I am scared of 24s ...

[Bille]

The glider I want to power is a 15m , (49.2-ft ) span Atos VRX that gets a (19 : 1 ) L/D
and I believe the newest E-Paramotor SP140 V2.5 , will be perfect for my project !
That system runs on 24s ,and uses the FOC type ESC ; it's suppose to be more efficient
at lower throttle settings. Even if the ESC has a break on it ; I will still place a disk break
from a motorcycle to stop the front mounted folding prop from windmilling.

I have foot launched Hang gliders since 1977 , and Paragliders since 1989 ; but launching
off a mountain with a 15m glider on 2 fake legs is really difficult in turbulence.

The Question :

I am Fine with handling a 12s LIPO , (or ION) as the voltage does not scare me , and I
use them a lot in my T-Rex 800 Heli ; 24s is a different story , and yes I am scared !
I will be building my own packs from the newest EVE 21700 50PL ; they bin tested to
180a , and can take 125a continuous.

High density solid state drone battery cell

The stable growth path from semi-solid to all-solid state battery enables a dual technology platform 17Ah 300wh/kg 3C-5C 22Ah 290wh/kg 3C-5C 24Ah 300wh/kg 3C-5C 29Ah 300wh/kg 3C-5C 31Ah 320wh/kg 3C-5C 32Ah 300wh/kg 3C-5C 35Ah 320wh/kg 5C-10C 38Ah 370wh/kg 5C-10C 11Ah 480wh/kg 3C-5C 12Ah...

arosenpower.com

If I build 2 packs, in a 12s , 3p configuration and connect each pack to one side of the
ESC , with a big honking insulated manual switch between them to complete the circuit for the
100v series ; would that be a good or Dumb idea ? I will not build a 24s battery pack ; and
don't even want to charge or carry one around.

Only other problem will be figuring out the prop pitch speed ; but a fixed ground adjustable
prop will solve that one , and I can get a folding one that size later.

Bille

 

[neptronix]

I've taken 125 volts of 10AH 20C RC Lipo to the hand and survived with nothing else other than some battery PTSD.
Such a pack will instantly turn whatever is in the way of the short into plasma and destroy it's own ability to conduct current at the battery pack assembly level.

Make sure there are no super short gaps between conducting surfaces, as the higher the voltage, the more likely something is to arc over a very short distance. ( 1-2mm ). That's the primary concern as the voltage goes up.

You will also need a great precharge resistor before the battery is hooked into the controller.

Otherwise i think it is not significantly more dangerous than if you had say, a 12S pack with double the amp hours.

 

[Hummina Shadeeba]

At these voltages an arc will only go a fraction of a millimeter.

I kinda feel safer with higher voltage or higher power cells as they are more likely to blow away any shorting material as apposed to continuing to short and possibly cause a fire

Id do a loopkey “switch” between the two packs but with a higher rated resistor inside the qs8 plug. I think im out but will order more. If ur interested write me and almost my cost

 

[mxlemming]

The glider I want to power is a 15m , (49.2-ft ) span Atos VRX that gets a (19 : 1 ) L/D
and I believe the newest E-Paramotor SP140 V2.5 , will be perfect for my project !
That system runs on 24s ,and uses the FOC type ESC ; it's suppose to be more efficient
at lower throttle settings. Even if the ESC has a break on it ; I will still place a disk break
from a motorcycle to stop the front mounted folding prop from windmilling.

I have foot launched Hang gliders since 1977 , and Paragliders since 1989 ; but launching
off a mountain with a 15m glider on 2 fake legs is really difficult in turbulence.

The Question :

I am Fine with handling a 12s LIPO , (or ION) as the voltage does not scare me , and I
use them a lot in my T-Rex 800 Heli ; 24s is a different story , and yes I am scared !
I will be building my own packs from the newest EVE 21700 50PL ; they bin tested to
180a , and can take 125a continuous.

High density solid state drone battery cell

The stable growth path from semi-solid to all-solid state battery enables a dual technology platform 17Ah 300wh/kg 3C-5C 22Ah 290wh/kg 3C-5C 24Ah 300wh/kg 3C-5C 29Ah 300wh/kg 3C-5C 31Ah 320wh/kg 3C-5C 32Ah 300wh/kg 3C-5C 35Ah 320wh/kg 5C-10C 38Ah 370wh/kg 5C-10C 11Ah 480wh/kg 3C-5C 12Ah...

arosenpower.com

If I build 2 packs, in a 12s , 3p configuration and connect each pack to one side of the
ESC , with a big honking insulated manual switch between them to complete the circuit for the
100v series ; would that be a good or Dumb idea ? I will not build a 24s battery pack ; and
don't even want to charge or carry one around.

Only other problem will be figuring out the prop pitch speed ; but a fixed ground adjustable
prop will solve that one , and I can get a folding one that size later.

Bille

View attachment 381267

This is a tricky one. From a regulation perspective, 100Vdc, 24s full charge is in the danger zone. And needs appropriate insulation and so on However, from a hobby perspective, the primary risk is fire which isn't really that much greater than with the equivalent capacity low voltage pack.

