMan

I use an 8x1100 long AAA pack for 20 to 25 min. flying time depending on T/C.

Chuck

mike1

My Feedback: (1)

If you have a batteries plus in your area, they can build you an 8 call AAA nimh pach that will run for around 11 minutes depending on throttle setting. (Not to expensive either)

let_it_fly

i use a 7 cell 1300mah nickel metal pack on my slow stick and have great power and run time with it. i am thinking about a lith. ion batt. setup but don't know much about them yet. i know they are lighter then the others and run longer but i hear they can explode if not charged right. THATS NOT FOR ME!

SalvageMan

Don't use a Zagi battery with a stock prop. A friend of mine found out the hard way. Fried his motor.



Chuck

Dr Kiwi

Dear nomercy - You have been getting good advice here, but I thought I'd add my 2 cents worth anyway.

Bottom line - you need to extract a certain amount of power from your pack to get your 14-16oz Slow Stick to fly - by rule of thumb you probably need a static thrust of about half the weight of the plane, say, 8oz. [Power-in is suggested at 40W/lb for trainers, perhaps a bit less for slow flyers]. My bench tests indicate that for the 300C motor with 6:1 (D) gearing and an 11x8 prop, to get a static thrust of 8oz, you need an input of about 30-35W. Power(W) = voltage(V) x current in amps(I). Nominally 6, 7, 8 cell packs are 7.2V, 8.4V and 9.6V respectively but when under load the voltage drops considerably, especially in the smaller packs, and moreso in NiMH than in NiCd.
If you look at most published motor performance figures (such as those you can find at aeromicro.com) you'll see that they appear to be derived using CONSTANT nominal voltage sources - i.e. 7.2V, 8.4V, 9.6V. Amp draws are quoted, and power(W) values are based on 'nominal V' x I. In the real world, voltage will drop as current draw is increased and as the battery pack is used up, so the figures given in these charts are unrealistically overstated.

Here are a few of my figures using the Slow Stick set-up of 300C motor, 6:1 (D) gearing and 11x8 orange prop: In each case, the figures given are peak amp draw (amps), voltage, power in (W) and static thrust (oz) measured at the start of a test run, using a freshly charged pack. Remember these are static figures only - in flight, motors and props unload so current draws will diminish, but you'll still be getting enough thrust.

6-cell 270mAh NiCd:
5.6A, 6.1V, 36W, 8.7oz

7-cell 300mAh NiMH:
4.2A, 5.4V, 23W, 7.0oz

7-cell 370mAh NiMH:
4.4A, 5.2V, 24W, 6.9oz

8-cell 370mAh NiMH:
5.6A, 6.0V, 34W, 8.8oz

7-cell 600mAh NiCd:
7.8A, 7.8V, 65W, 11.6oz

7-cell 950mAhKAN NiMH:
8.7A, 7.3V, 66W, 12.0oz

8-cell 600mAh NiCd:
10.7A, 8.6V, 94W, 13.7oz

8-cell 800mAh NiMH:
8.2A, 8.5V, 70W, 12.2oz

We can examine some of these in more detail:
Example 1: Let's start with the clearly hopeless scenario: using the 7-cell 300mAh NiMH pack you start at 8.4V nominal, but when you try to draw about 4amps [to get the 35W of power your Slow Stick requires] you find that its tiny cells struggle to supply that high a current, and even when they do (momentarily) your voltage drops to just over 5V - so you can extract no more than 24W from a pack like this! As the run continues the ability to supply current diminishes and the voltage drops even more - after only about 30 seconds the current draw dropped to 3.7A and the voltage to 4.7V (17W, only 5.8oz thrust) at which time the ESC cut off!

Example 2: the 7 and 8-cell 370mAh NiMH packs didn't fare well either - the 7-cell never managed more than 24W and 6.9oz thrust, the 8-cell momentarily gave 34W and 8.8oz, but within 20 seconds of the start [when the peak values were measured] neither pack could supply the required 35W and 8.0oz thrust needed.

Example 3: the 6-cell 270 NiCd just managed to provide what you'd need for a short time, but by the time half the capacity had been used, the power had dropped [4.6A, 5.5V, 26W, 7.4oz] - below the minimum required. I didn't have any other slightly larger NiCd's to test, but extrapolating, it seems probable that 7-8 cell 270-350mAh NiCd packs would be okay - however with packs of this size, run-times at 4amp draw would obviously be quite short [probably only 2-3 min or so, since as capacity is used up, voltage cannot be sustained at anywhere near previous peak levels].

Example 4: the larger 7-8 cell packs (600mAh or more), whether NiMH or NiCd, obviously fared better. You can see that their larger cells [4/5AA, 2/3A] can supply higher currents (8-10amps or so) and voltage drop off is less than in the tiny packs. Any of these packs would give you the 30-35W and 8oz thrust you need, at current draws of about 4-5amps, without straining the system too much. You would have a safety margin too, so that if you had to you could extract a bit more for brief bursts of full throttle - but , as mentioned in the post relating to the use of a Zagi pack, using full throttle continuously WILL fry your motor and battery too.

