Pictures - Battery bank clamp assembly

[Samsonite801]

I finally got around to putting together my 12v and 48v battery banks (holder/clamp assemblies)...

Just thought to post some pictures of it as a couple people had asked me before here.
Still have to mount the BMS's, install the heat pads on bottom plate, thermostats, wiring, etc...
But it's nice to get this far for today. Simple design, I basically did similar to a few others here had done...

I had the 6061-T651 aluminum plates all pre-cut out by cut2sizemetals.com
Used my drill press and c-clamped all the end plates together and drilled all the holes out at once using top one as template.
Took 2 evenings after work, not too hard so far.

 

[Samsonite801]

An important discovery to make note of here in my implementation of a home brew clamp assembly. A fatal flaw in my design...

As I connected up my bus bars, on one pack (seen on right in picture), when I connected the bridge cable (little red cable) on the right-hand side 48v pack, to connect the 2 halves of that pack, I was getting a spark, and could hear a rapid discharge (like a boiling sound from one of the cells). I quickly removed it. The red bridge cable was fine if I bridged the pack on the other end (bottom end in picture). But connecting the 2 halves on the top end between the 2 halves would get a spark...

So I removed all the bus bars, did some voltage testing and found that 12 of the cells across my 3 battery banks, the negative conductor of the cell is grounding to the aluminum clamp chassis. Wow, this is bad. I disassembled all of the clamp assemblies, and found that due to the sharpness of the threads on the threaded rods, some of the cells got pierced (the blue wrap on the battery cells is very delicate, and there is aluminum casing under the blue wrap of the cells, which is apparently the same conductivity as the negative terminal).

So my advice to anyone who is using metal/aluminum clamp assemblies and fasteners which are conductive, check each cell and make sure the blue wrap is fully intact with no breaches, and negative of the cell chassis is not grounding to the clamp chassis in any way. This can cause one or more cells to have impedance or dead-shorting in relation to other cells causing a drain or short on a cell. I had some cells which just had some impedance but not like a full dead-shorting condition. This kind of thing could cause a behavior like you have a malfunctioning cell, or in my case the one which had a dead-short making it obvious for me to find.

So now to regroup in my plan. I am going to put silicone tubing along all the threaded rod sections where they run along the cells, drill the end-plate holes a bit larger to give the wiggle room for extra clearance required with the tubing installed, put some blue electrical tape over the nicks on the cells, and confirm that each cell is insulated from the clamp chassis.

So I just thought I'd mention this, as others may have the same problem without necessarily knowing about it.

 

[DThames]

Did it drain any of the cells to low voltage?

 

[Samsonite801]

I only had it connected for a short time, but in that time I heard a boiling like sound coming from a cell (not even sure which one it was)... It may have caused other imbalances too, since I had all the other bus bars connected (maybe others not fully dead-shorting), for several minutes. I will probably have to rebalance all the cells and I hope I didn't damage the cell I heard boiling for a few seconds... I'll have to keep an eye on it, and make note of it in case I have some issue with a cell later.

 

[Boondock Saint]

Great catch, good plan. Thanks for passing along. I learned to use some type of tubing w a light larger ID than the rod OD in my design. I also learned to allow more space between the cells and the rod to allow of the thickness of the tubing, or use a solid plate in between such as HDPE board.

 

[Gazoo]

I only had it connected for a short time, but in that time I heard a boiling like sound coming from a cell (not even sure which one it was)... It may have caused other imbalances too, since I had all the other bus bars connected (maybe others not fully dead-shorting), for several minutes. I will probably have to rebalance all the cells and I hope I didn't damage the cell I heard boiling for a few seconds... I'll have to keep an eye on it, and make note of it in case I have some issue with a cell later.

It wouldn't hurt to put some type of insulator between the cells, between the cells and the aluminum plate, and between the bottom of the cells and the aluminum plate.

 

[Samsonite801]

It wouldn't hurt to put some type of insulator between the cells, between the cells and the aluminum plate, and between the bottom of the cells and the aluminum plate.

I agree on the walls. One of the items I'm installing on the banks are heater pads under the base plate, I am not sure to put something that insulates too much on the bottom of the cells as I would like for the heat to be able to dissipate quickly and easily into the cells. I suppose I am not as worried about an electrical short making connection on the bottom of the cells, as it appears the cell has a bit thicker of a black material stuck along the bottomside.

 

[Samsonite801]

Great catch, good plan. Thanks for passing along. I learned to use some type of tubing w a light larger ID than the rod OD in my design. I also learned to allow more space between the cells and the rod to allow of the thickness of the tubing, or use a solid plate in between such as HDPE board.

Oh crap, I ordered the 3/8" ID silicone tubing, and I am hoping it will even slide on easy over the threaded rod (maybe some lubricant can help). If not I may have to take your advice and buy a larger diameter tubing. Was trying to find a relatively thinner tubing that provides enough buffer (the one I ordered says 1/16" thickness), and since my end plates have already been drilled, my only choice at this stage is to make the holes bigger diameter with washers, and hoping I can get enough clearance moving the rods away from the cells... I have to work with what I got, trying to salvage the situation.

 

[curiouscarbon]

Thanks for posting this!

The blue wrap on the cells is not to be trusted!

Glad you caught it fast ??

I agree on the walls. One of the items I'm installing on the banks are heater pads under the base plate, I am not sure to put something that insulates too much on the bottom of the cells as I would like for the heat to be able to dissipate quickly and easily into the cells. I suppose I am not as worried about an electrical short making connection on the bottom of the cells, as it appears the cell has a bit thicker of a black material stuck along the bottomside.

Maybe consider silicone pad on lower side, that material should electrically insulate and thermally conduct. Probably downsides I haven’t thought of.

Cheers and best of luck with your continuing build!

