So it begins...... Battery spot welder

[sternwake]

When I needed some test cells for spot welding, I looked to my laptop battery, which uses a 3S2P configuration.
 It still worked, but not for very long, and would abruptly shut off when it said over 30% battery remaining.


3s is 12.6v max, 11.1v nominal, yet the laptop power supply is 19.5 volts.  There must be some sort of voltage Bucker booster tomfoolery going on within.

The cells extracted from the aftermarket Dell laptop battery were 'Wintonic, 2200 mah' cells  They are apparently a 6.6 amp(3C)  continuous discharge rating.

The cell cans on the negative side were crushed inward with whatever spot welder was used, and the two cells in the middle which had their cans crushed the most, were the ones triggering the BMS  low voltage disconnect, as when I discharged them separately they hit 2.8v when the others were 3.5v or more.

These cells with the crushed cans were not really great for testing spot welder settings, but better than nothing.

I recently rebuilt the Laptop's battery, using EVE 35V cells, rated at 3500mah capacity and 10 amps continuous discharge rate.

Mooch rates these cells highly, and My personal opinion is that EVE is one of the best cell makers, and the Eve 50PL is basically high discharge top dog21700, and the tested, but not yet widely available EVE30PL is the king of high discharge 18650's beating the very impressive Ampace JP30 by a little bit.

 The 18650 Eve 30PL actually outperforms the 21700 Molicel P42A at 40 amps continuous. it delivers more watt hours, and stays cooler.
The Molicel p42a is a well respected cell, but is now approaching 8 years old since it was first released.

Mooch has made this chart below public, which shows the top performing cells at various amp loads.  These do not take into account the voltage sag under load, nor the temperature rise of the cell, it is more of a which cell runs longest at that amp level.

https://www.patreon.com/posts/18650-2170...=web_share

It also does not take into account the cycle life, which like lead acid has many influencing variables.  But the Vapcells(a cell rewrapper, not a manufacturer) which are rated at the top on low amp discharges, are thought to not have great longevity when fully discharged to 2.5 volts, and are also kind of pricey for that fancy colorful wrap. 

I have some Vapcell 16340 and 14500's.  The 16340s have a lot of sag but I always have them stored fully charged.  No lithium cell appreciates that.

The EVE 35v at 5 and 10 amps is close to the vapcell n41, but is available for less than half its price, and probably has significantly longer cycle lifein the same usage.

The laptop had no issues recognizing the rebuilt battery and fully charging it.  It ran the laptop for over an hour and was saying 67% and nearly 2 hours remaining when I shut it down.  It really needs a full cycle to  somewhat accurately estimate the time left, but 7000 mah vs a degraded 4400 mah is a significant capacity increase, and 20 amps of CDR vs 13.2 will also have the new battery last longer. The Mah figure is a bit misleading, when the cells are not used at 0.2C

I have 14 Ampace JP30's looking for a home.  One is used in my Sofirn hs40 headlamp.  I recently used it without the headstrap, but with the pocket clip, in my left hip pocket, using it as a road illuminating headlamp when Skating with Fiona.  I just blasted it at the full 2000 lumen setting, and was surprised it never seemed to dim.  The airflow over the body, and the JP30 battery laughs at such a low load, that it barely gets warm.  With the Eve 35V the light at full output noticeably dims when kept at full output, and the light gets much warmer.

7 of the Ampace JP30's will be going into the cordless vacuum.   I pried apart the casing the other day to see how it was built, and it uses 7 2500mah Sunpower cells, which are rated at 20 or 25 amps CDR depending on which website you want to believe.  the vacuum struggles to do the whole house unless I am frugal with the motor's speed.  The JP30's can deliver their full 3000mah at more than 25 amps, so in theory I should be able to do the whole house at full power, instead of having to slow it down  to conserve the battery in order to be able to finish.

That will leave me 6 Ampace JP30's that need a home.  I was looking at my 2.0Ag Ridgid 18v battery, and opened it up, and am thoroughly impressed with the design and build quality.  I cannot see what cells are inside of it without ripping off the spot welds and sliding the cells out of the housing.
I am not sure I actually want to disassemble a fully functional 2.0 battery  just to make it into a stronger 3.0 battery, at this point anyway.  

