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

[sternwake]

i am a bit bummed, as it was a viable BSW for single 0.15 strips, at 85%+ power. It likely just needed a second Lipo battery.

The Deka gc2 agms just overwhelmed it, and i knew it was a possibility, but the ratatatta sparking hole drilling was, alarming.

The mosfets actually look okay, it looks like the solder at their bases just exploded, and there is that distinctive smell. I didnt need to bust out and check for continuity across mosfets, ut did and beep beep, shorted.

I saw there was a lack of solder between buss bar and the mosfet legs, but it was too tight an area, for me, to add more.

The purple BSW supposedly has larger infineon Mosfets rated at 300 amps each.

I really dont need to weld dual 0.15strips simultaneously, but was disappointed it had to be turned so high on level 3 for just one 0.15mm strip. It is probably fine for 0.10 or 0.12.

Anyway, wasted some time, and 21$ and didnt really learn anything

The purple one is about the same price,

[sternwake]

A late night full throttle cruise on the 538 watt skate, revealed some weirdness, that had me dreading the long push home, but a coast and resume throttle had it respond again with less torque and top speed.

Hub motors did not seem too hot and esc heatsinks below plastic housing did not seem to be radiating excessive amounts of heat, so perbaps it was the first time i waz at top speed and full throttle when some battery voltage threshold was passed and the esc had a transistor fart.

Or maybe some stray 2.4ghz signal interference.

But i now have even less faith in the reliability of the board.

I ordered a 10s Puaida branded ESC. The remote has a digital odometer and speedometer, , separate power and brake settings, field oriented motor ontrol, and hopefully the brakes are not dangerously erratic.

There is a slowboat 6s,7s,10s ESC en route too, so both skates will likely be getting 10s Batteries made for them but then I will have no use for existing functional chinese assembled 7s baTteries.

[Scott7022]

Perhaps a wired connection? Trippin along at 15mph on good payment doing a light back and forth and have an errant 2.4 ghz signal mash the brake channel. This would scare the shit out of me. Like hanging balls for mayhem Murphy to kick.

Just a thought. Perhaps a 5.? Signal. Shorter less interference. IDK just spitballing


Sent from my iPhone using Tapatalk

[sternwake]

The brakes dont apply at random, they are just bizarrely jerky and inconsistent when I do apply them, most of the time, sometimes, they are nice and linear.

Last nights weirdness was just an abrupt power loss. I let off throttle, coasted for a bit, tried the throttle again, and it responded with reduced too speed and torque.

Coukd have been stray 2.4ghz signals, i cant change frequency.
Inhave another hand remote from 38$ parts skate which might pair with the controller, but the pairing instructions are chringrish and vary wildly,

But this ESC has been disappointing since day one.

I did organize the wiring inside so the antenna was not wrapped around and parallel to motor phase or sense wires, but noticed zero difference in behavior.

The puaida ESC controller i ordered, the order was cancelled, and the seller apologized, said e bay was charging him a promotion fee he didnt sign up for, bla bla bla so incancelled it please reorder....

The new item number he forwarded has no hits
he said same price. no similar product listing was anywhere close to same price.

I said Eff it, and towed kayak t o lUnch and paddled a few miles. Radar sign spiked to 14phh briefly.

The water temp dropped several degrees, and is much clearer,.found a few new tight paths through mangrove tunnels, saw a lot of cool birds.

Probably just order new ESC directly from Puaida for a few bucks more.

[sternwake]

The ebay ESC seller sent me a flurry of emails,.mostly about how he/she is a victim of ebay and please reorder.

Histrionics and drama makes me disgusted and contemptuous of all humanity, to a higher degree than most all other ever increasing in frequency, and degree, of disgusting aspects of humanity.

I ended the exchange by saying all you had to do was link the new product listing and i woukd have reordered, but you sent me an invalid item number , which i was forced to copy and paste and search, only to find it non existent, and nowhere.else could i find it.
The ship has sailed, good luck.

Not sure what ebay was charging them for' promoting ' their listing, but if they just ate it and did not cancel the order.....

If it were not promoted i would not have seen it being 5$ less than any other listing, and that 5$ was ultimately not worth my time.

Been doing some reading on ebike forums about battery building, after searching for nickel strip ampacity.
Apparently 0.15 mm nickel strip at 10mm wide is equivalent to 22awg of copper and should not really pass more than 7 amps continuously, or.it will begin heaTing excessively.

copper is nearly impossibke.to spot weld on its own, but nickel coated coooer can, and the e bike anx e motkrcy le guys are apparently sucessfully stacking copper qwith nickle strips.on top to get the series connectcts resistance low

Im not going to be approaching Emotorcycle levels of dischaRge, and wi likely not even reach 50% of what the cells i ordered are capable of delivering.

