Headway cell links

All,

looking at this discussion, I was wondering whether we really understand the current path between the batteries in the "typical" headway pack.

As I see it:
battery 1 with endcap and thread, grubscrew inserted
bussbar with hole, grubscrew going through
battery 2 with endcap and thread, other end of grubscrew

I see several paths, but the main seem to be:
a) endcap 1 - thread - grubscrew - thread - endcap 2
b) endcap 1 - surface contact - bussbar - surface contact - endcap 2

Depending on the contact resistances and material properties, the grubscrew might be the dominant path. Does this mean this grubscrew should be copper?

Regards,


Huub

steven4601 said:

Hi Jack

I have only three battery interconnects/bars. All three are different regarding Iron content (magnet test)

One was way off, also corroding on the 'dark side' when it was bolted on.

Heck its cheap, its available.

Did the speedo signal get sorted? Just the speedometer being way off at low speeds?

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We are going through some of this right now with our Headway pack.

Our pack design is 150 batteries in 3 cell buddy parellel packs 15 cells to a row and 10 rows to the pack. There is a 1/8 x 3/4 inch buss bar between each 3 cell buddy stack. This is similar to what Jack Bauer has assembled, except we used Headway's assembly blocks.

We originally assembled the pack using a bronze lock washer between the buss bar and the positive end. After the battery was assembled we put a 200 amp load across one of the 15 cell rows, testing showed a 1 millivolt drop on the side without the lock washer and a 10 mv drop on the side with the lock washer. We have the battery half disassembed and reassembled now without lockwashers and will finish this week end.

So now the current path will be through the surface contact of each end of the battery and through the stainless 6mm by 12 mm set screws we used for connections.

We hope to see 1/2 mv or less drop on both sides of the buss bar with a 200 amp load an a single row.

Looking at the results you guys are getting and thinking about the battery construction I'm worried that Headway batteries are not going to be as good as we thought. I'm wondering just what those end pieces are made of.

I've noticed, through the years, that Chinese culture seems to equate a lot of "things that look the same are the same". A lot of the looks alike so it is alike.

I've seen this in the quality of some of their products, remember some of their early export wrenches that looked just like a Snap On, but bent like putty. So the idea that tin plated steel looks like tinned copper, so they must work the same comes out. (Plus it's a lot cheaper so there is a lot more profit). They eventually learn (especially when they need to use the stuff themselves) and the products improve, but a lot of people get hurt in the intrim.

I'm seeing batteries with the negitive end turning in the case. We only had 7 do this on the initial assembly of the pack but have at least 20 have turned so far on disassembly of 3 of the 5 rows. A really scarry part is we found two leakers while disassembleing the pack. It appeard that if the end turns in a counter clockway direction something may loosen and an internal plastic sealing disc starts leaking electrolite.

It appears that the negitive connection terminal end is supposed to be retained to the case by a ring of epoxy. We've seen the ring either popping out of the battery entirely or not bonding to the case or the terminal block.

We've run a few tests on several batteries from the initial assembly that we repaired with super glue or a new application of epoxy. On the first couple of loads they seem to hold up, they are being recharged and we will test them again next weekend.

Has anyone tried a magnet on the end connectors of the batteries? I know a few of you have disassembled batteries. Can you look and determine what the metal is. The positive end appears to be plated steel, anyone have an idea what the plating is? (I figure it's steel because some of the batteries I received had rust pits under the plating). Is the plating conductive or just decoration.

Right now we are using stainless set screws as connectors because stainless is what Headway uses. Can anyone think of a good way to test to see if a substantial part of the load goes through the screw and we need to use copper.

Jim

DavidDymaxion said:

Jimdear2, thanks for the real life data points.

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David, your welcome, we aim to please.

DavidDymaxion said:

Were they installed with the vents down? I was just thinking maybe a little electrolyte leak would cause loosening?

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The batteries were installed in a horizontal position. The lekage did not occure until we disassembled the pak and the batteries were turned in a counterclockwise direction.

DavidDymaxion said:

Do you think one should grab the end piece to tighten, to prevent torque on the main part of the battery?

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A good idea, except there is no place to grab. Look at your 3 batteries, imagine a flat bar between two batteries, you will see there is only about 1/16 of an inch of the actual negitive end exposed above the epoxy seal to grab onto.

Each battery could be modified by grinding 2 flats so a thin (0.060 to 0.080) sheet metal wrench could be slipped in between the buss bar and battery.

DavidDymaxion said:

Have these batteries ever seen extreme currents?

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No

DavidDymaxion said:

I'm the proud owner of 3 Headway batteries, still need to test them.

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The initial load testing we subjected our batteries to seemed to go well, that was not worrisome until we started to wonder about these batteries with loose ends.

How is the negitive end attached to the plates? What happens to that connection when the battery end turns?

Who was it that did disassmbly of a Headway, was it Jack Bauer? I'll go search his thread to see if he has a video of it.

Jim

Jim,

Here is an excerpt of my conversation with Michelle from Headway tonight:

A problem with the torque of 7Nm/61 inch lbs. we were twisting some cells loose with around 10 inch lbs. Is this a common problem with the cells? The epoxy end of the cathode end was cracking loose on some of them

What material is used to make the bus bars/connection plates?

Michelle Lu (9:59:07 PM):
for the first question, can you check the picture i send to you now? (See attached at bottom of post)
2. bus bars is Nickle plated copper

What metal are the positive and negative ends made from? I have cells that the the ends look to be rust pitted steel that has been plated with something.

Michelle Lu (10:05:30 PM):
3.the positive and negative ends made from nickle plated ferrous

Have you or your engineer ever heard about or experienced the negative end epoxy cracking and turning while using less than 7Nm torque?

Michelle Lu (10:12:51 PM):
yes, before one of our customer from taiwan, had the weeping problem, so our engineer did a lot testing and find out that the torque must be less than 7NM