That darn "Spot Weld WALL" !

[Nashville Kat]

I occasionally have explored the notion of building my own pack- probably with a case for that purpose- or repacking my own with new cells when the day comes it won't perform. I'm learning things all the time- but seldom happy with the conclusions I'm forced to reach then.

The latest round this past week started when I went pricing 18650 batteries and realized that I could replace all the cells in my 36v 12ah battery pack- for about $50 or maybe slightly more. NO, not just replace- replace with cells likely of HIGHER AMPERAGE (and I say likely because I've never had mine apart to confirm the configuration of the cells already in there- the number and /or the ah.) But chances are, maybe 2 t 3 TIMES the AMPS HIGHER and quite cheaply-

But what I see now after some study of cases and cell holders and BMS- of which I'm CLUELESS otherwise!- and nickel strip conductors for top and bottom- and with only a still quite vague understanding of series and parallel circuits- I find that both the marketing and the final need to apparently SPOT WELD the nickel conductor to the batteries- equipment and knowledge I don't posses and probably WON'T in my mid-60's to be a final end of my hopeful thoughts- I'm beginning to doubt I'll ever be able to rebuild the case I already bought whole and have used for a season- although the battery itself is now two years old- I couldn't get a longer ride together at the end of the Hurricane Window here in Jacksonville to sufficiently test the mileage the cells may or may not achieve. For most of my 5 or 6 miles rides- the battery still performs well.

Also discovered I can get fairly high amp 18650 cells that are 4.2 V and not 3.7- and totally just wondering how this might factor into using my 36v wheel hub and BMS of the battery I have- if I COULD repack it which I probably CAN'T.

Anyway- if they'd ever make a case and system where we could easily exchange cells as we can say in a flashlight (OK maybe a little bit harder than that) but easily without tearing it all apart and requiring spot welding, them I suppose the Big Oil Corporate Monopoly would just raise the cost of bulk 18650 cell,s which is quite tempting otherwise, and which has me exploring every now and then only to realize that spot welding seems currently required.

Phooey. I've used my 50cc China girl a few times in retaliation, but getting too old for that.

 

[Nashville Kat]

For my 36 volt hub, I think my 18650 magic number then is 10- 10 cells at 3.7 multiplied by series wiring gives me the 37 volts - at full charge- is this correct?

What if I put in cells of 4.2 volts- in the same configuration that would boost the power to 42 volts- would the hub handle it? probably- the BMS? less likely I'm guessing.

So I have to get groups of 10 18650 wired then together in parallel to multiply the ah, for range and amp hours of discharge

I've been looking then at other plastic holders that hold 18650- presumably that may be easier to load and reload- and the numbers usually DON'T add up to 10- they hold one (lots of wires then!) or two still many to lash together or 4 cells (at 14.8 v output total), but never 5 or ten cell holders-

They might be lashed together by plastic zips that could be replaced with the cells (???) but the issue of recharging isn't solved and they'd scarcely be practical to remove and charge 2 or 4 at a time, although theoretically possible I guess, it's a great deal to go through between every ride.

there are studier plastic holders that terminate in metal rods that still have to be soldered together somehow- has anyone gone this route at al? and then still my own confusion about adding a BMS for charging, etc.

One of my main motivations, beyond the insurmountable issues, is that I'd love to build a fairly smaller and lighter short distance battery- say 10 miles instead of 20, or TWO packs of them to rotate.

Anyway- if you are looing to make some money, for a young industrial minded person- especially if you have a SPOT WELDER- bike battery cases can be had cheaply these days and there might be money to make assembling and selling a better battery than most available now. Just use higher amp cells- I think the average battery now is probably packed with cells under 5000 mah, but I could be wrong. Or even simply repacking battery packs if you have the skill.

 

[Nashville Kat]

PS- just one more thing- if you're deciding between a front or rear hub- the one thing I regret about my front hub is that it makes the bike HARDER to throw into the back of my hatchback- it would much better fit if I could quick release the front wheel and put the rest in- and a smaller 26 wheel and frame might fit in better too, but not likely to roll as well as my GT step through with 700c x 28 mm wide tires.. I don't usually want to take it in the car, but occasionally and as I used to say back in the day "You can't ever really break down when you have a bike in your car". Happy motoring.

 

[junglepig]

A couple of notes, (and I'll admit I did not read your entire posts carefully), but, there is no difference in what you are calling 4.2V vs 3.7V li-ion cells. They are the same. 3.7V is the "nominal" or midrange voltage, while 4.2V is the full charge. Also, if you are looking at inexpensive 18650 cells that claim to have capacities in excess of about 3000 mAh, it is a lie. The values are grossly inflated, with each seller trying to one-up the next. 10000mAh cells are advertised, and you are lucky if they are even 1500 mAh.
I hope I don't regret not reading your post closer, and I hope this helps. I just need to get to sleep rn, lol.

