How are Wh's figured?

[pkinpdx]

I have been trying to do math and I can't make it work.  My understanding is if you look at an individual cell for example the Samsung 50E, it is 4900 mAh.  So (mAh)*(V)/1000 = (Wh) would mean 4900* 4.2 (individual cell voltage at full) / 1000 =20.58 Wh per cell. You need 24 cells to get 100.8 so every 100v wheel is multiples of 24 in parallel.  Each parallel pack would have 494 Whs?  That doesn't align with any of the wheels; so I have to be doing math wrong, or a basic assumption is incorrect.  Can anyone educate me?

Edited February 23, 2022 by pkinpdx

[Menace]

wh=ah*Voltage 

so an lg m50 RS is 5ah per cell * 4 parrallel cells= 20ah total

20Ah * 88.8 nominal volts (3.7 per cell in a 24s configuration)= 1776 wh

they then round that 1800wh because gotway

[pkinpdx]

Ah so its the lower voltage that is plugged into the formula.  Thanks!

[alcatraz]

Few mistakes. 4.2v is the max voltage and not the average (nominal?) voltage throughout a cycle. 3.7v is what you multiply with (for 4.2v li-ion cells).

The cells are 4900mAh cells but I believe they still use 5000mAh to calculate the pack specs. Because, why not? 

3.7v x 5000mAh = 18.5Wh

24 cells in SERIES is the smallest building block to produce 100.8v.

24 x 18.5Wh = 444Wh (round up to 450 because, why not?)

So you connect these building blocks in parallell to produce capacity/range. 450Wh in 4P = 1800Wh (nikola/rs). In 6P = 2700Wh (ex.n). In 8p = 3600Wh etc. (commander)

Some wheels like the Sherman still use 18650 cells with 3500mAh so the smallest building block is different. Also not all wheels are 100.8v.

[alcatraz]

100.8v 24s for 3500mAh 18650 cells would make the building block 311Wh. It makes me think that the 3200Wh Sherman can't possibly be using 3500mAh cells (or uses more accurate numbers below 3500 to calculate) because the count of blocks needs to be divisible with 4 (four physical packs). 311Wh x 12 ~ 3700Wh with Panasonic GA cells it claims it has, and 100.8v 24s.

So I'd say that the Sherman is underreporting its capacity, Gotway wheels are somewhat overreporting.

[meepmeepmayer]

@alcatrazThe og Sherman is 10p, so 10 * 24 * 3.7V * 3500mAh = 3108Wh "=" 3200Wh because that's how the manufacturers do (they round up the Ah of one cell or something and go from that...)

57 minutes ago, alcatraz said:

So I'd say that the Sherman is underreporting its capacity

Manufacturers underreporting? When pigs fly

At the very best they are kind of honest with a direct computation (Inmotion, KS) while still pretending it's 3.7V (instead of 3.65V or whatever the spec sheet says) and 3500/5000mAh (instead of like 3450 or 4900 mAh). For example: 1776Wh for the V12 instead of 1800Wh, or 1554Wh for the 16X instead of 1600Wh.

Or they round up this semi-honest result a little extra (Begode/Extreme Bull, Veteran).

[alcatraz]

3 hours ago, meepmeepmayer said:

@alcatrazThe og Sherman is 10p, so 10 * 24 * 3.7V * 3500mAh = 3108Wh "=" 3200Wh because that's how the manufacturers do (they round up the Ah of one cell or something and go from that...)

Manufacturers underreporting? When pigs fly

At the very best they are kind of honest with a direct computation (Inmotion, KS) while still pretending it's 3.7V (instead of 3.65V or whatever the spec sheet says) and 3500/5000mAh (instead of like 3450 or 4900 mAh). For example: 1776Wh for the V12 instead of 1800Wh, or 1554Wh for the 16X instead of 1600Wh.

Or they round up this semi-honest result a little extra (Begode/Extreme Bull, Veteran).

That makes sense. But how does the sherman split 10p among its packs? Aren't there 4 packs? Does it have two 2P packs and two 3P packs?

