Why are high capacity lipos so dear?

[Edgeflyer]

I need some 5s or 6s 5000mah lipos and looks like for the good brand high current types, it will be around £130 each 

I have an 18 volt Milwaukee drill which uses 5s 5000mah lion, I assume, batteries which cost around £60.

Why the discrepancy?

[leccyflyer]

Economies of scale probably - we're a limited market and high capacity, large cell count batteries with high C ratings especially so. They will sell many more batteries for drills than they ever would for electric powered model aeroplanes, especially the more exotic ones.

 

 

[Chris Walby]

Horses for courses, try sticking a drill battery in an edf model and see how far you get....but you might just run out of runway. There is a fair bit of price variance depending on your application and the C rating you need, edf's benefit from really punchy high C ratings where as my Renaissance (nose weight) does not pull much current so low C rating is acceptable.

 

I have used GNB and they perform very well short term with a noticeable improvement top end performance. Worth bearing in mind if you are stressing the battery less it should last longer so just going for a low C rating might prove counter productive in the long term, but it would be hard to prove.

TBH lipo prices have shot up, but then just look at diesel prices. 

 

PS Cost of materials, technology development/payback and lower production volumes

Edited September 23, 2022 by Chris Walby

[Brian Cooper]

They are expensive purely because people are buying them. 

 

It's a basic rule of commerce. . . If people didn't buy them, they would be cheap.

[kevin b]

1 minute ago, Brian Cooper said:

They are expensive purely because people are buying them. 

 

It's a basic rule of commerce. . . If people didn't buy them, they would be cheap.

If people didn't buy them, they wouldn't make them !

The answer is simples.

Supply and demand.

Everybody wants 3S 2200 30c lipos, so lots of companies manufacture them and compete for the market.

The demand for 6S 5000 30C lipos is probably less than 5% of 3S 2200 lipos, so the manufacturers produce fewer and ask a higher price (not as much competition).

The great thing about electrics is that you can wire the batteries in series, and / or parallel (see Tesla for details).

It also gives you the advantage of not having to scrap an expensive battery if one cell goes down.

You just need to develop a good service routine.

[Gary Manuel]

I have 6x 5000 60C Turnigy Heavy Duty packs I bought in 2019.

Never used. Still at Storage Voltage so should be as good as new.

I decided to sell all my large electric models just after I bought these.

Screen dump from my purchase history attached.

Yours for £240 for the lot (That's £40 each).

Located in Doncaster. Collection only due to postal restrictions. Includes a free cuppa and a chat.

 

 

[john stones 1 - Moderator]

They're expensive because they're very good, "You get what you pay for". 😉

[Simon Chaddock]

You can also blame the rapidly expanding Electric Vehicle market leading to "Where has all the Lithium gone?". A bit like "Where has all the balsa gone?" To the manufacture of wind turbine blades! 

RC modellers do not count for much in such huge multi $billion market places.

I am afraid the "Golden era" of cheap LiPo has passed.  

[Chris Walby]

14 minutes ago, Simon Chaddock said:

You can also blame the rapidly expanding Electric Vehicle market leading to "Where has all the Lithium gone?". A bit like "Where has all the balsa gone?" To the manufacture of wind turbine blades! 

RC modellers do not count for much in such huge multi $billion market places.

I am afraid the "Golden era" of cheap LiPo has passed.  

Perhaps you are right and someone could do a comparison between lipo vs petrol or RPI  to see what the actual differences are between pre and post covid?

 

Only comment I have is that the GNB lipos are smaller, higher capacity and seem to perform better than any of my older stock so perhaps there is a benefit to buying new lipos.

 

PS - does mean using larger capacity lipos to equal the old packs or double check where the new C of G is.

[John Lee]

LiPos have certainly increased in price since HobbyKing's heyday but are still a fraction of the price we paid in the early days of their introduction. Below is an extract from Al's Hobbies advert in 2008. Adjusted with inflation that is about £46 for a 3S 2200MAh and £280 for a 6S 5000MAh 25C battery.

