How to use threaded rod & plywood to create a clamping battery box for prismatic cells?

[happy]

So i've seen lots of pictures and recommendations of people using threaded rod & plywood to clamp their cells. I'm making a 4s battery with the 280ah eve cells now and am having trouble figuring out how actually build the dang thing with threaded rod (which i've never used before)

I have everything cut & setup with 2 wood endplates + 4 threaded rods + 8 nylock nuts. The problem I am having is that for the life of me I can't figure out how to tighten both ends of the threaded rod? I cant choose which end is the "locking" side and because when trying to turn the nut it instead turns the rod. Can anyone help a complete beginner out with this? I now have one of my nylock nuts screwed way too far onto the rod and can't figure out how to back it out haha

 

[Pyke13]

Put two nuts on one end and tighten together to lock them. Then the other end is the end you tighten up. To lock the two nuts together, screw them on to where you want them, then take two spanner’s and tighten together. Tighten one and slacken the other. That brings them together and locks them in place

 

[happy]

Put two nuts on one end and tighten together to lock them. Then the other end is the end you tighten up. To lock the two nuts together, screw them on to where you want them, then take two spanner’s and tighten together. Tighten one and slacken the other. That brings them together and locks them in place

Maybe I'm misunderstanding, but I believe I've tried that and still have the issue where the rod spins instead of the nuts? I tighten the single nut while fixing the opposite end's nut in place with another wrench. But instead of the single nut spinning down the rod & clamping down, it instead spins the entire rod so that the not i'm trying to keep in place is the one that ends up getting screwed in.

Sorry if that doesn't make sense

 

[Pyke13]

Sounds like you haven’t locked the two nuts together tightly enough. Two spanner’s and screw in opposite directions until you cant get any more force on them. Then hold the outer button when tightening the rod up. It shouldn’t spin the rod

 

[happy]

Sounds like you haven’t locked the two nuts together tightly enough. Two spanner’s and screw in opposite directions until you cant get any more force on them. Then hold the outer button when tightening the rod up. It shouldn’t spin the rod

You are 100% correct i just didn't have it nearly tight enough! Thank you so much

 

[Sverige]

What size threaded rod are you using @happy? I need to get some and just wondering if M6 or M8 is the way to go?

 

[HRTKD]

1/4" threaded rod is readily available at most hardware stores. That's what I'm using.

For those in the U.S., 10' lengths of threaded rod are available in the electrical aisle at Home Depot. It's less expensive than buying the threaded in the hardware aisle.

 

[happy]

What size threaded rod are you using @happy? I need to get some and just wondering if M6 or M8 is the way to go?

I went with 3/8" (close to M8) solely because I already had nuts, washers, and vinyl tubing of that size. I think 1/4 (close to M6) would work just as well for the amount of clamping pressure needed

 

[HRTKD]

I think 1/4 (close to M6) would work just as well for the amount of clamping pressure needed

The 1/4" superstrut rod from HD is rated for 900 lbs. Plenty for what we're using it for.

Superstrut 1/4 in. x 10 ft. Galvanized Threaded Electrical Support Rod (Strut Fitting) ZR1028 - The Home Depot

Superstrut 1/4 in. x 10 ft. Galvanized Threaded Electrical Support Rod. Threaded Electrical Support Rod suspends metal framing channel from the ceiling. With a pre-galvanized steel finish, the 12-Gauge

www.homedepot.com

 

[DerpsyDoodler]

Anyone have thoughts on this for insulating under and between the batteries:

https://www.amazon.com/Neoprene-Rubber-Commercial-Grade-Thick/dp/B076DKHRFM/ref=zg_bs_11260355011_5?_encoding=UTF8&refRID=HP9EK0BDKX41JW1DNS67&th=1

 

[DerpsyDoodler]

1/16“ and they have thicker (1/8, 1/4)

 

[HRTKD]

I wouldn't have a problem using that under the battery. Putting something between the cells is a subject that has been debated around here. I'm in the camp that doesn't think it's necessary to put anything between the cells.

My cells are in a fixture and the fixture is firmly attached to a subfloor in the RV. It's not going anywhere. In my case, the neoprene would be useful under the battery only for insulation, not padding.

 

[DerpsyDoodler]

I will be putting them in a fixture, but they will expand and contract with usage (fixture just limits movement and keeps them from bulging/case warpage). I still feel that over time their wrap will get weaker and eventually wear through. Seeing Will’s big battery issue, and the talk of shorts to the case being a potential cause, I would rather be safe than sorry. That said:

What are the pros and cons of putting this 1/16“ rubber between the cells to keep them conductively insulated?

 

[HRTKD]

I will be putting them in a fixture, but they will expand and contract with usage (fixture just limits movement and keeps them from bulging/case warpage). I still feel that over time their wrap will get weaker and eventually wear through. Seeing Will’s big battery issue, and the talk of shorts to the case being a potential cause, I would rather be safe than sorry. That said:

What are the pros and cons of putting this 1/16“ rubber between the cells to keep them conductively insulated?

I could see putting a very thin piece of double sided tape between the cells, perhaps at the corners. But that's only to limit movement.

