Wooden Storage Case for 24V DIY

[Coydon]

Is there a good generalized resource that lays out all the factors to consider when building a DIY battery box? I've been looking through threads and videos for a while to find a simple but robust design I could adapt but found relatively few things applicable. Invariably I end up wasting hours down some tangential rabbit hole instead of tracking down relevant info.

A couple months ago I found a video from this older British (Scottish?) gent that was working in his barn (seemed a bit cold, he was wearing a knit cap) who had what was the most appropriate wood box design I've found to date, but now can't find it in my history or come up with the same search terms. Does this description ring a bell with anyone?

My thoughts on a design are that I would like a basic compression design like in the above mentioned video, two end boards connected by four threaded rods. This design was not entirely closed, so would hopefully be able to deal with excess heat passively. I would then build a larger exterior box to drop this into that would have thermal panels in the bottom to provide for colder weather.

Would I need a full enclosure for warmer weather? It will be in a shed that is exposed to dust, insects, and rodents, so wondering if I need a 'summer box' that has some screening? How much better to have a fully enclosed box with a computer fan intake and exhaust to limit dust exposure? Thinking the fan might still pass some dust and need periodic cleaning itself. What does dust do to prismatics with an Overkill BMS attached to them, is this a big concern?

What are the merits of including the BMS and/or other components like a monitor, charge controller, etc. in or on the box vs nearby? I'm trying to picture flexibility of battery placement, but not experienced enough to have much to go on. I have a root cellar nearby if that would address the heat/cold extremes better, but not sure how practical that is with various wire lengths.

 

[Culchee]

Maybe check out "Ray builds stuff" YouTube channel..his diy battery builds are very good..there may be a few things that you will want to include that he doesn't..but worth a watch..

 

[740GLE]

Any cabinet diy video is worth while.

I had left over 1/2” Baltic birch plywood for my 230ah 24v, I built it wider than needed so I had room on one side for terminals and BMS, the other side I use for storage of odds and ends.

The cells are inside the box with “fixing walls”.

I don’t have compression per se but I did reuse foam from the cell shipping boxes and built a sort of tension device. One internal wall is fixed, the other end is free moving both walls have 2” of dense shipping foam before the cells. I cut some tension wedges that when uncharged have the slightest compression of the foam. Fully charged I can pull the wedges out.

 

[45North]

Dunno about wood but I've seen metal ammo boxes used for small systems and also heavy reinforced tool packouts used, some nested and some with wheels. Dollies too.
How big are you thinking?

 

[Coydon]

Maybe check out "Ray builds stuff" YouTube channel..his diy battery builds are very good..there may be a few things that you will want to include that he doesn't..but worth a watch..

Ray seems to trigger my OADD (Online Attention Deficit Disorder). His videos were a major time sink and it was hard for me to collate and retain info after going through them. I'm on a metered account so going through endless videos eats up my data allotment. That's why I liked the English guy's video- one cohesive build beginning to end, and I think it was under an hour.

 

[Coydon]

Any cabinet diy video is worth while.

I had left over 1/2” Baltic birch plywood for my 230ah 24v, I built it wider than needed so I had room on one side for terminals and BMS, the other side I use for storage of odds and ends.

I have softwood timber and a mill coming to make boards soon. It would be good to have an idea on dimensions but I will be making the widest boards I can out of the trees I have regardless. I found the nominal 1" (actual 3/4") board has made some nice, sturdy storage boxes about this size (24V8S of 290Ah cells, still deciding on 1x8 vs 2x4 arrangement) with a Kreg jig- solid enough to stand on but am still able to lift them. That would be my working material unless there is a reason to go thicker or thinner on the boards.

It seems like the BMS would best fit on top under the lid where room is needed to access terminals anyway, but if attached to the lid then makes the wire arrangement more complicated, essentially necessitating a hinged lid. Are you saying you positioned your cells on their side? How much space is needed to access the terminals and BMS that way?

 

[Coydon]

Dunno about wood but I've seen metal ammo boxes used for small systems and also heavy reinforced tool packouts used, some nested and some with wheels. Dollies too.
How big are you thinking?

24V8S of 290Ah cells, still deciding on 1x8 vs 2x4 arrangement.

