How many (V) per (1000w) Output to you drop?

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 10:57am

"Can you see why expressing voltage sag as volts per 1000w is misleading"
In you r example It tells me both batteries are very similar ( and are, identival in weight, cell capacity, and volume,)...And your example tells me perfectly... Absolutly, in using the weight, IR, output, and droop,

Which pack is more power dense.,Period.

That the 50v pack is more power dense. Absolutly. Been waiting for someone to compare two : identical component battery with different power density......

Speed, power, and weight are never misleading. Share similitude across the span of vehicles we drive. This is the power density of your pack. Power density is measured in W/lb. Cross section is the only thing I think we need to care about if the speed reached.

Power is power. Density is density. Power density is something I like to have. :)

I just like using "V" cause we all know the math for a "V" .... ad "1000w" cause it is a commonly know multiple of power measure.. ( watt... ?)

Yes, so using the above example, Both output 1000w, but ... the 50v pack will output 1000w and drop less ( given the ir is low enough, which on the cells I like, it is... ) all day. The 50v pack is much more power dense. Riding in normal ebike power outputs, if you can handle the amps, the 50v pack would be that much more fun.

Imo. BTW, I dont ever trust this "DCIR" ( as an accurate number when looking at power output) . I measure all mine on an accepted computerized datalogger, that has been accepted as an accurate reading. ONLY on charge, from 30% SOC, @ 59* for repeatability. This give me a much more accurate repeatable reading, and easier.

Its power density, people. That is all. Our bikes ( all of them) have a measure of similitude. All out packs weight is congruent ( small enough for two wheelers), all out packs outputs are congruent ( power to move a human/bike), and run at about the same temps( temp that supports human life) at the load of wind vs. thrust.....
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 11:02am

"How many V do you drop per A" isnt telling me anything when it comes to power .
"How many V do you drop per W" does tell me a thing or two about the power. IF ( ony if) our packs are all sharing some similitude, such as weight, and size.

Most ebike packs look similar to me. Maybe you can see the diffences from 10 feet away, but to mee they all just look like ebike batteries that strap or bolt to a bicycle.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 11:22am

Say the cells are 10Ah, weigh 100g each and put out a maximum 10C for 5min, where they exhibit that DCIR / Vsag

Same 20 cells:
10S2P 50v 20Ah battery
20S1P for a 100v 10Ah battery

Both are 1000Wh, both allow sustained 10kW output from the same 2kg weight, also same volume.

By definition both have the **same** power density.

Also energy density.

Drivetrain about the same performance curves if motor kV windings and/ or gearing get matched to the amp/volts of each pack.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 11:25am

What percentage Voltage do you drop at X C-rate

would be comparable

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 11:33am

Both are 1000Wh, both allow sustained 10kW output from the same 2kg weight, also same volume.
Where does this 10Kw sustainde come from? One drops alot more thn the other.

The 2p can sustain more POWER? No?
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 12:06pm

DogDipstick wrote:
Both are 1000Wh, both allow sustained 10kW output from the same 2kg weight, also same volume.
Where does this 10Kw sustainde come from? One drops alot more thn the other.

The 2p can sustain more POWER? No?
No. Twice the amps, half the volts means identical power.

C-rate usually is proportional amps thing, because volts are usually a constant within such comparisons.

But power is Watts which = V*A

20 of those cells will always be the same Wh no matter the xPyS layout.

So a 1000Wh pack, if 10C is the max sustained rate - direct function of that chemistry's DCIR

gets you 10,000W or 10kW

In reality going to 100V rather than 50V should be a bit more efficient, lower amps means less heat losses.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 12:42pm

So a 1000Wh pack, if 10C is the max sustained rate - direct function of that chemistry's DCIR



So the Crate stays the same with a 2p vs 1p because capacity. Is this right?

Both batteries ( the 1p vs the 2p) would BOTH be a 10C, regardless. Is this right?

I am NOT right when I would assume the 2p battery could handle 20C, IF 1P only handle 10C? Cause they are the same output.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 1:56pm

DogDipstick wrote: So the Crate stays the same with a 2p vs 1p because capacity.
Yes C-rate is the ratio between current amps - instantaneous measure of flow rate

and Ah capacity.

