New 14s battery pack, US18650VTC6 vs NCR18650GA

eMark said:

As a general rule it was my understanding that it's better to go with an 80% charge and 50% discharge than an 80% charge and 80% discharge? Maybe, for some an 80% charge and 65% discharge is the happy medium that best suits one's daily ebiking routine. Here's a real-life scenario that may be similar to Erik's daily ebiking routine with two possible options being 80/50 or 80/80 ...

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Repeating, again and again:

If there are two batteries the same size and one has a lot greater mAh capacity, very likely that will have a shorter lifespan.

How "easy-going" the usage "routine" is has nothing to do with anything.

Now, if you are happy spending more money and carrying around a lot more size & weight, that will extend lifespan, to the point that $/Ah **per year** may be cheaper.

And if you don't need high real-life C-rate discharge, you can likely save money there too. But often that factor correlates with good lifespan too.

And **please** stop propagating this 80% malarkey! Treat 4.05-4.1Vpc as **100% Full** and be done with it. How long you hold Absorb is a small factor, how long you **sit** at any definition of "Full" a **much** bigger one, but none of this has anything to do with this mythical "80%" number.

And (again again) 3.0Vpc and lower is where the cell vendors would love for us to go every cycle, so when you see that, make a mental note to discount that source for longevity advice, that is more like a

very stressful "avoid approaching" minimum level, like running chinese electronics close to their advertised rating, not at all a good idea IRL.

BU is not a canonical source, OK for 101-level noob orientation maybe. . .

0% is not "a low end" and is in opposition to longevity.

A shallower DoD is **always** going to give longer lifespan, and that tradeoff is a 100% personal variable, no rule of thumb can be generalized, other than

based on **resting** voltage

regularly allowing a drop to 3.2V will be a very large sacrifice of life cycles

while 3.4V or higher will be much healthier.

How much IRL % capacity you are "sacrificing" will vary hugely by cell model & chemistry.

Would a resting voltage of 3.85v per cell be damaging over the course of 2 weeks? Should I be draining the pack down to 3.6v or so when Im not using it the same day?

Well 3.85Vpc is much better than over 4V.

And a couple days not as bad as a couple weeks.

There are no hard numbers, all greyscale, too many variables, how do you even define "damaging"?

And such factors get lost in the noise if the use case demands very high C-rates or avg DoD cycling, or very hot climate, or or or.

So learn and make your judgment calls from awareness, not just careless ignorance. but

don't drive yourself nut to get every last possible cycle lifetime, these are tools for your pleasure and convenience not gods to enslave yourself to.

Getting back to Erik's choice of LG M36 compared to PanPF we can agree that his choice to cancel his PF order and go with M36 was a good decision :thumb: considering his daily ~ annual ebiking routine.

john61ct said:

docware said:

Your choice LG M36 seems to be for such case better option than Panasonic PF.

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Fantastic chart.

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At least john and i agree on docware's Fantastic chart ... "https://endless-sphere.com/forums/download/file.php?id=259829" ... LG M36 vs Panasonic PF

Doc's chart is most informative when choosing a SoC top-off and DoD cut-off to get the most cycle life mAh capacity when taking a closer look at doc's comparaitve M36 vs PF chart with respect to Erik's daily ebiking routine. Instead of my rather nefarious 80/50 or 80/80 i'll defer (for the time being) to the SoC/DoD cell capacity voltages (e.g. M36 vs PF).

Taking a closer examination of doc's M36 vs PF chart with a depleted difference in capacity of 250mAh (below Full SoC) when each cell has a 3.97V SoC there's a +50mAh capacity advantage favoring PF. However, at a DoD 3.3V cut-off there's a difference of +425mAh capacity favoring M36. Well, daaaah we kinda knew that, but a picture is worth a thousand words.

According to john (whom i tend to agree with) that twice as many cycles with a (1) daily routine versus compared to only half as many cycles with the (2) daily routine would shorten the total months/years cycle life longevity of Erik's M36 8P14S pack (maybe, maybe not)? This daily routine (1) vs (2) assumes the daily distance ridden is within the daily mileage routine of the SoC/DoD voltages shown for (2) ...

• (1) An 80% SoC and 50% DoD (4.00V-to-3.70V) twice a day

• (2) An 85% SoC and 85% DoD (4.06-to-3.43V) once a day

I used percentages above with respect to another Fantastic chart posted in docware's "ageing" thread (SOC % - versus voltage) ... https://endless-sphere.com/forums/download/file.php?id=261831 ...