Seems like options are BMS on a hinged lid, on some sort of shelf over the terminals, at the end of the box where the compression board would also be adjusted, to the side with the cells laid over, or mounted to the outside somewhere. Final size would depend on how much space one of these arrangements would take.

Not sure I'd be able to lift it, but should be able to pivot to position it myself or lift with another person if needed.

Building this barebones and having an insulated or ventilated box to drop it into seems like an option to consider.

 

[curiouscarbon]

Ray seems to trigger my OADD (Online Attention Deficit Disorder). His videos were a major time sink and it was hard for me to collate and retain info after going through them. I'm on a metered account so going through endless videos eats up my data allotment. That's why I liked the English guy's video- one cohesive build beginning to end, and I think it was under an hour.

Your description also faintly reminded me of Ray's build stuff thing, but that's not it.

If you find/recall the English/Scottish/Cap Wearing channel, please post it, because Ray's pace is also sleep-inducing for me, even though the methodology seems mostly sound.

What size cells are you thinking of? Building enclosure is a design step I'm still churning on.

 

[Coydon]

If you find/recall the English/Scottish/Cap Wearing channel, please post it, because Ray's pace is also sleep-inducing for me, even though the methodology seems mostly sound.

Found it! Offgrid Power Solutions

Not sure if it will keep you awake, but a British accent hypnotizes me for some reason.

I was looking at that build and thinking I could make a winter enclosure with heated pads to just drop that into. Possibly also a summer box if insects/dust show up as a problem. I haven't made a close up comparison, but I'm assuming the Overkill BMS will fit in a similar space to what he has here.

 

[curiouscarbon]

Thanks for the link

 

[Culchee]

Ray seems to trigger my OADD (Online Attention Deficit Disorder). His videos were a major time sink and it was hard for me to collate and retain info after going through them. I'm on a metered account so going through endless videos eats up my data allotment. That's why I liked the English guy's video- one cohesive build beginning to end, and I think it was under an hour.

A major time sink ..you only needed to watch one video..now you're triggering my WDIBTHPWOFMATHIO....WHY DO I BOTHER TO HELP PEOPLE WHO ONLY FU####G MOAN ABOUT THE HELP IVE OFFERED...

 

[Coydon]

Well, when i pulled up the name you gave, i got a wall of videos on my screen. My recollection is of going through some of them before, seeing references to other videos and never putting it all together. Do you have a link to that one video?

 

[Steve_S]

24V/280AH Pack.
I used 3/4" Finishing/Furniture grade plywood, 10mm Polycarbonate tops (could have used 7.5mm much cheaper)

Sitting on the shelf: (JKBMS Power Switch is on the Polycarb top)

I am NO LONGER using Plywood Cases. These have been migrated to commercial steel cases. When you crunch the numbers for the cost of High Quality 3/4" Ply, plus Terminals & Polycarbonate top and the extras, + Your time (which has value too), it makes more sense to go with the steel cases that are available AT A REASONABLE PRICE unlike some who are gouging horribly (up to 300% markup).

This is what I switched to:





This is the 8S version (dual terminal or single terminal avail.)
Cost is $168 USD + S&H which is about 100 USD pending where you are.
All that is included in the "kit" makes it worthwhile.

There are several vendors selling similar / identical cases but at considerably higher price points and "interesting" Shipping rates.

These are sourced from a Very Well Known GOOD Vendor, here is the link to these products. https://szluyuan.en.alibaba.com/pro...tery_box_case.html?spm=a2700.shop_index.88.10

TIP: If ordering a collection of bits & pieces from China, getting everything from 1 vendor can save you S&H (sometimes considerably big saving) because a single supplier can package things together and reduce the # of boxes (a fee per box avoided) and more.

Hope it helps, Good Luck.

 

[Culchee]

Well, when i pulled up the name you gave, i got a wall of videos on my screen. My recollection is of going through some of them before, seeing references to other videos and never putting it all together. Do you have a link to that one video?

So you want me to trawl through Rays videos to find " the one " ....the answer to that is ok...but it has one caveat ...if I spend my time looking for the most suitable video for you ..one that is least likely to trigger your OADD...and one that I think is most likely to be of help to you...and you don't like it ...then I do not want to hear you complain about it on this forum...do we have a deal..?

