Headway Pack Builders thread

I said earlier, we sell it, its just not on the website yet. Have to email us or call the warehouse..... website is being updated.
 
Successful day rummaging out at the Houston scrap yards today. I found appropriate copper for my bus bars for my pack!

Things learned today: "scrap copper" bars at scrap yards cost between $3 and $3.75 per pound, depending on the scrap yard. It looks like I'm going to do a combination of cut-from-pipe segments flattened for the majority of layer/card interconnects and proper copper bus bars at the extreme + and - ends of the pack for my interconnections. It looks like 1/4" thick by 3/4" copper bus bar with the M6 (1/4" really) holes drilled in for to bolt to the cells is enough to safely handle the 500 amp bursts that my Curtis controller and my 5p setup can produce.

Tomorrow we will be cutting and drilling the bus bar segments to match the spacing from the red-plastic battery "lego" blocks. Plastic "lego" blocks for cells: cheap. Used copper: medium-cheap. Friends with metal shops that can rip-cut copper bars: priceless!

Cheers,
--Adam
 
go here for bms
viewtopic.php?f=14&t=13380&p=200080&hilit=+30+headway#p200080

check out pipe hangers before you start cutting.
file.php

They worked perfectly for me, just had to drill the existing holes a smidgen bigger.
 
you can buy copper pipe hangers in other sizes too. i still think the lugs and soldered solid 8G is adequate. the sense wire connections between the cells can be as light as copper foil from the hobby shop.
 
Check your purchase carefully - out here when I looked for copper pipe hangers, the only ones I could find were merely copper coated. I can see from Lessss's purchase the bag says "Solid Copper", he found what I couldn't.

-JD
 
I know about cross current. The engineer was right.

it's exactly like in electronic desing, when old great AB class amplifier that used many parallel transistor for hihgher output power..

each transistor collector have a low resistor ( 0.1 to 0.5ohm) in serie to share equally the current between every mosfet.

Let me explain:

If you have 10 parallel cells that can give each 10A max.. you would assume that you can draw 100A max.. but it's right only if every cell will give 10A,

BUT.. it is rare that the current will share equally from each cells. You may have one cell that give 25A while some some other cells only give 7A... and we must avoid that for many reasons: parallel cells could age differently causing faster battery degradation, also the cell that give too much current can overheat and cause serious damadges.

Every of these problems occur because that between every cells and the main terminal or main wire, the resistance ( even though it's in miliohm difference) is important and the path the current choose is depending on that resistance. By puting many smaller gauge wire between every paralleled cells tab, the low resistance become more iniform because the resistance of that small gauge wire is more important.

Doc
 

Attachments

  • Current share by Doctorbass 2009.JPG
    Current share by Doctorbass 2009.JPG
    93.8 KB · Views: 902
Well thank you Doctor Bass. I have been trying to decide how exactly to make my cell connections. You have manged to, in a single stroke, help me decide how to go about it... and at the same time, you answered a few questions that have been rattling around in my head :eek:
 
I think the red/orange blocks are the same (according to my friend Rich). There doesn't seem to be much difference.
 
I think the red/orange blocks are the same (according to my friend Rich). There doesn't seem to be much difference.
Click to expand...

After spending more time with them I would agree - they are crackable and are extra snug (bordering on unusable) on the positive side of the cell can. I guess I just imagined them looking more orange in earlier pictures. :mrgreen: The blocks I have certainly are very red, however.

Speaking of the blocks I have, it's time for more show and tell. I've been working on the tedious parts - building the copper balancing tabs that will go between the set screws that screw my cells together. I've started the process of laying out my cells. Here's what they look like so far. A wooden jig is used to hold 5 set screws at the almost same width apart as the cells will be in the red end-caps. I then solder 16 AWG wire to the ends of the rectangular tabs. (see attachement 1).

View attachment makingBalancerTabs-640x480.JPG

I've made several sets of the tabs. I still need to punch holes in the ends and solder in a last wire that will run out to the BMS via a Molex connector. I've decided I'll use a Molex plug (5 x 0.92" I think?) for each connection out the G/F BMS boards. Here's my "production run" of balancing tabs (attachment 2).

