do not agree. I prefer LiPo to LiIon because they a slimmer and can draw more current/have less voltage sag. building a good liPo battery takes just as much skills if not more than building a LiIon pack.
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I will expand a lot on this tonight please bare with me. -Slimmer? I don’t fully agree. 18650s are twice as energy dense as LiPos.
Definitely not.
- A LiPo pack can be made with simple wire harnesses (one for mains and one for balancing) without any mods to the individual packs. Just soldering a harness.
- You can go further and solder the packs together. The process is still fairly simple with descent soldering skills.
-If you really want to go all out, you can unfold packs and make yourself a “slim lipo”, but again, all that is required is soldering skills.
For a Li-ion pack, you need more than just soldering. For starters, you need a battery tab welder, which is a very rare tool even for an electrical engineer or a hobbyist that does a lot of electrical junk. Welding batteries is also not trivial, as with soldering. If you have a high power pack you also need to solder copper wire on top of the nickel or do several layers of nickel tabs which cannot normally be done well with some welders. If you decide to solder batteries, you have to be very careful with heat and melting the heatshrink around the positive end as this could result in a short. Then, you still have to solder balancing leads and main leads which requires the same skills as soldering Lipos does.
I’d like to see your counter argument as to why soldering Lipos would require more skills than building a good Li-ion pack. I’ve built both not only for electric skateboards but also for rc boats, rc aircraft and military grade UAVs and I would always say that the Lipo packs are simpler than Li-ion packs.
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show me an 18650 that 5mm wide? plus the cylindrical package of 18650 means that you can fit more lipo battery with less air… so while what you say is true that lion is chemicaly energy denser than lipo. they are not as energy dense per space.
they have a higher volumetric energy density despite the packing … and in praxis you get your factor of 2 without any real downsides.
i sold a few sanyo ga 10S6P batteries for replacing the evolve carbon stock lipo battery, typically more than doubling stock range (in praxis, not theory!!) and everybody reported a subjectively stronger board with better acceleration and top speed. my guess is that compared to the stock battery, the large liion battery apparantly also didnt have as much sag!
even your 5mm argument isnt entirely true, because you cannot run lipo under enclosure pressure like the physically way more robust cylindrical lion cells because the lipo pouches can swell and build up pressure (up to 8mm thickness).
the only reason for me to pick a lipo pouch is for cheap high power densities (!= energy densities). most of these power densities are beyond what our setups can properly handle though … and in praxis id probably go for the much more robust A123 chemistry in that case.
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First I shall tackle the A123 and Samsung 25R cells
Here are some basic specs for the cells, you will notice that my continuous current values are higher than the datasheet values. This is tested maximum current for at least 5 minutes and not their entire charge. Also the volume has been calculated as if they were squares and not cylinders.
Energy Analysis
The most energy dense are of course the Sanyo GA cells with a whooping 578 Wh/L and 268Wh/kg. Not too far behind are the 30Q and Sony VTC6 cells. 25Rs have 71% energy density and 76% specific energy which is not great but also isn’t terrible. The one cell which is absolutely horrible in my opinion is the Lifepo4 cell with only 32% energy density and 40% specific energy of the Sanyo GA cell.
Power Analysis
Here is where the A123 shine. They can produce lots of power. Up to 200W per cell! The issue is they also produce a lot of heat at this high power output. If you limit them to 30A per cell they only produce 13% heat which is better than both 30Q and VTC6 and on par with the GA cell at twice the power output which is pretty incredible. The issue with doing this would be reducing the specific power and power density to the same levels as the GA cells.
Another good thing to point out is how mediocre the 25Rs are. They produce a lot of heat, 21% of the max power generated is heat. They packs good punch for their weight but get left behind by the VTC6 and 30Q cells when it comes to power density.
The GA cells only produce 13% heat but they also only output 50% the power of the 30Q and VTC6 cells both of these cells are more efficient at 15A producing only 8.1% heat. The 25Rs produce 14.8% heat at 15A in comparison.
The cells that shine the most here are 30Q and VTC6 in my opinion by producing almost 95W per cell and keeping the heat produced relatively low. They pack the most power for their weight and size when you take into account that the A123 need a heatsink in order to take full advantage of their 70A rating. Plus both of these cells can do higher bursts of power as long as the temperature stays below 80C.