   

Part of the reason I went with Ridgid was for the lifetime service agreement on the batteries and tools, but that decision was made before I got into esk8 and Spotwelding my own batteries.  There is a plug over a screw which is damaged when it is pried out, so the LSA is no longer valid anyway anymore. 
I'd only ever use it if the BMS failed anyway.

I was going to use the 5 cells in the Ridgid battery and install them into an empty 1.5 Ah Ryobi battery shell I have.  This battery failed several years ago. It used 1.5AH LG cells with a 22 amp CDR.  One of the 5 cells was below 2.0v when I opened it.  The other 4 have been in use in other things since, and have a solder blob button on them, and 2 are destroyed by spot welding experiments, but 2 others are still going.  they are down well below 1200mah though, and I have taken an angle grinder to their cans to remove all teh left over copper and steel spot weld experiments.  



The LG's  are from when the only way to get a high discharge 18650 was to have it be low capacity too, 1500 mah in this case.  For comparison the 3000 mah Ampace JP30 can provide 36 amps continuous without overheating, and has a 56 amp temperature limited rating.

My Ryobi leaf blower cant really take advantage of the JP30's super high discharge capability, but would be a good recipient for the  vacuum's Sunpower 2500mah 25 amp cells.

So I have more cells than devices to use them in.

My 22AH Universal AGM battery is now 6+ years old.  When new it was able to just barely start my van's engine by itself, and recently was still able to jumpstart a vehicle, but not instantly, it had to feed the vehicle's drained battery for 30 seconds before it could.

I have been gifted 19  lightly used Samsung 50E 21700 cells.  The lowest voltage one was used for spot welder testing, and was not ruined, but I have 18 more needing a task.

3s6p of Samsung 50E would yield a 30 amp hour capacity 58.8 amp continuous CDR 11.1v nominal, 12.6v max battery, which will be a fraction of the size and weight of my 22Ah AGM.  I have a 40 amp 3S BMS for it, actually 2 40 amp BMS', with balancing function, I can use.  So maybe two 3s3p batteries, as even though I don't live in a van anymore, I still think in 12 volts DC and am surrounded by 12v led lights and fans.

I also have 3 Eve 40PL's I can make a 3s1p battery with.

10 Bak 45D's I can make a 10s1p with, but already have a 10s1P of Eve 40Pl planned and half assembled.

The 10s2P of Bak45D I made in May have been performing wonderfully in my Esk8.  more range than I really use, so I only charge to 41v most fo the time, and return to 3.4+ volts per cell, and the battery does not get hot.

I wore out the 8x3" Pneumatic turf / lawn mower  on my front truck and replaced them with 9" x 2.5 inch tires which are made for a scooter, and are wobble free and balanced much nicer.  Their ride is smooth and quiet, and my hub motors now have 105mm sleeves which ride much nicer than 90mm, but I lose some torque. but not enough to be bummed.  I added a bunch of fiberglass to the skateboard deck to reinforce and reduce its flex.  it is running very well and Fiona and I will rarely do less than 10 miles a day and sometimes 15+ miles.

She is now deaf, and has turned 12 this month, and is not quite the ball chasing lunatic and cormorant hunter she  once was, but I intend to make every day with her count. She makes so many people smile when they see her rolling in her chariot.

[rvpopeye]

Nice chart !
Lots of builds with that new welder .... Wish I could just watch , lol.

Keep 'er rollin' and happy .

[sternwake]

I ordered some 0.07mm stainless steel,  thinking it would reduce the power required to achieve a good weld, but can tell no difference, and the 0.1mm SS is nicer to work with, and stronger.

I did remove 7 SunPower 2500mah 25 amp cdr cells from my vacuum battery, and installed 7 Ampace JP30  3000mah 36 amp cdr cells with 0.2mm copper under 0.07mm stainless.

The sunpower 25 amp rating is probably temperature limited, so is likely more of a max discharge rate. The Ampace JP30 can run the full 36 amps.continuous without exceeding 80c.  It has a 56 amp max rating, but have to end discharge before it hits 80C.

