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TOPIC: 20700 Li-ion battery

20700 Li-ion battery 3 months 2 weeks ago #351

Hi for all,

the new 20700 battery cells are coming.
www.imrbatteries.com/sanyo-ncr20700a-310...0a-flat-top-battery/
Is here someone how tested or knows more about this? Max amp is rated 30A, is this a real amp level or less is true?

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20700 Li-ion battery 3 months 2 weeks ago #353

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20700 Li-ion battery 3 months 2 weeks ago #354

Hi Simon,

thank you for the link. They wrote at 30 amp reached 75C temp. I think it is too high so the 30 amp is more for short periods not for continue. But maybe 10-20 amp is ok. Would be interesting to know how much discharge periods hold this battery. As far as I know the li-ion batterys have more lifetime than lipo (li-ion more than 500 cycles).

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20700 Li-ion battery 3 months 2 weeks ago #355

Hi, I think 10c is okey for most applications. Attached I try to compare the datatsheet with the test.
looks pretty much the same, but datasheed is a little bit better (pre selected cells? temparature?)
I try to compare the li-ion battery with a 3.500mah lipo battery. Take a test from www.elektromodellflug.de/sls-quantum-30c.php
This test ist mainly with 10C, I think very interesting. With li-ion I think its a good idea to choose slightly higher voltag in the beginning,
if this is possible, to have nearly equal power. In the datasheed
www.imrbatteries.com/content/sanyo_ncr20700a.pdf
on page 6, there is a chart with "Cycle Characteristics", 10A, 20A, 30A. I think very durable and maybee in total lighter than lipo.
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20700 Li-ion battery 3 months 2 weeks ago #356

Hi Simon, I agree with your argument. Only the price for the same capacity/voltage is higher with this Li-ion, but if we can use it more cycle it worth. And I think Li-ion is safer than lipo. Well how will be the first of us who test it? :-)

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20700 Li-ion battery 3 months 2 weeks ago #357

hi, I have a frame system which is dropable. so battery safty is not so important for me.
currently I have only 6 flights this year, because I only fly when there are nice thermals.
So I dont think I will fly so often a year. But I am really interested in reducing the weight.

currently I have four of these ones
www.stefansliposhop.de/Akkus/SLS-Multiro...V-30C-60C::1638.html
45V (average) with 16.000mAh (4,7kg)

These Li-Ion cells has an average of 3,5v under 10C load.
So I need 13 cells (45v / 3,5v) x 5 (16.000mAh / 3.100mAh) ?
65 cells * 61,2g = 3.978g (+ Wiring, Packing, BMS)

hmm, not such a huge step, and I am not sure if my 12S ESC accept 53,3V in the beginning.
also, I will need a bms systems (I have heard its horror to find the right one), spot welding,
special chargers ... and the cells a slightly more expensive. but maybe I overlooked something...;)

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Last Edit: by Simon.

20700 Li-ion battery 3 months 2 weeks ago #358

Hi Simon, the main reason I'm thinking on Li-ion battery is safety. I afraid from the lipo. Is something goes bad one way is to drop the pack but that means a danger when hit the ground. But maybe a box made from aluminium is enough to resist the heat and flames when something goes wrong. To be honest my electric project was slowing down because of this. I have lipos too, I'm making ground test a lot but don't feel the safety to fly with it.

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20700 Li-ion battery 3 months 2 weeks ago #359

hi roland.

I have the same toughts when my big lipos arrive here. so much energy.
but at youtube, in the newer videos (not 5 years old)
I have seen that you have to do - massive - damage to the battery (with an ax,
or huge nail complety trough the battery) and many of these trys resume
in massiv fume. and that lipo safe bags really work well. I bought
these safe bags, but after a time, I think I dont need them.
There are millions (!) of lipo batterys out there, and a lot of beginners,
and you really have be a noob to fly with lipo battery with such a
massiv damage, that you will get trouble in the air.

I make several ground test on a small scooter

and become familar with the hole system. And after a longer time, I try to fly.

But I am worried about clouds and icing. There are tiny balance connectors at the lipos,
and throttle, bec, receiver is not well protected ... But in case of emergency,
I can unhook only one side, or only sit up, to have distance between me and the
fuming lipos - I will not drop a frame over the city or something like this.
But these are case of emergency (life or death ..) I am pretty sure I will not
get in such a situation. Also I have batterys and esc in view all the time.

take a look at youtube how well safe bags and cases works. I think a
dropable system is very nice and good for mind - you can act. when you place a
batter bag between the carabiners, I think it is also a nice place. You
can make it dropable, you have it in view, and its the best position
to place a lot of weight, especially for thermalling ;)

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Last Edit: by Simon.

20700 Li-ion battery 3 months 2 weeks ago #363

Hi Simon, agree with that, maybe I need more time to thrust my lipos. The emergency drobbing with some extension is a good idea. MAybe a steel cable 1-2 meters long so it is at safe distnace but not falling on the ground. You wrote are using your gear for thermalling. What is your tipical flying style? Are you climbing out from flat land with the electric unit or from a hill? how much height you gain average before catching thermal?

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20700 Li-ion battery 3 months 2 weeks ago #364

hi roland,
regarding lipo, I think about it. you need a strong connection for a long therm shortcut. a weak connection will burn up. even steel. have seen this here, during soldering. normally you can see any damage on battery or cable, if you are carefull, and know how to test, charge, store and use:
www.elektromodellflug.de/lipo-leitfaden-faq.html (I really trust this site)
then i think, it is okay, dropable (with a rope is very good idea) or with a good fire protection. li-ion are maybe safer, but more complicated (nothing ready to run) and not so good for small packs. send you also a privat message ;)
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20700 Li-ion battery 3 months 1 day ago #420

RolandFalusi wrote: Hi for all,

the new 20700 battery cells are coming.
www.imrbatteries.com/sanyo-ncr20700a-310...0a-flat-top-battery/
Is here someone how tested or knows more about this? Max amp is rated 30A, is this a real amp level or less is true?


Hi all, just following up here a bit. I learned today that ANOTHER of our pouch cell batteries have failed: a Hi Flite 15 ah NMC 52 volt pack. Only two years old and about 80 cycles. The guys at Hi Flite offered a new one under warranty for half price, but that is still $1200 US for a 30 ah battery... too much

We have had 4 prismatic/pouch cell batteries fail now, so I am considering the cyclindrical because I think heat dissipation is better and one cell won't ruin your day. I had a look at the Sanyo, but calculate the energy density at 180 wh/kg. These look to have about 213 wh/kg. I think with a spot welder, making up these batteries might not be so difficult. Welcome your thoughts.. best, Peter
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Last Edit: by ozeflightclub. Reason: mistake

20700 Li-ion battery 2 months 2 days ago #502

a nice documentation about current batterie development



at 30:30 they show a solid state battery, very impressive.

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