If someone dared me, I'd touch each terminal of the 24s pack. It's unpleasant, but I've done it many times accidentally and come to no harm. A few years ago I sat with a 20s pack and worked my way up it to find out how bad it was being zapped. 16s was the threshold of being bothered by it. Your mileage may vary. I don't encourage you leaving live 100V terminals accessible to yourself or laypeople.

Building two packs in series carries problems with BMS and breakers capability. Your primary risk is fire and inability to break the circuit.

 

[Nix Liou]

I will be building my own packs from the newest EVE 21700 50PL ; they bin tested to
180a , and can take 125a continuous.

They are technically capable of 125A continuous, but with a temperature limit, and not in a pack. In a pack at 125a you will only get ~2Ah before the temperature limit cuts you off, without more involved cooling.

Most BMSes are explicitly not supposed to be put in series, I would recommend simply making one pack and avoiding and hassle with series battery packs, which is probably more dangerous than a pack.

Use appropriate connectors like QS with anti spark, and the female plugs on the battery, and while building make sure to cover everything you aren't actively working on to prevent accidental shorts.

In regards to carrying or charging a 24s battery pack, it's about as much risk as plugging stuff into a non-gfci outlet, you will be fine.

TL;DR I can't recommend putting packs in series, and 24s is not that scary. Perhaps you can find a local builder to make it for you, or just wear gloves during assembly if you are worried. The risk from li-ion cells is still primarily burn risk from the high power of a short, not electrocution, at 24s IMO.

 

[neptronix]

When i shorted some 25S lipo, some solder interconnecting the cells on cell 1 went plasma and interrupted the flow of electricity pretty quickly.

If you are going to use powerful cells, it's a great idea to make the bus interface weaker than the maximum power output so that it blows before the cells go thermal in case of a short. It was one smart aspect of the design of those RC Lipo packs.

 

[sternwake]

They are technically capable of 125A continuous, but with a temperature limit, and not in a pack.

The most recent EVE 50PL Data sheet removes the 125amp continuous and 180 amp pulse ratings.

Tabless design cylindrical cells tests

Yeah also einhell since a long time ago

endless-sphere.com

 

[Nix Liou]

The most recent EVE 50PL Data sheet removes the 125amp continuous and 180 amp pulse ratings.

Tabless design cylindrical cells tests

Yeah also einhell since a long time ago

endless-sphere.com

That too, yes. It's interesting, because while it does bring them more in line with other tabless options, it's definitely a downgrade from what they have been tested to be capable of. My guess is it's because of the addition of an official cycle life for the first time, but I'm not sure. Either way, I've heard from one supplier that they expect new 50PL cells with the EVE logo and CCC stamp december-january, to go with the new spec sheet, and I'll get my hands on some of them as soon as I can xD

 

[Bille]

Thanks a Bunch for your replies guy's ; it was mostly (Ignorance) that I was afraid
of on the 24s thing !!!

Because I enjoy flying 12s EDF jets , and helicopter's so much ; I will still build 5a ,12s
packs to use in my RC's , and have the ability to series and parallel them for the
ultralight project. Once I find the perfect balance for weight to KWH on the ultralight
pack ; I can build a dedicated pack just for that use.

... I've heard from one supplier that they expect new 50PL cells with the EVE logo and CCC stamp december-january, to go with the new spec sheet, and I'll get my hands on some of them as soon as I can xD

That works out for me because a battery maker I met yesterday told me to wait for the
the new 50PL cells ; as they may have some changes coming.

Bille

 

[amberwolf]

That works out for me because a battery maker I met yesterday told me to wait for the
the new 50PL cells ; as they may have some changes coming.

If you poke around here on ES, you'll find threads by Pajda, BatteryMooch, etc., that show detailed testing of various cells over time, including those cells.

 

[Nix Liou]

Thanks a Bunch for your replies guy's ; it was mostly (Ignorance) that I was afraid
of on the 24s thing !!!

Because I enjoy flying 12s EDF jets , and helicopter's so much ; I will still build 5a ,12s
packs to use in my RC's , and have the ability to series and parallel them for the
ultralight project. Once I find the perfect balance for weight to KWH on the ultralight
pack ; I can build a dedicated pack just for that use.



That works out for me because a battery maker I met yesterday told me to wait for the
the new 50PL cells ; as they may have some changes coming.

Bille

I've heard through the grapevine that the difference with the new 50pl is self discharge improvements, and minimum of 5000mah. Luckily, those were the 2 problems with the cell, so maybe it'll just be perfect

 

[Papa]

Residentual and commercial electricians have a "one hand in the pocket" rule when poking around inside a hot breaker panel. it's a suttle reminder to always know what is "grounded", and what is safe. The electrical path from one hand to the other hand, is through your chest....where your electrically sensitive heart is.

I have heat shrinked a set of my screw driver's shanks, leaving only the steel tip exposed.

 

[Nix Liou]

Residentual and commercial electricians have a "one hand in the pocket" rule when poking around inside a hot breaker panel. it's a suttle reminder to always know what is "grounded", and what is safe. The electrical path from one hand to the other hand, is through your chest....where your electrically sensitive heart is.

I have heat shrinked a set of my screw driver's shanks, leaving only the steel tip exposed.

Also some non-conductive ceramic tipped tweezers or similar are convenient when you need to push things around without the risk of bridging bus bars or similar.