Sooo, is it likely no one wants to go out on a limb and venture a guess as to whether (1) or (2) will provide the greatest longevity in years/months IF doc were to do a rigorous bench test comparing (1) vs (2), as to a daily M36 mileage routine applicable to (2) round trip daily mileage even during a Viking winter.

FWIW, it does give Erik something to experiment with (twice a day vs once a day) as far as which SoC (% voltage) and DoD (% voltage) makes the most sense over the long haul. The percentages in my (1) and (2) are just "what ifs" ... it would be interesting if Erik would post the daily beginning M36 SoC voltage he's decided to use and then the voltage DoD resting voltage after arrivng at work during his winter runs. ... then a comparative DoD voltage in the summer months. It's very possible that the (2) routine isn't applicable in the winter, but may be applicable in the summer.

john61ct said:

How "easy-going" the usage "routine" is has nothing to do with anything.

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Do you not realize that comments like that in your contiuous attempt to discredit me actually does more to discredit you ?

john61ct said:

And **please** stop propagating this 80% malarkey! Treat 4.05-4.1Vpc as **100% Full** and be done with it.

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Another example of misinformation bordering on disinformation. Have you not considered docware's excellent chart ... https://endless-sphere.com/forums/download/file.php?id=261831 ... SOC % versus voltage. The reason why many refer and may prefer the use of percent instead of a specific voltage is because as example at 90% different cells have slightly different voltages. Same would be true for slightly different cell voltages for those that charge to 85% or 95% which is NOT considered **100% Full** as you mistakenly believe. If you don't believe me than take it up with docware and his chart ... https://endless-sphere.com/forums/download/file.php?id=261831 ... According to docware "Full"(100%) is between 4.17V and 4.18V NOT 4.05(85%)-4.10(95%) as you mistakenly believe. In affect you are trying to undermine docware as if your **Full** opinion is superior to docware's documented research tests based on industry standards. Accepted standards which are more creditable than are your opinions which call into question the trustworthy contributions by docware.

john61ct said:

0% is not "a low end" and is in opposition to longevity.

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According to docware's chart ... https://endless-sphere.com/forums/download/file.php?id=261831 ... 0% is a low end voltage between 2.81V (30Q) to 3.29V (PF) for those 18650 cells he is testng as indicative in his very informative chart.

john61ct said:

regularly allowing a drop to 3.2V will be a very large sacrifice of life cycles

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That is so obvous from docware's chart. The lowest percent of pack voltage with my easy-going routine (i.e. Docware's chart graph) that i've experienced in 400 miles since July this year is 35% of remaining pack capacity which is approximately 3.6V ... https://endless-sphere.com/forums/download/file.php?id=261831 ... on another graph posted previously 3.3V was shown as the low end cut-off. Apparently you misinterpreted that chart graph when its purpose was not to suggest depleting a pack to 3.3V, but rather to show the adverse affect on a pack when depleted to 3.3V.

In your attempt to discredit me with your misinformation you actually do more to discredit yourself.

I have no need to nor interest in discrediting anyone.

You're simply misinterpreting what I'm trying to get across to you.

But that's OK, nm

Have explained in my prevous post that your opinions such as the use of a percentage (e.g. 80%) of capacity is indeed valid and that some of your opinions are ill-founded. You find it difficult to admit when you are wrong. Another such example is when you said a 36V pack is 12S and then proceeded to change the subject when confronted by another member. Such is also true with your misinformaton quoted in my previous post.

Not during my lifetime, but maybe by the time Erik is 75 his latest DIY pack will outlive him even when he reaches 100 ...
https://modernsurvivalblog.com/wp-content/uploads/2019/06/lithium-iron-cycle-life.jpg ...
even with a 100% discharge 70% of capacity remains :? (advancing technological innovation)
Thought john would get a chuckle at that disconbobulating comparison of percentages to boolster his dislike for % of capacity.

Happy Trails and Holidays to John,
eMark

The problem is people go by "ballpark" guesstimates of SoC based on voltage anyway, and correspondence between the two varies widely between cells even of the same chemistry, age, temperature, how long resting etc.

Ah counters only measure the current that passes their measuring point, not the **useful** Ah actually stored in the cell ready to be withdrawn.

At the "useless" extreme in-the-shoulder tail ends of the standard voltage vs SoC curves, many mAh are getting logged by coulomb counters, of which only a tiny fraction are **actually** stored in the cells.

And since the activity in those regions is harmful to the cell anyway, voltage areas we have no business going in **normal** cycling, it seems stupid to me to count them as capacity.