Those plates are CHUNKY! ?

 

[Diysolar123]

as you have a "conductive enclosure" consider using something like PVC show pan liner between your batteries and the aluminum.
The material is readily available, durable, and cheap ;-)

and yes...you should always place plastic tubing over your threaded rods to avoid "oopsies"...

 

[Boondock Saint]

and yes...you should always place plastic tubing over your threaded rods to avoid "oopsies"...

Oh yeah?! Where was your fancy-pants advice WHEN WE NEEDED YOU? :D JK man, have a great weekend, cheers.

 

[Samsonite801]

Version 2.0 prototype (started on 12v pack):










Looks good so far. Checked all the voltages between positive terminals and chassis and all read 0.00 V so looks good so far. Drilled the endplate holes out to 1/2" diameter, now have extra room for the silicone tubing. The tubing fit perfect around the 3/8" threaded rod. I don't think I need any fancy paper separators or anything. I just needed to carefully inspect every surface of each cell, to make sure no breaches anywhere...

Pardon all the dust on everything. My projects haven't been easy lately, working out of a storage unit since I sold the house and shop, as I'm working to build my off-grid homestead. We had a dust storm here while I was working on this and it blew way too much dust inside and on everything, what a mess...

 

[brb58]

Hope you are using insulators between the cells. As you already found out, you don't want the blue plastic wrap wearing through and shorting adjacent cells.

 

[Northernchateau]

Two things:
1. For a fast and dirty insulator on threaded rod you can use shrink wrap.
2. Nice job on the box but how did you determine how tight to make the hardware?
You might want to do a quick calculation on how much load you need, divide it by 8 and get some of these to use between the nuts and aluminum plates. https://www.mcmaster.com/belleville-disc-springs/

 

[Samsonite801]

Two things:
1. For a fast and dirty insulator on threaded rod you can use shrink wrap.
2. Nice job on the box but how did you determine how tight to make the hardware?
You might want to do a quick calculation on how much load you need, divide it by 8 and get some of these to use between the nuts and aluminum plates. https://www.mcmaster.com/belleville-disc-springs/

I used my Arm-Wrench®, it's the torque wrench I trust when I need to make very fine optimizations... I torqued the threaded rods in a sequence from criss-cross, center-to-edge, and torqued them all to 'just-right-tight' ft lbs...

 

[Samsonite801]

I managed to finish the 48v banks tonight. All went well, cells are all insulated from chassis now, got them all torqued down with a bit of pressure. I am chalking two 2x4's under each battery chassis running down the sides for extra support for the weight on the bottom plate. It holds the weight fine without the boards, but felt better to put support for sure on the 48v packs (so it doesn't run risk of sagging with time). I may screw those boards on permanently later on, or instead use some box tubing to make rails for foot supports.

I may look into the spring thing later down the road, I have too many bigger fish to fry for now, enough to keep me busy for a couple years really. We'll see how things go, thanks for the ideas and suggestions guys...

 

[Samsonite801]

Just working on mounting for the BMSs lately. Also going to put active balancers on the two 48v packs since these BMSs don't have bluetooth monitoring, the active balancers I purchased have bluetooth app so I can login and check the cell voltages if desired. The 12v will use the Overkill 120a BMSs so they came with bluetooth already.







2a Active balancer:

 

[Samsonite801]

I just thought I'd post the last couple pics from today. Progress has been slower since my Mother was in town for a week, but in case anyone is following, I got the Overkill BMSs mounted onto the 12v pack, and was able to mount the BMSs and 2a active balancers onto the 48v packs. It will be awhile yet before I actually get these into service (waiting to get a contractor to put me up a steel building) so I'm coming into a holding pattern, other than to test them out and confirm proper function. I will probably start installing the 12v pack into my RV soon though...

 

[Sanwizard]

I finally got around to putting together my 12v and 48v battery banks (holder/clamp assemblies)...

Just thought to post some pictures of it as a couple people had asked me before here.
Still have to mount the BMS's, install the heat pads on bottom plate, thermostats, wiring, etc...
But it's nice to get this far for today. Simple design, I basically did similar to a few others here had done...

I had the 6061-T651 aluminum plates all pre-cut out by cut2sizemetals.com
Used my drill press and c-clamped all the end plates together and drilled all the holes out at once using top one as template.
Took 2 evenings after work, not too hard so far.


View attachment 47871

View attachment 47864

View attachment 47866

View attachment 47867

View attachment 47868

View attachment 47869

View attachment 47870

What is your plan to protect the terminals? I found one solution which may fit yours, is place the banks in a truck toolbox.

This one fits two 48V banks perfectly.

Amazon.com: TUFFIOM 48 inch Heavy Duty Aluminum Truck Tool Box, Trailer Pickup ATV Truck Underbody Bed Storage Toolboxes w/Lock & 2 Keys, Rectangle (48 inch): Home Improvement

Buy TUFFIOM 48 inch Heavy Duty Aluminum Truck Tool Box, Trailer Pickup ATV Truck Underbody Bed Storage Toolboxes w/Lock & 2 Keys, Rectangle (48 inch): Truck Bed Toolboxes - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[Sanwizard]

I agree on the walls. One of the items I'm installing on the banks are heater pads under the base plate, I am not sure to put something that insulates too much on the bottom of the cells as I would like for the heat to be able to dissipate quickly and easily into the cells. I suppose I am not as worried about an electrical short making connection on the bottom of the cells, as it appears the cell has a bit thicker of a black material stuck along the bottomside.

I used the Facon heating pads attached to an aluminum plate that i covered with Polyimide tape. Seems to work well. Between each cell, I used thin heat resistant rubber floor matting. I covered the inside of my aluminum toolbox with felt, and used cutting boards on top to protect each cell and house the BMS.