Yes… it sounds too good to be true. I did however, check some of their info. They are a legit company and part of the Silicon Valley mob and have some talent and $ behind them. time will tell.
I am a bit suspicious. According to Stanford University the best carbon-14 diamond battery to date will produce 15 jules per day in the size of a AA battery. Compare that to a standard AA which can discharge it’s 15,000 Jule capacity in a few hours. If we run the math that equates to a battery that weighs OVER 1.5 MILLION pounds just to get the 4kw required for level flight. To make this realistic we need over 50,000x the gravimetric power density that has been previously achieved. I’m not saying it’s impossible, I’m just very sceptical.
Yes… did some more checking and agree this is mostly BS…SIGH… a bit like going out and finding the perfect mate… who later turns out to be the opposite gender…oopsie…
https://www.foxtechfpv.com/foxtech-diamond-6s-22000mah-semi-solid-state-li-ion-battery.html
Now also 7S version available from the Diamond Series Solid-state Li-ion Battery.
Interesting for the 150KV versions of the X4.
Is there someone that have tested the Solid-state Li-ion batteries and compared them with the Bonkas in real flight? Did it result in longer flight time?
RichardG was testing the Foxtech batteries at 150 A. Someone else reported that their full-power climb would draw 300-350 A. So simple math would demand that at least two Foxtech batteries be connected in parallel just to handle operational loads. Three would be better, and thus each battery would be required to supply only 100-120A under max load. Am I mistaken? And wouldn’t this configuration yield 90 Ah, or still only about an hour of flight time presuming that the average current draw was 90 A? Thus, if max-power climb consumed 120 A for 10 minutes, then the remaining 50 minutes of flight would have to consume no more than 60 A (actually, 58.3 A). Is this a reasonable expectation? Or would we wish to, say, double that capacity? What was the weight of those batteries again? Maybe it’s not terribly unreasonable if one can afford them.
You would need at least 4 batteries as you need two connected in series.
What’s the voltage? The 30Ah Foxtechs are available up to 51V. Do we need 100V? In another thread I asked Voltair to clarify specs for the X4 battery and motor operating voltages which are not posted with other specs on the OpenPPG X4 ordering page. So at 100V really we would need 6 rather than 3 just to meet the 1-hr flight duration estimate and not overdrive the batteries (per my calculation above). Can you state the level-flight current draw? Is it close to 60A per battery pair (180A overall), or something less? Maybe the estimated duration at altitude could be longer than my simplistic estimate above.
The X4’s electronics are setup for a max of 60V. Three 6s or 7s batteries in parallel would be six batteries total. If you get a 12-14s battery then it’s exactly like a pair of 6s or 7s in series but you’d save a connector. However a charger capable of handling a 14s battery might be really expensive and hard to get. Custom unit maybe?
Comparing the specs on the foxtech page they may be a slight gravimetric density improvment vs the Bonkas but are 2X the price!
Hyperion makes chargers that can bank together to charge 14S, I own two of them and the are great chargers; however, I’ve yet to use their network feature. 1420i is the model. The smaller packs are just more practical in my opinion.
I heard in a previous thread that the foxtechs were 6 or 7s, but if they have them in 12, 13, or 14s you could use two.
Last I heard a X4 needs about 4.7kw to maintain level flight. Foxtech say they get about 250w/kg gravimetric energy density and under load in the real world it will likely be less than 225w/kg. So It sounds like you would need about 46 pounds of batteries to get 1 hour with Foxtech.
So I’m curious – has anybody thought of using some kind of high discharge supercapacitor in connection with these batteries? How long do you truly need to go full-throttle for, anyway? 30 seconds at most?
At that point, you can ease off for a bit and allow the capacitors to recharge from the battery output.
At least then you’d be able to fly with less overall weight.
Interesting. Still think it might be easier in the present time to use LiPo cells that are super easy and cheap to find. For example I could use 12 batteries like I use on my racing drone to make a 24s 3 Ah battery compatable with the sp140. It could handle 15 kw constant with bursts of 27 kw and it would only weigh 5 pounds. With more expensive batteries you could likely go even smaller. The only downside would be that they would likely get under 100 cycles.
I am exited to see where capacitors will be able to do in the future. I heard about the NTGS capacitor which is testing at over 200wh/kg with a near identical discharge rate to current capacitors.
My typical flight profile is 3-5 minutes full power initial climb out. Thirty seconds would not get me high enough to do anything but circuits around the field which I sometimes do. A five minute climb gives me 300+ meters above the field. Is sixty meters per minute (180ft/m) a good paramotor climb rate?
180 ft / 60 meters per minute = 1 m / sec.
this is common for an 80 kg pilot and a 26 m2 wing with around 42 - 45 kg of thrust.
a top 80 or eos 100 petrol or standard e-ppg has around 50-54 kg of thrust and then around 1.2 - 1.4 m / sec.
only as comparative examples.
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How much power output is happening for that 3-5 minutes? 30 hp?
Btw, I notice on that Foxtech page, they now say they have a 7S battery with 30,000mAh @25.9v for $669
I’m right around 80kg fully clothed and well fed. My wing is a Buzz Z3 ML 23.5m2 Projected area.
I’m flying the batch4 X4 (150KV motors) on 6cell Bonkas. Seems my aging wing is still producing the lift. Thank you. It’s really nice to keep an eye on the numbers like this.
I’m right around 10kw (240amp @ 42V) for that entire climb. The only time I’ve notice the Bonkas sagging under full power is at the end of a 14minute flight so probably nearing 7 mins full power equivalent.
Bonkas are $250 for a 7s 22Ah that weighs 2500g - 1.13kg/ah and 11.3 dollars/ah
Foxtechs are $670 for a 7s 30Ah that weighs 2965g - 1kg/ah and 22.3 dollars/ah
If they have the same punch as the Bonkas is the slight capacity/weight advantage worth double the price? Not for me. Also I’m thinking they’ll actually perform about the same as the Bonkas in real world. They’re trading that “C” rating for capacity I think.
If they have the same punch as the Bonkas is the slight capacity/weight advantage worth double the price?
It’s important to remember that the Diamonds are supposed to have much, much better safety characteristics. If it’s true that they’re hard, if not impossible, to abuse to the point that they catch on fire, the equation changes to:
Is it worth spending double the price to have a similarly performing battery but with minimized fire risk?
To me, having seen the damage wrought by lithium fires, it’s an easy choice.
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They’re the same chemistry and form factor. All LiPos ‘vent with flame’ when they get overcharged overheated or punctured. I see they have a thin aluminum side plate to help prevent impact/puncture damage. They may have some type of built in overcharge and/or overheating protection. That could be worth the extra bucks for you. LiFe (round cells) are more robust and are also way cheaper but you’d would have to either custom source a 16S X 14P pack or build it yourself from over 200 cells and some connector system. That sort of negates the cost savings but LiFe will have a much higher cycle life. This is something I’ve been seriously considering. Esp if I can find a deal on 200+ LiFe cells.