 

[Nashville Kat]

hmmm.... where did you get this information?

These are some I looked at, advertised as Japanese manufacture
https://www.ebay.com/itm/50pcs-18650-3-7V-10000mAh-Li-ion-Rechargeable-White-Battery-For-Flashlight-USA/401513858975?_trkparms=aid=333200&algo=COMP.MBE&ao=1&asc=55164&meid=cea2d46be8724a998c511e354be8afde&pid=100752&rk=2&rkt=12&mehot=pp&sd=123045447095&itm=401513858975&_trksid=p2047675.c100752.m1982

Here are some advertised as 42 v and 6000mAh
https://www.ebay.com/itm/60x-4-2V-1...Q:sc:USPSPriorityFlatRateEnvelope!32254!US!-1

The picture is another product available- notice how the cells are snug in each others round crevices and not aligned perpendicular side to side like some of the interlocking plastic holders- apparently these would need some kind of perimeter binding or case to hold them together.

 

[Nashville Kat]

It's really not clear how much these cases on ebay are complete or in need of other components (other than the cells). This one has some "guts, but these typically never fully describe what is included and what still may be needed, in true Corporate Oil Rat fashion I think.

.


Again I think the nickel strips are missing and it all invariably leads to spot welding. What we need is a case that hinges and clamps down tight with the nickel all ready in place, then we'd simply only have to load the cells. As these must generally be reversed top to bottom in some rows to achieve the correct series and parallel configurations, perhaps these could be color coordinated to indicate which way the cells go. Some enterprising American company could really slam dunk the need for the china connections if it could buck the Big Oil Monopoly and supply such a case in this time of polar meltdowns. This might eventually lead to battery packs for all kinds of electric transport applications.

 

[junglepig]

The 18650 cells you link to are total hoaxes. There is no such thing as a 6000 or 10000 mAh 18650 li-ion cell. These will run in your flashlight for a little while, but you'd be disappointed. If you weigh them, they are probably 20g or so, vs the normal 44g or so for a real cell. (Sometime they do fill them with sand to make them weigh more to try to fool buyers.) Usually they are 500-1000 mAh. They will supply neither the current, nor the capacity to satisfactorily operate in an e-bike battery. Sorry. Yes it is false advertising. Lying. Dirty. And totally unregulated.

You can buy good real cells and make an affordable battery. The spot welding is not difficult, and these forms make it easier to arrange the battery sometimes. But the non-spot-welded construction systems do not stand up to real world use very well. You really don't want weak electrical (or mechanical) connections between the cells.
If you are up to learning to build batteries, even having to buy a spot welder, you will come out ahead building your own.
That said, you must know what you're doing and work very carefully. One wrong connection and you can create a massively energetic short circuit situation.

 

[junglepig]

Just one more point. You suggest that it would be nice to just be able to swap new cells in when they go bad.
The trouble is the fire hazard danger. You don't have a problem if you install your batteries wrong in a childs toy, e.g.
The connections are usually series.
But if you build rows of parallel contacts (Like would be part of any bike battery, and someone puts a cell in backward, the smoke comes out in a hurry, and very hot!.
I have some little USB powerbanks that take 6 or 8 cells in parallel. I'm careful, but if anyone not technically up to speed tried to mess with the cells, they could put one in backward, or put cells in that were not equally charged and cause a big problem.
This issue would be worse in a big bike battery.
Most human apes just aren't going to be able to handle this safely.

I'm not saying these issues couldn't be solved with some engineering, but I'm just pointing out why is isn't quite as simple as you'd like.
The current draw through the connections can be massive too. Spot welding is really a good construction technique for these for both safety and functionality.

 

[Nashville Kat]

OK- given this, I'm still wondering just how you seem to have come across what seems 'inside" knowledge. You are basically calling a whole marketing interest worldwide a sham. Considering petroleum and how they weight and overpower cars to sell it- not to mention encourage our entire culture to drive like car razy and destroy our own transport as soon as we can, even as our homes go up in flames and more often float down the river- your claims may or may not be far fetched. I just wonder where and how you gained this inside track.

And also in my own defense, in the end, they're just batteries- I think they COULD be made easier to replace, I just have a feeling that Big Oil and Pro motorsports are sandbagging this- the way they've had a negative hand in cycling for all the more than 50 years I've known it well.

