APL's Pressure Contact Battery box

Batteries, Chargers, and Battery Management Systems.
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Re: APL's Pressure Contact Battery box

Post by APL » Dec 18 2021 1:39pm

Thanks for the info fechter, that's enough to convince me that that this is probably not the best way to go at this point. :thumb:
I don't understand the BMS circuit enough yet to be skirting this close to the danger zones.

Pretty much decided to forget the connectors and go the traditional route, and use a straight up wire harness. I'll try to beef up the balance wires a little for more harness abuse, and I think the whole thing will be easier to manage without all the connectors.

Looks like I can slip the BMS through the frame without too much trouble, and attach it to the frame tubes in back as the battery is installed. (wasn't sure I could do this before)

The problem still exists when I put the battery together though,.. with the side plates. I'll have to heed your warnings about the sequence and clamp the side plates with the balance wires first, and the main battery cables last.

Hopefully the clattering of contacts in the initial clamp-down won't send the BMS circuits into any confusion.

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Re: APL's Pressure Contact Battery box

Post by TorontoBuilder » Dec 19 2021 1:48am

drdrs wrote:
Nov 22 2021 3:59pm
Trampa boards used a PCB with a small disk with a resettable fuse inside for current carrying. They didn't give any details about that proprietary part.

Does anyone know of an available part that could be surface mounted on a PCB to provide electrical contact to a perpendicular cell?
Got a reference for your above claim? I hate to disagree but the trampa boards shown are not using proprietary components. They just use contact pads, pogo pins and a PTC fuse that is separate from the contact pads it is adjacent to.

IF you look closely at the lower trampa boards they use a smt contact pad to make the battery connection to the board and then a smt PTC fuse connects the area of the board with the smt contact pad to the broader area of the board that holds a parallel group of seven contact pads. The boards are dual sided with each parallel groups PTC fuses alternating between the front and back of the board. See attached image... yellow highlighted components are the PTC packages

Image

The upper tramp boards on the other hand use a short pogo pin with internal spring that maintains compression on the batteries to maintain the electrical circuit. I'm not too sure how robust the springs in the pogo pins they use are.

You can easily replicate this design if you have some experience with pcb design or want to learn a bit

I'm such an idiot... i originally had smt and thought that does not look right so changed to smd and all day I thought something isn't right.... so came back to edit this a second time to make it correct again
Last edited by TorontoBuilder on Dec 19 2021 9:54pm, edited 2 times in total.

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Re: APL's Pressure Contact Battery box

Post by drdrs » Dec 19 2021 2:42am

Thank you very much for spotting the PTCs and giving me "SMT contact pad" to google. You're right, it is straightforward to replicate this design on a PCB.

The announcement from Trampa on esk8 news (linked below) claims: "The connection is made via a special, 25A fused contact element". I assumed they were using a single element with an integrated contact pad and PTC. Your highlights in the detailed photo contradict my interpretation and the scales have fallen from my eyes.

https://forum.esk8.news/t/the-trampa-ve ... tems/41630
viewtopic.php?f=6&t=101184
5kW ASI 2000, Crystalyte, Vruzend 14s5p

viewtopic.php?f=6&t=104324
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viewtopic.php?f=6&t=109860
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Re: APL's Pressure Contact Battery box

Post by TorontoBuilder » Dec 19 2021 1:42pm

drdrs wrote:
Dec 19 2021 2:42am
Thank you very much for spotting the PTCs and giving me "SMT contact pad" to google. You're right, it is straightforward to replicate this design on a PCB.

The announcement from Trampa on esk8 news (linked below) claims: "The connection is made via a special, 25A fused contact element". I assumed they were using a single element with an integrated contact pad and PTC. Your highlights in the detailed photo contradict my interpretation and the scales have fallen from my eyes.

https://forum.esk8.news/t/the-trampa-ve ... tems/41630
Thanks for the link. They do seem to be laying it on a bit thick and implying a single component when that is not the case. Shame on them.

