# Bolt recommendations for Thundersky batteries



## dtbaker (Jan 5, 2008)

yes on stainless... with both AL and CU on terminals the stainless with noalox is a very good idea.

people seem to get by fine with the M8 bolts and lock washers usually, but I ordered a box of 30mm long set screws, nuts, and start washers because I kinda want to be sure I am getting full engagement all the way to the bottom of the blind hole.

I'll have a set of regular bolts/washers available in a couple days if you are interested to buy, let me know. I could price match a regular retailer and ship'em to you.


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## corbin (Apr 6, 2010)

dtbaker said:


> yes on stainless... with both AL and CU on terminals the stainless with noalox is a very good idea.
> 
> people seem to get by fine with the M8 bolts and lock washers usually, but I ordered a box of 30mm long set screws, nuts, and start washers because I kinda want to be sure I am getting full engagement all the way to the bottom of the blind hole.
> 
> I'll have a set of regular bolts/washers available in a couple days if you are interested to buy, let me know. I could price match a regular retailer and ship'em to you.



Cool, thanks for the advice! I think I'll definitely use stainless. Where did you get your SS M8 bolts from? All my local sources are pretty lame (i.e.: OSH or Home Depot), so I'll probably have to buy them online.

corbin


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## corbin (Apr 6, 2010)

And another question: I just realized that you probably are using threaded rod as a battery post, and then a nut on top with a lock washer; is that correct?

corbin


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## dtbaker (Jan 5, 2008)

corbin said:


> And another question: I just realized that you probably are using threaded rod as a battery post, and then a nut on top with a lock washer; is that correct?
> 
> corbin


this is essentially what I am doing, except not just threaded rod. Set screws are socket-head, and can be tighened down all the way into that blind hole. the regular bolts have more or less engagement depending on stack height of stuff.... which can vary for the ones you put regular (thicker) cable lugs on, or if the holes are not all tapped the same depth. Going into soft stuff like AL and CU, I worry about over-torque pulling the threads out if not engaged enough.

Like I said, I will have a set of regular bolts and lockwashers available, or you can order your own stuff from somewhere like http://www.boltdepot.com

Shipping is a little high, but it comes out to about what you'd pay local retail, if your local people don't have boxes of stainless metric stuff.....


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## Lordwacky (Jan 28, 2009)

I have to say that the set screw Idea is a damned nice idea... wish I had thought of that, I might just switch over to that setup. you should be able to tourque the nuts a bit higher with that configureation.

I recommend you using belleville washers in place of the standard star or Slit lock washer types. People seem to be having good luck with them on the forum.


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## dtbaker (Jan 5, 2008)

recommended torque (per thundersky) is 20-22N-m, which is about 15-16 ft-#...

The place I bought hardware didn't have belville washers, so I went external star. I will probably put a drop of loctite on set screws, and use paint-pen on set/nut after final assy for quick visual inspections.

Next time around I may skip the factory multi-strip bus bars, and source some braided bus bars. They will probably cost a little more, but not tons would be my guess. My instincts tell me that terminals that are jiggling around between stacks of cells and moving a little with thermal expansion would do better with more compliant connections.


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## EVfun (Mar 14, 2010)

Like this? I didn't like those copper straps that come with TS cells either.

I used stainless steel button head allen bolts. I covered my allen wrench with heat shrink so only about 4mm of the tip was exposed. Even if dropped on my battery pack it couldn't short anything out.


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## Roy Von Rogers (Mar 21, 2009)

Use Nord-Lock washers.

Roy


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## dtbaker (Jan 5, 2008)

EVfun said:


> Like this? I didn't like those copper straps that come with TS cells either.


what did the price work out to in USD for those braided bus bars from AU? I was poking around a couple weeks ago, and I remember finding some for about $7.50 USD, but I had already bought all my TS straps....