Seems the vacuum only charged the sunoower cells to 4.04 volts. Which is better for longevity, but leaves some run time on the table.

The JP30's were at 3.47v when I installeded them.  Vaccuum still said 100% though.

It fired up and when i cranked it to max power it was obviously spinning far faster than ever before.  

   

The stock series connections were 0.17mm nickel plated steel, So 0.2mm copper has about 10 times less resistance, and the cells themselves likely have 1/5 the resistance if the sunpowers.

Gonna install 5 Sunpower cells into a  formerly 1.5ah Ryobi battery tomorrow.
still have 6 Ampace JP30's needing a home.  5 for the 2.0ah Ridgid  battery probably. Make it a 3.0ah battery with far less sag.

It has 2000mah 30amp Lishen cells in it now, I think. Still works fine though.

[sternwake]

Just vacuumed the whole house at top speed 85%+ of the time.  I used to have to use 50% power only going to 75 and 100% on the stubborn rugs in order to be able to finish the whole house.

The spinning brush seems to benefit greatly from the added voltage of the JP30's

At first the SOC % display seemed to drop at the same rate, but then I realized I never ran it at top speed the whole time on the rugs before.

No doubt the BMS/ controller has to learn the new cell's capacity and voltage curve, as after I finished vacuuming everything It still said 12% remaining, but I wanted to run it down until it stopped on its own.  So I kept going  at 4/5th power, and it went down to 1%, and stayed there for another few minutes before shutting down.   

Often in the past it would still be displaying 12-18%, and would just shut down if I had it at full speed or 4/5th speed, and when I put it in the charging cradle said 0%.

The amount of crap picked up was considerably more than usual too, as would be expected when running at full power over the rugs, even though I vacuum nearly everyday, and certainly did yesterday.

These Ampace JP30 ( Jumbo Power) cells certainly live up to the hype.

This vacuum with its 7s1p battery just got way more powerful, and can run for significantly longer.

The Sunpower cells I removed claim to be 2500mah and 25 amp CDR, basically the same rating as the Samsung 25R, and which are found in a majority of power tool battery packs that claim 2.5 or 5.0 amp hours capacity. in 5s1p or 5s2p configurations.

Samsung might have great brand recognition, but in terms of tabless power cells, or high capacity energy cells, they have nothing that can compete with EVE, Molicel, Ampace, BAK, Tenpower, Reliance, and several others.  I hope they get on board soon or they will dwindle to irrelevance in terms of batteries.

If you want the most powerful 21700 available, you can preorder the EVE 50PL here, and it arrives on Friday, having just cleared customs on Monday.

https://diy500amp.com/products/eve-50pl-21700-battery

The Reliance RS50 is Nearly as powerful( in terms of voltage held under load) , and actually delivers more Wh of energy if Discharging to 2.5v.

https://diy500amp.com/products/reliance-...erformance.

Most of the 50PLs Nelvick ordered have been bought up by the Red Bull drone racing team, and the remaining stock is going fast.
 Another shipment is at least  40 days away.

The Reliance RS50 is  also almost sold out, and more at least 35 days out.

The Best High capacity 21700 Energy cell is likely the EVE 58E, and it has an impressive( for an energy cell) CDR of 16.7 amps.  These would be the best for long range Ebike packs where 4+ cells are in parallel.  I know a lot of Ebikes stuck with 18650's and suffer for it, as 21700's were the focus of cell development for the last several years, and 2 21700s in parallel can outperform 3 18650's in parallel and cost 30% less.

The Ampace JP30 is the current king of 18650's, at least until the EVE 30PL becomes more widely available, and they are pretty close in performance.

  Nelvick got them from a drone company who had to wash the Ampace logo from the cells in order to sell them to a third party. They are reprinted with LT19660, but I have a few cells where Ampace JP30 can still be read, as well as the CCC logo, which means they passed the Chinese compulsory certification. All cells sold in China and made after August 1 2024 have to have this Logo, and it is a strict safety standard, and a sign of a high quality and for now, a fresh cell.

https://diy500amp.com/products/ampace-jp...000mah-36a

[rvpopeye]

Just received a couple of those white boosters you linked....stay tuned for further developments. THX !

