# CALB battery tterminal torque and temperature



## Mr_tim (Dec 13, 2010)

I have my new 180AH pack of 48 in the garage waiting for me to get the box built. I have a couple of questions. Does anybody have a torque spec for the Al and Cu terminals? The battery manual warns about the batteries getting a fever if the connections aren't kept tight, but doesn't give any specification for what tight might be. I was wondering what others have used for a torque spec. I want them tight, but aluminum is a soft metal and I don't want to pull out any threads either.
Secondly, I've decided to go with a BMS. It includes temperature monitoring thermisters. Where's the best place to monitor the cell temperature, on one of the terminals I'm guessing. Does one get hotter than the other? Whats the best way to mount the temp sensor to the terminal? conductive epoxy into a ring terminal maybe? Questions, questions, time to go to work on the box....

Thanks,

TiM


----------



## JRP3 (Mar 7, 2008)

18ft. lbs rings a bell but I can't promise that's accurate so look for confirmation.


----------



## ElectriCar (Jun 15, 2008)

If you torque them to a 5/16 bolt specs which may be 18ft lbs, you're way over torquing them. I read somewhere that for an aluminum bolt that size to use 80-95 inch lbs. To convert to foot lbs, divide by 12! I decided to use 85 which seems low but I don't want to risk stripping out a hole which I think I did on one using the steel bolt specs. I'll know if I ever remove it! That's when I switched to Al specs since one post is aluminum.


----------



## EVfun (Mar 14, 2010)

I agree on the much lower torque values ElectriCar. I would go with about 7 ft-lb for the 8mm bolts and only about 4.5 ft-lb for the 6mm bolts used in the smaller cells. 

I used button head cap screws and tightened them with a short handle allen wrench with my thumb over the screw head. That is not much torque. I like that choice in fastener because it is easy to cover all of the allen wrench, except about 1/8 inch of the tip, with heat shrink. These wrenches also get you hand a little further above the tops of the cells and other connections.


----------



## Lordwacky (Jan 28, 2009)

I used 16.5 ft-lbs on my cells (CALB 180s as well) with no problem


----------



## JRP3 (Mar 7, 2008)

Remember the bolt is SS and the hole is aluminum. It's not an aluminum bolt. I just found this calculator and used a 5/16 SS bolt size, 1 inch of thread depth, going into aluminum, with 10lbs of applied tensile load, and it came up with 12.76 ft.lbs recommended torque, 17 ft. lbs max torque.
http://www.futek.com/boltcalc.aspx?mode=american


----------



## ElectriCar (Jun 15, 2008)

JRP I'm not a mechanical engineer but isn't an aluminum hole identical to an aluminum bolt? Same surface area, same thread pitch etc. That said, I don't see any difference. I'd rather strip bolt threads than the hole which isn't replaceable.


----------



## JRP3 (Mar 7, 2008)

I was thinking that with an aluminum bolt you also had to consider shear forces on the shank, not just thread pull out, but you may be correct that it's the same value if the threads are the weakest link. Either way 7 ft. lbs is at least half the recommended torque for 5/16 in aluminum, and 8mm is slightly larger.


----------



## Beemer (Jun 2, 2011)

Thermistor:
Yes, the only useful part of a BMS in my book.
It depends on what you have. Ideally, you will drill down the centre of a bolt and slide it right down into the bottom of the hole into the cell. Silicon into place.

This is assuming your thermistor is not conducting to the cell anywhere. (Doubleblind) The temperature swaps from one pole to the other depending on charging or discharging.

Don't forget, add fuses everywhere; too many over cell fires!


----------



## EVfun (Mar 14, 2010)

I'm trying to figure out how that is related to the question of bolt torque Beemer. This really isn't another BMS debate thread.


----------



## JRP3 (Mar 7, 2008)

Well the thread topic is "CALB battery terminal torque *and temperature*"


----------



## tomofreno (Mar 3, 2009)

> I'm trying to figure out how that is related to the question of bolt torque Beemer. This really isn't another BMS debate thread.


He is responding to the second part of the original post:


> Secondly, I've decided to go with a BMS. It includes temperature monitoring thermisters. Where's the best place to monitor the cell temperature, on one of the terminals I'm guessing. Does one get hotter than the other? Whats the best way to mount the temp sensor to the terminal? conductive epoxy into a ring terminal maybe?