But minimizing resistance is almost always a good thing, and while my hub motors cant ask for more tha 538 wattS AT ~25V, i intend to go to 36 volts, and perhaos they then can draw the 700 watts they claim.

Also, the crappy QC on ths imprecise hub motor has me shopping for other hub motors, and there are some with 540 watt ratings each, 1080 watts total, so i want my series interconnects to be able to handle tha much continuously, at the minimum, even though continuous will never happen in Florida unlezs i want to find the tallest bridge around and cross it over and over until something melts.

Towing the laden Fionayak is however exeeding the Load rating oc the esc, by at least 80lbs.

Good thing it is only a mile there and back, but that 2 miles uses at least half the 4.0ah battery capacity, and I've no idea what the individual ell rating is. I meazurex 538 watts acellerating just me to 17mph ish, but towing the Fyak i neex a slight downbill and tailwind to just barely hjt 14mph, so i got to assume 538 watts nearly continuous for the mile there, and back.

Something i did not yet confirm, is that going slower seems to use just as much battery, and the damn twitchy ESC cant just keep an 8 out of ten throttle but seems to jump from 5 to 10 averaging about 8.

[sternwake]

One problem with watching youtube videos on a smart TV, versus a laptop, is no comments section, which often has valuable info.

The endless sphere forum has a thread on the cheapo spot welders i am employing, and i learned one way to help prevent magic mosfet smoke ejection, possible at least on the red one, is to power the Mosfet driver circuit with a separate 12v battery, that is not subject to the the mosfet cooking voltage drop of a brief 300amp spotwelding direct short.

Which I can easiily pull off.

I'm not sure if the purple one would benefit similarly.

Welding to the center of the negaTive electrode is to be avoided especially so on Molicel p42a, and a split in the nickel strip with welder pens on either side, helps the spot welding current run through cell cap, rather than just shoot sideways through the nickel strip, and therefor shorter pulse times can be as effective as longer when done with the split/slot in the strip.

With Nickel being 4 times less conductive than copper, jt is a source of baTtery heating at higher currents, and heat kills Batteries.

The copper nickel strip sandwich method is becoming more appealing to me, and the purple BSW should have enough power to pull it off.

A lot of nickel strip sold, is really nickel plated steel, and in a copper strip sammich, the plated steel cap works better than pure nickel strip cap.

Apparently the power tool batteries use copper strips for high amp serial connections, sometimes nickel plated copper, but they use a la$er spot welder when assembling those.

Pure copper by itself is apparently nearly impossible to spot weld by resistance welding.

My Eskates are not.going to require huge currents from the battery, and i dont need to go nutty trying to reduce resistance, but why stop now?

Looks like 34 gauge copper sheet is 0.15mm.

[sternwake]

One thing I had never considered when spot welding cylindrical battery -ve terminals, is the weld heat will burn the electrolyte inside, immediately opposite the welds, which introduces impurities which then increases self discharge.

Tesla uses some sort of super high frequency vibrational welding method that prevents this occurrence and each cell positive uses a short length of fuse wire between cell and buss.
It adds resistance but with so many cells in parallel it supposedly makes no difference but increases safety.

My 10 Molicel p42a 2!700's and 20 dmegc 18650s are out for delivery., But im not ready to staRt assembling a pack yet. I dont have a 10S BMS, Nor a 42volt power supply, nor a 10s enclosure, nor any 34 gauge copper for the desired nickel copper sandwich, wbich my cheaPo BSWs might not be able to weld properly anyway.

Also my test welding cell has a hole nearly blown through it from when i smoked the black BSW.
Say i were to get the pen pressure and MS duration diialed in perfectly on one cell, well the negative and positive ends require different settings, as will different cells.
the cell ns are usually nickel plated steel, 0.3MM Thick, but some are aluminum.

The electrode tips change shape slightly with each weld, and holding them at a slightly different angle changes the contact patch shape and pressure which then changes the weld.

So many variables. Trying to achieve precision and repeatability with imprecise tools and little experience with something which can burn down the house, is why it makes sense to have a pro do it and why so many sites discourage DIY battery packs.


My 3s holder with leafaprings and the one time matched LG cells pulled from failed ryobi battery pack, shows alarming cell disparity after just a few cycles. The BMS cant do any bLancing, it just shuts down if one cell gets too low or too high.

