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Another 280Ah 4S Battery box build - Compact Case

ChadClancy

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Mar 19, 2021
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I just wanted to post some pics of my first LiFePO4 battery build using four 280Ah cells and an Overkill Solar BMS. This is for an RV to replace our current lead acid deep cycle batteries.

This battery bank will be located inside a storage compartment in the RV so it will be well protected but there are other things stored in the same area so I wanted it to be self contained and protected. I also wanted it to be as compact as practical so I went to the local box store looking for storage bins of the right geometry. This wasn't as easy as I originally envisioned. I was looking for something with an inside footprint of 12x8 inches and a height of around 10 inches. When looking to see what was available, it seemed like most containers of that size had a limiting height with most of them in the 8.5 inch range which was insufficient. I did find one that would be a tight fit with a height right around 9 inches. I wanted to have studs on the main +/- terminals so I knew that I would have to size these just right for everything to fit with this case. Here is a pic of the box which is about $13.50 at Home Depot. This is a waterproof case so I drilled holes in the top for some ventilation. A small PC fan could be added to help circulate airflow through the case.

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And here are some pics of the assembled battery. I made some 3D printed bulkheads for the box battery terminals and I still want to make some color coded magnetic covers to shield the terminals. If you need more clearance for a cell clamping and/or spacing setup, I would suggest putting the battery posts on the side, alongside the BMS (but separated to avoid shorting).

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Not a great deal of clearance inside but there is just enough to have a little room to spare on the BMS side and to be able to make the bulkhead/terminal connections on the front.
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Since this is for a mobile installation, I will probably make some sort of strap system to secure it to the floor of the RV storage bin where it will reside.

One thing I forgot to mention is that this case comes with internal deviders that I removed and I also cut out the ribs ob the side of the case that these slide into. Quick work with one of those multi-tool saws.
 
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Which box is this? I’m currently searching for cases to build my batteries and I like the looks of this.
 
See the first pic that shows the label. Some vendors label this as a Plano tactical box because it is perfect for ammo but that must be too hardcore for Home Depot.

Plano storage box
Thanks for the link. None of the local Home Depot’s had them but the one out by Utica had four so my brother in law is picking two of them up for me.
 
Which box is this? I’m currently searching for cases to build my batteries and I like the looks of this.
I recently used a Quantum Storage box (150 pound rating, handles, used in warehouses). I didn't include the lid in a photo but it's an average or slightly loose fit not something like an ammo box which clasps shut and is weatherproof. They come in a variety of sizes; I got mine on Zoro. Photos are in my thread on it; I just got the system up and running yesterday. I put a baltic birch plywood and 80/20 aluminum frame tucked into the bottom stacking insert to prevent sag. I also have bolts coming up through the bottom so this gives a place for the bolt heads to go.


Some of the cheaper/harder plastics can fracture or crack when you weaken them by cutting holes (if you plan to cut holes). You want something which does not do that as it would be bad news if the bottom gave out all of a sudden when you're carrying around 3kWh of energy!

Anyway, may not be your cup of tea, but wanted to share my recent box experiences.
 
I recently used a Quantum Storage box (150 pound rating, handles, used in warehouses). I didn't include the lid in a photo but it's an average or slightly loose fit not something like an ammo box which clasps shut and is weatherproof.
Could you post the link to the one you ordered from Zoro? I am thinking about getting the one in the link provided below.


The inside dimensions will be just big enough to fit my 8 EVE cells with a compression fixture. But it is taller and longer than I would like. I have looked at so many of these I am tired of it...lol.
 
It's this one:


I had to get the lid elsewhere (Northern Tool & Equipment) so I doubled my shipping cost. But you might be able to find it if you search a bit.
 
With springs it might be a bit tight in the "short" direction like I had for 4x2 280Ah. I squeezed two 3/4" sheets of plywood and one 1/4" or 3/8" sheet on the outsides and had no compression fixture. However, the plastic is soft and easy to drill so your fixture could go "through" the sides of the box and/or be attached to it. It's flexible enough that it would bend in if you applied the recommended amount of force from the outside.

Also, I don't think the cells fit sideways in the other direction! You've seen my pictures, I think, so imagine rotating all 8 cells 90 degrees: they don't fit sideways in there. I could measure and double check.

Unfortunately it's the only one that's the appropriate height:


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Also, I don't think the cells fit sideways in the other direction! You've seen my pictures, I think, so imagine rotating all 8 cells 90 degrees: they don't fit sideways in there. I could measure and double check.
I don't think so either. Each of my EVE cells is 6.84 inches so side by side so that would be 13.68 inches total just for the cells plus I would have to allow room for the threaded rod that goes down the middle.. I am using 1/4 inch plywood and 5/16 threaded rods. With the nuts and washers bolted to the threaded rods I can't go less than 14" for the box width. The length and height of the plywood is 8"X18". Also the MRBF fuse adds to the height but I could move it. For now the battery is sitting on a cart.

I have experimented with the compression vs SOC and what I have done is applied red loctite to the nuts on one side. I still need to cut of the extra length of the rods on the other side and will use blue loctite on those nuts.

I have the cells fairly snug at full SOC, and when they are fully discharged the plywood (fixture) is loose enough to easily slip off. When I redo the pack and install it in a box the cells will be discharged so I can easily slip the fixture over the cells. I will also be installing thin insulators between the cells. I am not getting into the weeds applying a scientific PSI compression using springs and what not, but I am being careful to not apply too much compression.

I haven't been able to find anything smaller then the box I linked to that will work with my cells. Akro-Mils doesn't make a lid for it but it would be easy to find something that would work.

I do like the clear one I will link to. Even though its's load capacity is 70lbs I am fairly sure it would be ok with plywood installed in the bottom which you did and so will I no matter which box I decide to go with. It's quite large but plenty of room to work in. The non clear ones cost less.