So keeping Wh capacity constant, the 1p layout is double the voltage, while the 2p layout is double the Ah

but Wh total (power stored) is constant between the two.

> I am NOT right when I would assume the 2p battery could handle 20C, IF 1P only handle 10C? Cause they are the same output.

Yes, the voltage level, and **absolute Amps number** is different, but

as long as the chemistry and build quality are the same, the xPyS layout makes no difference to

the C-rate and Watts power capacity, those are constants.






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Re: How many (V) per (1000w) Output to you drop?

Post by Sunder » Jan 28 2020 3:25pm

Edit. I'll take another shot later.

All I'll say now is that DCIR isn't a thing to be trusted or not trusted. When you are doing data logging, you are measuring real world DCIR. It's how you are interpreting those numbers which is at odds with the rest of the scientific community.
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Re: How many (V) per (1000w) Output to you drop?

Post by Sunder » Jan 28 2020 4:53pm

Alright, if John61ct convinced you, then there's not a lot more to be said about my example. But that explanation was only a stepping stone to explaining why Vsag/1000w is misleading. What matters is the percentage of power that your load is asking for, that's not reaching it that matters: Although the 100v drops more volts, due to Ohm's law, it's also dropping fewer amps, meaning the total loss of power is equal. (With otherwise "ideal" other components)

DCIR is also not the least confusing representation either, as you still need to adjust for voltage. A 3mOhm 3.7v battery can't deliver the same power as a 30mOhm 37v battery, even though it has a lower internal resistance. However, for identical voltage sources, it's a good comparison, hence when you buy individual cells, they usually use DCIR as an easy way to compare. Also, as it aligns with Ohm's law, it's the international standard for describing cells.

C Rate is usually used for describing whole batteries as it requires less maths for the end user, but still require adjustment for capacity. A 10C 10Ah battery, would outperform a 15C 5Ah battery for example.

If power density is all you care about, then W/L is the only unit of measurement that's easy to compare like for like in theoretical situations, but again, in practical situations, can be somewhat cumbersome. People want to maximise their use of space, so a really nice battery that is 1cm too big for your space is of no use to you, and a superconducting battery with no voltage sag at all is also of no use to you, if your entire space is taken up by a battery that can only take you 10m.

Hope this is starting to make sense to you.
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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 7:22pm

I know it is like aasking "How fast do you go from 10-35mph"... when you got the data on the time i t takes to go 40mph and that is all you have for empirical data.

Hope this is starting to make sense to you.
It has made sense for much longer thanyou give me credit for, friend.

W/L is all I care about. Well known, for the same amp output, the power will be greater for the higher voltage pack. Congruent amperage load.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 8:01pm


Sunder wrote:Alright, if John61ct convinced you, then there's not a lot more to be said about my example.
Was there any conflict between my simplified explanation and your (Sunder's) understanding of what would be a more accurate one?

I welcome your feedback and correction being a noob to the finer points of electrickery, not just DCIR, ohms but inductance wut?

> C Rate is usually used for describing whole batteries as it requires less maths for the end user, but still require adjustment for capacity. A 10C 10Ah battery, would outperform a 15C 5Ah battery for example.

(for dogdipstick) Only because it's bigger, the 15C cells would perform a lot better if both packs were the same size.


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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 28 2020 8:58pm

Sunder wrote:
Jan 28 2020 4:53pm


If power density is all you care about, then W/L is the only unit of measurement that's easy to compare like for like in theoretical situations, but again, in practical situations, can be somewhat cumbersome. People want to maximise their use of space, so a really nice battery that is 1cm too big for your space is of no use to you, and a superconducting battery with no voltage sag at all is also of no use to you, if your entire space is taken up by a battery that can only take you 10m.

Hope this is starting to make sense to you.

Can you teach me anything else about W/L and how it is correctly measured?
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 28 2020 10:46pm

Usually per kg, weight usually more imprtant than volume.

Volume being liters.

This is for energy density (Wh storage capacity)

________
battery nominal voltage (V) x battery capacity rating (Ah) / battery weight (kg)=specific energy or energy density (Wh/kg)

For example, for a 18650 cell, nominal voltage, 3.6 V, capacity rating, 3.0 Ah, cell weight, 45 g, then the energy density will be roughly 240 Wh/kg.