View attachment balancerTabs-ManySets.JPG

From there I've laid out 30 cells in their end-caps. I've mounted the balancing tabs on two 5p rows for illustration. (attachment 3).

View attachment 1

Here's what the gapping looks like with a couple of cells from the next layer installed. (attachment 4).

View attachment nextLayerWithBalancingTabs.JPG

Cheers,
--Adam
 
wow wow

how do you tighten them? can you get your finger around them enuff to torque them down? build from the corner out like painting a floor?

maybe a little strap wrench?

you have to build the walls first it seems to hold them in place as you go up. you have really done a neat jig set up.... so many pieces.
 
Ahambone.... do you have any concerns about the copper tabs creating a short on the postive end if it reaches over to the outside lip of the can and touches :? ? I can't quite tell from the pictures whether the tab would reach over far enough to touch if they were innadvertently bent downwards. I have recently seen a thread on insulating the end of the can using a segment of used bicycle innertube. It might be a worthwhile precaution if you are not using a plastic block between the cells you have connected end to end.
 
how do you tighten them? can you get your finger around them enough to torque them down? build from the corner out like painting a floor? maybe a little strap wrench?
Click to expand...

When I first place the set-screws in the ends of the cells I place then in with a hand-tightness. Then I place the balancing tabs on the set-screw ends that are pointing up. From there the next layer of cells gets tightened with firm hand-tightness. The set screws and the copper tab make the connection very firm from what I can tell. I may torque the set screws in with a 4mm hex wrench, but I haven't tried doing that yet.

do you have any concerns about the copper tabs creating a short on the postive end if it reaches over to the outside lip of the can and touches?
Click to expand...

Not really. The tabs are 0.75" tall and the center of the 1/4" hold drilled for the set screw is something like 0.303" from the bottom of the tab. If I bent the tab all the way down there would still be 2 to 5 MM of space between the positive can of the cell and the tab that is bolted to the negative end cap. As a precaution against any shorts from the solder joints I place the solder-side of the tabs facing the positive end of the two cells that are meeting at the tab. If you look closely at the tabs in the picture you can see the solder side and blue wires "face" the positive cell.

I've tried the headway "condoms" from bike tubes and have come to a couple conclusions. 1) It's a really great idea for insulating wires from touching the can of the cell. 2) It's a real pain to try to place the bike tube segments on the cells. Mountain bike tubes fall off and road tubes are too tight. Maybe I should try cyclo-cross tubes! I built a 2-pole jig from some wood and nails to hold the tube segment while I inserted the cell - event that was extremely error prone. My hands ached after getting 5 tube ends on and it took me 1/2 an hour to do it. Since the cells are going to be sandwiched in the red end plates I don't think it's worth my time.

There will be 3 places in all: two on the ends and one in the middle. The layout will look like this (P = red end-cap plate, - = set screw):

P - [cell+] - [cell+] - P - [cell+] - [cell+] - P
P - [+cell] - [+cell] - P - [+cell] - [+cell] - P

This should handle the weight of the cells reasonably well. The challenge will be putting that mid mounting plate on the cells without cracking it.

Cheers,
--Adam
 
ahambone said:
My hands ached after getting 5 tube ends on and it took me 1/2 an hour to do it.
Click to expand...

That was funny :lol:

I was recently fortunate to find some red 1.5" heat shrink locally for the postive ends on mine, and already have some black for the other end. I need all the help I can get to keep every thing oriented correctly :roll: .

Since I will only be combining the cells in pairs, and don't have room for the blocks in my build, I'll most likely just use a single copper tab to join them. I am also contemplating joining 2 cells at a time end to end like you are doing. I just need to have the cells in hand before I decide... soon I hope :) I'm ejoying reading and watching your build ahambone. :wink:
 
I wouldn't recommend to tighten the allen screws too much in the beginning. Because on the positive side you put permanent pressure on the can and perhaps the pole gets ripped of or you damage the can inside.
When you screw two batteries together you can tighten them as much as you can, but be careful that the copperpad in between doesn't get twisted.

-Olaf
 
I'm ejoying reading and watching your build ahambone.
Click to expand...

I'm glad I can provide some entertainment.