Cost Analysis
This is where the A123 fall apart and the 25Rs start looking like not such a terrible cell.
The A123 only bring 0.89Wh/$ to the table while the top three are well above 3Wh/$.
They also dont bring the best to power per dollar to the table, in fact they come in third just barely edging out VTC6s 20.78W/$ to 20.40W/$. The top two produce above 30W/$.
The 25R cell is the most economical one with 3.59Wh/$ and 34.1W/$. The downside being that you’ll have to have a larger and more inefficient pack whether you want power or endurance.
In my opinion, the 30Q is the best cell overall when taking into account cost. They are slightly inferior in every way to VTC6 but they also only cost 66% which is not worth it to me. The GA cells are the best for endurance packs but the 30Q cells cost 78% of them.
Once I add Lipos to the top end, you will see how these are wedged out of the race, since Lipos cost even less than Li-ions and have a higher power density than lifepo4s
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to be fair I never said that lipos are best or better… its well known that LiIon is a superior chemistry, but it was insinuated that they are only the poor mans choice.
this is not the case. I choose lipos because I can fit 12S into a 15mm deck thickness and that would be impossible with 18650s
https://esk8content.nyc3.digitaloceanspaces.com/uploads/db2454/original/2X/b/ba85bf1f793027aafff8e1541b44d4f6ac5a78ae.jpg https://esk8content.nyc3.digitaloceanspaces.com/uploads/db2454/original/3X/3/7/37aed8e31bd8dd2b2914803aae39f32258208a17.jpg
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That was meant as a self reminder really. The whole tone will change once I start adding in information. Please add links to any LiPos that you would like for me to add to my analysis as there are a massive choice and I don’t know where to start other than turnigys and zippys.
That makes more sense now. I will add a Lipo section this weekend since I spent all night analysing lifepo4s and 25Rs
Thanks for the comparison of the different Li-Ion batterys. I would like to see how they compare to these LiPo batterys:
Until now I mostly used these Lipos (in 3s 2p) because they offer a good tradeoff in terms of price, capacity, discharge rate and convenience:
These would be the choice for absolute high power racing use. Two packs (2x1kg) in series for 12s could deliver 17kW constant!:
@PXSS which source did you use for battery price points?
Maybe one day someone makes a tool that compares battery prices from different sources and outputs them in one place 
with customizable options to choose / complect the battery pack you desire.
Nice work non the less 
Could you shed some light where did you get the heat data? Did you obtain it yourself?
@Okami I used Nkon with a quantity of 40 cells for the price.
The heat data was calculated by taking the voltage drop across the cell from no load to the loaded condition and multiplying it by the current. Heat = Vdrop x I = IR x I^2
@Duffman I will look into these. I will most likely end up buying a few to do my own testing as I can’t find discharge curves for them.
@PXSS Ok, so as I understand, you just took maximum current rating of the cell + voltage drop witnessed at 1.5ah capacity (no load/load) and then just extracted the watts for heat from the formula, correct?
The ‘‘truth’’ that Sanyo GA produces the least heat for its power level was an interesting find.
Though, it is also the least ‘‘power dense’’ cell but still manages to show that at its max rating it does not overheat excessively, correct?
In contrast, 25R at 20A cont, produces a whopping 24W of ‘lost energy’ as heat… That is quite a heater, if you ask me
And I also remember vaping forum’s tests, where it showed cells beings at 80+ degrees C (~176F) when outputing constant 20A current. So yeh, I might say numbers are convincing…
Now… when ‘‘investigating’’ this further, it would be interesting to hear why you chose ‘‘1.5Ah’’ as reference point? Was it because it somewhat resembled nominal voltage for these ~3ah cells or it was something else?
I must assume this also plays a bit against Samsung 25R, for the reason that most of its capacity is spent beyong 1.5ah point, as less than 1ah of ‘usable capacity’ is still left in the cell…
Correct.