Like most of the other correspondents I would recommend you use 7-cell NiCd or 8-cell NiMH packs of 600mAh or more. You will have to balance the power you want, with the weight of the selected pack, and with the run time you are looking for!!!!

And for all the logic/science of this testing, the only real way to find out what works is to fly the plane anyway!

Hope this helps, Cheers, Phil

Derek_TX

My Feedback: (1)

Dr. Millener, that was a top notch post!
Clear, concise and accurate. Matches the empirical/observational results I have seen.

I seem to have as step one, when 'designing an airplane' is determining the battery to be used. I like using bargain batteries, NiMH, Li-ion and lipo types which I buy in larger numbers in order to have more packs available on flying days. Since I can make an 8-cell 700 mAh AAA NiMH pack for $5.96, I built to suit those batteries.

From there I find a motor that is happy with the current the battery can handle. With 9.6V 700's the speed 300 seemed to be the sweet spot. Then I decide what type of plane I feel like making. From there I choose whether to gear the motor, how much reduction, or whether to go direct drive. Backwards approach?

ElectriFan-RCU

My Feedback: (1)

Great post Dr. Millener.

My non-scientific experiments are now validated with your data. I fly with either 7x350 NiCd packs (5-6 min flights with throttle management), 8x700 NiMH packs (10-15 min flights with throttle management), 8x1100 NiMH Zagi pack (haven't logged flight time, but it's long enough with great authority). The 700 NiMHs are best compromise as I like to fly light (this combo gives me an AUW of 14oz). On breezier days, the extra weight of the 1100 NiMH Zagi pack comes in handy. Note that mine came with the C gearbox and a 10x8 prop.

Another experiment I tried yesterday was flying indoor with the GWS 100C-1S + 10x8 prop and 2x830 LiIon Qualcomm pack (AUW lower by 1.63oz). The protection circuit is still on the pack, so I know that the pack will cut off on any current draw as it approaches 3A. It flew fine (with less authority) for about 20 mins - towards the end it sagged enough to barely stay in the air. I know I was approaching LVC and didn't want to crash on the concrete floor, so I kept just above the surface. Sure enough, a minute or two later the LVC kicked in and the SS landed a little harder than normal. With this experiment, when the SS is having trouble staying in the air, land it. 20 mins of the SS and then I'm ready for some adrenalin rushes.

I have some spare 1500mAh LiIons that I need to get out of their cases. These can take about 5-6A and weigh only 3oz, so I'll try them out on the 100C and 300C motors (plan to also try with 11x8 prop). I think this will be a great combination for calm/light breeze days.

NoMercy - where in WA do you fly?

ElectriFan-RCU

My Feedback: (1)

Finally got a chance to fly outdoors when it was calm in the morning. I couldn't attempt full duration on each pack as I had to head to work

Note: all my LiIon packs are connected thru the protection circuit.

100C + 10x8 w/ Pan 2x1200mAh LiIon (AUW: 13oz): I forgot to set the timer on the Tx, but I estimate flight time between 25-30 mins. Loops required a little dive and some airspeed since there isn't adequate thrust needed towards the top of the loop. It flew with a little more authority than the QC 830 pack, and the comfort of being able to fly without fear of sudden deadstick. Approx 66% throttle is min required to maintain altitude, flew at about 85% throttle most of the time to guage duration. At the end, the motor was just a little warm, packs were cool to the touch. Since I was flying in the cool morning air, I do expect the motor to get a warmer. WOT is required for ROG.

300C + 11x8 w/ Pan 2x1200mAh LiIon (AUW: 13.5oz): First, one can't take it to full throttle as the pack shuts down. I couldn't estimate flight duration, but the SS can ROG at about 50%-60% throttle. Loops from level but one has to be careful to stay under 90% throttle. Also, quick increase in current draw (suddenly moving throttle to 90%) causes the pack to shut down. Overall, flying with this pack is almost like walking on eggshells. I think the option here is to try a 2S2P pack for longer flight duration than the 8x1100 HECELL pack (or equivalent).

I'll be trying with the following combos on the 2S 1200 packs:
100C + 11x8, 300C + 10x8.

NoMercy

Well. Its been quite a while and I have been flying my slow stick. ITs great it runs on the 1100 really well. I just got my GWS P-51 yesterday and I ordered 2 packs of the 8 cell KAN 950 pack from www.electricsquadron.com If anyone has used these in their p-51 do I need to modify thebattery compartment. Also any tips on the bulding part. Also will the KAN 950 pack work great with my slow stick

NoMercy

Sorry I forgot to mention that I live in Issaquah and I either goto merrymoore(Like today I am gonna go with some friends) or I goto a local school