[alcatraz]

Ok. I discovered that while it may look like having 4 packs it's actually only two packs. Each pack is two individually heatshrinked subpacks of 60 cells each making one 120 cell pack. So it's 50.4v per subpack connected in serial. They don't look like they can be separated. Also they shouldn't because if you mix differently aged cells within a pack, then it would change its charge/discharge characteristics, and become dangerous.

[Freeforester]

They do say we are living in inflationary times, let’s hope it doesn’t become ‘runaway’! 🔥🔥 

Generally speaking, if every manufacturer is inflating their power capacity spec proportionally and similarly, then it doesn’t really matter - well, except for those of us who would be wanting a nailed-down accurate spec, but hey, made in Switzerland they ain’t, its an ‘industry-wide’ thing - it’ll only become an issue when a new wheel comes out with obviously ‘more-false’ or overly-inflated figures, or starts to get reviews that compare it to ‘known wheel’ range/speed stats and under-delivers; if the hype says it’ll out range or out clock another wheel already widely used but real life use doesn’t match up to their touted spec, it’ll not go unnoticed nor unremarked for very long. 

Edited February 23, 2022 by Freeforester

[UniVehje]

1 hour ago, Freeforester said:

They do say we are living in inflationary times, let’s hope it doesn’t become ‘runaway’! 🔥🔥 

Generally speaking, if every manufacturer is inflating their power capacity spec proportionally and similarly, then it doesn’t really matter - well, except for those of us who would be wanting a nailed-down accurate spec, but hey, made in Switzerland they ain’t, its an ‘industry-wide’ thing - it’ll only become an issue when a new wheel comes out with obviously ‘more-false’ or overly-inflated figures, or starts to get reviews that compare it to ‘known wheel’ range/speed stats and under-delivers; if the hype says it’ll out range or out clock another wheel already widely used but real life use doesn’t match up to their touted spec, it’ll not go unnoticed nor unremarked for very long. 

Spot on that it doesn't matter as long as everybody uses the same standard. Just like old TVs and monitors were never as big as claimed but it didn't matter because any 17" monitor was comparable to other 17" monitors and about the same amount bigger than 15" monitors. 

Unfortunately in EUC world we don't have commonly agreed standards for range, battery size or tire size. Last couple of years we have seen escalation of abuse in the spec sheet numbers. And unfortunately it seems to work, which encourages others to join the race. KS just joined the game with upping the tire size by 2" for the exactly the same tire as on the previous model, following the lead by GW and LeaperKim. I think they still report battery size more correctly, though. When spec numbers matter, it makes a difference whether you announce 1600 Wh or 1554 Wh. I don't care what battery or tire size standard you use as long as it's always consistent.

Same goes for range in kilometres. Each company has their own unrealistic way of measuring it and the first company starting to measure range with more realistic terms will take a hit in sales. 

[meepmeepmayer]

6 hours ago, alcatraz said:

I discovered that while it may look like having 4 packs it's actually only two packs.

Yep, each side has one, physically split, pack. Abrams does the same.

How the internal adding up goes, I don't know. Are they are actually two 50.4V 5*12 cell packs that are (at the end) serialed up? Can you tell from the cabling? (This sounds like the better way to do it.) Or might the 12+12 split cells simply be connected to 24s on their own, like they would be in a normal pack form factor, along with the other 24s blocks?

[meepmeepmayer]

4 hours ago, UniVehje said:

KS just joined the game with upping the tire size by 2" for the exactly the same tire as on the previous model, following the lead by GW and LeaperKim.

I think that's different. The actual outer tire diameter, which the manufacturers purport to specify, is closer to the new numbers. So here they got more honest, it's just the older wheels were stated the old, less true, way.

-

I agree that battery sizes are to be read relative anyways, so as long as the manufacturers use the same methodology (they do... mostly), who cares about the "real" (whatever that means) numbers.

Edited February 23, 2022 by meepmeepmayer

[alcatraz]

10 minutes ago, meepmeepmayer said:

Yep, each side has one, physically split, pack. Abrams does the same.