If you read the text, I mention what the heat produced is for cells at 15A which is what the GA cells max output was. The A123 generate the least heat, only producing 6.97% heat. The VTC6 and 30Q produced 8.85% and 8.89% respectively. The GA cells produced 12.73% heat and at last place the 25R produced 13.13% heat.
I realized that I had made a type when inputting the 25R data and it seemed worse than what it is but it still comes in last. I want to take more time to do the analysis properly and double check all the values before adding it to the main post as well as adding Lipos to the mix.
I chose the 1.5Ah mark as it seemed like a good average for all cells, given that I have a few at 2.5Ah and some at 3.5Ah
Okay, now I see it… So it still points out that basically, at 15A, the Sanyo GA still outperforms Samsung cells right?
This is also fascinating, in a way that Sanyo Ga is usually ‘labeled’ as 10A cell, where 25R is 20A cell.
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So yeh, in contrast, 25R is a good cell to use (because of cost) with its shortcomings in terms of heat / capacity. Then comes the 30Q which is quite a lot better but a bit more expensive.
This is why I hate when people quote the limits without truly understanding them. Most of the time the limits are based on using the cells for their entire charge at said current and meeting a life cycle threshold that varies from manufacturer to manufacturer.
Correct.
Correct
This is a good point you are referring to. The same thing happens with VTC4 and maybe VTC5 cells too. They were initially ‘‘labeled’’ as 30A cells, when tests showed, they are more like 22-24A cells (for safe usage and no overheating)
Mh, so this probably brings us back to the ‘‘heat problem’’ that some cells just heat up more than others, which then again shows the ‘true picture’ of their real performance I think, and how much (and whenever at all) they can be pushed past their limit a bit more for momentary gains of power etc…
Maybe this can be pointed out later on about Li-ion 18650 cells… that their ‘‘safe usage’’ is in between 2-3C of their capacity, with 5C usually ‘‘topping them out a bit’’.
Of course, for vtc6, this ‘‘C rate’’ is a bit higher than for Sanyo GA, but still.
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This was somewhat the early ‘‘confusion maker’’ for me, when deciding which cells to use, as the lipos used C rate and I had to do the calculation all the time myself (plus, no reliable way of telling whenever max rating labeled on the lipo pack is true or not)…
So when different C rates mix up together with different Ah pack’s it gets confusing…
So while li-ions use amps for their rating usually, the c rate still remains a good way for telling the max or recommended power level of the cell I think… also works good for when deciding at what charge rate to charge your cells (0.3c , 0.5c, 1c)
I hate the C rating. Think about it, a 20C 5000mAh cell can output twice as much as a 20C 2500mAh cell. Whereas 30A is 30A regardless of capacity.
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@PXSS hah yes, we are on the same line here
Though, for low 2-3 and 5c calculations it is not as bad, as long as capacity is not over 4ah or something
At least for Li-ions I find it much easier to calculate capacity, of course it is still messy, because the capacity’s number change but at least they dont go over 100-200A mark.
Maybe they should make some sort of ‘‘standard’’ to include both numbers automatically, Amps and C rate, though I think the c rate is partly because of rc stuff’s guys, who use it a lot to determine the battery’s output, since they tend to use very narrow bands of capacity’s… For example ~2-3ah for 3s battery. Then, since they are working with 3s all the time anyways, they can multiply the C rate easly with the right data straight ahead…
Or some, just like to refer 20-25c rate as good for their size battery… and lower as bad
I don’t understand how you calculate the Vdrop at peak current (from datasheet?) but think that this website will help as it has loads of discharge curves and battery reviews (http://lygte-info.dk/review/batteries2012/Common18650comparator.php). I would also like to know your opinion on these two batteries (https://eu.nkon.nl/rechargeable/18650-size/panasonic-ncr18650pf-3-7v-2900mah.html) and (https://eu.nkon.nl/rechargeable/18650-size/samsung-inr18650-29e.html) as I am planning on a 7s 6p setup for commuting and found these are cheaper than the samsung 25Rs have a larger capacity and still a decent discharge (hoping that I won’t need to pull more than 40A on a 7S on flat tarmac roads.
I already have all of Henrik’s data (the owner/writer of Lygte) for the relevant cells along with my own experimemtal data.