For power just use the max Watts (for Xminutes) not static Wh.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 29 2020 11:39am

john61ct wrote:
Jan 28 2020 10:46pm



For power just use the max Watts (for Xminutes) not static Wh.
... Ok... how does one figure "max Watts (for Xminutes)" ?

I have an idea, but I want to know the consensus first.

Hint: Involves temp ?
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by john61ct » Jan 29 2020 1:57pm

Yes, that and voltage drop

Almost every battery has tests available by googling, some with videos as well.

You get to know the tester guys and find what forums they hang out in.

https://lygte-info.dk/review/batteries2 ... %20UK.html

The RCGroups one is best place for LiPos, highest power densities used in airplanes of course, have no hard case.

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Re: How many (V) per (1000w) Output to you drop?

Post by leffex » Jan 29 2020 2:39pm

DogDipstick wrote:
Jan 23 2020 12:07pm
Is this good? How many volts do you ( on average) drop for every 1000w output? Curious here. Never had an 18650 pack.
Your battery pack drops 1,25v for a 1000w output from an input of 82,5v x 12,5A

One measure point to use is to draw the same amps from another pack. If that pack is double the amp and the same pack as yours the pack voltage drop vill be 1,25/2 = 0,625

If you like to compare what battery is better it is rather the battery that gives the most amps and lowest voltage drop that kings all other batteries.

Like if I draw 92v x 150a or 13800W (13,8kw) from a battery and the voltage drop here is 7,5v then I can give an answer of percentage. About 8% voltage drop here in this case or (13,8/7,5= 1,84v dropped per 1000w / kw.) - How will you compare your battery with mine? Mine is 3-4x bigger.

So percentage is a better comparison. Best comparison is between a same voltage and amp hour battery. Difference goes from what cells and brand they are. There are 2,5ah cells making 20a power so 20/2,5=8. Meaning its power factor is 8 and specified as 8C. Max C cells that exist today that I know are 150C. So from that cell with a rating of that magnitude you can use cell ah times 150 = w power. Normally cells however are rated at Amps continuos. Tesla cells 2c. Panasonic pf 3,3c. Samsung 25R 8c.

So if your friend has 25R cells and you told him, what he know are lesser cells then of course his cells are stronger or you will now which one is stronger when you learn more about batteries in the soon future.

In essence there should be a specification of C-rate for your battery because its a named battery. If you find out your friends battery name, cell type and amp hour capacity then you can start calculate.

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Re: How many (V) per (1000w) Output to you drop?

Post by Sunder » Jan 29 2020 3:39pm

Sorry for not replying sooner and letting all the comments build up between replies. We must be in very different time zones.
john61ct wrote:
Jan 28 2020 8:01pm
Was there any conflict between my simplified explanation and your (Sunder's) understanding of what would be a more accurate one?
Nope. Your explanation was pretty good. Apologies if I came across as a bit patronising. This whole concept really is very simple mathematically, but in trying to explain it in writing, I realised how difficult it is to explain it in English, because of the different variations of what people want to know, and not being able to assume their level of prior knowledge.

DogDipstick wrote:
Jan 28 2020 8:58pm
Can you teach me anything else about W/L and how it is correctly measured?
If I could, I should probably be on some committee on the IEC, or IEEE. :mrgreen:

Seriously though, there's marketing fluff and there's real standardised measurement, and almost nobody (as far as I know) uses standardised measurements for our hobby kit. Just go to any RC Hobby site, and watch people complain about how their "75C battery won't even put out X amps", or reviews showing that the new <favourite brand> 15C lipo outperforms and runs cooler than <cheap chinese crap> 35C lipo.

When I first got into this hobby and destroyed my first LiPo battery within 6 months, another kind member explained to me that there was no standardised rating for batteries - One manufacturer would put down the C rating they recommended for a long life, another would put the C rating that their pack would survive essentially just one run. Back then, the advice was to never run it more than 2C constant, or 3-4C burst if you wanted your pack to last. Of course, back then the expectation was about 200-300 cycles, against the newer graphenes and nanotechs which are expected to last upwards of 700 cycles now.

