APL's Pressure Contact Battery box

[APL]

Awesome stuff! Thanks for the input.

For sure, no-contact is no-good. I want to avoid that. But that's the experiment, so into the loins jaw we go.
(I still have welding as a safety net.) Compression bolts about every 3 - 4 cells sounds about right,.. when I
get a little further I'll post a pic. of the estimated bolt layout and check back again.

I didn't think about the P charging difference from no contact, good point drdrs, and thanks for the app link.
Thanks for the force calculation link goatman, I have to digest that yet,.. get to it tonight.

Looks like some massive packs DogDipstick!!, looking forward to the pic.

Too bad you have to rip your 20s battery apart ZeroEm, I've been trying to take apart a 10P pack for dummy cells,
but gave up after a few. I want to save that drudgery for the good cell packs. Let me know how to do it, and how
to clean the battery caps off, (welds). I don't want to remove to much nickel,.. using the Dremmel and small stone
at the moment.

Part of me is screaming "just buy new cells you idiot!", but I have thousands of these used ones.

[ZeroEm]

I'm just going to take it out of the case, cut the outer covering (shrink wrap) not going to break the cells out yet unless they are below 2V. Have a pair so Will put the another on the trike and work on it. Have to many projects at the moment. Winter is coming so try to winterize before it gets cold not wait until something freezes.

My brother took my last Dremel. Had a shop full of tools sold it all, the shop and house too. Not wanting to get all that back. One of the others like Doctorbass should have some threads about cleaning up used cells or Goatman, .

[agniusm]

Hey dog, is that offer open to anyone? APL inspired me to take this approach rather than the NESE boxes.

I intend on making a few large battery packs, including one for under the floor of a sidecar using compression and stamped copper bus bars. That way I can make use of cheap low Ah cells I can source here in Canada.

Managing pressure in one large pack is more complex then splitting it into modules like i do. Its far more forgiving. Then there is disassembly in case of fault. Again disassembling whole large pack instead of taking out one module. Benefits vs drawbacks. You have to weigh

[spinningmagnets]

I would be reluctant to draw high amps from a 12V or 24V battery pack with pressure contacts. That being said, 48V or higher can overcome "soft contact" on some of the cells, and also some mild oxidation. The higher the voltage, the more viable pressure-contacts are.

That being said, there is a thread on making a DIY conductive grease that can protect pressure contacts from oxidation and the corrosion that can happen from humid salty air near the ocean.

Many thanks to Luke/LFP for doing the experiments and publishing the data.

"Conductivity improving grease project"
viewtopic.php?t=61542

[ZeroEm]

Wondering what range is high amps. 2a per cell? I'm thinking of a 64p at 90a.

by spinningmagnets » Nov 07 2021 12:28pm

I would be reluctant to draw high amps from a 12V or 24V battery pack with pressure contacts. That being said, 48V or higher can overcome "soft contact" on some of the cells, and also some mild oxidation. The higher the voltage, the more viable pressure-contacts are.

That being said, there is a thread on making a DIY conductive grease that can protect pressure contacts from oxidation and the corrosion that can happen from humid salty air near the ocean.

Many thanks to Luke/LFP for doing the experiments and publishing the data.

"Conductivity improving grease project"

[john61ct]

Wondering what range is high amps. 2a per cell? I'm thinking of a 64p at 90a.

Use C-rate not absolute amps.

Bigger mAh cells can usually sustain higher amps

so cannot answer that question without knowing mAh capacity

ideally the specific cell model

and if not new Grade A, then it's pure guesswork

[ZeroEm]

ANR26650M1-B Specifications
Nominal Ratings
Voltage: 3.3 Volts
Capacity: 2.5 Ah
Energy: 8.25 Wh
Specific Power: 2600 W/kg
Impedance (1KHz AC Typical) 6 mΩ
Cycle Life at 1C/1C, 100% DOD: > 4000 cycles
Cell Type: 26650 Lithium Ion Power Cylindrical Cell

Discharging
Max Continuous Discharage: 50 A
Max Pulse Discharge Current >50% SOC (10s): 120 A
Minimum Voltage: 2 Volts
Temperature: -30ºC to 55ºC

Charging
Recommended Standard Charge: 2.5 Amps
Max Charge Rate: 10 Amps
Max Pulse Charge Current <50% SOC (10s): 25 A
Float Voltage: 3.45 Volts
Recommended charge V & Cut-off Current: 3.6 Volts, taper to 125mA
Temperature
(reduce charging current to 250mA when under 0ºC): 0ºC to 55ºC

[john61ct]

So 2500mAh at best, more likely 2200mAh at 1C rate so that is

2.2A

Make that your continuous / average

allow for say 3-4A peak a few seconds at a time for accelerating

and you might get over 30min range if the load is reasonably light, the route doesn't have high headwinds, not going uphill too much.

All of that is per cell of course and ASSuming brand new Grade A.

