What does 9 kWh of LiPo look like?

jonescg

jonescg

100 MW
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Aug 7, 2009
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Location
Perth, Western Australia
I have been commissioned by Entecho to build another two flight test battery packs. They consist of 3 x 28s3p packs each. The triple redundancy is an aviation thing... It's the same number of cells going into my race bike 8)

Behold!

YouFly battery construction 002.jpg

Company director Kim Schlunke checks his texts while I take a photo :) We have sorted them all into piles based on their cell voltage. We go for anything over 3.86 V. 3.85 V cells are put aside, and anything less then 3.80 is left out (only 8 cells in 510). It indicates a higher self-discharge, and that means balance is lost pretty quickly.

Peeling the Kapton tape off 510 cells is a pain in the thumb. Should have one of them done by tomorrow afternoon :)
 
When handling them, it's not a bad idea to always keep them separated by a thin foam sheet. When you chafe through the 1mil PE film coating on the outside of the pouch, you introduce new failure modes.

Also, sweep any surfaces you're going to set them down upon to be free of bits of sand or grit.
 
Awesome. What cells are they. What the hell kind of plane are they going in?

P.S. Oh I see, just a hovercraft ATV. If I had a dollar for every electric hovercraft ATV on ES...
 
How heavy is 9kwh of battery?
I was expecting to see much more battery then what was showed 8) ..... Nice lol
 
liveforphysics said:
When handling them, it's not a bad idea to always keep them separated by a thin foam sheet. When you chafe through the 1mil PE film coating on the outside of the pouch, you introduce new failure modes.

Also, sweep any surfaces you're going to set them down upon to be free of bits of sand or grit.
Click to expand...

One of the first things I did was set up on the lunch table as it was the least dirty tables in the workshop. That's cause we tend to eat our lunch at the test rig :)

We noticed a few cells with good cell voltages but they had clearly leaked some electrolyte either during production of after. Needless to say it got put aside. The polyethylene film coating is surprisingly weak, but we do our best to keep them happy.
 
grindz145 said:
Awesome. What cells are they. What the hell kind of plane are they going in?

P.S. Oh I see, just a hovercraft ATV. If I had a dollar for every electric hovercraft ATV on ES...
Click to expand...

Haha, yeah Troy they are going into the hoverpod / YouFly. The website is here: www.youflyentecho.com
The craft is still a prototype but we've had it doing tethered test flights in the car park.

Trackman; 504 of these 40C LiPo cells with copper conductors will weigh about 70 kg. The box to contain them is very light - carbon fibre all that. However, in this case we'll be just building two 4.6 kWh packs for rapid testing and calibration. 5 minutes of flat out run time gives us hours of data to work with.
 
That thing looks like a UFO. Cool. Any idea what the run time will be?

I'd hate to be around if that pile of lipo lit up :shock:
 
It's hard to say, but the flight test packs only give us 5 minutes at full speed. That's about 15C from the batteries. The triple two-stroke motor version was like a sack full of cats on crystal meth, so electric is a vast improvement.

Once this prototype is behaving how we want it we'll hope that investors hand over more money to develop mark II which will be lighter and more efficient. At the moment we've got all sorts of stuff strapped to it while we develop the technology, but it's weighing it down like a brick. We know the intakes can be improved and the triple redundancy means lots of extra copper, so we'll try to change that too.

Longer term we will aim to have at least 14 kWh on board, but projections on lighter batteries are not yet forthcoming.
 
jonescg said:
The triple two-stroke motor version was like a sack full of cats on crystal meth
Click to expand...

Bet it sounded like one too.

Considering a hydrogen peroxide jet pack only runs 5 minutes, it's not all that bad.
 
Hey Agnius, it's Chris by the way ;)

No, the kit is still sitting there alongside the shitty B and C grade A123 cells we waited months for. I have been trying to convince Kim he should try to hock them off on ES or something - I know there's plenty of takers for cheap crap batteries here :lol:

But yeah, they were just too heavy and more importantly, bulky. The space they would have occupied interfered with the skirt controls, and the sag at these discharge rates would have been unacceptable. The current sag isn't great, but there's 10 Volts we have with LiPos that we wouldn't have with LiFePO4. Since lift is the cube of RPM, those few extra RPM can make a lot of difference.

Will put some photos of the completed battery packs up soon. They're looking great if I say so myself :)
 
Have you guys thought about using a small RC turbo-shaft engine to power the youfly?
There are quite a few around, some can output 10KW or more.

Like the ProX shown here, http://www.jakadofsky.com/htm_en/daten.htm

It weighs ~8lbs, and you can run it for about 20 min off of 1 gallon of jet A

That one might not have enough power for you, but the considerable lower weight vs. a 4.6 kWh pack might help out quite considerably.
 
Thanks for the tip - I assume Kim knows about them already since he used to work in the turbine field, but I'll mention it to him. The craft currently has about 90 kW of motor installed. They are a brushless inrunner powered by MGM controllers; 6 motors and controllers all up.

Anyway, I'm probably breaching all sorts of agreements so I might just keep it quiet :oops:
 
jonescg said:
Hey Agnius, it's Chris by the way ;)

No, the kit is still sitting there alongside the shitty B and C grade A123 cells we waited months for.
Click to expand...

Yeas, meant Chris, was thinking about John and punched in wrong. My multitasking sucks :D
Since it is possible now to acquire genuine A123 cell, maybe you will find another use with the kits ;)
 
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