I am sure you will find a way to compress your cells from the outside of the box. I have never had one of these storage boxes and maybe the box itself will apply enough compression to keep your cells nice and tight.
 

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Great Build @Gazoo! How did you affix your BMS to the side of the battery? What size are the two wires you using from the BMS to the negative? And what size are the main positive and main negative? and what load do you expect to draw? I'm trying to build a 280 ah 4S battery with the Overkill 120a BMS. So, a single row of what you did in a smaller plastic tool box with plywood on the bottom. Cells are still in transit. I picked out this box as my first try: https://www.amazon.com/gp/product/B00CBY2EIO/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1. The battery is going into a 2005 Airstream replacing two 92 ah SLA batteries . . .

Have you thought about running a couple straps around the plywood on the bottom and then over the top of your compression sides, so you have a single bundle you can lift out of the box rather than moving the compression jig in and out and placing the batteries separately? The 8 cell battery might be too heavy for that?
 
Great Build @Gazoo!
Thank you. But it's going to be rebuilt ..lol

How did you affix your BMS to the side of the battery?
I used wire ties and they are supported by the threaded rods. I used double sided tape to mount a bottle top to the BMS's heatsink on the side that faces the battery to allow for clearance between the BMS heatsink and battery.

What size are the two wires you using from the BMS to the negative? And what size are the main positive and main negative? and what load do you expect to draw?
They are 10awg cables, same on the other side of the BMS. Steve (Overkill) assured me they would be fine. I have a 2000 watt UPS that can pull apx. 100 amps from the cells. You may read my review of the UPS here. I will never use the full 2000 watt rating of the inverter. I do plan to test it further and all of that is explained in my review.

I'm trying to build a 280 ah 4S battery with the Overkill 120a BMS. So, a single row of what you did in a smaller plastic tool box with plywood on the bottom. Cells are still in transit. I picked out this box as my first try: https://www.amazon.com/gp/product/B00CBY2EIO/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1. The battery is going into a 2005 Airstream replacing two 92 ah SLA batteries . . .
I looked at that box too when I was looking at others. It should serve your needs well. I was thinking about ordering a custom size steel battery box from China but decided to go with plastic. Much easier to drill.

Have you thought about running a couple straps around the plywood on the bottom and then over the top of your compression sides, so you have a single bundle you can lift out of the box rather than moving the compression jig in and out and placing the batteries separately? The 8 cell battery might be too heavy for that?
Yeah I thought about it and 8 cells we are talking around 95 lbs. I am not a spring chicken anymore but I would have help if I needed to lift the whole bundle.

I have had the cells since Oct. and still have not finished everything. I have run them through 22 full cycles with no problems. Once I have everything mounted in the box I don't anticipate any problems. I might relocate the BMS so it's easier to get to. I am confident the cells will last for years. The BMS is another story but so far I don't recall anyone having an Overkill BMS fail after installation.. If a cell fails it's just a matter of disconnecting the BMS wires and replacing the cell.
 
Yeah @Gazoo looks like you and I are building very similar things. Agreed: on the height of the BlueSea MBRF, that's why I mounted mine on standoffs. I can send you part numbers / links if you want to do that too.
 
I don't think so either. Each of my EVE cells is 6.84 inches so side by side so that would be 13.68 inches total just for the cells plus I would have to allow room for the threaded rod that goes down the middle.. I am using 1/4 inch plywood and 5/16 threaded rods. With the nuts and washers bolted to the threaded rods I can't go less than 14" for the box width. The length and height of the plywood is 8"X18". Also the MRBF fuse adds to the height but I could move it. For now the battery is sitting on a cart.

I have experimented with the compression vs SOC and what I have done is applied red loctite to the nuts on one side. I still need to cut of the extra length of the rods on the other side and will use blue loctite on those nuts.

I have the cells fairly snug at full SOC, and when they are fully discharged the plywood (fixture) is loose enough to easily slip off. When I redo the pack and install it in a box the cells will be discharged so I can easily slip the fixture over the cells. I will also be installing thin insulators between the cells. I am not getting into the weeds applying a scientific PSI compression using springs and what not, but I am being careful to not apply too much compression.

I haven't been able to find anything smaller then the box I linked to that will work with my cells. Akro-Mils doesn't make a lid for it but it would be easy to find something that would work.

I do like the clear one I will link to. Even though its's load capacity is 70lbs I am fairly sure it would be ok with plywood installed in the bottom which you did and so will I no matter which box I decide to go with. It's quite large but plenty of room to work in. The non clear ones cost less.


I am sure you will find a way to compress your cells from the outside of the box. I have never had one of these storage boxes and maybe the box itself will apply enough compression to keep your cells nice and tight.
 
My wife works at Merck. They use those Orbis boxes, but are blue. Ship in drugs and throw them out. She brought home about 20 now. Time to measure them up for my soon to be deliver 8 272ah batteries
 
Yeah @Gazoo looks like you and I are building very similar things. Agreed: on the height of the BlueSea MBRF, that's why I mounted mine on standoffs. I can send you part numbers / links if you want to do that too.
Thanks but I ordered a terminal block and might mount the fuse directly to that providing it fits. I will keep your offer in mind. Thanks again.
 
I saw this plano box at home depot. I had already committed to using the seahorse cases which are more substantial but about $60. The plano cases are a bargain and sized perfect.
 
I went belt and suspenders; plywood compression which fits snugly in a DeWalt Tool Box $40 (with straps around it I can lift the battery frame out of the box).

Installed in trailer this weekend with Victron SCC, Renology DC-DC charger and Victron Shunt. So far, seems to be working.

jps
 

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