Battery terminal torque

Johannlog

The sun shines even on cold days
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Apr 28, 2021
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So I've done some reading other posts on the topic and it looks like most every thread people are bemoaning how their torque wrench stripped of the bolt before it reached the specified torque... it seems like I could just do it by hand at that rate or do I need to buy a wrench that's $$$ more than the cheap bicycle ones?
 

boondox

Chief Engineer, RedNeckTech Industries
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Well...

I do it without a torque wrench. But then I have close to 50 years of tightening bolts under my belt. I've stripped my fair share. But it is very rare for me now. Although truth be told I did strip a threaded hole on a 1953 ChrisCraft engine just a couple of months ago.

I do use a torque wrench on things like heads, wheel bearings and such. But the small stuff I just do by hand. I think my inch/pound wrench is a Capri if memory serves. If you do buy a torque wrench, buy the best you can afford. A cheap torque wrench is a waste of time.
 

time2roll

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I believe my $25 Presa beam style torque wrench from Lowes works perfectly for the battery terminals.
I am probably in the minority but I believe a little less torque is fine. 25 in-lbs or 3 nm works for me.
 

RCinFLA

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I believe the torque spec is about 5 ft-lbs, but the big wild card is with bus bar thickness, cable lugs, bms terminal lugs, and washer stackup, impacting the depth of screw thread penetration.

I think the longer threaded posts with allen head tightening break and separate nut to tighten are better. You can screw in threaded stud until it bottoms out then back out a half turn to ensure maximum thread depth penetration.

The recent batteries with welded on studs have smaller lug contact surface interface shoulders and just provide a protrusion to get wacked and bent sideways during shipping.
 

DJSmiley

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Its always a bit of luck...

I haven't stripped a thread yet on any of my cells, but I do use the studs for maximum thread depth, not the screws (Since thats more depending on the terminal and busbar thickness)

In my expericiene, torque is only part of a good connection. Sanding it with high grain grit, deburring any crap from the busbars and cleaning properly did gave me better results than just tightening a screw

For the laser welded studs: I recently had 1 failing... Wasn't weld properly, the whole stud came off...

Now i need to try to tap a thread, can't use the cell now (as I don't have access to laser welding equipment)
 

timmeh

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I have 280ah eve cells with m6 grub screw studs. I have been using 5nm of torque on the nut and the stud itself i just finger tight with a hex key. 4nm seems to loose while if i try to reach 6nm i get a few turns past firm and it dont seem to get any tighter and it feels like its not going to get to 6nm before i may strip the thread out. so 5nm is what i'm using. i also use a spring washer and serrated nut.
 

Scph9002

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I believe the torque spec is about 5 ft-lbs, but the big wild card is with bus bar thickness, cable lugs, bms terminal lugs, and washer stackup, impacting the depth of screw thread penetration.

I think the longer threaded posts with allen head tightening break and separate nut to tighten are better. You can screw in threaded stud until it bottoms out then back out a half turn to ensure maximum thread depth penetration.

The recent batteries with welded on studs have smaller lug contact surface interface shoulders and just provide a protrusion to get wacked and bent sideways during shipping.
What?

0.5-0.7 mV drop at 83 amp between terminals and bus bars. I can tighten these nuts pretty damn hard i think welded studs are great :)
 

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time2roll

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I have 280ah eve cells with m6 grub screw studs. I have been using 5nm of torque on the nut and the stud itself i just finger tight with a hex key. 4nm seems to loose while if i try to reach 6nm i get a few turns past firm and it dont seem to get any tighter and it feels like its not going to get to 6nm before i may strip the thread out. so 5nm is what i'm using. i also use a spring washer and serrated nut.
5 should be fine for studs. The discussion above relates to directly treaded aluminum terminals to keep the torque 3 to 4 Nm
 

Ampster

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it looks like most every thread people are bemoaning how their torque wrench stripped of the bolt before it reached the specified torque..
I think if you read between the lines, most of those situations used the wrong torque settings. In some cases "not to exceed" was misunderstood to be the torque setting.
 

timmeh

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I think if you read between the lines, most of those situations used the wrong torque settings. In some cases "not to exceed" was misunderstood to be the torque setting.
Data sheet says not to exceed 8nm. I have just now found one of my studs is stripped and only using 5nm. they need welded studs. these shallow small gauge studs are useless.
 

Boondock Saint

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This works quite well for me.

KiWAV Digital Torque Wrench Adapter 3-200Nm compatible for 1/2 3/8 1/4 Inch Drive Socket Buzzer Alarm Audible Alert

61NtANYU5wL._AC_SL1000_.jpg
 

time2roll

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Data sheet says not to exceed 8nm. I have just now found one of my studs is stripped and only using 5nm. they need welded studs. these shallow small gauge studs are useless.
If those studs are treaded into the aluminum terminal.... 3 to 4 Nm max.
 

Hedges

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Data sheet says not to exceed 8nm. I have just now found one of my studs is stripped and only using 5nm. they need welded studs. these shallow small gauge studs are useless.

I think the data sheet referred to a cell before anyone tapped threads in it. We understand 8 nm to be not-to-exceed torque for the terminal, to avoid rotating it.

The female threads were later put in the cell terminals by some back-alley "machine shop", which the manufacturer (and author of the data sheet) know nothing about.
 

Ampster

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We understand 8 nm to be not-to-exceed torque for the terminal, to avoid rotating it.
Yes, that is what I meant to clarify. Earlier someone posted that 3 or 4 NM was safe. There are several threads on the subject including the use of studs and thread locker to give those shallow terminal tops some likelihood of holding the studs. It is difficult to find screws or bolts with the exact length given the varying thickness of terminals and bus bars. Studs can be inserted to the bottom of the threads regardless of the thickness of the bus bars and terminals.
 

Boondock Saint

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I mixed some JB Weld Marine and applied a tiny dab to the bottom and last threads and then hand turned into the batteries. I set my torque to 35 in-lb and went slowly holding for a couple of seconds as they sometimes still move a little under pressure. It turned out well.

After hand threading I used Q-Tips and paper towel to clean around the edges.

.
 

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