I'm way too far along on my 5 battery packs for my salvaged Alizeti e-bike kits but for my other build I may give this a try from scratch if I can figure out how to plate heavy thru holes or buy bare boards cheaply enough

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 20 2021 1:34pm

Looks like the Trampa spring mechanism is cut out fingers in a plastic sheet, maybe something I'm not seeing? Pins?
Trampa spring design (1).jpeg
Trampa spring design (1).jpeg (78.41 KiB) Viewed 735 times

I bought some 3/8" Poron, and some 1/4" silicone sheet to try out for the spring on this box,.. put a C-clamp on each for a week or so, and checked for memory loss. The Poron test left a mark for a day, but then disappeared, and the silicone still has a slight mark.
(clamped them pretty hard)
Spring clamp test (1).jpg
Spring clamp test (1).jpg (25.2 KiB) Viewed 734 times
Poron is too soft though, I can squeeze it all the way together with my fingers easily. I just cant see it giving enough pressure to each contact. The silicone is much harder and seems about right, so I think I'm going to start out with that first.

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 27 2021 9:05pm

Had a better idea for the bolt insulators,.. bought some nylon standoff's and some 5/16" springs, and it all fits perfect.
Now they'll stay pressed up against the side covers, and the nylon is a lot tougher stuff.
Nylon spacers .jpg
Nylon spacers .jpg (90.49 KiB) Viewed 686 times
The magnet idea was a bust, but it helps with positioning. I'll just use wire ties, like everything else on the bike.
Magnet mount.jpg
Magnet mount.jpg (54.55 KiB) Viewed 686 times
Current state of the build,.. still need to solder the balance wires yet. Half still thinking about balance connectors...hate the
umbilical already. But if I glue some sheet steel pads to the box, the BMS will stick to it, which should help.
XT150.jpg
XT150.jpg (80.02 KiB) Viewed 686 times
8awg wire and some XT150 clones. Copper strips are riveted, flex sheet is done, and now I can see where the compression plates will settle. Looks like I can narrow the box thickness by 13mm.

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Re: APL's Pressure Contact Battery box

Post by fechter » Dec 28 2021 12:04am

What do the springs do? Somehow I'm not picturing the assembly.
"One test is worth a thousand opinions"

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 28 2021 1:59pm

Sorry about that, I'll get a side view picture of the assembly today. Should have had it earlier.

I didn't want to fight the polyethylene tubing when it gets clamped. They have 'some' crush, but don't know how much. (20 pieces)
So either they have to be shorter, and loose in the box,.. or cut to exactly the right length, which changes with compression.
Springs will make up the difference.

Not really a problem on the flex sheet side, since the nylon goes through the cover, but on the hard side the copper strips are flush
to the surface. So it would be nice if the insulators were always pushed tight up against it there.
Not that anything is going to be moving around anyways, but this should be an improvement.

It's going to be hard to 'feel' how much pressure the cells are getting. Would be nice to have a sensor on a cell that reads it out, so I can stay within a safe range.

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 28 2021 7:52pm

Here's the crusher. Most of the thru bolt is inside the cell holder stack.
Layers.jpg
Layers.jpg (115.71 KiB) Viewed 641 times
The question is, will the 3/16" side plates be stiff enough for even pressure, and how much is needed. I plan to clamp it on something solid first, to help set the contact-copper flatness. The contacts won't need to move very much, so it should only be about flatness.

Cover to cover OD is 85mm, 2cm wider than the battery.

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Re: APL's Pressure Contact Battery box

Post by fechter » Dec 29 2021 1:42am

I see now.

The end plates won't stay perfectly flat. They will flex. The trick is to get the contact pressures as uniform as possible despite the flex. Overkill engineers would do FEA to model the flex and shape the end plates or the rubber so all the contacts are even when things get all tightened up. You can measure the flex once things are assembled by placing a straight edge across the plate and measuring the gaps. Just visually you can backlight the straight edge and look at the gaps to see where they are and estimate whether they are big enough to be a problem or not.
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Re: APL's Pressure Contact Battery box

Post by john61ct » Dec 29 2021 4:48am

more through bolts, every other batt if needed

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 29 2021 1:53pm

That's the grand experiment. Phenolic is pretty stiff, and it will be interesting to see how much. I have some 1/4" Garolite to try next, which is much stronger, still might not be enough though.