Therefore, for a given cell in a given use case, I as owner, arbitrarily decide how my "working 0%" and "working 100%" are determined, with actual behaviour "recipes".

For SoH testing - using precisely timed CC load discharge tests, **not** Ah counting - I will define a "benchmark 0%" lower than "working" and a higher "benchmark 100%", but again these are in essence arbitrary, my own invention.

The battery maker's definition of the highest and lowest possible voltage before risking death of the cell, to me have nothing to do with any of this, so would be stupid to use for capacity or cycle life testing.

The fact is if there is 6.7% Soc between **that** definition of 100%. and mine, is actually irrelevant to me, since IRL I would never inflict that stressful treatment on my pack, that capacity "sacrificed to longevity" might as well not exist.

Same at the low end.

Same as capacity ratings, depending on chemistry and form factor, in many niches those are pure fiction. Even the top quality makers may deliver cells far lower (or sometimes far higher!) than what's printed on the label. The discharge rate used is, again, arbitrary, so it's up to **you**, as their owner, to choose how you benchmark that variable at commissioning time.

So, does that help explain why talk of a "80%-35% routine" drives me nuts as incredibly imprecise?

The actual "recipes" you might use to get to those numbers, when SoC is objectively and precisely measured to yield **actual useful** energy stored

using timed CC load discharge tests

will very likely show them up to actually be "96% to 14%" or something, and as optimized for longevity as possible.

Or, if you really are using those 80% & 35% numbers accurately, that means you are spending lots of exyra money and carrying lots of expensive "dead weight" around unused, to no useful purpose.

So, my usual chemistry for mobile / "House bank" use cases, is LFP.

Here are four alternative definitions of 100% SoC

A. nameplate Ah rating of the pack (as opposed to actual tested Ah capacity)

B. 3.65V CV/Absorb, stop-charge when current tapers to 0A absorption, call that "theoretical / vendor 100%" SoC level (may never be used in practice, I consider too destructive)

C. 3.45V CV stage, taper to 0.03C and Stop, call it "actual usage 100% Full, for regular testing or BM calibration" (requires a higher charge rate, say >0.1C)

D. 3.xxV and Stop, Bulk / CC-only, no-CV, call it "daily usage cycling Full" (should vary, depends on charge rate)

LVC / 0% in practice (D) might be 3.2V at rest, while for benchmarking purposes (C) I'd use loaded 2.99V at 0.5C discharge, and be sure to quickly start recharging once that's hit.

Obviously the actual numbers are dependent on chemistry, and temperature matters.

Just showing one real-world example.

john61ct said:

Vruzend no longer relies on "friction fit", as of v2.1
https://youtu.be/rylbFnTgFI8

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Being that Erik's 8P14S thread is as much about the Vruzend V2.1 kit(s), as any 18650 ES thread, a couple misconceptions need to be corrected about the Vruzend kit(s) and that's in no way meant to be an endorsement as spot-welding is still preferred by far.

1. Micah never implied that the V2.1 no longer relies on a "friction fit" in that youtube john posted. Both the V1.6 and its successor the upgraded V2.1 both make use of compression barrel bolts which shouldn't be interpreted as being a frictionless fit with the use of those compression barrel bolts. The V1.6 kit comes with 12 barrel bolts (4 more barrel bolts than with the V2.1 kit).

The difference between the V1.6 and V2.1 are the contact springs and buss bars. The V1.6 uses stainless steel cell contacts and stainless steel buss bars. The V2.1 uses nickel coated copper contact springs and buss bars eliminating the voltage sag experienced with the V1.6 kit when under duress. However, for my easy going etrike routine (8-10mph) with pedal assist on both the level and uphill (good exercise) the Vruzend Team agreed that the V1.6 would do the job. Besides it was a few dollars less expensive and included more buss bars and 4 more compression bolts than does the V2.1 kit. Thankfully, i no longer have a need for speed as does 999zip999 ...

999zip999 said:

I'm 61 and my street bike goes 47mph on flats and 36mph on most hills. 7,000 watts. Funny I don't feel old yet.

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At 75 i don't feel old either (well, maybe some days), but no hurry any more to get where i'm going (well, maybe some days).

Jan-Erik-86 said:

Edit: Since i don't have a spot welder I'd like to use a kit like Vruzend, so i think going with 18650 instead of 21700 is the best option? Or are there similar kits for 21700 as well?

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flippy said:

please dont, friction fit kits are a disaster in real life.

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docware said:

Find somebody with spot welder, for 18650 also.