The closest you will get if you want a rigorous test using logged data is IEC 61960: https://webstore.ansi.org/Standards/IEC ... gItJvD_BwE

Unfortunately it costs money to buy the standard.
DogDipstick wrote:
Jan 29 2020 11:39am
... Ok... how does one figure "max Watts (for Xminutes)" ?

I have an idea, but I want to know the consensus first.

Hint: Involves temp ?
There's a test within IEC 61960 for that as well, but again, this is simple yet complex... What does "Max Watts" actually mean? The maximum you can draw before a catastrophic fire? A full short circuit? For 10 Cycles? For the expected battery life?

Across a single chemistry temp and voltage drop is good for an apples vs apples comparison - well, voltage drop only if both the capacity and state of charge were equal during the test. But comparing across chemistries has the potential to mislead.

For example, Lithium Titanate has a flat as a tack discharge curve. It doesn't matter if the test is done at 100% SOC, or 20% SOC. It also suffers almost no voltage drop regardless of if you're discharging 0.5 C or 10C:

Image

(BTW, if Vsag/1000w is all you were interested in, LTO would be your ideal battery! But we're past that point - LTO has poor energy density and only okay power density)

LiPo on the other hand has a graduated curve, and sags a lot more depending on the power drawn:

Image

You can see the first 10% of the curve is much steeper than the rest of the curve. So the voltage drop from 4.2v to 4.0v would be much more significant than say a 3.9v to 3.7v test. Again, across the same chemistry and the same capacity, not a problem. As soon as you want to compare an 18650 vs a Turnigy Graphene, or something else, it may not necessarily be a fair test.

This whole thread started it seems from a single comment from a friend of yours (DogDipstick) that your battery was sagging too much - a comment based on an unreliable metric. It's come a long way since then, and I'm not sure where you want it to go now, but I think the discussion has shown that there are so many different ways of comparing batteries, and all of them are "fair" in certain conditions, but nothing universally fair in all situations to compare batteries.
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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 29 2020 4:24pm

OK. Google has my answer. Check. Lol. Lemme just open up the browser.....
....Uhm... anybody know what entropy is? Word.
john61ct wrote:
Jan 29 2020 1:57pm
Yes, that and voltage drop

Almost every battery has tests available by googling, some with videos as well.

You get to know the tester guys and find what forums they hang out in.

https://lygte-info.dk/review/batteries2 ... %20UK.html

The RCGroups one is best place for LiPos, highest power densities used in airplanes of course, have no hard case.

Yes i have Pm'd Wayne Giles (maker of the Wayne Giles Meter and later copied by Hobbyking) on RCGROUPS a while ago and use the calculator often. I am and have been fully aware of the going ons there for a few years. I Pm'd with intent on walking away with the current formula for the Contin/Maxpeak rating of a lipo that is commonly tested by MCS Guy there. I have offered MCS Guy to test a free 15Ah Volt lipo for me with a decline.

They are all Plankers. Im a Rotorcraft flyer. :.(

So: I can do this with multiple temperature probes for repeatable datalogged accuracy. I have a powerlab of corse, a good accepted measuring tool for hobbyist.

This is what I was told, I'm sure Mr. Giles wouldnt mind me sharing the Pm. His testing is almost legendary by this point.

So: For Lipo, all things being (mmmm lipo) equal... :

"Current squared x IR = 6Watts/Ah/cell
Thus the max current = Square root of (power/IR) where IR is in Ohms."

Quote:
Originally Posted by DogDipstick
Wayne could you point me to the formula that takes heat generated from lipo discharge into the account when figuring Max and Contin C rate?

I remember reading it but cannot find it anymore. The formula, I think it had a .5 for contin Crate and a 1.0 in it for max or something? So much to pawn through in the last ten years I cannot find it, it is important to me for my hobby.

If you want to test a 15 Ah Chevy Volt NMC Lipo cell, or battery I will donate some. Also have SmartoFor car cells, 50Ah, or Kia cells, 5 Ah, among others.

Noone seems to care, but they have Ir of 1 mOh.... most of them. Super powerful. I have data loggers and load arrays for testing. I dont want to test to destruction though.

