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  #11  
Old 06-18-2012, 06:05 AM
mharvey mharvey is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

Quote:
Originally Posted by Zak650 View Post
Hi,
You might look into NORD-LOCKŪ washers available from Mcmaster-Carr. You use 2 washers/bolt. They lock against each other using a wedge system and actually have to see more compression in order to be removed or loosened. I think the zinc coated might actually be the best for this application. They come in two different OD sizes. Also braided straps, stainless bolts, & nord-lock washers are available as a kit from EVTV.me site/store. I really feel this is the best way to connect these brick type cells.

Agreed on all points, except the minimal advantage of the nord-lock over the bellville washers doesn't justify the cost of those nord-locks. Of course I only looked at McMaster and Fastenal. About a buck per pair...crazy talk. I dont have issues at all with loosening bolts so it would be like thowing money away. As for SS v zinc, I'll stick with my SS b/c I'm a neat freak and hate stains .
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  #12  
Old 06-18-2012, 09:18 AM
TigerNut TigerNut is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

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Originally Posted by Roy Von Rogers View Post
So those braided strap lugs are tinned copper, then we have aluminum terminals with stainless fasteners and zinc-plated Nordlocks... obviously it works so long as everything is tight, but has anyone actually done an analysis of what the various half-cell potentials are if you do get moisture in the connections? Would it be a good idea to clearcoat the connections after doing initial testing, just to ensure that there is minimal moisture ingress?

Second thing - the straps have some ability to flex and accommodate variation in cell spacing, and you can get them in 60 and 70mm widths. So why are the lug holes ovalized? You're giving up about 1/3 of the contact area on the battery terminal...
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  #13  
Old 06-18-2012, 10:05 AM
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Roy Von Rogers Roy Von Rogers is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

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Originally Posted by TigerNut View Post
So those braided strap lugs are tinned copper, then we have aluminum terminals with stainless fasteners and zinc-plated Nordlocks... obviously it works so long as everything is tight, but has anyone actually done an analysis of what the various half-cell potentials are if you do get moisture in the connections? Would it be a good idea to clearcoat the connections after doing initial testing, just to ensure that there is minimal moisture ingress?

Second thing - the straps have some ability to flex and accommodate variation in cell spacing, and you can get them in 60 and 70mm widths. So why are the lug holes ovalized? You're giving up about 1/3 of the contact area on the battery terminal...
Discerning smokers, smoke Camel dung...lol

Geez man, buy some and see, and btw they are not oversize holes, they are elongated, and you should be able to figure out why.

Btw, I have no association with the seller exept watching his videos, just in case your wondering why I posted the link.

Roy
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  #14  
Old 06-18-2012, 10:27 PM
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Lightbulb Re: Bolts or screws for LIFEPO4 Cells

Those copper braided straps look pretty good and the prices are reasonable. We use such straps for grounding on our high current circuit breaker test sets, and as flexible connections to breakers where we have pulsed several thousand amps. But we have always used copper for high current connections, and silver plating makes the connection even more reliable. Silver oxide is much more conductive than copper oxide. Here is a link to a company that specializes in copper products, and they have laminated copper bus bars that may be useful:
http://store.electrical-insulators-a...ed-busbar.html

At one time I made a high current transformer using aluminum bus bar, and it worked, but even when I wire brushed the mating surfaces before assembly, there was always significant voltage drop, and after a while they deteriorated. When I replaced the bus with copper I got almost twice as much current. There is a lot of information about connection of bus bars, and it requires a clean, flat surface, and sometimes brushing the mating surfaces at right angles creates thousands of small point contacts which make good connections when tightened. And it is also good to use a bit of grease which excludes air and water and retards corrosion.

But aluminum is a special case. Aluminum oxide is one of the best insulators known and it forms almost instantly upon exposure to air. You can use Ideal Noalox as a joint compound, and you can also get silver-bearing conductive grease. But it might be worthwhile to plate the aluminum with copper, nickel, or silver.