While I haven't taken my cells apart to look for friction wear marks, I doubt that I would find any anyhow. I picked up the battery by the threaded rods when I installed the battery, moving it from my garage to the RV parked on the street. If the cells could move around, they would have dropped out the bottom of the fixture.

Unless you're charging/discharging at a high C rate or overcharging/discharging, there isn't much expansion.

 

[DerpsyDoodler]

I could see putting a very thin piece of double sided tape between the cells, perhaps at the corners. But that's only to limit movement.

While I haven't taken my cells apart to look for friction wear marks, I doubt that I would find any anyhow. I picked up the battery by the threaded rods when I installed the battery, moving it from my garage to the RV parked on the street. If the cells could move around, they would have dropped out the bottom of the fixture.

Unless you're charging/discharging at a high C rate or overcharging/discharging, there isn't much expansion.

about the max I plan to be able to push to 2p 24v 272AH batteries continuously is about 120amps (between solar at peak efficiency and either shore (grid or gen) charging or alternator charging. Generally speaking, my discharge won’t see more than that too often, either. So a little less than (if my math serves me correct) .25c. Discharge may spike as high as .5c or more, but I don’t anticipate sustained loads that high.

 

[HRTKD]

about the max I plan to be able to push to 2p 24v 272AH batteries continuously is about 120amps (between solar at peak efficiency and either shore (grid or gen) charging or alternator charging. Generally speaking, my discharge won’t see more than that too often, either. So a little less than (if my math serves me correct) .25c. Discharge may spike as high as .5c or more, but I don’t anticipate sustained loads that high.

Those batteries will be loafing along, you'll get a bazillion cycles out of them.

Max charge rate for my 560Ah battery bank (combined for two 280Ah 4s batteries) would be 140 amps. That's a very theoretical number though. I doubt it would ever exceed 100 amps. If the solar panels are cranking at max output, I would have no reason to fire up the AC-DC converter.

 

[happy]

I will be putting them in a fixture, but they will expand and contract with usage (fixture just limits movement and keeps them from bulging/case warpage). I still feel that over time their wrap will get weaker and eventually wear through. Seeing Will’s big battery issue, and the talk of shorts to the case being a potential cause, I would rather be safe than sorry. That said:

What are the pros and cons of putting this 1/16“ rubber between the cells to keep them conductively insulated?

I put 1/32 thick rubber in between each batteries for insulation purposes. It cost me around $5 and took 2min to cut to size. I think that's worth it for the peace of mind & it's so small it doesn't really affect the reach of the bus bars at all

Rubber-Cal EPDM Rubber Sheet - 1/32 in. Thick x 4 in. Width x 36 in. Length - Black - 60A Durometer 31-016-032-004-036 - The Home Depot

Rubber-Cal's EPDM sheet rubber is a versatile product with superior resistance to intense physical conditions. This synthetic rubber compound is made of a combination of ethylene propylene diene monomer

www.homedepot.com

 

[Catsandsolar]

Can anyone help me with the correct type of steel bar for compressing a pack ( 16s - 280ah cells ) there are so many choices with big difference in price. Is the cheapest mild steel ok for this kind of application ? What have other people gone for? My pack will be static sitting in my attic.

Thanks. Alex

£3.08 per M - M8 X 1000mm Threaded Bars (DIN 975) - Mild Steel (Grade 4.6)
£4.71 per M - M8 X 1000mm Threaded Bars (DIN 975) - Zinc Plated Mild Steel (Grade 4.6)
£4.76 per M - M8 X 1000mm Threaded Bars (DIN 975) - 8.8 Hardened Steel
£6.83 per M - M8 X 1000mm Threaded Bars (DIN 975) - Stainless Steel (A2)
£9.75 per M - M8 X 1000mm Threaded Bars (DIN 975) - A4-80 Stainless Steel
£12.61 per M - M8 X 1000mm Threaded Bars (DIN 975) - Duplex Stainless Steel
£13.76 per M - M8 X 1000mm Threaded Bars (DIN 975) - High Tensile Steel (10.9)

Buy Stainless Steel Metric Threaded Bars | Bespoke Threaded Bars - Accu

Buy Threaded Bar From Accu, The Online Store For Precision Engineering Components.

www.accu.co.uk

 

[chrisski]

I use Zinc Plated threaded rod, 1/4”, 20 TPI.

Everbilt 1/4 in. - 20 tpi x 36 in. Zinc-Plated Threaded Rod 802217 - The Home Depot

Perfect for anchor bolts, clamps, hangers and U-bolts and many more projects where a metal rod with continuous threading or no head or fashioned tip is required. Everbilt exclusively offers a variety of sizes, diameters and lengths to suit the individual needs of your job or project. These rods...

www.homedepot.com

I would be interested to see the response of a Materials Engineer, or at least someone with the technical experience.

 

[HRTKD]

I used what @chrisski used, but in a 10' length. The 10' length was less expensive. I found it in the Electrical aisle with the Unistrut type products.

My take on this: We're not putting a huge amount of force on these threaded rods. Just enough to keep the cells snug. I wouldn't use aluminum rod, but any form of steel rod should do just fine.