I've used 10 ft-lb on my 180Ah CALB cells. I've had bms boards on and off a few times now, re-torquing to 10 ft-lb each time. No problems with stripped threads so far. I used a bit longer bolts on connections where the 2/0 lugs connected to ensure I had at least 1/2" length of bolt engaged on all, also checked that they didn't bottom out.


----------



## EVfun (Mar 14, 2010)

Sorry Beemer, must have blocked that last question out. BMS questions have an unfortunate tendency to turn a thread in a flame war.


----------



## electricpolo (Mar 15, 2011)

The recomended torque is 20-22Nm but it depends greatly on the amount of thread engagement. 
I have had no problem tightening the nuts up to that figure however I did not use the bolts that the batteries came with. The bolts are a bit short by the time you have a lug, a flat washer & a bellville or spring washer on them. You won't have enough thread engagement in the soft aluminium & the problem becomes even worse if you stick another lug for a BMS in there as well.

I made up a heap of stainless steel studs out of threaded rod & screwed all of them fully into the terminals & used a bit of locktite too.
I made the studs long enough so there is enough thread protruding to fit the cable lug, the BMS lug, a stainless flat washer, a bellville cone washer & a stainless hex nut.

You should also wire brush each battery terminal as you assemble each connection & use some Noalox or similar on every connection too.
If you clean the terminals properly, use Noalox & bolt the terminals down tightly enough, your batteries will not get a 'fever' as the Chinese so eloquently put it.


----------



## Beemer (Jun 2, 2011)

EVfun said:


> I'm trying to figure out how that is related to the question of bolt torque Beemer. This really isn't another BMS debate thread.


Point taken, sorry. I should add that drilling the centre of the bolt, if done properly should not affect the bolt torque.

I get it.. BMS = Flame war


----------



## EVfun (Mar 14, 2010)

Temperature measurement is part of this thread so...

I agree that in the bolt is a good way to get a quick reading on temperature changes. I'm not sure if the positive or negative terminal would be better. You need a quality drill press to drill out bolt centers.

Another idea, that would work if you have your cells restrained in rows, is to insert the temperature sensor into the middle of the row. The Winston and CALB cell cases have ridges leaving little gaps that could fit a sensor. The plastic case will slow the heat some, but heat build up should be pretty slow when charging since it is perhaps 10% of the amps seen on discharge. I think the fire risk of over charging is greater than over discharge. Plus, charging is when the vehicle is left unattended and often parked indoors.


----------



## JRP3 (Mar 7, 2008)

You might be able to get predrilled bolts for safety wiring. It's drilled sideways but would still do the trick.


----------



## ElectriCar (Jun 15, 2008)

Locktite? I don't think I'd use that stuff as it likely increases contact resistance between the bolt and terminal threads which isn't good. I think I read once that if a bolt is torqued properly it won't back out. Too much and something gets damaged, not enough and it may back out with vibrations. 

I doubt it's the norm that people torque bolts to specs but in my dealings with bolts over three decades, it eliminates damaged bolts & nuts and the possibilty of under tightening. Though it means you have to have the proper torque wrench, it's worth the extra effort IMO.


----------



## spdas (Nov 28, 2009)

Aloha, All. I am changing out my cell bolts for SS studs with locktite (or without) and torquing the battery leads semi-permanently with washers and nut. The stud will still have some threads to attach other battery monitering things (cellogs etc) on the outside with another SS nut, therefore not having to bother the alum/copper threads. I think 35mm is just about right. (assuming you have ample free space on battery tops) 
Another possible advantage is that if you have a terminal come loose, you will be melting the stud and above, rather than the bolt that is set in the battery terminal and therefore less risk of screwing up the battery threads.

Good idea?

here is the sample

http://cgi.ebay.com/Stainless-Metri...150?pt=LH_DefaultDomain_0&hash=item5d2d475d26

Francis


----------



## GerhardRP (Nov 17, 2009)

ElectriCar said:


> Locktite? I don't think I'd use that stuff as it likely increases contact resistance between the bolt and terminal threads which isn't good. I think I read once that if a bolt is torqued properly it won't back out. Too much and something gets damaged, not enough and it may back out with vibrations.
> 
> I doubt it's the norm that people torque bolts to specs but in my dealings with bolts over three decades, it eliminates damaged bolts & nuts and the possibilty of under tightening. Though it means you have to have the proper torque wrench, it's worth the extra effort IMO.