[sternwake]

The white booster seems a solid unit, but I don't know the amount of ripple. I saw a video on the Red 400 watt booster and the guy found lots of ripple, but then he also said the current control didn't work. His also seemed to get way hotter than mine boosting from 12vdc.



I installed 5 of the Sunpower cells in 5s1p Ryobi Shell which formerly housed the LG 1500mah 22 amp CDR cells. I used 0.2mm copper under 0.7mm Stainless steel sandwich for all series connections to and from BMS. It ran the leaf blower far longer than expected. In fact I ran out of debris to relocate, before it gave up.

I did not take pictures of the 2012 era Ryobi battery before disassembly years ago when I harvested the LG cells, and I had cut the balance wires a bit short, and had to replace them. I made a mistake as I welded SS tabs to the series connections, to solder the balance wires to, as solder does not stick to stainless. I had used low power to weld the SS balance strips to the SS sandwich, and they came off easily enough. So I welded 0.15mm pure nickel and soldered the balance leads to that easily enough.

The balance wires have little immobilization slots, but I suspect That newer Ryobi batteries have eliminated stranded wires.

The more I look at and study the Ridgid 2.0 AH battery, the more impressed I am with the design, and build quality. The cells and busbars, the PCB, everything is locked, secured, and protected. it would be very difficult to actually damage this battery unintentionally.

The Main + and - from the 1st and 5th Lishen battery, to the PCB, are where I see the most difficulty in installing the JP30's into this battery.
I'd like some solder wick. I think I am going to hold off for now, as there is nothing wrong with the 2000 mah Lishen cells, the battery works well as is.

The positive side strip has a big hole in it, a choke point, and is basically a fuse.

My quest for minimum voltage drop would eliminate this 'fuse.'

My 4 Makita batteries are 4 amp hour, probably Samsung cells. They were likely several years old when I got them a few years ago.

Thre are Kits for making 5s2p and 5s3p of 21700 cells for Makita. I think one of these in the leaf blower needs to be ordered, and I'd use reliance RS50, or Eve50PL and just have a lot more wattage on tap, and not have it cut out way before I am done.

I am interested in seeing the inside of the Stock Makita battery. See the design and build quality. No plans on replacing the cells, but perhaps do a manual balance of them. I see some come off the charger at higher voltage than others. and I read that Makita batteries do not have cell balancing, and when one cell falls way outside the others it bricks the battery and the BMS, but this info could be wrong or outdated.

[sternwake]

I keep meaning to drill and tap a heatsink to attach my backup white booster, for benchtop charging at higher rates, but I honestly have very little need to charge my esk8 faster than the 150 watts of my blue booster.

The BAK 10s2p capacity and range is big enough that I often don't even bother to charge it between rolling sessions, where before I could tell just by the throttle response  if i had charged the dmegc pack to 41v vs 42.

The AwithZ p20b spot welder has various bells and whistles, such as double and triple pulse, and adjustable interval between those pulses.
It has adjustable preheating, and an adjustable 'intermittent' between that preheating pulse and the first welding pulse.

I have been trying to determine the effect of changing these settings, as the instructions say nothing regarding them.
Last night I tried, and failed, as I am trying to use test cells that I had previously welded to, then dremelled off the remains of those welds.
The scratches left behind, and perhaps the softening of the cell's steel from the previous welds, throws any weld consistency out the window.
Very frustrating.
I have other cells on which I could test outside the previously welded areas, but I intend to actually assemble these 18 cells into functioning packs at some point.

I had done a few welds with all the bells and whistles neutered, to mimic potential abilities of welders without any bells or whistles, and there is something to be said for that, but that second pulse really does seem to allow a lesser gear, weld just as strongly.
Spot welding to cells is done, as soldering requires too much cell damaging heat to enter the cell, even with a professional using a big old iron which can do the task quickly.