 

[Coydon]

So you want me to trawl through Rays videos to find " the one " ....the answer to that is ok...but it has one caveat ...if I spend my time looking for the most suitable video for you ..one that is least likely to trigger your OADD...and one that I think is most likely to be of help to you...and you don't like it ...then I do not want to hear you complain about it on this forum...do we have a deal..?

It sounded like you had the video in mind when you mentioned it. If you have a link to share here, please do, but no need to put yourself out over it...

 

[Coydon]

Cut the pieces.

My first problem was I put the pocket holes on the inside of the end pieces, thinking it would come out nicer with the holes hidden by the batteries. Then I realized I wanted to secure the batteries between the ends before screwing them to the bottom, otherwise the compression would not equalize properly, so drilled another set of holes on the other side. I designated an inside to the ends based on how the grain would cup, so that any warping would add to the compressive forces.

Fed the all thread into one screw post, through one end board, covered it with latex tubing, and threaded it into another post in the other end.

My current problem is that I cut the bottom to match the length of 8 2 3/4" cells, plus 1 1/2" for the ends. It appears the cells are bulging enough to add just under an inch. I tried to compress them with the all thread but the post shoulders are starting to dig into the pine.

I tracked down the specs and these cells are supposed to be 71mm thick, meaning my 2 3/4" estimate brought me about a half inch short calculating the total assembly length. So the cumulative bulge is about 1/4". Is this to be expected? I bought these just over a year ago and have had them sitting around with whatever charge 18650.com sent them with.

I'm thinking I will cut a new bottom board at the extra 3/4" length, insert washers under the screw posts to prevent them digging into the wood, reassemble with the present level of 'snugness', and screw the ends down there.

My next step will be to figure out if I can/should do top balancing. I had read many posts for other builders saying the BMS will eventually work out the balance with enough cycles itself. But I also read that the Overkill BMS is not a strong charger in that regard. the 6.5k Ahs is probably way more than what I will need until next winter, so should have more than 100 cycles for the BMS to work on it before I might be looking for some extra Ah. Does the BMS eventually arrange for max capacity itself without top balancing first?

 

[Culchee]

Cut the pieces.
View attachment 222258
My first problem was I put the pocket holes on the inside of the end pieces, thinking it would come out nicer with the holes hidden by the batteries. Then I realized I wanted to secure the batteries between the ends before screwing them to the bottom, otherwise the compression would not equalize properly, so drilled another set of holes on the other side. I designated an inside to the ends based on how the grain would cup, so that any warping would add to the compressive forces.

Fed the all thread into one screw post, through one end board, covered it with latex tubing, and threaded it into another post in the other end.
View attachment 222259
My current problem is that I cut the bottom to match the length of 8 2 3/4" cells, plus 1 1/2" for the ends. It appears the cells are bulging enough to add just under an inch. I tried to compress them with the all thread but the post shoulders are starting to dig into the pine.

I tracked down the specs and these cells are supposed to be 71mm thick, meaning my 2 3/4" estimate brought me about a half inch short calculating the total assembly length. So the cumulative bulge is about 1/4". Is this to be expected? I bought these just over a year ago and have had them sitting around with whatever charge 18650.com sent them with.

I'm thinking I will cut a new bottom board at the extra 3/4" length, insert washers under the screw posts to prevent them digging into the wood, reassemble with the present level of 'snugness', and screw the ends down there.

My next step will be to figure out if I can/should do top balancing. I had read many posts for other builders saying the BMS will eventually work out the balance with enough cycles itself. But I also read that the Overkill BMS is not a strong charger in that regard. the 6.5k Ahs is probably way more than what I will need until next winter, so should have more than 100 cycles for the BMS to work on it before I might be looking for some extra Ah. Does the BMS eventually arrange for max capacity itself without top balancing first?

I like the handles..did you look into having some type of insulating material between the cells ..it's probably wise not to have bare cells touching each other under compression..top balancing us always a good idea..I'm doing that myself at the moment..

 

[Coydon]

I looked around for examples of where friction between cells caused a failure. All I found were some experienced folx that said they had never heard of it happening. Seems a theoretical risk if it were in a vehicle, especially if left open so dust or something that could get in between cells, but this one will be stationary and only carted short distances on rare occasions.

My 12V cooler died last week and I'm putting this together ASAP so I have an inverter to run my fridge and can store food. If I can run the battery and top balance later or just let the BMS take care of it eventually without degrading cells in the meantime, it would be a great help.