It has done so numerous times. When charging i will see 12.56v and 0.0 amps earlier than expected and disconnect charger, then battery voltage falls to 11.97. One cell had exceeded 4.25v for long enough to trip the bms and the other cells were nowhere close. it is worse when charging at higher rates.

same with discharge. it disconnectsoad and one cell is 3.06 and the other 2 are 3.4x. its always the cell.in the middle too, whichever one of the three cells i put there.

can thjs all be due to the resistance of leaf springs or 10 year old cells or some combo of those and other factors i cant yet say.

I do have 6 2000 mH cells from the failed 7s battery from 38$esk8, and more.of the same 3s bms, so i guess i need to gain some more experience and data with those see if the spot welding them is far far better than leafspring holder.

The 4.0 ah 7s2p pack in the 538sk8, is kind of pathetic in speed and torque once it falls to 2 (of 4) bars but not as soon as it goes from three to 2.
I had e perienced saMe weirdness, on saturday ,kick in , where it just staRts losing speed and i got to get off throttle and back on it just to keep going at reduced speed. I Dont think it coukd tow the Fyak once it does this, and Im returning to base at 2 bars, so i might just be making it back, as is. with a battery that has less than 30 cycles on its 14 unknown 18650 cells

I suspect the battery BMS is bypassed for discharge, so either the ESC is throttling back from lowering battery voltage, or too much heat in ESC. i dont think my motor sensor wires include a thermocouple.

I could start building a 7s 2p 5.2ah pack with the 2$ Dmegc cells, later today, and not have to build a new enclosure, but i am finding i am almost always at full throttle when doing cobweb clearing jaunts, and only way to get more speed is with a 10s battery, unless the shitty ESC is limiting max rpm which seems likely, as jt accellerates past its too speed then lowers back to it.

I dont think 10 21700s will fit innthe enclosure.

The one new ESC which can be used with 6s,7s, or 10s did just clear customs.
the other new ESC which is 10s only, well no email saying it even shipped yet, from somewhere inside USA.

Indecision mode.

The purple spot welder is in the wang state, it might arrive tomorrow.

[sternwake]

All 20 DMEGC -26E cells were 3.599volts plus, but not minus.0.001v

The 10 Molicel INR 21700P42a were mostly 3.536v with one at 3.486, and one at 3.545.

Molicels are made in Taiwan, DMEGCs made in China.

Liion wholesale packaged them very well. Nothing coukd move around within the properly sized box.

The Molicels came within their own individual cardboard boxes, the Dmegs cane 2 per hinged plastic box.



I bought extra cell top insulators from them too. not sure why they often are called fishpaper, but the ones i bought on ebay were peeling off the paper backing and stuck to the packaging, and are a bjt thicker and more rough cardboard paperlike than the ones from Liion wholesale, which are more white plasticy, but in perfect condition.

The cell tops have one insulating ring under the heatshrink, but all the battery builders say to add more protection to further reduce the possibility of a direct short.

basically the nickel strios, across two cells is a few fractions of a mm of being a direct short. Shoukd an imoact or chafing oush nickel strio through the heatshrink and ring, then fire and boom, so at 5 cents each additional ring, its just stupid not to.

[sternwake]

Wishing I did not properly recycle the dead LG 18650 pulled from the failed Ryobi, as i don't have a cell for practice welds unless i sacrifice an OK cell.

The dual battery trick for the spot welder seems so simple, in theory, one strong battery for the actual spot weld, one just to open and close the current gates.

To accomplish this both battery - are tied to BSW negative but red welding pen goes to strong battery instead of bsw input/output which are circutly the same. The second battery for gate opening positive goes to BSW +.

Luca's recommended 'gate decoupling modification' are all about insuring the gate trigger voltage does not drop too low during the weld, and on the Purple bsw requirez a capacitor resistor and a diode and the ability to solder to a 0.75mm trace on the circuit board.

He sets up and oscilliscope to measure the microseconds for the gates to fully open and close, wbich revalss the purple is 4 times faster than the red on both rise and fall times, and the purples infineon MOSFETs are supposedly far better tha those used on ole red.

But apparently if the mosfets are not reasonably well matched, then you are kinda screwed as the lowest resistance one will take a majority of the load and eject the magic smoke.

The purple one has room for 5 more mosfets on the bottom of circuit board, to share the load, but no point in adding more unless they are matched to original 5, which means ordering 10 matched mosfets, which with shipping will likely cost 2x as much as the spot welder itself.

So maybe just ordering a second purple for backup purposes is the call.

The 3S 5.2ah 80C lipo battery i ordered, has two plugs, an xt 60 on 12 awg leads, and a 4 pin connector, not sure what it is called, that is designed for charging and cell balancing via a 'hobby' charger.