Using the least amount of welding power as is possible to achieve a strong weld is the goal, and having 14.6kW available allows me to weld 0.35mm copper, which in itself is excessive, but 12v lead acid habits die hard, and I want minimal resistance and will use oversized conductors whenever possible.

That said, I think I want 0.25mm copper, possible nickel plated 0.25mm copper.
but I have a good amount of 0.1, 0.15, and 2.0mm copper.At the same time stacking 0.1 and 0.15mm copper to achieve 0.25mm copper is likely different in performance than a solid layer of 0.25mm.

So far, with this AwithZ welder, I have rebuilt my laptop battery with Eve 35v cells.  7000 mah  and 20 amp cdr vs the  highly degraded 4400 13.2cdr of the previous battery.  It works amazingly well.

I have installed 7 Ampace JP30's into the cordless vacuum, 3000 mah cells with a 56 amp CDR, versus Sunpower 2500mah cells with a 25 amp CDR.  I can basically vaccuum everything at full speed and still have battery left over now.  HUGE improvement in vacuum performance.

I took 5 of those Sunpower cells, and installed them into a 5s1P Ryobi battery, that used to have 1500mah LG cells with a 22 amp CDR.This battery now powers the leaf blower for nearly as long as a 5s2p stock 4.0ah ryobi battery. I dont know what 2000 mah cells are within that battery, and it is several years old.  The Sunpower cells are not bad cells, they are just nowhere near Ampace JP30's amazingly impressive performance.

My dad has an old Ryobi screwdriver, that has a single 18650 cell.  I dont use it much as it had very poor battery life and unimpressive torque.   I always had to use a hand tool to remove or final torque any screw when using this screwdriver.  Opening the casing on this cell carefully, with a flush cut japanese pull saw, was not too difficult, and I found a 1200mah 18650 Sanyo cell in there, rated at 10 amps.

I waffled over what cell to throw in there, as there is a 15 amp inline fuse, and why put a 56 amp rated battery in a device built around a 15 amp fuse?
Any 10 amp rated cell would be an improvement over a well degraded low performance(originally) cell.

But it got an Ampace JP30, and it can now drive a 4 inch deck screw through a 2x4 on low gear.  It wouldnt even try to do this before, it would just stall and squeal as soon as the threads started to dig.
I have 10 more BAK 45D.   I could build a 10s1P for my Esk8s.
I have 10 EVE 40PL's, already fishpapered and glued together for an Esk8 battery. 
 
I have 18  lightly used Samsung 50E.  not a great 21700 cell. 5000mah  with a 9.8 amp CDR, but 4 in parallel make for a 40 amp battery, So I am going to make a 3S4p 11.1v nominal, 12.6v max 40 amp battery.  I already have a 40 amp BMS with balancing function for such a battery, and it will outperform my old 22Ah 12v AGM, which was recently strong enough to jumpstart a chevy 350, although it took 40 seconds of feeding its battery first. 

I also have 3 extra EVE 40PL. These are 4000 mah cells, that test at 4100mah at 0,2C capable of a temperature limited 70 amps, and will not overheat at 40 amps continuous, so I could make a small 40 amp 11.1 nominal 'pocket sized' battery, that could basically help jumpstart a vehicle with a weak lead acid battery.

I also have 5 more Ampace JP30's that need a home.
  Installing them into a 5s1P Ridgid battery  casing is their likely home, however I am not quite sure how I want to attach the main + and - to the PCB, yet.I am not sure this BMS will allow the full performance of this cell to be realized, but the JP30 can deliver 3000mah at 30 amps, where the 2000 mah Lishen cells in there cannot deliver their 2000mah rating at half of that.

These Lishen cells will need a home once removed.  they have plenty of life left in them, the battery works quite well with them, and the Ain't broke dont fix it mindset is winning, so far, regarding this battery.
I also have some lesser New  Tenpower cells, and 2 DMEGC cells.

I made my first esk8 battery using  20 DMEGC-26E cells, 2600 mah, 15 amp CDR.  It  has at least 2K miles on it but now gets way too hot.  I intend to use it as a range extender pack, plugged into the charge port when both batteries are the same full charge voltage, but I have not needed extra range yet with the BAk battery.