 

[Culchee]

I looked around for examples of where friction between cells caused a failure. All I found were some experienced folx that said they had never heard of it happening. Seems a theoretical risk if it were in a vehicle, especially if left open so dust or something that could get in between cells, but this one will be stationary and only carted short distances on rare occasions.

My 12V cooler died last week and I'm putting this together ASAP so I have an inverter to run my fridge and can store food. If I can run the battery and top balance later or just let the BMS take care of it eventually without degrading cells in the meantime, it would be a great help.

At the end of the day it's up to you how you approach your build...I t would be a good idea to monitor your cells closely once it is up and running..

 

[B-ManFX4]

I looked around for examples of where friction between cells caused a failure. All I found were some experienced folx that said they had never heard of it happening. Seems a theoretical risk if it were in a vehicle, especially if left open so dust or something that could get in between cells, but this one will be stationary and only carted short distances on rare occasions.

My 12V cooler died last week and I'm putting this together ASAP so I have an inverter to run my fridge and can store food. If I can run the battery and top balance later or just let the BMS take care of it eventually without degrading cells in the meantime, it would be a great help.

I would re-think your stance on not separating the cells with something non-conductive. Most of the kits I have looked at all include something to insulate the cells from each other.

 

[mikejoconnor]

I had a LifePo4 explode and catch fire. Thankfully I had them in a heavy duty metal cabinet. I would not put them in wood.

 

[cs1234]

I had a LifePo4 explode and catch fire. Thankfully I had them in a heavy duty metal cabinet. I would not put them in wood.

Custom built or store bought?

 

[740GLE]

Cut the pieces.
View attachment 222258
My first problem was I put the pocket holes on the inside of the end pieces, thinking it would come out nicer with the holes hidden by the batteries. Then I realized I wanted to secure the batteries between the ends before screwing them to the bottom, otherwise the compression would not equalize properly, so drilled another set of holes on the other side. I designated an inside to the ends based on how the grain would cup, so that any warping would add to the compressive forces.

Fed the all thread into one screw post, through one end board, covered it with latex tubing, and threaded it into another post in the other end.
View attachment 222259
My current problem is that I cut the bottom to match the length of 8 2 3/4" cells, plus 1 1/2" for the ends. It appears the cells are bulging enough to add just under an inch. I tried to compress them with the all thread but the post shoulders are starting to dig into the pine.

I tracked down the specs and these cells are supposed to be 71mm thick, meaning my 2 3/4" estimate brought me about a half inch short calculating the total assembly length. So the cumulative bulge is about 1/4". Is this to be expected? I bought these just over a year ago and have had them sitting around with whatever charge 18650.com sent them with.

I'm thinking I will cut a new bottom board at the extra 3/4" length, insert washers under the screw posts to prevent them digging into the wood, reassemble with the present level of 'snugness', and screw the ends down there.

My next step will be to figure out if I can/should do top balancing. I had read many posts for other builders saying the BMS will eventually work out the balance with enough cycles itself. But I also read that the Overkill BMS is not a strong charger in that regard. the 6.5k Ahs is probably way more than what I will need until next winter, so should have more than 100 cycles for the BMS to work on it before I might be looking for some extra Ah. Does the BMS eventually arrange for max capacity itself without top balancing first?

3/4” pine boards?

Let us know how it handles the cells expanding at full charge, my guess it’ll split at the threaded rod.

 

[Coydon]

I liked the idea I saw in another thread of bridging the top two rods with some angle on each end. If something happens to these pieces I'd redo and add that, maybe with flat bar across the bottom.

I'm using wood mostly because of ease of access to raw material and ease and experience of DIY fabrication. Not sure if I'd go metal even if I was more used to working with it. Seems better to avoid fires than to mitigate fuel in an unknown context.

 

[Coydon]

My Overkill BMS has two temp probes. They are pretty small in diameter. The official Overkill recommendation is to tape them to the side of a cell with Kapton tape. Does the Kapton tape exclude ambient temperature somehow? Does it work to place them between cells (which would give a more accurate reading of the actual temp inside of the battery)? I'm thinking with compression this could be something that would damage the protection around the cells as they expand, no? If so, could they be integrated with some sort of separation material to prevent that?