How the internal adding up goes, I don't know. Are they are actually two 50.4V 5*12 cell packs that are (at the end) serialed up? Can you tell from the cabling? (This sounds like the better way to do it.) Or might the 12+12 split cells simply be connected to 24s on their own, like they would be in a normal pack form factor, along with the other 24s blocks?

The pic I posted shows 12 cell groups on each board. 

Each subpack has 60 cells which isn't divisible by 24. That's what caused the confusion in the first place. I assumed it was an underreported 3700Wh pack with 72 cells in each subpack.

[meepmeepmayer]

Just now, alcatraz said:

The pic I posted shows 12 cell groups on each board. 

I can't read BMSes I guess two BMSes means it's 2*50.4V?

I wondered if the 12s extra cells were directly connected to the other 12s extra cells to form 24s, which would only need some cabling to do it, so in theory it's possible.

But I can't read that cabling in the picture you posted, too. And the 2*50.4V way of doing it makes much more sense. Just build regular half-voltage battery packs and serial them up, done.

[alcatraz]

To be nitpicky and go by the cell rating

Gotway M50T packs are 888Wh (98.67%)

50E packs are 870Wh (96.67%)

48X packs are 852Wh (94.67%)

Veteran Sherman is 3108Wh with GA cells. (97.13%)

The 48X cells are superior to the other two so you could argue that while you get 4% less range, your wheel should be noticeably more reliable because of a greater current supply.

Edited February 23, 2022 by alcatraz

[alcatraz]

1 minute ago, meepmeepmayer said:

I can't read BMSes I guess two BMSes means it's 2*50.4V?

I wondered if the 12s extra cells were directly connected to the other 12s extra cells to form 24s, which would only need some cabling to do it, so in theory it's possible.

But I can't read that cabling in the picture you posted, too. And the 2*50.4V way of doing it makes much more sense. Just build regular half-voltage battery packs and serial them up, done.

See those blue cables? They link cell group 12 with cell group 13. It connects the two subpacks in series to form 50.4 + 50.4v.

The terminal to the control board has one lead coming out of each subpack. That's another clue. 

When the packs are all "equal" and 100.8v each of them, then they each have their own 2-lead terminal that connects them together with an external harness.

[houseofjob]

11 hours ago, alcatraz said:

24 x 18.5Wh = 444Wh (round up to 450 because, why not?)

Never connected the dots, but food for thought: 24S "100V" building block with max 5A 21700 cells, 3.7V nominal, is 444Wh, but 4 means death in Chinese/Chinese-character utilizing languages, even worse the more consecutive 4's you have, so it makes even more reason to round this up (eg. majority of buildings in Asia do not have a 4th floor, they name it "F" or skip it altogether). 

Edited February 23, 2022 by houseofjob

[meepmeepmayer]

Nah, they were lying the same way before.

Also, one actual pack is 2*444Wh = 888Wh, so that number would just as much be a reason to be honest (8 is good in Chinese right?) about their magical 888Wh packs

[Planemo]

44 minutes ago, meepmeepmayer said:

I can't read BMSes I guess two BMSes means it's 2*50.4V?

I wondered if the 12s extra cells were directly connected to the other 12s extra cells to form 24s, which would only need some cabling to do it, so in theory it's possible.

But I can't read that cabling in the picture you posted, too. And the 2*50.4V way of doing it makes much more sense. Just build regular half-voltage battery packs and serial them up, done.

Right, what specific bit are you confused on?

I thought we went through all this a few months back 

[houseofjob]

2 hours ago, meepmeepmayer said:

Nah, they were lying the same way before.

Also, one actual pack is 2*444Wh = 888Wh, so that number would just as much be a reason to be honest (8 is good in Chinese right?) about their magical 888Wh packs

touché, 888 is a good wealthy prosperity number 

[meepmeepmayer]

3 hours ago, Planemo said:

I thought we went through all this a few months back 

If I ever knew more about the Sherman battery other than it has split packs, I forgot