13S15P Battery Pack Build

OK that will work thx

Hi there,
Thanks for sharing your build process
How heavy will this pack be?
Thanks,

Artur

Hi… you might consider copper strips instead of nickel. I’ve heard (but not used) that this is much better for high current situations. Makes sense…

@Artrec this is going to weigh around 10kg

@pofries yes, copper strips would be better (lower resistance), however you can’t weld copper with the copper electrodes of the spot welder. another option would be nickel plated copper strips, or simply weld two or three pure nickel strips on top of each other, which is what I am going to do.

@etienne What’s the run time estimate for OpenPPG with this battery pack?

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@dpack I don’t know.

However I think I remember that @Pdwhite said somewhere here in this forum, that with 8 of the multistar 16000 mAh Batteries (2 in series, 4 in parallel, total capacity 4x16000 = 64000 mAh) we would have a flight time of around 40 minutes (see quote below).

My battery will have 45Ah with a little more voltage (48V nominal instead of 44V nominal, so a bit more RPM for the motors) - you do the math.

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I added it to a copy of the battery comparison link. You can find the copy here:

https://docs.google.com/spreadsheets/d/1VDiMgdWye7eQTgzYSdsmFcgFx1_5bVhWPgO-YggOWqY/edit?usp=sharing

Look on the last row. This is my best guess for the values.

From those numbers, it looks very competitive at 0.83 $/s. It may also be less likely to explode on your back (these are more stable?) and longer lasting than Lipos.

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Great work on the spreadsheet. Very useful!

Yeah, that spreadsheet is amazing. Here is the original thread:

I’ll tag the author so he can add it to the original.

@DanielArnett is the original author.

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Okay, I added it, but I added more weight than you were estimating. I’m expecting that people will use a battery kit when using these cells, like the Vruzend kit, which will weigh around 5kg to hold all of your cells. Feel free to correct me, I just would rather overestimate weight of harnessing and everything until someone can give me a definitive answer on how much the batteries + harness will weigh.

This is an interesting similar battery:

240 cells, 15S16P.

By now, I received the cells, nickel strips, plastic holder/spacer as well as the BMS.
as soon as I start putting everything together, I will post more pics!

20180529_100533

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Watching with interest.
Would also like to hear your impressions of the spot-welder when you get to it.

Hi Lukas,
I completed the spot welding of the first layer of Nickel strips yesterday. I will have to add more layers for the serial connections, to support the high current of 300A max, but I need to wait for more nickel strips to arrive.

It was the first time for me to use my newly purchased arduino/car battery spot welder. It was quite easy, no hassle. However it took some welding to figure out that the pressure of the electrodes being applied also makes a different in the welding quality, just like the amount of milliseconds (duration of current applied) makes a difference.

It took about 90 minutes to spot weld all 195 cells. I had to pause every few minutes for a few minutes, as the electrodes got quite hot in my hands.

Overall I think I am quite happy. Will post more pictures later.

I wondered how this would fit in the current frame. I assumed these were about 70mm tall with the plastic connectors, and 19mm between the centers. A 13S15P pack looks like it fits nicely, assuming the motors aren’t too squat:
Fusion 360ScreenSnapz014Fusion 360ScreenSnapz015Fusion 360ScreenSnapz013

For fun I also did a 13S20P which might extend the flight time from about 24 minutes to 32 minutes:

Fusion 360ScreenSnapz017

This would also add an estimated 4kg in weight, from 12 to 16kg. I’m not including the BMS or cables in these size or weight estimates.

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That looks pretty cozy. You could add in the motor model (step file is in github) and assume a prop mount. Might give you a better measurement.

There’s 190mm space between back plate & props, so you could probably double up the packs…

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This raises an interesting question- Assuming that two packs are only 140mm tall, and that they are not too heavy when stacked, I wonder if we can arrange the electronics so that a second pack could be added for some flights? I do this for my FPV planes and lipos by just putting them in parallel. I don’t know if the BMSs fight with each other with these packs, however.

One pack is about $1200, so this gets expensive, except when you consider that a Carbon Scout is about $9k plus all the maintenance, drama with airlines and fuel, and noise. I’m not saying I’d turn down a Carbon Scout if I could afford one, but it does put things into perspective.

@tombusey thanks for checking whether this fits, or not. However I am thinking to place the battery rather lower, between the legs. In either case this is probably going to be a trial and error process, and see what works best, when the whole setup is on my back.

Here’s the battery with the first layer of nickel strips:

and a closer look

The serial connections will definitely need a second and third layer of nickel strips welded on top, to support the high current flow, I also still need to add the BMS and the cables to connect the whole thing to the openppg.

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Nice work! Which cells did you wind up selecting?