I think it is in the FOM thread... maybe if you could even confirm that for me I would appreciate. I am trying to find a good way to estimate large format pouch cell C rates without manufacturers publication.

Anyway, thankyou for the good work. -Jp ( looking for the right formula in PA)
Hi DD,

The formula used for forecasting the max safe continuous current used in the Lipotool was derived from my testing of many lipos when I was trying to forecast performance based on IR.
Every time I carried out a set of tests on a lipo, I measured IR at 25*C and tried to correlate that with the max continuous current discharge that the lipo was capable of without signs of overstress; ie excess temperature rise and/or voltage sag and recovery.

As the temperature rise is due to the heating caused by the current through the cell IR, I reasoned that I could probably forecast the max continuous current capability based on that premise.

I found that when the initial power dissipated in the cell as heat exceeded about 6 -7 watts per Ah per cell, then that current was about the maximum the lipo would tolerate without overstress/overheating. I discussed this with John Julian and Mark Forsyth and we came up with an agreed figure of 6Watts to be conservative.

Thus the formula is Max power dissipated = Current squared x IR = 6Watts/Ah/cell
Thus the max current = Square root of (power/IR) where IR is in Ohms.

eg for your 15Ah Chevy cells:-

Max current = Square root of {(6 x 15 ) divided by 0.001} = 300A = 20C.

this assumes that the cell IR is 1 milliohm.

|We later dropped the temperature to 22*C because we agreed that was a more likely temperature as it was approx. room temperature. This made it more conservative as IR falls with temperature rise.

Hope this helps.

Wayne

There are other ways I have read about in "Google". Plus the good ol traditional ways like a 20 Hr rate, intrinsic resistance AND short circuit current measure.

I mean, its not that hard to submerge a cell in a graduated cylinder and see how much water is displaced. Theres your volume.

Now about that power again..... That Pm was over a year ago. I think. This still applying? What do you guys think? Calculating heat through IR is easy. Measuring it is tough, I think.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 29 2020 4:32pm

Sunder wrote:
Jan 29 2020 3:39pm
Sorry for not replying sooner and letting all the comments build up between replies. We must be in very different time zones.
john61ct wrote:
Jan 28 2020 8:01pm
Was there any conflict between my simplified explanation and your (Sunder's) understanding of what would be a more accurate one?
Nope. Your explanation was pretty good. Apologies if I came across as a bit patronising. This whole concept really is very simple mathematically, but in trying to explain it in writing, I realised how difficult it is to explain it in English, because of the different variations of what people want to know, and not being able to assume their level of prior knowledge.

DogDipstick wrote:
Jan 28 2020 8:58pm
Can you teach me anything else about W/L and how it is correctly measured?
If I could, I should probably be on some committee on the IEC, or IEEE. :mrgreen:

Seriously though, there's marketing fluff and there's real standardised measurement, and almost nobody (as far as I know) uses standardised measurements for our hobby kit. Just go to any RC Hobby site, and watch people complain about how their "75C battery won't even put out X amps", or reviews showing that the new <favourite brand> 15C lipo outperforms and runs cooler than <cheap chinese crap> 35C lipo.

When I first got into this hobby and destroyed my first LiPo battery within 6 months, another kind member explained to me that there was no standardised rating for batteries - One manufacturer would put down the C rating they recommended for a long life, another would put the C rating that their pack would survive essentially just one run. Back then, the advice was to never run it more than 2C constant, or 3-4C burst if you wanted your pack to last. Of course, back then the expectation was about 200-300 cycles, against the newer graphenes and nanotechs which are expected to last upwards of 700 cycles now.

The closest you will get if you want a rigorous test using logged data is IEC 61960: https://webstore.ansi.org/Standards/IEC ... gItJvD_BwE

Unfortunately it costs money to buy the standard.
DogDipstick wrote:
Jan 29 2020 11:39am
... Ok... how does one figure "max Watts (for Xminutes)" ?

I have an idea, but I want to know the consensus first.

Hint: Involves temp ?
There's a test within IEC 61960 for that as well, but again, this is simple yet complex... What does "Max Watts" actually mean? The maximum you can draw before a catastrophic fire? A full short circuit? For 10 Cycles? For the expected battery life?

