200Ah Pack

[expresso]

I am about almost finish - these are 100ah Cells - - i tested them - i get on avg. 90ah out of them tested down to 2.9v - i was expecting to have a new chair end of this year - turns out i have to wait till next year to start the process - this will sit here till then - pictures of the build -

nothing special really - this fits in my group 24 battery tray from a Quickie 636 or 646 chair - on my next chair - my only choice is really going to be the 636 at 6.5 MPH - or Maybe another bounder 300M - havnt decided yet - so here goes - wiring is 7 awg for everything except the charge cable which is 10 Awg and 8 Awg for the ADD On cable - i am not looking to use an ADD ON once this is in a chair - but made the cable for it anyway in case - and can come in handy for other things having another connection.

i hope to have this connected sometime next week and then do a full charge - will also do a full discharge once done - will use a dumb load to discharge it down enough and then finish it off with the PL 8 - i welcome any input if you see something is wrong or suggestions -

[expresso]

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[expresso]

last for now

125amp fuse used - so far so good - i like 7 awg wire - i had some 6awg but decided not to use it - i feel 7 awg was more than enough - i used XT90 to keep it compact and easy to connect and disconnect - SB50 used for the Main power cable going to the chair - and will have a SB50 end on the ADD ON cable also going to XT90
using 8 Awg for that.. its a bit hard to solder 8 awg on the XT 90 but it can be done - and works fine.

[terry2]

Well done dude.
It looks epic

[Irving]

Hi Expresso

Impressive

Did you Loctite the studs in, and how long are they?

What did you use to insulate the cells from each other? It looks like some self-adhesive film?

[Dan]

Expresso, making lithium packs in his smoking jacket, slippers and a glass of Barolo.

[foghornleghorn]

Any reason you've used busbars rather than cable between the pairs? I would have expected them to be a source of problems.

[Burgerman]

Me too. Throw those copper bus bars away.
download/file.php?id=12310&mode=view

I hope all those cables are soldered.
download/file.php?id=12314&mode=view

Otherwise, yes, epic!

[rustyjames]

Wow, good job on that Expresso, how much does it weigh?

[expresso]

Well done dude.
It looks epic

thanks - looks good but we see how it works once its charged and tested -

[expresso]

Hi Expresso

Impressive

Did you Loctite the studs in, and how long are they?

What did you use to insulate the cells from each other? It looks like some self-adhesive film?

thanks - yes i did loctite the studs in using the stronger one - cant recall the number now it was green and thicker than the blue for sure - 270 i believe -

the studs are 16mm high - half in the cell so about 8mm sticking up exposed - i wanted to keep them as low as i can - lower than a group 24 MK Gel - not knowing for sure what chair it will end up - mostly like another 636 or 646 but better safe - in doing so - it does limit me how many ring terminals i can fit on each stud - the most i can do is 2 on each stud - since i have two cells together as one - i have two studs on each cell i can use. trying to keep it neater -

i used kapton tape over the top and bottom i believe and also wrapped it around with a similar tape which is Green - it was wide enough to cover the cell but a pain to do also - i wanted to make sure dont trust the blue wrap they came with - i placed two orders - 2nd set was wrapped better so didnt have to over do it -

i used silicone sheet in between the Cells - - not each cell - only the ones that are needed and on the side since they would be side by side - once in the battery tray - i can see how to wrap it all around on the outside and top once wiring is in place

[expresso]

Expresso, making lithium packs in his smoking jacket, slippers and a glass of Barolo.

i cant stay dressed when i am home no matter what time it is - once i get home - back in my PJ

[expresso]

Any reason you've used busbars rather than cable between the pairs? I would have expected them to be a source of problems.

Well i hope it works out this way - i got them with the Cells - and they made it easier and neater to connect two cells since they are so close together - on my very first pack 5 years ago - going on 6 next year - i have used the copper ring terminals believing its the best thing - they are still going strong and no issues - but if i have to change a wire or do something to that pack - i will redo the wires as i need too - unless i have to take it apart and redo all the wiring. but its not giving me any issues that i know of yet - i havnt looked at it or opened that battery box in years -

if i have to use cables instead of the buss bars - i need another 16 cables to make and loop them etc, - i then may be limited on the space since i have about 8mm of stud to use - not knowing for sure the space i will need - i went to keep it as low as i can - i think its 9 inchs high or less at top of stud.

or i have to rearrange the cells in a different order if it comes down to that - i will see how it works once done - charged - discharged tested - i hope to make it once - tighten it down and thats it - the way i wrapped the Cells - two together - then all around - would be a pain to take it apart now -

i didnt think of another way and this was how i ended up - i hope it works out - i have a hard time finding rings for the cables that are not so thick - - if i can find thin ones - if i have to replace them - maybe i can do that and make it fit - if i use 7 awg - its thick i need a ring that can fit it and thin so it dosnt take up much room -

only have 8mm to play with. i could have used maybe 20mm studs instead - they just seemed high to me - so i went with 16mm -

[expresso]

Wow, good job on that Expresso, how much does it weigh?

you know i dont know - its less than two lead bricks for sure - maybe 60 lbs at most for the whole thing -

[expresso]

Me too. Throw those copper bus bars away.
download/file.php?id=12310&mode=view

I hope all those cables are soldered.
download/file.php?id=12314&mode=view

Otherwise, yes, epic!

Yes all cables crimped and soldered - Since Day one - thats one thing i learned from the start and always done it that way - the Only cable i never soldered are those balance wires - i double them up and stick them in the ring 3m with glue - crimp it - heat it and always worked fine so far - everything else always gets soldered after the crimp

if the buss bars give me issues - then have to redo with cables - i hope not - would be alot more cables looped around and like to keep it simple clean as best i can - any suggestions if i have to go down that road ?

i have 8mm stud to work with - thats the reason i made the charge cable and add on cable together using one Ring Terminal Lug for both -

[Gnomatic]

Wow, great job expresso! That's one hell of a battery pack.