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## corbin (Apr 6, 2010)

So, as a follow up, I'll probably buy a box of M8 x 1.25 SS socket set screw bolts, 30mm length. Box of 100 is $30:

http://www.boltdepot.com/product.aspx?cc=25&cs=127&cm=67&cd=1553

A box of 100 SS metric nuts for $10

Either traditional lock-washers, or Nord-Lock. Nord-Lock look awesome, but are really expensive. McMaster-Carr:

http://www.mcmaster.com/#nord-lock-washers/=a6c6z9

$7.41/per 5. For 100 that's $148!

I'm going to see if I can find them cheaper. $148 might be too expensive for me at this time.

I'm also first going to double check the screw length; The cell hole is 14mm, so that leaves at least 16mm exposed -- that should be enough for bus bars + bms + nuts, but I need to check my math.

corbin


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## dtbaker (Jan 5, 2008)

corbin said:


> So, as a follow up, I'll probably buy a box of M8 x 1.25 SS socket set screw bolts, 30mm length.


yes... I ordered 30mm long, and this gives about an extra 1/4" length of engagement possible compared to stock bolts... should ensure that they can be cranked down all the way to the bottom of the blind holes and have enough threads to prevent pull-out in the soft terminals.

I also though the nord-locks looked great, but way too expensive. A little lock-tite, proper torque, and paint pen on top for inspection ought to do it...


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## EVfun (Mar 14, 2010)

The price in AUD is almost the same as USD. The Australian dollar is typically worth between 90 and 98 cents US. It is shipping that will hurt, it will cost about $80 to ship 50 interconnects. They are heavy! Still, the total is less than $5 each when you buy enough to do a pack.


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## ElectriCar (Jun 15, 2008)

So are the TS terminals still steel or something else now? I laughed the other day when I saw someone had a shipment of them arrive with steel terminals and said they already had rust on them.


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## EVfun (Mar 14, 2010)

My batteries where made in February of this year and the terminals are copper on the negative and aluminum on positive side. The available thread depth is different on the terminals, measure both sides so the bolts don't bottom out before tightening. I think it's the aluminum terminal that is slightly less deep.


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> So are the TS terminals still steel or something else now? I laughed the other day when I saw someone had a shipment of them arrive with steel terminals and said they already had rust on them.


I don't think any of the terminals are or were steel... one side is copper, other is aluminum. Hence the need for SS bolts and noalox or other anti-oxidant recommended. Also highly recommended to lightly sand off oxidation, and apply the noalox just before final assy.


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## azdeltawye (Dec 30, 2008)

corbin said:


> So, as a follow up, I'll probably buy a box of M8 x 1.25 SS socket set screw bolts, 30mm length. Box of 100 is $30:
> ...


No need to spend the extra money on socket head set screws. Just get standard stainless steel studs. Install them in the battery terminals by using two nuts tightened against each other. Then once installed in the battery, remove the jam nut and you're done.

The same way you would install a stud in an engine block or motorcycle case...


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## ElectriCar (Jun 15, 2008)

Just a note, I've taken SS threaded rod, aka all thread, and cut to my desired length on another project. Of course I think it was a 10' piece I bought so screws may be cheaper if that's the minimum you can purchase.


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## corbin (Apr 6, 2010)

azdeltawye said:


> No need to spend the extra money on socket head set screws. Just get standard stainless steel studs. Install them in the battery terminals by using two nuts tightened against each other. Then once installed in the battery, remove the jam nut and you're done.
> 
> The same way you would install a stud in an engine block or motorcycle case...


Cool -- that looks nice too. I already ordered the set screws...so I'm using those. I like the idea of only having to have one nut -- it reduces the top clearance a little bit, which I need for my front pack. 

ElectriCar -- the pos terminals are copper and the neg are aluminum.

corbin


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## EVfun (Mar 14, 2010)

corbin said:


> ElectriCar -- the pos terminals are copper and the neg are aluminum.


Other way around, the negative terminals are copper and the positive terminals are aluminum. (the red metal is NOT positive )


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## corbin (Apr 6, 2010)

EVfun said:


> Other way around, the negative terminals are copper and the positive terminals are aluminum. (the red metal is NOT positive )


Ooops  Yeah, I didn't have them in front of me when I wrote that.

corbin


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