 

Edited September 24, 2022 by John Lee
Typo

[leccyflyer]

14 hours ago, john stones 1 - Moderator said:

They're expensive because they're very good, "You get what you pay for". 😉

If there was ever an arena where that old adage is blown out of the water it is in the arena of Lipo batteries. The best lipos I've had were the Loong Max packs, marketed by Giant Cod and confirmed as representing super value for money in the BMFA tests at the time. The worst lipos I've ever had were the extortionately overpriced Flightpower packs which were amongst the first lipos to be widely (over)marketed at about the same time. They were more than 3x the cost of Loong Max at about 80 quid for a 3s1p3000mah pack. I like to tell the story of a very experienced electric flyer who, when I told him there was a half-price Flightpower sale, after the overhype had been seen through - "Don't you mean a Half-Power Flightprice sale?" 😄

[GrumpyGnome]

@leccyflyertotally agree with you there.

 

My experience has been "the more expensive they are, the shorter the lifespan". Maybe they expect to be treated better.

 

But I also keep getting told that ASP, Magnum, SC engines are 'useless', but I have examples pf each that are many years old and run beautifully....... maybe cheap and I suit each other. 🙂

[Edgeflyer]

now realise that at full power my drill pulls only about 10 amps and would go continuuosly for about half an hour.

So we are saying drill batteries use cheaper cells that are only good for 10 amps? 

In my circular saw that same battery has enough energy to cut through an 8 foot length of 3 inch timber. These batteries have been in use for 3 years. Charged 100s of times and can't get puffed.

But it can't pull an EFlite 2m Cub for 5 minutes!

Something strange somewhere.

I can't imagine electric cars using cells that are so unreliable. Or maybe?

[Edgeflyer]

Incidentally, what is the gas that puffs up the soft case variety and how does that work with hard cases? Presumably venting? Also how does one salvage good cells from a pack with a weak cell? Are they just soldered in series?

[leccyflyer]

38 minutes ago, GrumpyGnome said:

@leccyflyertotally agree with you there.

 

My experience has been "the more expensive they are, the shorter the lifespan". Maybe they expect to be treated better.

 

But I also keep getting told that ASP, Magnum, SC engines are 'useless', but I have examples pf each that are many years old and run beautifully....... maybe cheap and I suit each other. 🙂

My old modelling pal Mal Jones used to swear by ASP and SC engines and used them widely. Stranglely enough he had less engine problems than many other users, due to doing things right. He even had several very reliable MDS engines that had been breathed on -mixing and matching different parts. So much so that, more than once, these budget engines were shown to be able to start just with a twirl of the fingers on the spinner.

[John Lee]

1 hour ago, Phil B said:

now realise that at full power my drill pulls only about 10 amps and would go continuuosly for about half an hour.

So we are saying drill batteries use cheaper cells that are only good for 10 amps? 

In my circular saw that same battery has enough energy to cut through an 8 foot length of 3 inch timber. These batteries have been in use for 3 years. Charged 100s of times and can't get puffed.

But it can't pull an EFlite 2m Cub for 5 minutes!

Something strange somewhere.

I can't imagine electric cars using cells that are so unreliable. Or maybe?

 

Drill, car and most consumer batteries use Lithium Ion batteries as opposed to the Lithium Polymer batteries in RC Models. There is plenty of information about the differences readily available but the Li-Ion batteries will not tolerate the current draw demanded of LiPos.

 

RC Models must be amongst the most demanding application for batteries anywhere. Who else discharges their batteries in 3-10 minutes as a matter of course? Typically the cycle time of batteries in other applications approaches or exceeds hours, so the batteries  have a much easier time and last longer.

 

The typical electric car has a 60KwH battery. To discharge it in 5 mins, like we do our models, the motor will need to be producing about 1000 horsepower throughout that time. Conversely if you want a longer life for the battery in your EFlite Cub then only run it at 1-2 amps. Of course the model would not move but the battery won't puff and will last 10 years😀.