It's interesting that despite the dangers you've eloquently stated- and I've seen some reports about exploding recharge batteries in the past few years- the electric bike industry continues- like gas bikes- to encourage and tilt more toward more speed and power- more voltage batteries and higher watt motors to go much much faster and ultimately demand much heavier bikes and wheels, and MORE and MORE CELLS- IT invariably all becomes more of a motorcycle than a quick trip to the store or around an area. The price also just rises and so the simple and cheaper transport needs are pushed aside in favor of new toys for speed demon brats it often seems.

 

[Nashville Kat]

I'm not meaning to be hostile, merely wondering if you've studied or career in electronics or what you may have read where- short of constantly monitoring cells- and I've seen people on youtube who've built their own batteries who measure the charges of the cells etc. It does strike me odd that Corporate could sell batteries of bogus amperage hours. And a disappointment if you are right- But at least- they're still inexpensive except for the problems of use- that's the gripe of this thead!

 

[junglepig]

I'm not meaning to be hostile, merely wondering if you've studied or career in electronics or what you may have read where- short of constantly monitoring cells- and I've seen people on youtube who've built their own batteries who measure the charges of the cells etc. It does strike me odd that Corporate could sell batteries of bogus amperage hours. And a disappointment if you are right- But at least- they're still inexpensive except for the problems of use- that's the gripe of this thead!

I have a lot of past experience in hobby R/C and robotics. I'm a chemical and control systems engineer with BS ChE, and I've carefully measured the capacity of many cells and batteries. It isn't insider knowledge at all. Just personal study, testing, and experience.

I think Li-ion batteries are great, and not dangerous if well managed. Their energy density just poses some unexpected hazards for those who are used to thinking of batteries in terms of alkaline AA, C, or D cells. I've triggered thermal runaway in lipo cells with an accidental pin prick exposing the cell to oxygen, and off she goes. But a well built battery with a good BMS is very safe for consumers.

As far as the capacity of the bogus cells, you don't need to take my word for it. You can buy some cells and test them yourself. But the very best capacity 18650s on the market today are about 3500 mAh. Look and see what you can buy from a leading edge manufacturer like Samsung. The eBay cells boasting more are kinda like our "80cc" bike engines that aren't. Only they've gotten ridiculous with their numbers.

If you'd rather take a more passive approach, there are many you tubers that test and compare 18650 cells, weigh them, tear them down, etc. It's youtube though, so some of them know what they're talking about and doing, and others really don't.

I didn't think you sounded hostile at all, btw, just healthily skeptical. I've been down the road you are on too, looking for inexpensive high capacity cells. The best source I've found is NOS replacement batteries for laptops. Not rebuilt China ones, but never used originals from HP or Toshiba that have high quality cells. They're usually discharged so low that the internal BMS will not allow them to charge. Usually you can find these for about $10 for a 6-cell battery. Take it apart and SLOWLY charge those cells, and they will come up to their full 2600 or 3000 mAh capacities. It's a myth that letting the voltage go low hurts them. Overcharge is very very bad for them though. So that's about $1.66/cell. Testing and matching these carefully can yield great batteries. These are older cells though, and not as good as the new ones produced today. The very best way to go is to order several hundred brand new cells at a time from a high end manufacturer. Cells purchase this way will be ready to assemble—just check the voltage of each cell carefully.

Good luck. I just wanted to save you from the disappointment of buying a bunch of junk cells off eBay that said they were 10000 mAh each, constructing an eBike battery from them and discovering that you couldn't get beyond the end of your driveway!

 

[Nashville Kat]

OK- thanks- things to think about, and I usually arrive at the same conclusion: Paying the piper for an entire pre- assembled battery- and now further in doubt that I can ever repack any old ones I have.

The one I have shows no real signs of slowing- two years later with one year of use- but at almost 65 I don't get out and around much anymore.

I do love the electric experience and largely because I can still turn it into a normal cycling experience when my body couldn't possibly. I grew up on a bicycle and raced 14 seasons in my younger days. I live in a very annoying over-industrial are and can't do more than very short rides- this setup keeps me spread out a bit, and I love the quietness that the China girl builds don't have, and all much lighter too. The bike above is almost as fast as my 50 build, and I've got a great CAmpy knock-off with a bigger front sprock now than the Stronglight 93 on it then, so I can pedal assist almost to the top end, and the bike rolls forever at speed too. I've also put some different alloy bars on it that have a good rise and perpendicular ends that give a safer grip. I may someday put a shock fork on the front like my China Girl builds because that just works at higher speeds.

I once got around, but that's irrelevant here, Cowboy.