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flippy said:

its basically a different iteration (Nishi) of that vurzend crap.
prehaps it's fun to play with but friction fit connectings should never be used in batteries. period.

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2. Unlike some that mistakenly believe Vruzend is "crap" ... au contraire. It would be worthwhile for those naysayers to watch/listen to the conclusion (09:07 to 9:53) of that youtube posted by john ... https://www.youtube.com/watch?v=rylbFnTgFI8&feature=youtu.be

Dak77 said:

There's nothing wrong with a "friction" contact connection if it's kept clean and has sufficient pressure. I am in my 8th month of using a V2.1 on a 14s7p of PF cells and I couldn't be more satisfied with the performance of it so far. I've checked for loose bolts, nuts, corrosion ,voltage drops, and cracks every other week since I built it and nothing of issue so far. I wouldn't use one on a mountain bike jumping hills, but for a rack mounted setup on a commuter or scooter, I'd recommend any day.

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Also, it's become apparent that Erik's decision to cancel PF and go with M36 has merit ...
https://endless-sphere.com/forums/download/file.php?id=262267

Again, my point was that it is better to not **only** rely on the friction fit for compression of the contact points against the cell ends.

The fact that the barrel bolts were added with v1.6 as opposed to later is besides the point.

Personally, I am working on a much less expensive DIYer design that is also solderless / no-weld.

The main challenge currently is keeping weight down as well as cost, while still resisting the enormous shocks/vibration factors in mobile use cases.

Also handling 26650 and 32650/32700, basically all "flattops" style with the same basic components.

Those with threaded posts at the ends are very intriguing, G10 FR4 laminates fiberglass looks like a promising board for that - other suggestions welcome.

But easy breakdown for cell-level testing and replacements really is essential IMO.

yeah, dunno about all the ^, but I have a couple of useful data points on NCR16850GA cells and they're not great. I have a Giant Road E and ride about 10,000 miles a year. First battery went down to ~55% capacity after 18,000 miles and ~450 charge/ discharge cycles. Second battery, bought at the beginning of September this year and with ~3000 miles on it suddenly dropped 10% of it's capacity last week. I know exactly when it happened - putting the hammer down to get through a traffic light from a stop (didn't make it) remaining capacity for that ride went from 19% to 8% in about 150ft. It was chilly, around 35F, but not super cold. Got the bike tested at the LBS and total capacity is down by 13% after 63 charge/ discharge cycles.

Not a very happy camper after an $800 outlay 3 months ago - I did try and rebuild the original but screwed up the BMS in the process, hence having to buy new. When this one needs rebuilding (sooner rather than later I'm guessing) I'll be looking at more robust cells, even if I lose a bit of initial capacity. It's a 10S4P pack powering a 250W (normal)/ 500W (boost) mid-drive motor.

john61ct said:

Personally, I am working on a much less expensive DIYer design that is also solderless / no-weld.

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Here's a different Vruzend 3-cell holder Hexagonal kit for spot-welding ... https://vruzend.com/product/hexagonal-18650-battery-holders-3-cell/

This photo and text of a 14S7P trianguar pack using the Vruzend Hex kit was posted on IMR's PanasonicPF cell review site ... https://cdn-yotpo-images-production.yotpo.com/Review/103013808/87199641/original.jpg?1562639795 ... Correction: It isn't the Vruzend Hex 3-cell kit -- what kit is it ?
"Amazing performing batteries! Built a 14s7p battery pack for my e-bike project. Every single battery tested was the same voltage, only varied by 0.01 volt! Great cells, ... . Yesterday I finished building a 52 volt, 35 Amp Ebike. Couldn't take the smile off my face while riding all day today, and still have over half of a charge left. Thanks guys!!"
(posted by Christopher R. on 7/7/19).

john61ct said:

But easy breakdown for cell-level testing and replacements really is essential IMO.

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That's what attracted me and imagine other DIY buiders to consider a Vruzend kit(s) ... "testing and replacements" (no spot welding)... as well as the fun and satisfaction of one's battery preference, cost savings and "i did it my way" :thumb:

mattthemuppet said:

yeah, dunno about all the ^, but I have a couple of useful data points on NCR16850GA cells and they're not great. I have a Giant Road E and ride about 10,000 miles a year. First battery went down to ~55% capacity after 18,000 miles and ~450 charge/ discharge cycles.

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Pretty good! Which cells comprised that pack?

john61ct said:

Pretty good! Which cells comprised that pack?

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The first one was definitely Sanyo/ Panasonic NCR18650GA and I'm pretty sure the second one is too, based on capacity and the assumption they'd make a bunch the same.