I have a build thread going in another forum for a B-36.

We have had a discussion about the proper batteries to use.

I am trying to achieve a reasonable compromise between battery capacity and battery weight. My B-36 has 6 brushless motors so if I use one pack per motor that means I will have to purchase 6 LiPo packs. I realize that I could also power the 6 brushless motors with 1 large battery pack, 2 packs (one for each wing), 3 packs (one for outboard, one for middle, one for inboard), and I can also use 6 smaller packs with one pack per motor. I have already gone through the pros and cons of each and that is not what I need help with.

It is my desire to use six packs of Thunder Power 11.1 volt 2100 Pro Lites (TP2100-3S4PL) because they have the highest energy density which is 22.11 mah of capacity per gram. FYI, this ranged from 22.11 mah per gram down to 10.11 mah per gram. I figure why not get as much capacity as possible for the same weight, or, get the same capacity out of a much lighter pack.

I am trying to confirm my battery choice with MotoCalc 8.

So here is where I am having difficulty and I could really use some help.

To make my question clear, let's change the batteries for a moment back to NiCads.

For my example, assume that I wanted to use a 7 cell pack of Sanyo 800AR cells. The first image posted here shows that I selected a 7 cell pack of Sanyo 800AR cells wired in series. Series wiring will not change the capacity so you get 800mah. Series wiring will change the pack voltage to 7 times 1.2v per cell which is 8.4 volts. It will increase the weight times 7 and the Impedence by 7. The result of this is a 800 mah, 8.4 volt pack that weighs 8.155 ounces with an impedence of .042 ohms.

The next image shows the same cells in a 8 cell pack. You get a 800 mah, 9.6 volt pack that weighs 9.32 ounces and an impedance of 0.048 ohms.

To make a point the third image you can see that I specified the same cells, 7 in series 2 in parallel. MotoCalc still show the capacity of a single cell as 800mah and the weight and impedance also stay the same. The result is a 8.4 volt, 1600mah pack, weighing 4.075 ounces and an impedance of 0.021 ohms. So, in parallel the capacity and weight are multiplied by 2, the voltage stays the same, and the impedance is divided by 2.

Now let's move on to LiPos for my plane. I select Thunder Power TP2100 (Pro Lite) from the list. If I am still specifying a cell, and not a pack, then I should enter 3 series and 1 parallel to get an 11.1 volt pack with 2100mah capacity as shown in the 4th image.

The Thunder Power website lists this pack as a 3S4P (3 series and 4 parallel) configuration. If I specify 3 series and 4 parallel as shown in the 5th image won't I really have a pack made up of 12 cells? This would give me a 11.1 volt, 8400 mah pack that weighs 20.04 ounces?

I suspect that the proper way to specify the TP2100-3S4PL pack in MotoCalc 8 is 3 series and 1 parallel.

Taking this discussion to the final step, for 6 of these packs in my B-36 shouldn't I specify 3 series and 6 parallel?

I need to know how to specify this correctly. My battery purchase will be a bit spendy and I want to get it right the first time.

Thanks,

Mike Roerig
[email protected]

Sorry, I was in a hurry and mis calculated the weight for 800AR 7 in series, 2 in parallel. The weight would be 14 time 1.165 ounces or 23.1 ounces.

I was trying to finish my post before it timed out so I didn't proof read it.

Mike Roerig
[email protected]

Here is the 5th image that I referred to in my post.

Mike Roerig
[email protected]