Across a single chemistry temp and voltage drop is good for an apples vs apples comparison - well, voltage drop only if both the capacity and state of charge were equal during the test. But comparing across chemistries has the potential to mislead.

For example, Lithium Titanate has a flat as a tack discharge curve. It doesn't matter if the test is done at 100% SOC, or 20% SOC. It also suffers almost no voltage drop regardless of if you're discharging 0.5 C or 10C:

Image

(BTW, if Vsag/1000w is all you were interested in, LTO would be your ideal battery! But we're past that point - LTO has poor energy density and only okay power density)

LiPo on the other hand has a graduated curve, and sags a lot more depending on the power drawn:

Image

You can see the first 10% of the curve is much steeper than the rest of the curve. So the voltage drop from 4.2v to 4.0v would be much more significant than say a 3.9v to 3.7v test. Again, across the same chemistry and the same capacity, not a problem. As soon as you want to compare an 18650 vs a Turnigy Graphene, or something else, it may not necessarily be a fair test.

This whole thread started it seems from a single comment from a friend of yours (DogDipstick) that your battery was sagging too much - a comment based on an unreliable metric. It's come a long way since then, and I'm not sure where you want it to go now, but I think the discussion has shown that there are so many different ways of comparing batteries, and all of them are "fair" in certain conditions, but nothing universally fair in all situations to compare batteries.
Thankyou for the input, . Most of this I know already. I have been ( many different) teasing cells for some time now.


I have read many many papers about the specific methods of testing cells, including trends that manufactures follow in their approaches.

I might be able to get that standard, complete. I know an engineer or two,.. I have chased standards in the past, and have a good ideas as to what is out there both domestically and internationally. Thank you though. I will look into that specific one. I think I have already too.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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DogDipstick   10 kW

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 29 2020 4:34pm

leffex wrote:
Jan 29 2020 2:39pm
DogDipstick wrote:
Jan 23 2020 12:07pm
Is this good? How many volts do you ( on average) drop for every 1000w output? Curious here. Never had an 18650 pack.
Your battery pack drops 1,25v for a 1000w output from an input of 82,5v x 12,5A

One measure point to use is to draw the same amps from another pack. If that pack is double the amp and the same pack as yours the pack voltage drop vill be 1,25/2 = 0,625

If you like to compare what battery is better it is rather the battery that gives the most amps and lowest voltage drop that kings all other batteries.

Like if I draw 92v x 150a or 13800W (13,8kw) from a battery and the voltage drop here is 7,5v then I can give an answer of percentage. About 8% voltage drop here in this case or (13,8/7,5= 1,84v dropped per 1000w / kw.) - How will you compare your battery with mine? Mine is 3-4x bigger.

So percentage is a better comparison. Best comparison is between a same voltage and amp hour battery. Difference goes from what cells and brand they are. There are 2,5ah cells making 20a power so 20/2,5=8. Meaning its power factor is 8 and specified as 8C. Max C cells that exist today that I know are 150C. So from that cell with a rating of that magnitude you can use cell ah times 150 = w power. Normally cells however are rated at Amps continuos. Tesla cells 2c. Panasonic pf 3,3c. Samsung 25R 8c.

So if your friend has 25R cells and you told him, what he know are lesser cells then of course his cells are stronger or you will now which one is stronger when you learn more about batteries in the soon future.

In essence there should be a specification of C-rate for your battery because its a named battery. If you find out your friends battery name, cell type and amp hour capacity then you can start calculate.

epic right

Well, those are certainly all words. Thankyou, for the answer I see friend.

