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-   -   Batterys (http://www.Wattflyer.com/forums/showthread.php?t=73581)

egrave1 04-18-2014 02:00 PM

Batterys
 
Is it better to buy all your battery's the same cells say like 3s then if you need to series them you can or should you buy the cell size that the model calls for

fhhuber 04-18-2014 03:07 PM

It comes out a bit cheaper to be able to fly all of your models using the same batteries...

That would mean careful model selection to avoid having to get different size packs.... Or flying some with oversize (capacity, not voltage) packs. Oversize packs can be acceptable because most of our models can easily handle some extra weight, but added weight will often mean reduced aerobatic performance.

Do not try to fly with undersize packs as that is a good way to ruin a battery.

You can select models that use differing voltages and buy batteries as 2S and 3S packs. Putting these in series you can get just about any cell count the model might require. When putting batteries in series they need to be the SAME capacity and C rating.
This can allow more flexibility of model size/type and not have you needing to buy as many batteries as if you bought 3S packs for 3S models and 5S for 5S models and 6S for the 6S models. For example a pair of 3S packs could give one flight of the 3S model opr 2 flight of the 3S model.

Then we get into the odd case such ad Dynam's 1250mm P-51 which does much better with 4S 3300 than the OEM 3S 2000... But you need to know what you are doing and use a wattmeter to ensure you are not going to create a fire when changing voltage.

solentlife 04-18-2014 03:39 PM

As fhhuber ...

It's great if you can standardise on one size pack ... the 3S 2200 pack must be about the most common I reckon ...

But as I found - you soon start looking at other models that need other sizes ... so I soon had 4S and 5S in the boxes .. I don't so far have any needs for 2S ... so joining packs together is not really an option for me.

I think in early stages of modelling and when only 1 or 2 models - buy the packs that you need in size you need. Later on think about creating packs ...

Nigel

egrave1 04-18-2014 06:08 PM

But if your model calls for a 4s and your motor & esc can handel a 6s why not use two 3s and back off on the throttle

fhhuber 04-18-2014 06:21 PM

Quote:

Originally Posted by egrave1 (Post 945779)
But if your model calls for a 4s and your motor & esc can handel a 6s why not use two 3s and back off on the throttle

Then you probably bought the wrong motor and ESC for the model. Its rare to install a motor that can use 6S and not use it with 6S. The Kv of the motor will generally make that a bad choice.

solentlife 04-18-2014 07:04 PM

Quote:

Originally Posted by egrave1 (Post 945779)
But if your model calls for a 4s and your motor & esc can handel a 6s why not use two 3s and back off on the throttle

Is the model capable of carrying the weight ? 6S vs 4S is a very big difference .. and why penalise a model ?

Nigel

hayofstacks 04-18-2014 07:21 PM

My dads eflight advanced we used two 1800 mah 3 cells which gave use 3600mah capacity and weighed over an ounce less then a single 3200 3 cell which was the called for battery if i remeber correctly.

i bought two 4000 mah 3 cells with the idea of running them in series for a cheap 6 cell pack that i could test on larger motors, but still fly my ultra stick and other .15-.25 sized models on down the road.

two parrelell 3 cells and then stacked in series with 2200mah would give you 4400 mah 6 cells equivilent, but the cost of y-cables, connectors, and weight i think would make it a wiser choice to just get two larger 3 cells. at least that was my thinking...

egrave1 04-18-2014 07:37 PM

I am running a Ultra Stick 40 with two 3s 2450mah in series on a 4/5s 670kv mtr. When I get in the air I back down to 1/2 throttle I have plenty of speed and power o0n take off

hayofstacks 04-18-2014 07:41 PM

Sounds like about 3-5 minutes of flight time max to me.

I'm was running a single 4000 mah 3 cell in my .25 ultra stick pulling 350 watts. it was a bit anemic, but i didn't have to swap props between 3 and 4 cells. on 3 cells i would get at least 20 mins, maybe more like 30. on a 4 cell 3000mah i would only get 10 minutes or so, but i generally had my foot in it on 4 cells.

fhhuber 04-18-2014 07:47 PM

Quote:

Originally Posted by egrave1 (Post 945789)
I am running a Ultra Stick 40 with two 3s 2450mah in series on a 4/5s 670kv mtr. When I get in the air I back down to 1/2 throttle I have plenty of speed and power o0n take off


Bad practice... mid range throttle is harder on the ESC than full throttle.


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