[expresso]

Wow, great job expresso! That's one hell of a battery pack.

Thanks ordered the dumbload to use when I discharge it. Would take too long with pl8

[Burgerman]

If the buss bars give me issues

They will. Already are. The 4m threads are fragile. They are mechanically levering on the terminal posts, and will also oxydise and work loose. But nobody listens. Already they are not sitting flat, not making good contact on any 2 cells at once. They physically cant without twisting in the battery cell. But dont listen to me. Just wait and see,

[expresso]

Funny. I will finish this way and see how it tests using lock. Nuts should be very tight won't come loose making contact Maybe. Could be something. The cells won't move for sure they r wrapped good once in tray In chair. If I find thin ring terminals maybe I make one In place of buss bar to see if i have the room to screw ot down. Didn't rule it out.

[Irving]

I have to agree with BM re the bus-bars. At best they are going to be unreliable and could generate localised hot-spots. At worst they could fracture the battery posts internally. If you look at the battery bank in almost any military vehicle there is never a solid connection between cells and the primary bus-bar(s); they tend to have multiple cells in parallel to provide high current for avionics etc. But mechanically all the cells float with respect to each other as the vibration levels are very high, so the connections to the cells are all wire pig-tails. Those connection pieces (they aren't really bus-bars in the true sense) are fine for static cells, eg a solar power bank, but have no place where the cells can move relatively to each other and, however well taped together, they will move quite substantially.

[Burgerman]

Plus theres half a volt potential difference (0.5V!) between aluminium, and copper. Ensuring that with the humidity in the air alone that there will be considerable electrolytic corrosion over time. Once this causes some oxides, this voltage will become a real measurable thing. And possible balance issues since the joint develops 500mv on its own, and we are trying to balance to 2mV accuracy!

So for at least 3 reasons, pure copper bus bars are a bad idea. Nickel plated, or even zinc plated, and if flexible to allow for heat and vibration movement, and to allow the bars to sit FLAT on the contact as tightened across two cells then no problem.

Any minute, shirley will be along to explain some weird balance problems he had when trying to use a bare copper bus bar on smilar cells. And got the exact result that I exepected that he might!

But again. Nobody listens!

[expresso]

i recall that about Shirley with his buss bars - but then Snaker dosnt have that issue i believe and he is using buss bars also

but i get it - i guess i will make cables instead - better i do it now before i start putting it together - i need to make 16 more cables now -

the ring terminals i have are for 8 awg wire and i have enough of it - so i may just make them using 8 awg wire - and see how that works out

what would be the least size wire to use in place of buss bars ? 10 awg or 8 awg - ? since i am not in a rush to use this pack i will make the wires instead - i rather do it once and thats it - dont want to revisit it because of something i could have avoided

wont be as neat in the end now - alot of wires looped all over the place -

would 10 awg wire work or just stick with 8 awg ?

thanks

[Scooterman]

Re the crimp vs solder debate. I personally think crimping alone is fine, I know no one else will agree with me but wtf?

A circuit is only as good as it's weakest connection and a properly executed crimp terminal is as good as, or better than the terminal to cell connection. And the rest of the power electrics are just crimped connectors anyway. And I've notice what this article mentions, in that no matter how careful you are solder migrates up the strands of the cable through capillary action and makes the short stubby link connections stiffer than they would be than if crimped alone. (But I just scanned the article, couldn't be arsed to read it in depth).

And just my opinion, I don't mind being a black sheep. BAA!

https://millennialdiyer.com/articles/mo ... or-solder/

[expresso]

i feel better with both crimp and solder - the key is to make sure you dont let the solder wick up the wire much if at all and if you dont need to make a sharp bend at the ends where you solder - no stress - the chances of breaking the solder are very low - -

i just reordered the same ring terminals i used already and may just use the same wiring size 7 awg if i have enough of it - or 8 awg -

[Burgerman]

When properly crimped, the individual strands effectively micro-weld together forming a gas tight connection.

By MICROWELD he means they get pushed together. And thats no better than it sounds. And by airtight he means not airtight... Because they just are not! If you added say a solvent or some fuel, it is drawn in by capilliary attraction. Try it. So air tight its not. And by cutting it apart at the one bit thats been stamped it looks good. But I can pull the ends clean off large crimps with thin walled weak copper terminals like that pretty easily. And this business about the solder wicking up the cable and making weak failure points is EXACTLY the same if the crimp holds the copper cable solidly in any case so thats bollox too. Plus it only does that if you overheat the joint in the wrong place anyway...

So unless you have REAL solid cast terminals, and a proper scientifically tested crimp joint made on a production line, solder it. The solder ALSO wicks into the so called airtight joint too. Which it would not be able to do if it was really welded or airtight. But its not.

Its almost impossible to do a GOOD crimp, on the bench at home. And impossible with the terminals we are using.
If you want problems down the line, just crimp away.

[Scooterman]

When I did mine i clamped the terminal part of the crimped crimp in a vice and a pair of mole grips on the other end of the cable. Then pull and twisted every which way. And what I found was that the crimp held solid but the copper strands where they entered the crimp work-hardened and snapped at that point.

But I didn't use silicone insulated cable, I used bog standard PVC insulated stranded cores, and the strands tend to be thicker than the silicone insulated stuff. And I can understand/appreciate that finer and more flexible the strands are more likely they are to work loose from a crimped enclosure.

Changing crimping subject...

These are quite nice, but a bit big for the links. They looked like they're specifically for soldering???

https://picocanada.com/en/view_product/5275