I was using my dmm leads to check individuLcell voltage, but the test leads are basicaLly 0.5mm from a dead short, which would likely weld the test leads tigether frhing it and shorting the cells and cause them to catch fire. One can put negative on the one end, and measure 4.01 on cell 1, 8.02 on cell2, 12.03 on cell three. easy peasy but when they are at ~3.876, doing the math to figure out individuL cell voltage, is not as easy.

There is this nice little cheap device which will display voltage of uoto 7cells, and there is a blue 8 cell model too for a few bucks more

https://www.ebay.com/itm/141854296686

10bucks. sold!

The Lipo batteries are the most dangerous litbium chemistry with their volatile huge energy density and suoer low resistance.

And they have no BMS. they require the bobby charger to keep them in balance, or a human BMS with the tools and temerity to keep the cells close to each other.

The directions my ZEEE lipo battery came with, and the consensus on Lipos say to not store full charged, even for a week as it will destroy it, so unlearning lead acid habits is paramount.

Ill assume the lipos in phones and such are not ever brought upto 4.2v, but if they are, it explains why those who keep their phone plugged in all the time, can have very short battery lives.

I got to find out what the lipo balance charge connector is called, so i can more safely balance the 3 cells when they begin to drift, as purchasing a hobby charger just for it, is unlikely in the extreme, when I can use my CCCV xl4015 buckers which i employ on so many other tbings.

The comparatively inexpensive Zee lipo battery i have, with the 12 awg leads and xt60 connector, well the higher end lipos use 10awg. My xt60 connector was the hottest part of circuit when practice spot welding, and i susoect a poor solder joint under heatshrink.

My lipo has a plastic cover which will split apart once the pouch cells inevitable swell up. Id like to get 10awg to the buss instead of 12awg, and use an Xt90 antispark connector, but might just carefully splice 10awg and an xt90 into the existing 12 awg.

Kind of crazy this little LIPO battery can so easily staRt my 3!8 on its own.
I did staRt it with the 18amp hour mightymax agm battery, once.

pretty sure the lithium jump starter packs use these LIPO pouch cells.

I am wondering if they have a bms or a way to prevent charging them to 4.2v, but if lipos are as volatile as they apparsntly are, it seems these litbium jump starters would be splitting the pack open and or catching fire far more often than we hear about.

Anyway the purple BSW should arrive today.
Wish i had a fully discharged junk practice 18650 cell, but llenty of other stuff to do anyway, first.

[sternwake]

So, i  used a razor to cut the sticker over the Zeee's  cover, on one side, and it looked like it had no desire to easily open and allow me to out 200c silicone 10awg leads directly to the cell buss.

So i cut a 2" long Pigtail off with provided xt60 connector, cut off the heatshrink, and the solder joint was far from perfect, but ive seen worse.

What i did notice was, in comparison to the Amass  XT60s i bought, is the yellow housing was slightly different color, and the contacts were not gold plated but plain brass.

So  The Zee Lipo battery came with generic xt 60s only adequately soldered with 12 awg.
i had a closer look at the 38$esk8 xt 60 and it was obviouslyy generic too

   

So I put an xt 90s antispark on the Lipo, and  it should have far less resistance than an actual Amass XT60, much less than generic.

I also wired up the dual battery leads for the red BSW, and put a 10awg Xt 90s antispark  connector on My 22ah agm,  next to dual 8awg 45amo anderson powerpoles to drive the optocoupler that drives the  mosfets.

Then the mail came, and the purple bsw. 
somehow i managed to order the one without an enclosure or leads, but woukd have used the leads from old red anyway,  bjt do miss the acrylic enclosyre.

When checking to see what i ordered,I i saw there was a slightly different purple version, when one spies the circuit board closely.

Not sure if my Mosfets are actually infineon.
Ive not hooked it up yet, nor tested old red with the dual battery feed.

I have a two for 10$ cheaPo led headlight intowhich i installed a larger capacity 18650, but i soldered it, and i think it  drawss the cell below 2.5v too, if i allow it to dim.
so this battery is likely the least safe 18650 I own, and i might frInnit fully and use it as my BSW test cell.

It should really get a protectexd cell withi  it, if it  indeed draws the cell below 2.7v.

I did notice the last time i recharged it from dim, it took far less MAH thaN the last time i measured using the same meter.

my new regular inline wattmeter which doez not save peak amos or watts, does show ah to three decimals, opposed to mynolder wattmeters which have two decimals.

inline they agreed on amp voltage and amlerGe, but did not agree on amp hours consumed.

I dont know which one to believe, and will have to test.  I know the timer on old wms is off and the kwh figure is way off, but using a regukar  clock and a steady current they checked out ok when i got them.

But they never seem to register as much ah delivered or returned as id expect, so wbo knows.