The other Tenpower cells are just 2600, 2800, and 3200 mah rated and 6 to 10 amp CDR.  Nothing special and likely will end up in weaker flashlights.

Tenpower is a little known battery manufacturer, but has teamed up with Molicel, as very respected  cell manufacturer.   They have made the Tenpower 40XG, and recently Nelvick got these into Mooch's grubby paws, and should have them in his store in the near future..  At 100 amps, this cell initially has significantly less sag than even the mighty Eve 50PL, and delivers more wH before the temperature cut kicks in.

Molicel has been teasing the market with the release of several cells which will set new benchmarks in stored energy capacity and power delivery, but they recently had a fire in one of their Taiwanese manufacturing sights so their release will likely be delayed.

7000 mah cells with a 30 amp CDR is likely 6-12 months away and such a cell in an ebike would add some serious range.  Molicels are known for their longevity and consistency, and performance, So when they do start dropping these newer cells, prices of all the other cells which are now latest and greatest, should drop significantly. 

 Molicel released the P50B over a year ago, and it was the benchmark 21700 for a very  short while before tabless cells came out.  It can almost compete with tabless at high rates, capacity wise, but gets a lot hotter.  It has a very good cycle life, and the fastest advertised maximum charge rate of any cell at 5C(25 amps) , although this degrades capacity quickly.  Molicel has not released a cell since then, but has teased the market with a bunch of new cells which will likely set new benchmarks and hit the market within a short period of each other.

Interesting times to be a battery nerd. 
Shame that none of them are made on this side of the planet, and probably never will be.

[sternwake]

3S lithium ion at 3.6v nominal voltage range of 12.6 to 7.5v make such an arrangement a poor substitute for lead acid's range of 10.5- 15v+, and 4S is just too much at 10v- 16.8v

At no point should 3s lithium ion ever be exposed to charging  voltages above 12.6v.

4S Lifepo4 has a much better range for lead acid substitution at 10-14.6v. 
Lesser energy density but better safety than  nickel maganese colbalt.

This will be a 20AH 11.1v  nominal battery made with  lightly used Samsung 50E cells.
These cell rated at at 9.8 amps CDR, and 4900mah minimum capacity,  y no means impressive figures in tohe current marketplace, but cannot argue with free.
   

I am using a 6$ 40 amp BMS with balancing function.  
I am trying to decide how I want to attach it to the 3s4p  50E..

These BMS usually cut power when the lowest P group touches 2.8v,  but there s so little energy below this voltage that is fine with me.

Powering leds, their max brightness will be limited at 11.1v and below, as will maximum fan speed, but  is not a huge  concern as I rarely run either  at max output anyway.

These 12 21700 cells are a fraction of the weight and size of my 22AH AGM battery.  I could fit it in my cargo short's pocket if required.

My 3s1p EVE 40PL(tablesz power cell)  will be getting same  40 amp BMS. These cells can output 40amps.continuous without overheating, and can handle 70amos, limit temperature to below 80C.

Mooch has tested them at 100amps continuous, and they handle it far better than all but about 4 of the very best power cells.

I will likely add a heatsink to the BMS mosfets.  They look to be poorly matched, and that means their resistances will vary, with some taking far more.of the  load than others, getting far hotter.

Ill likely never use either 3s 40amp  BMS near their limits,  but one needs to know those  limits and stay under them, or only flirt with them briefly.

[sternwake]

There are so many cylindrical NMC 3.6v nominal cells in the 18650 and 21700 formats out that one can get easily confused as to which are power cells and which are energy cells.

Mooch tests these cells and sees how they stack up against their claims.

He has these Handy charts, which are not locked behind the usual patreon paywall.

https://www.patreon.com/posts/18650-21700-e-138053835

His E scores are the watt hours delivered down to 2.8v. So higher is better.

The charts do not account for cycle life specs, or actual cycle life. The manufacturers cycle life specs are not a universal standard, and they are basically minimum expected cycles accumulated before reaching 60% or 80% of their original capacity. They are not comparable between manufacturers and often not even within a manufacturer, as no reason to test a power cell at energy cell rates and such.