More bolts should be the answer alright, I'm starting out with 20, but that might be minimum,.. can only hope I don't need more.
It's a long way to go just to be able to dump your batteries out on the floor, but I'll give it a whirl.

There's other spring ideas to be tried yet too, or maybe individual contact screws & springs.

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Re: APL's Pressure Contact Battery box

Post by APL » Dec 29 2021 2:16pm

One idea I had was to tape Plasti-gauge to the cell ends, and then clamp it down first. It should reveal different cell crush forces.
Plastigauge is used in engine building for bearing clearance. Worth a try.

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Re: APL's Pressure Contact Battery box

Post by fechter » Dec 29 2021 2:41pm

If the end plate deflection is small compared to the amount of compression in the rubber, it won't matter much. Both can be measured.
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Re: APL's Pressure Contact Battery box

Post by APL » Jan 01 2022 1:00pm

Yes, the durometer of the rubber will likely be key. The silicone is around 40 - 50, which might be a little stiff, and the Poron is
really soft, but still might work if compressed enough. Might need something in between,.. but would like high temp.

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Re: APL's Pressure Contact Battery box

Post by APL » Jan 01 2022 1:33pm

One last shot of the contact sheets. Pretty much finished except for a few odds and ends. The left side is the flexible side, with
the strips riveted between two thin .032" fiberglass sheets. And the right side is the solid side, with the strips riveted to the phenolic board, and the insulator sheet is loose.

(Would have been nice to double-up the main power wires from both sides of the end strips, but I didn't think that far ahead.)
Contacts finished.jpg
Contacts finished.jpg (150.73 KiB) Viewed 575 times
Now it's time to work on the cells,.. something I haven't been looking forward to. I need to take some battery packs apart, clean the cell ends, and prep & condition 176 cells. Very tedious, and will take a while.

I can take a Dremel to the spot welds, and it works well, but time consuming. I saw a YouTube video of a little grinder unit that a guy made, that looks like it works good, but it takes all of the Nickle plate off.

Battery jig: https://www.youtube.com/watch?v=QYe9cmwc3S4

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Re: APL's Pressure Contact Battery box

Post by fechter » Jan 01 2022 3:06pm

You probably don't want bare steel for the contact surface on the cell ends. If you grind off the plating, I think that's what you'll get.
If you can grind just the spot welds and leave the plating intact, it will have less chance of corroding.
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Re: APL's Pressure Contact Battery box

Post by APL » Jan 03 2022 1:19pm

I'll try it the hard way and keep the plating, .. usually gets easier as it goes, so we'll see. I took apart several packs and found different cells in most of them, but settled on some Dynabat brand 2600ma units.

Did some research and found Dynabat to be a 75 acer Asian factory that makes batteries for high production cars,.. so I guess I could do worse, they're free and it's an experiment, so whatever.
Dynabat 2600ma.jpg
Dynabat 2600ma.jpg (40.9 KiB) Viewed 527 times
Good enough for now anyway, they should be good for 10A each, and 11P is 110A. I only plan on 60A - 80A for starters, so I'm good for now.

I still have to figure out how to make this thing street legal somehow. :lol:
I could set the CA for legal watts, and put a bypass 'off road' boost switch on the bars, or something retarded like that. :wink:

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Re: APL's Pressure Contact Battery box

Post by HalbachHero » Jan 03 2022 11:31pm

This is getting exciting. Its looking great, I look forward to seeing how it all performs.

If that photo refers to the discharge current (3C) wouldn't that mean they are capable to 2.6A * 3 = 7.8A each? Even that may be a generous value. Could you try stress testing one and checking the temp over time?

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Re: APL's Pressure Contact Battery box

Post by APL » Jan 04 2022 2:59pm

Yea, I can't believe anything they say very much :wink: ,.. I've seen so many different specs for this cell and there doesn't seem to be too much regulating advertising claims in the battery market, at least for some brands.

