Flying with 8 batteries

Power System
#1

For all you that fly with more than the standard 4 batteries.

I see most mount the bottom batteries vertical (as per Glydrfreak’s excellent method). I’m thinking of doing the same as it is obviously better for keeping the wire lengths as short as possible.

Just one thing that keeps nagging me. With all the weight of the batteries hanging off the side of the batteries, there will be a moment on the connection points. Have any of you experience cutting or marking of the zip ties into the battery casings? Or is there some foam support between the printed part and the battery?

Or would it better to have an angle at the bottom to support the weight of the batteries on their ends?

Or a box like Grassyellow’s installation?

Thanks.

#2

Credit for that printed track method goes to my dad (@GliderPilot). He will be able to answer your question better, but I don’t think there has been any damage caused by the zip ties. I wondered the same thing at first, but they seemed to have held up for a long time now. I even flight tested it to 3.5 G’s.

#3

The batteries have a thin aluminum plate under the
heat shrink that keep the zip ties from damaging the pack. I use foam tape on the printed part just to help hold them in position so they stay lined up.

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#4

How about when the batteries are turned on their side (to allow for 4 down there). That would put the plate perpendicular to the ties.

I noticed that you rotated batteries 2 and 3 when you went from the velcro to the slide. Is this the reason why?

Thanks.

#5

The aluminum plate would still protect the corners the same. The pressure of the ties are on the corners not the surface.

Do you really think you will be able to fit 4 batteries at the bottom?

The way I arrange my batteries makes the wires as short as possible both inside the motor as well as the leads from the batteries which are cut approximately in half.

#6

8 does not look to be a problem. Although I want the connection side of the batteries to be facing up, which means I need a little more support at the top of the bottom frame (just below the hinge) as the frame isn’t wide enough for 4 batteries.

From a wire length point of view, 8 is just as short as 6 (maybe even an inch or so shorter).

I’m thinking of using angle aluminum to support the batteries both top and bottom, with velcro back and straps (similar to the original four batteries) to hold them. I think the batteries will almost be hanging from the straps in flight because of the angle of the bottom frame and hang angle. We’ll see.

Lower Battery Holder-Model
Lower Battery Holder-Model1600×1280 63 KB

#7

We keep the total wire length short to reduce induction spikes. It’s the total length of all wires including the leads that matter. How could 8 be shorter than 6 if you have two more sets of leads?

#8

My apology, forgot total wire length.

So it adds another 4" of wire and the associated battery leads for batteries 7 and 8. I think the extra batteries would out weigh the issues of the extra wires.

#9

So wired for 6 or 8. Comments welcome. I think the wires are about as short as they can be without too much physical stress on the wires.

IMG_20201001_1709001
IMG_20201001_17090012664×3996 3.11 MB

1 Like
#10

That looks really good! I like that you are putting my 3D print designs to use too.

Did you add capacitors to the ESCs? Even though your wires are as short as possible they are still longer than intended for the ESCs we use.

#11

I did add the capacitors, and the precharge. It has all the little upgrades now. :slight_smile:

Really like your 3D parts. They have a very nice fit and finish, especially compared to some other parts. Thank you so much.

I did print your lower battery connection. But it didn’t work because the sides of the bottom hinge does not have the bottom slots. The slots are also slightly narrower. So designed my own two part connector for the bottom. Always fun to swap colours halfway through a print :slight_smile:

IMG_20201001_2016205
IMG_20201001_20162052664×3996 2.19 MB

2 Likes
#12

nice
can you share the 3D files?

#13

Here you go. I mirror it in the slicer to get the left and right versions.

Lower Battery Plug_Bottom.stl (52.7 KB) Lower Battery Plug_top.stl (69.2 KB)

1 Like
#14

Brackets made and installed. First flight, 33 minutes long. I don’t like to push my batteries. They barely warmed up at all.

Not difficult to do, but I wouldn’t want to blow too many take-offs with the set-up. You do know there are 4 more when you have to carry it around. Not cumbersome, but noticeable.

IMG_20201018_1604495
IMG_20201018_16044952664×3996 3.08 MB

Brackets
IMG_20201022_1121383
IMG_20201022_11213831332×1998 1.69 MB

Installed on unit.
IMG_20201022_1133295
IMG_20201022_11332951332×1998 1.75 MB

Batteries installed, ready for flight.

4 Likes
#15

Nice. I’m hoping to receive 4 more Bonkas soon. 33 minutes! great. Looking forward to some more altitude (maybe get above clouds) or range.

#16

The first four rows are numbers from the Paracell singe prop unit with a comparable 4.2 kwh battery (75Ah 14S) and the last row the x4 flight time with 8 Bonka’s:

OpenPPG 947
OpenPPG 947798×192 58.6 KB

The 55 minutes number is from the video where Javier Hernández is flying real 55 minutes, his weight is
67kg. The 85 kilo pilot number is from the german test magazine.

The 75 Ah 14S battery would be the equal to a 88 Ah 12S battery…

8 Bonka’s 6S are 12S 88000 mAh = 4.2 kwh
75 Ah 14S = 4.2 kwh

The SP140 uses a 4.0 kwh battery.

The single prop uses 22-27 % less watts which translates to 10-12 minutes longer flight times than
the OpenPPG with 4 motors. I still believe that the X4 can achieve the same watts as a single prop unit
in the future…

#17

I have been playing with some numbers in the past on how to get a 4 motor paramotor with the efficiency of a single prop. The biggest problem is that the X4 uses 22 inch props which is equal to the sweep area of a single 44 inch prop which isn´t efficient. If you wanted close to the efficiency of a standard single prop unit, you would need 26 inch propellers. The problem is that it would take a REALLY big cage!

#18

I flew my 8 6s bonkas from 4.15V/cell to 3.8V/cell, resting voltage. 33 minutes wasn’t an endurance test, it was simply the length of the flight. I think I could have gotten another 5 to 8 minutes, but I get jittery towards the end of flight, constantly checking the voltages as we drop off the curve and the flight simply isn’t fun anymore (I fly for fun, not work). I land when the system reads 40 volts running.

Just for your data, I’m 100 kg pilot on a 26m Advance Epsilon 6. For my weight and equipment, a 28m would probably have been a better selection for endurance flights but you fly with what you have.

Jim.

#19

67" diameter cage size, to be exact. You would drop 35 amps for the same power at take-off, but only 8.8 amps lower at cruise.

Seems like a lot of added danger during take-off for a relative small amp drop.

I think the compromises in the X4 is very reasonable. What we need is better battery technology…