The charts also do not account for the temperature rise of the cells, and if these cells are used in packs wrapped in fishpaper and heatshrink, the inner cells can be significantly hotter than exterior cells, and exceeed their 60 or 80C limits. Most will have no issues when run below their CDR, but it is something to be aware of.

I chose my BAK45D not as the coolest running Tabless cell, as several run cooler, but I am not pushing them at their limits with my ESC and motors.

I did not choose them as the longest running cell (My ESC has a hard cutoff at 3.2v per cell, not 2.8v as in the charts in the link.)

So if I was seeking ultimate range from 10S2P there would have been slightly better choices than the BAK 45D, at the time I ordered them, but it was the combination of Price and capacity and temperature gain which had me choose the BAK 45D, and I lucked out as Nelvick was stocking the A04 version, not the A02 version, which does not test quite as well.

If I were to build a 10S2P today, I'd likely choose the Reliance RS50, and If I were feeling a bit richer I would choose the EVE 50PL, but I doubt I'd be able to tell a difference between the two underfoot. The perform very similarly, and their cycle lifes are not yet known in actual use. and the manufacturer specs cant be used to compare them.

The cooler running cell should last longer just from not getting as hot as often in use, but that is no Guarantee it actually will.
But charging to only 4.1volts per cell instead of 4.2 can double the cycles and not really affect range all that much.
Likewise discharging to 3.2 rather than 2.5v will also greatly increase longevity.

I am still amazed just how much better these cells are than lead acid. That 20 BAK 45D under my feet can push Fiona and I 10 miles at 20MPH.

I have not yet finished my 3s4P of Samsung50E, but was thinking about ways to test its capacity. These cells were 'lightly used' before I got them.

I was rechecking the minimum input voltage of the 3 different Vboosters I use to charge my Esk8, and the Blue and white are 10v minimum, but the least favorite red is 8.5v.
I am not sure if feeding them less than their rated minimum voltage just decreases their output or if it damages them.

I still have range brain, even though I rarely use the full capacity of my BAK45D 10s2P.
I think about the What Ifs, and ways I can range extend and ways to charge off grid.

This 20AH Samsung50E 3s4P should be 216 watt hours.

My BAK 10s2P is 324 watt hours.

My premade 7s2P in my portable charger is 103.7 watt hours, and I can plug a 7s1P into its charge port and gain another supposed 55.4wh.

I will have a 6S1P 50E at 108Wh

I have the 10S2P DMEGC pack at 187 watt hours
I will h build a 10S1P BAK 45D at 162wh.

The 10S batteries should all be in parallael at the same voltage. cant use a booster with them to charge the same nominal voltage pack.

I could add a second XT90s direct feed to the ESC and just pull the loopkey, disconnecting the battery in the enclosure and plug a fully charged external 10S battery, to extend range.

Fiona and I did extend our range crossing one of the bridges to the key the other day, but returned home with battery to spare.

[rvpopeye]

Range brain infects me too ! Arrrrrgh , need a crew that rows faster and longer...

I'm not at the level you're testing things as all I have is the factory batt pack so far . (I have ordered another for now though , lol ) The current plan is just don't let the pack go below 20%, ever. (1 of 5 bars on the display)
It's hard to decide when to turn around now (3 bars?), the extra pack will let me run it down to 20% and THEN turn around ! Not sure of the actual voltage levels at each "bar" but am trying to check as I notice the bar level changing.
I have been trying different speeds to determine the resulting range and going 10 mph vs 20 mph increases range a LOT.. not to mention wind chills are more comfy on my old arthritic extremities ! (42* yesterday and 48* is today's wake up temp, highs still making it to the 60s and maybe 70 this weekend).

Of course I have been following your efforts so other plans are forming as well.. So far I have a couple of B-boosters ...

A year from now we will probably be in a solid state or maybe aluminum ion or sodium world . (it's all vaporware for now) I like the 5 minute charge and greatly increased range but the devil is in the details , we'll see I guess.

Hold yer course , keep your crew happy .