Use this?
http://hybris.cms.henkel.com/medias/sys_master/8504059296977264.pdf
Gerhard


----------



## Beemer (Jun 2, 2011)

*DO NOT USE LOCTITE!​*It is an insulator. Even the conducting stuff will not handle your currents.

The early Skyflash missile had a terrible time with testing because some half asleep dude who designed one little bit called for loctite on two screws on an electrical assembly. In those days getting master specs changed on the say-so of the shop floor was as simple as holding your poo in whilst on a diet of molasses.

Jack Rickard has a relatively expensive system which I would endorse wholeheartedly. Nord-Lock washers. They are good providing the bolts are not very hard.

If the cells can move or vibrate at all. you are inviting the bolts to come loose. He also uses those braided links to negate that but they are $4.50 apiece.
I've noted Cedric Lynchs FFEV has had a judicious use of the spray foam can to glue them up.

Cell temps. You really do need to monitor the electrolyte temps. The rest is plastic and metal. The Professor that same JR once linked to said it's the electrolyte that is the only worry and if you can get the probe right inside, all the better.

The best way to drill the bolts will be with a centre lathe with a centre drill and then drill to size because it will centre the drill much better.

If I'm not mistaken, its the anode (-) that gets hot on discharge. But I would pick a centre cell in the block and monitor both Anode and Cathode temperatures.


----------



## GizmoEV (Nov 28, 2009)

I have not had any issues with brass bolts, brass flat washers, and bronze split washers on my TS-LFP100AHA cells. They are much easier to center drill (and tap for extras on top) than SS and much more conductive.


----------



## Beemer (Jun 2, 2011)

GizmoEV said:


> I have not had any issues with brass bolts, brass flat washers, and bronze split washers on my TS-LFP100AHA cells. They are much easier to center drill (and tap for extras on top) than SS and much more conductive.


David, did you use any conductive anti galvanic lubricant on assembly?

Just a thought when mixing metals like coppers and Aluminium and the ability of aluminium to spall on the thread if there is any roughness. 

Andy


----------



## JRP3 (Mar 7, 2008)

I have not had any problems with the stock hardware and a "calibrated hand" for tightening  I did lube the threads and coat the mating surfaces with NO-OX-ID A Special http://www.sanchem.com/aSpecialE.html 
This prevents galling, corrosion, and allows smooth torquing.


----------



## GizmoEV (Nov 28, 2009)

Beemer said:


> David, did you use any conductive anti galvanic lubricant on assembly?
> 
> Just a thought when mixing metals like coppers and Aluminium and the ability of aluminium to spall on the thread if there is any roughness.


I actually bought a spiral bottom tap and tapped all the threads then used a cotton swab to put NOALOX in all the terminal holes. A few of them weren't quite threaded all the way to the bottom. I used NOALOX as a threading lubricant too. I wire brushed all the terminal tops and immediately put NOALOX on them then assembled the pack.

At the time I didn't know about the aluminum tending to spall or ball up if there was any roughness. I think tapping and using the NOALOX both smoothed things and lubricated. Every bolt turned smoothly.

On a related note, make sure all the aluminum nuts which hold the terminal in place are tightened enough so that the terminal sticks above the nut. Out of 40 cells I had 3-4 which were too loose. On one of them the terminal top was completely below the nut.


----------



## tomofreno (Mar 3, 2009)

The current path should not be through the bolt. It should be from the lug or strap to the terminal. Nothing, save maybe a thin layer of Noalox or similar, should be between them. Stainless steel is fairly resistive and the bolts would get hot with that much current going through them. The bolt is just there to apply enough pressure to the joint to give intimate contact.


----------



## GizmoEV (Nov 28, 2009)

tomofreno said:


> The current path should not be through the bolt. It should be from the lug or strap to the terminal. Nothing, save maybe a thin layer of Noalox or similar, should be between them. Stainless steel is fairly resistive and the bolts would get hot with that much current going through them. The bolt is just there to apply enough pressure to the joint to give intimate contact.