Several of these 10P packs I'm taking apart state 26ah on the outside and have 2400mah cells inside, (should be 2600). Even that is probably boosted, who knows, never look a gift horse in the mouth they say.

I think 3C is continuous, and I'm talking burst, so I'm guessing they're good for that,.. we shall try to find out. Mostly, I just need a way to test out this pressure pack, so they will do for now hopefully, and if I can get a summers use out of them,.. then better yet.

Ahh, but here's the beauty of the pressure pack! If it works well, I can just dump and refill with better cells. Done.

Anyway, .. trying to figure out how to test this thing for the time being, since the bike is fairly torn apart and all the roads are snow covered. I'm thinking maybe trying several 100w incandescent bulbs in parallel for the smaller drain, and then re-check all the cell voltages. But the big-amp test will likely need to be through the motor/controller.

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Re: APL's Pressure Contact Battery box

Post by APL » Jan 07 2022 2:50pm

OK, I have some of the harvesting done, and now I have a lot of clean cells to play with. :)
Harvest cells.jpg
Harvest cells.jpg (94.53 KiB) Viewed 458 times
Started to use the Dremel tool with a pencil stone on it to remove the weld spots, but it doesn't go well. Will likely take weeks this
way, and there isn't much of the nickel left on the top cap afterwards anyway. I'm a patient guy, but not that patient.

Since these are used, years old, and not exactly your Sunday-go-to-meet'n cells, I think I'm going to sacrifice the number of cells I need for this project for now, and put the rest back in storage. (Time is short, it's cold in the shop, and heat is $$$)

So, it's time to get the C-clamps and V-blocks back out, and make a "grinder gadget" to spin-clean the batteries. See how that works.
I think the Dremel will work well for that too, I'll know in a few days.

The batteries will likely be ready for the recycler before they oxide too much, and maybe I can coat them with something that helps slow it down a bit. (Burnish with lead or graphite?,.. I also saw some rub on silver plate crap on youtube.) I'll give it some thought.
At any rate, I need to test this and move on.

Another good thing I realized about this compression box is that I can put all the cells in the same direction and easily parallel balance the lot of them. Temporarily jump the contact strips, or use tin foil.

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Re: APL's Pressure Contact Battery box

Post by john61ct » Jan 07 2022 6:13pm

Maybe just let the contact surface be irregular, look at conductive paste to fill the gaps?

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Re: APL's Pressure Contact Battery box

Post by APL » Jan 08 2022 1:58pm

Yea, I've been searching a lot for different things to use on the sanded battery ends, but electrical joint compounds look like they're made to order. I never knew about EJC's before, so I'll have to do a little more research on that.

Alum to alum, copper to copper, copper to steel,.. lot's of different brands, Alcoa, Noalox, Harger, Burndy, Penetrox,.. too bad the ES carbon nanotube stuff from 2014 didn't pan out.

Anyway, I'll just go bare-back for now and see if it's even an issue at first. (This could actually turn into a nice test for these kinds of coatings & compounds.)

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Re: APL's Pressure Contact Battery box

Post by john61ct » Jan 09 2022 7:02am

3M also makes electrically conductive tape that is compressible / cushioned

Had a reco for their ECG7000H series in my notes

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Re: APL's Pressure Contact Battery box

Post by APL » Jan 09 2022 8:02pm

I put together a crude cell grinder with some V blocks,.. not pretty, but it works good. The course sanding drum is too aggressive, and the fine one wears out too fast, luckily the stone one works the best.
Cell grinder.jpg
Cell grinder.jpg (79.58 KiB) Viewed 363 times
Of course if I'd just get new cells all this would be mute,.. but these will make good test subjects and need to get used up anyway.
There's a good chance that the battery box might crush or mutilate the cells, so it's best to find out with these.

The grinder makes it easy and flattens the ends nicely, although I need to be careful because the steel is not very thick. Should be done with all these guys in a couple of days and can start some balancing and testing.
Finished cap.jpg
Finished cap.jpg (80.49 KiB) Viewed 363 times

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