I output ( from the battery, into the controller, 101.5 A) about 10 horsepower into the controller, what it does with that is just magical wizardry, who knows how many elves there are running in there.... I know they are well fed at that.
"Your battery pack drops 1,25v for a 1000w output from an input of 82,5v x 12,5A"
No, My battery is dropping 7.5v on an 8,000w 10 horsepower 85.8V charged pack... 101.4A current. Approx 1v/1000w for a total of 7.5v for 8000w output.
"In essence there should be a specification of C-rate for your battery because its a named battery. "
Good luck trying to find some old proprietary datasheets.. LG will not release this specific datasheet that I can find. I have looked for 2 years now. . I have seen close, ( diffent revisions of the same cell) but not exact (LGXP1.5B). Sometimes they just never give em away or publish them.
"If you like to compare what battery is better it is rather the battery that gives the most amps and lowest voltage drop that kings all other batteries."
I agree, friend.
"Like if I draw 92v x 150a or 13800W (13,8kw) from a battery and the voltage drop here is 7,5v then I can give an answer of percentage. About 8% voltage drop here in this case or (13,8/7,5= 1,84v dropped per 1000w / kw.) - How will you compare your battery with mine? Mine is 3-4x bigger."
Yes, and from this data, If my battery was 4x bigger (60Ah) like yours, I would drop much less than 1v/1000w.. compare to your 1.84v drop... Maybe? I would say probably around 0.34-0.35v/1000w, on a 150A control. ... like the example in this thread above concerning Chevrolet Volt cells. However, this 8,000w pull is only from a 21s1p.
Last edited by DogDipstick on Jan 30 2020 1:07pm, edited 6 times in total.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 29 2020 4:39pm

I mean, I do know a thing or two, guys. Cant ya just answer my non empirical baseless unlovable non proven doesnt make sense formula question again? Lol.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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Re: How many (V) per (1000w) Output to you drop?

Post by DogDipstick » Jan 30 2020 1:09pm

leffex wrote:
Jan 29 2020 2:39pm
DogDipstick wrote:
Jan 23 2020 12:07pm
Is this good? How many volts do you ( on average) drop for every 1000w output? Curious here. Never had an 18650 pack.
About 8% voltage drop here in this case or (13,8/7,5= 1,84v dropped per 1000w / kw.) - How will you compare your battery with mine? Mine is 3-4x bigger.


epic right
As a percentage, I drop 6.43% of the voltage on a 8000w output with my battery.
83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Broke 10 horsies :twisted: (..about 80% healed..).. :? Anybody.. what equals √3 times the line to neutral voltage? Asking for a friend.. :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

leffex   1 kW

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Re: How many (V) per (1000w) Output to you drop?

Post by leffex » Jan 31 2020 8:18am

DogDipstick wrote:
Jan 29 2020 4:39pm
I mean, I do know a thing or two, guys. Cant ya just answer my non empirical baseless unlovable non proven doesnt make sense formula question again? Lol.
My research is to cut corners where there are no safety guards around. With more sources the value of the info exponentially increases. Just because you can't find information doesn't mean it doesn't exist, somewhere or naturally works in your own supposed theoretical thoughts until proven, the more the merrier.

All of us have different experiences with batteries and such learn from our own projects and learning capability.
Some of us build and repack our batteries
Some build total bms, charge and safety systems.
Some build whole vehicles
Salestech in an ebike store

leffex   1 kW

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Re: How many (V) per (1000w) Output to you drop?

Post by leffex » Jan 31 2020 8:31am

DogDipstick wrote:
Jan 30 2020 1:09pm
As a percentage, I drop 6.43% of the voltage on a 8000w output with my battery.
Are you happy with your battery and the power it gives to you or do you want a better one?

The Chevy volt battery is probably the best in terms of longevity. Maybe because of the internal "cooling system" that cools the cell in the car. Statistics shows it is better than all other electric cars. I would like to buy that car when it cost 8-12 grand although not before I have any use if it. (Why is it so? Beacuse they use only the best percentage from the battery, about 80-25% I don't know the exact figure however about 10kw of the batterys' 16kwh capacity)

Performance wise as you se your battery is pretty nippy. If I had it I wouldn't worry. However if you still want more power from it then cut resistances in positive and negative wires by increasing the diameter. Also increase the diameter of the phase wires. Upgrade wires on your battery if possibly without safety issues. and more things to do. Put settings in your controller to xx 99% and 150% in 3 speed setting. So setting 2 will never use flux-weakeing if your controller has it meaning more efficiency and less wh used per mile in that setting. The end result is less power or watts lost in heat or inefficiencies or "voltage drop" (voltage drop is for example higher in a thinner, weaker cable - - -> meaning losses)
Salestech in an ebike store

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