[Geoff S]

Our electrically assisted bikes have 10S Li-Ion batteries (40ish volts), which means, at the maximum legally power output of 250 watts, the motor draws about 6 amps.  Not very demanding in aeromodelling terms.  Plus we almost never use full power except for a bit of fun on the last climb up to our house.  There are 5 levels of assistance on the system I've installed and I tend to think level 1 just compensates for the extra weight 🙂

 

We've been using the same 7 cell subC NmH 3000 mAh in our bathroom radio for about 10 years and it still recharges to its full capacity with a 2 amp charge.  I don't know the current draw but the radio was originally designed as a mains/battery unit with 6 D cells primary cells (very expensive) until I modified it to take the 7 cell sub Cs so, as they're slightly under voltage, it's not much.

 

So using batteries with modest current certainly makes them last a lot longer and pushing them the way we do in models is the main reason they're both expensive and have limited life.

[MattyB]

2 hours ago, Geoff S said:

Our electrically assisted bikes have 10S Li-Ion batteries (40ish volts), which means, at the maximum legally power output of 250 watts, the motor draws about 6 amps.  Not very demanding in aeromodelling terms.  Plus we almost never use full power except for a bit of fun on the last climb up to our house.

You are right that ebike batteries are discharged at much lower rates than our flight lipo batteries, but your calculations actually underestimate the peak draw substantially.
 

Pretty much all crank and hub drive ebike motors are capable of way more than 250W; systems from the likes of Brose and Bosch can transiently put out 700 or even 800W in the top assistance level. The EU 250W rating is actually a maximum continuous power value over a period of an hour, not a peak rating. In reality the whole system is pretty much a fudge - as per CE compliance it is essentially a self certification model.

 

Example from the Specialized Levi EMTB, the latest versions of which are capable of around 720W peak measured in certain tests.

 

https://www.emtbforums.com/community/threads/understanding-support-vs-peak-power-in-mission-control-app-v2-0.4038/post-56053

Edited September 25, 2022 by MattyB

[PeterF]

Interestingly, I have looked at Overlander 35C Supersport batteries from Overlander. 3S 2,200mAh = £21. 6S 6,250mAh = £145. If you purchased 6 of the 3S 2,200mAh packs you could form a 6S 6,600mAh battery for £126, cheaper and higher capacity than the large pack. This illustrates either (1) the economies of scale or (2) increased competition in the marketplace for the smaller batteries.

[Geoff S]

2 hours ago, MattyB said:

You are right that ebike batteries are discharged at much lower rates than our flight lipo batteries, but your calculations actually underestimate the peak draw substantially.
 

Pretty much all crank and hub drive ebike motors are capable of way more than 250W; systems from the likes of Brose and Bosch can transiently put out 700 or even 800W in the top assistance level. The EU 250W rating is actually a maximum continuous power value over a period of an hour, not a peak rating. In reality the whole system is pretty much a fudge - as per CE compliance it is essentially a self certification model.

 

Example from the Specialized Levi EMTB, the latest versions of which are capable of around 720W peak measured in certain tests.

 

https://www.emtbforums.com/community/threads/understanding-support-vs-peak-power-in-mission-control-app-v2-0.4038/post-56053

 

I haven't measured the current drain on our systems so I can't really comment with authority.  I've converted our ordinary bikes with a FWD motor in the hub with the battery carried in a special rear pannier frame with an LCD display/controller on the 'bars.  I'm sure both the motor and the esc are well under stressed. In fact IIRC (it's while since I set them up) the power rating is adjustable but as the 250 watts setting is more than enough, I'm happy with that.  I still like to feel I'm working when riding though my days of thinking a 100 (160km) mile ride is no big deal are long gone 🙂   I wish one of the display options was current draw but it's not.

 

In any case I think Remco Evenpoel would be quite capable of dropping me on a climb even with my electric help - but I'm 60 years older than him.