I saw a picture of a SS bolt that Jack Rickard had which had welded to a strap because the bolt came loose. I missed the final tightening of one of my brass bolts and discovered it after driving 68 miles. There was no welding of the bolt and I'm sure my battery currents remain higher in my 64V system than Jacks 100+ volt system. I think a big difference is that the brass bolts conduct much better than SS.

In any case, there is no harm in having bolts with lower resistance so that they too conduct a larger portion of the current. For my system this is a positive byproduct of needing to have bolts with a tapped hole in them for my BMS boards.


----------



## electricpolo (Mar 15, 2011)

There is nothing wrong with Locktite on the studs into the battery terminals. If you have cleaned the terminals correctly & & used Noalox or similar & torqued the nut down to the correct torque setting, the current path will be straight from the battery terminal to the cable lug which incidently is the path it is supposed to take.

The stud & nut (or bolt) is merely a method of keeping the lug in proper contact with the terminal & not there to conduct any current.
The electrical resistance of stainless steel is about 27 times higher that aluminium & about 42 times higher than copper!
Locktite would make a negligable difference.
Brass does conduct better than stainless but its electrical resistance is still about twice that of aluminium & 4 times higher compared to copper.
Brass bolts are not really required because as I stated before, the bolts are there only to maintain proper contact between the terminal & the lug.

The reason why it is so important to maintain the correct torque on the bolts is if they are too loose, you create a potential high resistance joint which can overheat & fail or too tight & you risk stripping the thread out of the terminals.

After 30 plus years in the engineering game including building machines with huge heating elements using copper bus bars 3" wide & 3/8" thick, we never, ever used anything except stainless fixings because they did not form part of the current path.. The current was carried by the bus bars straight into the cable lugs. If your bolts are part of the current path, your system has not been designed correctly.
(& yes I did buy a proper small torque wrench just to do up the battery terminals)


----------



## ElectriCar (Jun 15, 2008)

electricpolo said:


> ... If you have cleaned the terminals correctly & & used Noalox or similar & torqued the nut down to the correct torque setting, the current path will be straight from the battery terminal to the cable lug which incidently is the path it is supposed to take.


I didn't think about that polo. Even it SS weren't that high in resistance most of the current would be through the battery post in high current situations as that's how current travels down a conductor, mainly on the outer portion of the wire. That's how copper clad aluminum came about I believe in an effort to save copper in large size conductors.


----------



## Beemer (Jun 2, 2011)

Edited to catch certain items, sorry. 


electricpolo said:


> There is nothing wrong with Locktite......................... & used Noalox or similar .................................... the battery terminal to the cable lug which incidently is the path it is supposed to take.
> ................... The electrical resistance of stainless steel is about 27 times higher that aluminium & about 42 times higher than copper!
> Locktite would make a negligable difference.
> ..........................
> The reason why it is so important to maintain the correct torque on the bolts is if they are too loose, you create a potential high resistance joint which can overheat & fail or too tight & you risk stripping the thread out of the terminals. ............................


So, what if Mr. Loctite user gains an excess of loctite between the link and the terminal?
What if long term vibration thins the soft conducting metals and/or creeps the thread upwards. It happens on aluminium that is why so much stuff is wire-locked on aircraft. If anybody wishes to wire-lock their terminals down, please consider the implications of all those high amperage terminals crying out for a bit of wire to short with another pole.

What if someone has, (as stated before) accidently under-torqued a bolt. You cannot tell after the Loctite has gone off.

A re-torque as part of a service will not be a clean and easy job.

To apply Loctite properly, you have to clean/degrease both bolt and hole with Loctite primer. This leaves a coating which ensures the Loctite goes off properly. I wouldn't want that between my cells posts and bus bars.

The conducting area of a bolt thread is far, far greater than its washer. Even so, the extra area of conduction of the thread and the bolt face is a plus, not a minus.

If it is a highly loaded battery pack and there is constant heating and cooling then Loctite will weaken. On normal jobs that require servicing to remove loctited bolts, heating up to 125C often needs to be applied to weaken its grip and turn the bolt. Something that cannot, must never be done on these cells.

Another point you made is using Noalox AND Loctite on two parts of the same bolt. I doubt any engineering office would prescribe this due to cross contamination.