I have a small plating kit from this company, and although I have not tried it on aluminum, they have the following which says it works on "zincated aluminum", although I'm not sure exactly what that is:
http://www.caswellplating.com/electr...ting-kits.html

Here is an article that describes how to zincate aluminum so it can be plated:
http://www.dalmar.net/aluminum_plating.htm

I am surprised that these batteries have aluminum terminals and aluminum screws. It also makes me wonder about the internal connection between the aluminum terminals and the electrodes.
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  #15  
Old 06-19-2012, 03:54 AM
pedm pedm is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

I found this:

Nut height
Connection to a cell must be such that the current flows directly from the cell's terminal to the bus bar or cable terminal. You must not rely on the mounting bolt to carry the current.

Unfortunately, in some cells (namely Shandong HiPower) that can be hard to achieve:

The large nut securing the terminal to the case is installed with a locking compound
That locking compound creates an insulating layer
The large nut may be taller than the cell's terminal
The connecting bus bar (or the terminal on the connecting cable) rests on the large nut
Since the nut is isolated, current flows through the mounting bolt instead
The bolt is usually made of a coated steel which has a relatively high resistance
This results in a high temperature rise
The solution is to ensure that the large nut does not extend past the cell's terminal surface. If you cannot screw in the nut further, you may need to use a planer to file down the top surface of the large nut.


Original text from: http://liionbms.com/php/prismatic_tips.php

So If you have Hi Power cell it is an important tip.
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  #16  
Old 06-19-2012, 08:22 AM
pedm pedm is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

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Originally Posted by PStechPaul View Post
You can use Ideal Noalox as a joint compound, and you can also get silver-bearing conductive grease.
Can't find IDEAL Noalox in Portugal. Is there another product that does the same but with a different name?

I can see that it is a compost of Polybutene (80%), Zinc Dust (20%) and Silicon Dioxide (5%). I can't find a compost whit this specs.
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  #17  
Old 06-19-2012, 02:20 PM
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Lightbulb Re: Bolts or screws for LIFEPO4 Cells

Quote:
Originally Posted by pedm View Post
Can't find IDEAL Noalox in Portugal. Is there another product that does the same but with a different name?

I can see that it is a compost of Polybutene (80%), Zinc Dust (20%) and Silicon Dioxide (5%). I can't find a compost whit this specs.
Probably best to go to a major electrical supplier and ask for a joint compound designed for aluminum splices and connections, or bus bar compound. Otherwise, if you can brush or file the aluminum surface so that it has ridges and grooves, then coat with grease (petroleum jelly, or Vaseline), and then torque the connection, you should be OK.

You might be able to read the mV drop from the exposed part of the battery terminal to the bus bar, under a substantial load. If you can get 20 amps or so, then see what the voltage drop is. Maybe do a before and after test to see if it improves.

You might also try brass or silicon bronze bolts. Even though they are not as conductive as copper, the threads will have a lot of surface area contact with the aluminum, and if you put grease on the thread it will keep the aluminum from oxidizing. And the scraping action of the bolt in the threads will remove some of the aluminum oxide. In that case, use a brass or copper washer under the bolt head and make sure the surfaces are clean and flat.
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  #18  
Old 06-19-2012, 02:46 PM
nucleus nucleus is offline
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Default terminal paste

What I use is a paste that is sold in the hardware stores for both copper and aluminum connections in house wiring. It is conductive and prevents dissimilar metal corrosion when you connect copper and aluminum.

Nucleus
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  #19  
Old 07-04-2012, 04:53 PM
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GizmoEV GizmoEV is offline
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Default Re: terminal paste

I use brass bolts and bronze split washers. In over 2.5 years I haven't had any problems and no bolts have loosened. I did use NOALOX in the threads and contact surfaces. If I were to do it again I'd use No-OX-ID A-Special.

http://www.sanchem.com/aSpecialE.html
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  #20  
Old 07-04-2012, 05:44 PM
Zak650 Zak650 is offline
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Default Re: Bolts or screws for LIFEPO4 Cells

Here's the item on ebay $5+$4 shipping:
http://www.ebay.com/itm/NO-OX-ID-A-S...item43b0e4e690

Last edited by Zak650; 07-04-2012 at 05:47 PM.
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