So if your Groups are actually x64 cells each

really? at 20S that is 1280 cells total, add 15% for infrastructure what's that volume, and total weight??

141Ah makes 90A only 1.56C (peak? continuous? ) you may be able to lose some weight...

or your packss' lifespan may double...

[ZeroEm]

Was wondering about amps thru the compression connections, not the cells. 2a will be peak/max for a few seconds then less than 1a the rest of the time. Will not mount this on my bike.

The idea is to have many low amp connections and not try to get maximum thru a few. Spinningmagnets was talking about not trusting high amp compression connections. I was wondering if a short duration 2a/per cell would be feasible.

Don't want to pollute APL's thread but was wondering about, Copper Aluminum Sheet? Solid Aluminum sheet with Anodized Copper finish. Was thinking about getting some and see what the resistance is thru it. Not sure with the treatments done to it. It's made to be ornamental not conductive.

[spinningmagnets]

When a new "compression contact" battery pack is assembled, everything should work fine.

However, over time, issues may slowly begin to make themselves known. If the contacts begin to form a "little bit" of oxidation, that can cause a lot of resistance. One of the things that helps current to use sub-par connections is higher voltage.

For instance, raw copper connections should start out with a shiny reddish sheen, as we all know. The plugs on a vacuum cleaner might be plated, but if they are raw copper, they are likely a dull brown color.

That amount of oxidation is not an issue when using 120V, obviously.

Raw copper at a thin 0.15mm is flexible, which can provide a good contact with a cell-tip. However, once we use nickel-plating to reduce oxidation, we make the connecting tab stiffer.

I approve of nickel-plated copper contact tabs, I'm just pointing out things to keep in mind so we can have years of carefree reliability.

A 12V pack near the ocean needs lots of attention over the months. A 48V pack in Arizona should require less attention...

[john61ct]

But corrosion is less an issue with sandwich spotwelding?

Full potting as a last resort...

[APL]

That's OK ZeroEm, pollute this thread all you want, this project is moving at glacial speeds, so there's plenty of time
and I need the info.

Personally I don't see where cells moving around on contacts are that big of a problem, so long as they don't lose contact,
and that's the springs function. Things that are built too rigid tend to brake, (hence, earthquake designs). It does cause
wear though.

It depends on the use I guess, compression packs may not be the best idea for off road, but asphalt is a little better.
Smaller packs should have no problems with any of this, but this is a big guy. Time will tell if this is a foolish endeavor.

I'm glad there's been some discussion about contact grease, I read Luke's nanotube thread with great interest, but it
still seems out of reach. In the thread there was mention of copper and aluminum anti seize, silver paste, and different
kinds of dielectric grease.

I have to make the decision on copper coating pretty soon, and have been leaning heavy towards a tin plating, (solder),
because it's cheap, easy, and re-doable.(hope) Still oxidizes, but not that much in one season.

The solder will have a crush or 'fill' to it that should help make contact. Solder isn't the best conductor, it's true, but
conduction is relative to length. Any conductor that's only a few mills thick should still pass great current.

I'm thinking of just melting solder in a cast iron pan outside, and dipping the strips? Maybe smear them with flux first.
(Now I'm getting hungry)

Not much progress on the box, (the weathers been too nice), but I have the two side covers cut out, and the strips are
cut and ready to dimple,.. so it's back to that repetition. Once I get past this, it will be time to coat the strips and
mount them.

Side Plates.jpg (136.22 KiB) Viewed 582 times

I have a feeling that it might come down to tensioning, just like spokes, and that might be the real battleground on this
deal, at least with the 'sheet' spring idea.

[spinningmagnets]

I'm a big fan of searate springs pushing on the bus material. I think this design has a lot of potential.

If the pack is oriented so the sides of the cells take the jolt of a pothole (contacts on the left and right sides) I think experiments may show that this works well.

Especially if the cells are cradled by cell holders.

[goatman]

i tested the copper anti-seize mentioned in lukes thread by okashira, wasnt sure if she was serious or just messing with him,

it screws up the connection when being observed with a tester

viewtopic.php?f=14&t=106190&hilit=magne ... 0#p1558285

[ZeroEm]

The idea of this type would be to service the battery. Check for corroding metals, bad or low cells. Would not even think of having the cells on end. My goal is to build a house battery by then my eTrike will be ready for a new or rebuilt battery.

Here is something to think about. The idea of spot welding is for years of trouble free service. Buy yet we need to rip them apart break the spot welds then put them back together again. My batteries are three years old but going out of balance so I need to remove the cases take off the shrink wrap and if some are to low break the welds. So what is worse corroding or welding on the Cells. I get trail riding needs a good battery welded together. I'm with APL on some that ride roads may have better luck with compression. Then there are the people who service to get longer use and those who want to but a new one and not be bothered with service.

by spinningmagnets » Nov 08 2021 6:05pm

I'm a big fan of searate springs pushing on the bus material. I think this design has a lot of potential.

If the pack is oriented so the sides of the cells take the jolt of a pothole (contacts on the left and right sides) I think experiments may show that this works well.