Polo, please don't assume this is a put down. Your car is going well and any choice is down to the personal preference of the builder.
Thank you for the differences in metal resistances. That's useful.
~~~~~~~~~~~~~~~~~~~~~~~~~

Oh yes, Jack Rickards welded bolt was in his AC Mini. I think that has 100 cells of 100AH. So it must be like 335Volts.​


----------



## rwaudio (May 22, 2008)

ElectriCar said:


> I didn't think about that polo. Even it SS weren't that high in resistance most of the current would be through the battery post in high current situations as that's how current travels down a conductor, *mainly on the outer portion of the wire.* That's how copper clad aluminum came about I believe in an effort to save copper in large size conductors.


That is 100% false in DC applications... 

But on another note I have used copper clad aluminum wire in car stereo applications, it's great stuff, cheaper/lighter than copper, just upsize a bit for the same current handling.


----------



## electricpolo (Mar 15, 2011)

Just to clarify a couple of points.
I used stainless studs not bolts.
The studs were screwed in to full thread depth.
The studs were locktited into the terminals.
They will never come out again. They are in the terminals for good.
The batteries were left for several weeks after the studs went in before they werer assembled into packs. Only then did every ternimal get cleaned. No cross contamination was possible.
Once locktite has gone off, it is inert.
A properly assembled battery terminal connection should only get slightly warm irrespective of the current. If it gets hot, it has not been designed correctly or put together properly.
Bolts do not and should not form part of the conduction path.
Locktite must never be used if you are only using a terminal bolt as you would not be able to check bolt torque nor would you be able to get it out easily.
In any given situation, there are generally several ways to do a particular task. In this, I have drawn on years of engineering experience to do things the way I have done them.
So far, every single one of my battery terminal connectioins gets barely warm with currents of up to 400A.


----------



## spdas (Nov 28, 2009)

electricpolo said:


> Just to clarify a couple of points.
> I used stainless studs not bolts.
> The studs were screwed in to full thread depth.
> The studs were locktited into the terminals.
> ...


The above stud/loctite is what I was thinking of doing, then torquing down the cell bars with paste, lockwasher and SS nut. That setup never gets disconnected, except to change out a cell. The stud comes up another 10mm or so and I attach all the monitoring things Cellog8, BMS, and any other stuff that proves to be worthwhile. The original cell bars never get loosened. Also the second set of misc electronic items will help keep the first nut tight.

Francis


----------



## electricpolo (Mar 15, 2011)

Here is a pic of the assembled connections. There are only stainless flat washers & stainless nuts at the moment. I have yet to put on the bellville spring washers or the BMS wires.
You can also see that all the battery interconnects are tinned. Every single leaf of every interconnect got the tinning treatment to stop the copper oxidising & causing a high resistance joint.
Every terminal & every interconnect was wire brushed them immediately smeared with Alminox (a conductive electrical jointing compound that the electrical supply companies use) before assembly & tightening up.


----------



## GizmoEV (Nov 28, 2009)

electricpolo said:


> Bolts do not and should not form part of the conduction path.


If the bolt is conductive at all it will conduct. Using a higher conducting bolt does not mean the connection is not as good compared to a lower conducting bolt. If the force holding the terminal to buss bar together is the same with either bolt then it doesn't matter. The higher conductivity bolt is a bonus.

As I said, the brass bolts were chosen because they are much easier to center drill and tap. Since some have had issues with loosening SS bolts and the coefficient of expansion of brass is closer to aluminum than SS is there is a chance that is one reason I haven't had any issues with them loosening. (Other than the one bolt I missed the first time around.)


----------



## dtbaker (Jan 5, 2008)

spdas said:


> The above stud/loctite is what I was thinking of doing, then torquing down the cell bars with paste, lockwasher and SS nut.


I sanded the terminals flat for max contact and no oxidation, 
installed SS stud+loctite, 
light sanding of bus bar bottoms to get off any oxidation, 
and applied Noalox just before final assembly in series
using star washer, nut...


----------



## Beemer (Jun 2, 2011)

I'm somewhat won over.
I can buy E-Polo's use of Loctite with studs. *Not with bolts!*

Most people do seem to be happy with the same method Jack Rickard (for instance) had reliability issues with.

However, you'll still need to monitor electrolyte temperature at a place that is least affected by outside influences. That would be deep inside the centre of the cell you can get to.