I made a ton of progress last night. I got the pack mostly assembled. All four layers of batteries are assembled, with end caps and mid-caps for weight distribution. The pack will probably lay with the 6 cell dimension on the bottom with each 5p set of cells "stacked" vertically. For safety reasons the end-caps have none of their bus bars, balancing wires, or connector bars attached while assembling the pack. This makes sure there are no potentials of more than 12 volts (relatively safe voltage) in the pack while assembling the pack.

Starting where we left off I was installing the second layer of cells on top of the balancing tabs.

buildingLayer2-row6-top-445x600.JPG

Those went on without issue. I used a 4mm hex-wrench to tighten the set screws where they were coming up from the negative caps of the first layer. I found that the cells were easy to tighten by hand to a nice firm hold on the copper tabs.

Once the second layer was complete I installed the mid-pack end caps. The mid-pack end caps help carry the weight load of the cells. I didn't want the cells to be bending in the screw tabs with significant weight load. I played with several "sticks" of cells and while they are firm, I wouldn't suggest going more than 2 cells without some weight-bearing structure between the cells.

View attachment building-midCellCaps-640x480.JPG

First I aligned the cells by hand and then wiggled the end caps down on the cells. This took some time, patience, and fuddling. Using the wood block to tap the end-blocks down helped ensure that I didn't crack the end-caps and that they got placed on securely.

After the mid-caps were installed it was back to another set of balancing tabs and another layer of cells.

View attachment buildingLayer3-row1-640x480.JPG

I did have one SNAFU at this point during construction. I had one of the set screws fall between the cells while I was installing it. Fortunately it didn't short anything and I was able to remove it easily. Anyone looking to "clone" this pack should be very very careful to not drop a set screw down the gap between the cells.

Finally I started on the 4th layer on top of yet another set of balancing tabs.

View attachment buildingLayer4-allRowsInstalled-640x480.JPG

From there it was time to install the last end-cap.

building-topCellCaps-640x895.JPG

Here's the "assembled" pack, still minus end-connectors, end balancing tabs, and end bus bars. This is laying in the orientation that I expect to use in my car. The wight is on the 6-cells-wide side so only 5 cells of weight stack through the end-caps.

assembledPack-640x408.JPG

And finally I went through and measured the voltages to make sure I was in the correct 3.3v/cell range for each of the six 12 volt "sheets".

View attachment assembledPack-readingVoltage-640x408.JPG

Later on (probably next week, on the road for work now) I'll cover installing the end-balancing tabs, copper connectors, fuses, and the bus bars.

Cheers,
--Adam
 
Nice (battery) Rack!!!!!

:)

Seriously, don't you like those cell holders? Makes assembly much easier. I'm glad I got mine.
 
I am glad to see you have chosen to orient the length of the cell against the direction of travel/braking. I have to agree, since you are using the cell caps that gap between the cells (instead of resting each row on another, protected by a layer of Phenolic plastic or something), you need to have caps at each junction. I think those endcaps are strong, but I think a good bumpy road on the unsupported endcaps could do damage. Also, did you use locktite blue on the set-screws between the cells?

Since my cells are currently all in a single sheet, heat dissipation has not been an issue. For my next iteration of the pack, I am considering stacking them in layers of sheets, effectively similar to your layout. I will be very interested to see the thermal loading on your pack, you might want to get a few cheepo LCD thermometers with a wire and sensor for "outdoor temperatures", drop one sensor in the middle of the pack and one on the outside to determine if you need convection or forced-air cooling.

-JD
 
Thermal monitoring is going to come.. at some point. Right now I just want to get version 1.0 of the pack working. And I'll probably do a plastic rack every cell - it only adds about $1 per cell cost to the pack and it's probably worth it from a longevity of the cells. If these things can really last 1000+ charge cycles then the physical wear and tear is definitely a concern.

Cheers,
--Adam
 
Lessss said:
My BMS is on it's way back to KAE. I put in a note on the inside cover stating...bubblewrap is not an anti-static packaging material.
Click to expand...

Actually Lessss, pink bubble wrap is a well known anti-static material for packaging electronic components. Google it.
 
You must log in or register to reply here.
Back
Top