Especially if the cells are cradled by cell holders.

[zzoing]

The price of copper is brutal.

Because of that, copper theft is a huge problem. Thieves will rip the wiring off the studs of an unguarded construction site.

I hope that everyone who has an ebike uses a 12-80v sinotrack 3G GPS tracker ST-906W inside their battery, after spending 50 hours building a rig, it's essential to have a gps tracker on it. While Xi Ping now knows of my every mountain ride on the bike, I can also call my bike up too and the accuracy is about 2-5M on google maps.

[john61ct]

Can Xi Ping do truly custom?

Not just shape but say external balance leads, easily swapped BMS...??

[agniusm]

@APL
Could you give me a favour and weigh your pack when finished along with final dimensions? I am curious how single compression battery is smaller and lighter vs my module equivalent. That would be fantastic.
Thanks in advance

[APL]

Sure agniusm, be happy to. Although, I'm not holding back on weight with this build, there's nothing light about phenolic.
I'm sure your system will be lighter,.. the size difference might be interesting though.

GPS tracker sounds interesting zzoing, might have to look into that. Never know when those blankty-blanks are going to
ruin your day.

Not just copper of course, all the metals. Looking at the cost of 60/40 solder is a wake up call for me too. I have an old
HUGE roll of Zenith solder that I was given 30 years ago, (still only half the way through it), so haven't noticed the current
prices.

But need to dip these strips to tin them, so I'll need a pound or two for that. I'll have to do a small trial experiment first,
to see if this is even feasible, but the price is between $20. (bar) - $40. (roll,) a pound. Must be the Tin content.

[agniusm]

If you mean FR4 board, there is some difference but not much. PET-G is 1.23g/cm^3 vs 1.85g^cm3 phenolic infused glass fiber laminate.

[ZeroEm]

I'm finding the materials more expensive than could have imagined. Almost bought some copper sheet it fix my specs. at checkout when I seen shipping canceled the order. They wanted $10 per 8oz and the copper was $12 per 8oz.

Just have about given up on cell holder/spacers for the 26650's. Started with wanting to do 4s 18p batteries so could reorder them from 12v to 60v. the most common sell holder's are in odd numbers and snap together from smaller pieces and would cost hundreds of dollars for the number i'm doing. This seems like an odd Can size or not to popular as yet. Have tried to reorder the shape and grouping to find something to fit. Not giving up just much hard to get all the materials to match the shapes with in a reasonable cost. If not careful it will cost more than just buying a new battery.

Have more time than money. I will play with making my own holder spacers while looking for a better option.

Not venting, knew shipping and copper was high but the two in conjunction is crazy.

[BalorNG]

I'm thinking about kind of 'big flashlight' kind of battery arrangement (series connection in a tube), it is easy for me because I"m building a recumbent with a long run of straght tubing, using 33140 cells (15ah kind - https://www.alibaba.com/product-detail/ ... 95493.html).

They are notoriously hard to solder/weld due to copper tabs as far as I understand, but pretty good when it comes to weight.

But protecting against corrosion is indeed pretty important, the contants look unplated. Shouldn't mixing a ton of graphite into typical grease and applying thin coating on the contacts help more than hurt I wonder?

[APL]

Don't know BalorNG, I'd read through Luke's post in the link above, where that's discussed pretty well,.. different greases
and such. But those are some hefty cells you have and pressure contact might not work as well for them, although I guess
it depends on how much current you wish to draw.

viewtopic.php?t=61542

I've thought about the 'tube' idea many times since it seems attractive and simple, but the parallel charging connections
don't work out very well, unless you have a way around that.

[ZeroEm]

Glad you brought that up! Was starting to entertain the idea of tubes. Now unless they are slotted. Just in my mind it seems like a wiring nightmare.

y APL » Nov 14 2021 2:19pm

Don't know BalorNG, I'd read through Luke's post in the link above, where that's discussed pretty well,.. different greases
and such. But those are some hefty cells you have and pressure contact might not work as well for them, although I guess
it depends on how much current you wish to draw.

viewtopic.php?t=61542

I've thought about the 'tube' idea many times since it seems attractive and simple, but the parallel charging connections
don't work out very well, unless you have a way around that.

[BalorNG]

Don't know BalorNG, I'd read through Luke's post in the link above, where that's discussed pretty well,.. different greases
and such. But those are some hefty cells you have and pressure contact might not work as well for them, although I guess
it depends on how much current you wish to draw.

viewtopic.php?t=61542

I've thought about the 'tube' idea many times since it seems attractive and simple, but the parallel charging connections
don't work out very well, unless you have a way around that.

You mean for cell balancing? I think if batteries are decently matched, you can get away with 100 cycles or so and than simply 'unscrew' the tube (again, light a flashlight), take out the batteries, inspect them, balance them individually, put them back in
I can live with 8s1p configuration of those for instance... for larger, more poweful packs this will be unwieldy, right.