----------



## Beemer (Jun 2, 2011)

Beemer said:


> I'm somewhat won over.
> I can buy E-Polo's use of Loctite with studs. *Not with bolts!*
> 
> Most people do seem to be happy with the same method Jack Rickard (for instance) had reliability issues with.
> ...


oopps!
Forgot to mention. I wouldn't attempt Loctite on the nuts either. In case of capillary run through etc.


----------



## JRP3 (Mar 7, 2008)

electricpolo said:


> Every single leaf of every interconnect got the tinning treatment to stop the copper oxidising & causing a high resistance joint.


I've been told that the copper oxide does not cause much resistance, though obviously minimizing it is preferred. Looks like a very clean setup.


----------



## JRP3 (Mar 7, 2008)

Beemer said:


> However, you'll still need to monitor electrolyte temperature at a place that is least affected by outside influences. That would be deep inside the centre of the cell you can get to.


I don't see any realistic way of doing it any better than a terminal bolt. I've also not seen any significant heating of cells so I don't see it as a major concern.


----------



## MN Driver (Sep 29, 2009)

JRP3 said:


> I don't see any realistic way of doing it any better than a terminal bolt. I've also not seen any significant heating of cells so I don't see it as a major concern.


It depends on how much current is being pulled from the cells, but you are a good example though because of your pack capacity versus vehicle size but it might be something different if you put a driver behind the wheel of your car with a lead foot that merges onto the highway under full throttle at maintains high speed. How hot have your terminals been after a few hard accelerations or high speed extended runs? Even under those conditions I think CALB cells would be fine.

...I agree with you to an extent but there are certain limits to discharge performance before heat becomes a bigger issue especially with higher powered Soliton setups, especially with small capacity packs with heavier vehicles where the capacity doesn't need to be sized too big for range but might take a beating in a short period. It seems a 4C for the time it takes to accelerate is no problem for these cells and 5C for a short period seems to be no issue either from peoples experience here but pulling higher draws might need some temperature probes on terminals. I was, and might still be looking at using the old 2008 HiPower cells because there are closeout deals if you know where to look and those cells would definitely need it to find out how far I can stretch their performance, CALB cells not nearly as much.


----------



## JRP3 (Mar 7, 2008)

It's not exactly scientific but any time I've touched the terminals they are only slightly warm, no matter how I've been driving. I can't spend much time at all above 3C or so without breaking speed limits.


----------



## tomofreno (Mar 3, 2009)

> I don't see any realistic way of doing it any better than a terminal bolt. I've also not seen any significant heating of cells so I don't see it as a major concern.


 I haven't had any problem either - over 1 1/2 years, ~ 12k miles now using the supplied ss bolts, flat, and lock washers. Haven't had any come loose so far. Granted, I am just buzzing around in a light car pulling less than 1C (C = 180Ah) even at 65 mph. Pulling many 100's of amps as racers do is a completely different ball game where I have no experience. Most I have pulled is about 160 - 200A for around 20 - 25 minutes up a long hill (mtn pass). The terminals felt barely above ambient at the top and the cell temps were less than 5 F above ambient. I think the whole over-temperature thing is overblown for normal driving in most circumstances, but not for racing. I would be worried if I lived in Phoenix and did extended highway driving pulling 1C or more. More so if I had cells mounted exposed under the hood or inside the car where the ambient temperature might get over 50 C just sitting in the sun. I'd be really interested in hearing from people with LiFePO4 cell evs who live there. Curious as to how the Leaf will do there and in a cold climate since there is no cell heating.


----------



## JRP3 (Mar 7, 2008)

Next year's LEAF gets a winter package, including a heated pack.


----------



## Beemer (Jun 2, 2011)

Overheating is something that usually shows up when overcharging.

You know. When the cells cease to become storage devices and become storage heaters instead.


----------



## spdas (Nov 28, 2009)

If you are gong with the SS stud/flange nuts/locknut route, and any other off-ferrous fixtures, I would recommend using albanycountyfasteners.com .... he was very helpful and had reasonable prices, combined freight.

Francis


----------



## JRP3 (Mar 7, 2008)

JRP3 said:


> Next year's LEAF gets a winter package, including a heated pack.


Just thought I should update this, the pack is only heated enough to keep the temperature above something like -10C I think, it does not preheat the pack when plugged in to increase range.


----------

