Looks great! So what flight time are you going to get from this battery pack and how much does it weigh?
Looks great!
I still think that the 13s pack at full throttle sucks too many ampsā¦
Hope this works out for youā¦ if not change it to 12s with the KV180 motors or 14s with the KV150 motors!
This is my approximation for 14s KV150 motors:
@tarifachris - are you from Tarifa in South of Spain? I went there once for a week of kitesurfing 
Hope this works out for youā¦
I think it does, the amp draw does not seem to be an issue. after I added 5 parallel groups thereās even less stress on each individual cell when going full throttle - even thoug the LG HG2 cells are rated for the minimum setup of 15P as well.
if not change it to 12s with the KV180 motors or 14s with the KV150 motors!
I am confused, I donāt even know which KV rating my motors have. I ordered and received the batch 3 kit ā¦
but switching isnāt so easy, as I spot welded all the connections in between the cells (except for the bus bar, which uses screws) and since the case has been designed around the 13S width, and the 20P height.
If I remove the fans (as it looks like, they are not needed) and place the BMS elsewhere, Iād have additional space for another 5 parallel groups, but no space for an additional series connection.
Could you explain, in which way the KV rating changes the Amp draw?
from what I know is that the KV rating determines the revolutions per minute if it is multiplied with the Volts.
so 50 Volt input on 150KV means 7500 revolutions.
I can not have less thrust than what I have now:
When the battery is full (and the full voltage is at my disposal) I have enough thrust to lift off and gain altitude. However when the battery is only at 50%, the thrust is only sufficient to keep level flight.
I think the question with the flight time is extremely difficult to answer.
I donāt have many flights with the new battery and the OpenPPG on my clock yet, but let me give you some insight as follows:
Flight time
(Info: 1 Meter = 3,28feet)
-
Flight A: It was around 5pm on a sunny, cold day, thermals were looking good.
I launched and climbed to around 400m over ground, then found thermals and climbed further up around 700m slowly (it was already late in the day, so slow but steady thermals).
it probably took me 10 minutes to reach the 400m on full throttle.
I was then stupid, flow over a small hill range in our area and went into a Lee situation. The wind really pushed my down hard, I could not climb back up because of the half depleted battery, so I went half throttle trying to keep altitude, I barely made it back half way around the hill, had to walk the rest of the way to the launch area. total flight time: 40 minutes.
If I hadnāt been so stupid to fly behind the hill range into the Lee situation, I probably could have kept flying for another hour or soā¦ (using the rest of the thermals. -
Flight B: I launched, climbed to 400 meters over ground or so, stayed there for a couple of minutes, total time probably 15 minutes. No thermals at all, rather the opposite: downward moving air. then noticed on the throttle controller that the battery was almost empty (I trusted the pourcentage shown, which was stupid - the throttle controller is set to a LiPo 12S battery voltage than the actual 13S Lithium Ion that I use, which has much higher voltage when full, and much lower voltage when empty. So I can not rely on the pourcentage, rather than the voltage shown.)
being in the air, I did not remember how to change the display to the actual voltage. So I landed.
I then noticed that I still had some capacity left, launched again and flew another 3 minutes at low altitude. with the battery almost depleted I can not go full throttle to climb again, and the thrust is also lower due to the lower voltage. If I stayed higher up, I could have flown for probably a lot longer -
Flight C I launched, climbed to 300m or so and was looking for thermals, did not find any, after 10 minutes of flight time or so I decided to practice spiralling, did like 4 turns which made me loose a lot of altitude of course. with the battery half empty I decided to fly very low over the ground (1-3 meters), which is a lot of fun, but of course also kinda dangerous.
Stupid me did ignore that with half empty battery I have not much thrust anymore, to stay level, I pushed the throttle once too hard (Voltage Sag) which led the BMS to shut off the battery due to low voltage.
I immediately landed hard, with the wind - very very stupid maneuver!
Bottom line: The loose of thrust on an half empty battery is a problem, if your plan is to fly around, up and down.
You will get most out of the battery and have it be as efficient as possible when you only gain as little altitude as necessary to fly safe and comply with aviation rules, and then just fly level.
I have yet to test that, to really be able to tell you the possible maximum flight time.
What really is a good scenario, should I not make the battery even bigger in the future, is to fly midday, climb to a thousand feet or so, let go of the throttle and continue flying by riding the thermals!
By the way: I have IGC tracks from my Vario of all the above flights. if anyone wants to see them, Iād be happy to upload them
Battery Weight
the original 13S15P pack was 10.2 kilograms without the case.
I then added another 65 cells (5 parallel groups) and an aluminum case.
I donāt have the weight of the aluminum case, maybe 1-2 kilograms
but the cells weigh 48 grams per cell, thatās a total of 3,12 kilograms
so total weight now should be around 15 kilograms.
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@tarifachris can you help me with my questions above?
- how does the KV rate of the motor affect the Amp draw?
- I assume your list is a spreadsheet - could you share it with me/us?
- how would the numbers look if Iād be using a prop with a higher pitch (22x12) ?
Really looking forward to your insight.
thanks
Etienne
The KV 180 MAD motors where not designed for 13s - sure you have great power but your prop tips
speed is at full throttle at 800 kph and should be very loud. Ideal noise reduction would be in the lower 600 kph tip speed regionā¦
Here is the link to play with:
https://hackermotorusa.com/resources/downloads/
then you go to motor calculator!
The xoar pjn electric props are the same as the gemfan electric!
You should find a great combination of prop/KV motor/13s
Howās your pack been working @etienne? How many flights have you had on it? Whatās your average flight time?
The pack is doing great. it works.
I donāt fly very often with the open PPG, because we were able to secure a new location for free flying
right around the corner of where I live
(for anyone whoās interested: Start des Erprobungsprogramms "Gleitschirmfliegen an der Wittekindsburg" - YouTube ), and also because I had to repair the hoop and the net (will post info/pics about that in a separate thread.
If I donāt catch any thermals (which I always try to) and if I donāt go full throttle the whole flight, but fly in a conservative way, I probably get around 25 minutes of flying.
The OpenPPG is for me a method to actually get in the air, if flying from a hill/mountain is not an option, and that works great.