560ah 12v Battery with Clean, Modern Case

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
This is my first post here, but I wanted to share my DIY battery bank. This forum and Will's videos were so helpful that I wanted to share a few things I learned, as well as a few things I created that I haven't seen before (specifically the asthetics of the case). I'd also appreciate any critical feedback or suggestions, I've learned a lot in the last few months and would love to learn more!

Here is my finished battery, total cost was ~$1,400 ($0.20 pWh vs Battleborn at $0.67 and SOK at $0.42):
20211216_201031.jpg

20211216_200841.jpg

I build custom campervans and rent them in Seattle, Washington. For one of my upcoming builds I will have an induction stove, hot water heater, a 12v Domestic RTX2000 AC, and 2 electric bikes. I needed a large, cost effective battery bank, in addition to A LOT of storage for the bikes.

I typically use Battleborn batteries (I need rock solid electrical systems), but they are just too big for this build, so I decided to build a custom battery bank - I'm glad I did. Look at the size comparison of my 560ah battery vs. 6 Battleborn batteries (I'm currently building 3 other vans which will have 3 Battleborn batteries each, so I had a few laying around 😀):

20211216_202757.jpg

This battery bank will allow me to have an electrical cabinet no wider than my wheel (560ah battery, 60 amp DC to DC charger, 3000w Victron Inverter, 150/60 Victron MPPT, Lynx distributor, Victron Cerbo gx, fuse block, AC breaker, solar switch, and a weBoost), which will allow for a much larger storage area.

How I built my case:
1. Frame. I used 1/2" cutting board from Amazon and cut it down to size for my batteries. These were then attached with screws and heavy duty epoxy (only compound I could find to glue hdpe together beyond extremely expensive products).
2. Compression: I drilled holes and used all thread plus polyethene tubing to protect the cells from the allthread.
3. Structure: I used aluminum angle iron for handles/to help with compression and the same on the inside to hold my BMSs.
4. BMSs: I mounted 1/4 acrylic to the angle iron above the batteries, velcroed 2 4S overkill solar BMSs to it, and drilled 2 terminals with 1/4"x1.5" busbars for the positive and negative connections.
5. Battery connections: I used 1/8" x 1" busbars for the batteries, heat wrapped to identify positive and negative sides of the batteries. I attached with M6 16mm studs, noalax, and serrated flange nuts.

Here are a few more photos of the build:

20211216_201042.jpg

20211216_200848.jpg

20211216_200909.jpg

Now, onto my learnings:

1. Building your own battery is probably not worth your time unless you do this a lot, are just curious and want a challenge, or need a big battery bank for cheaper than you can buy (although I'd argue some alternatives are better and only marginally more expensive). I spent many hours researching, finding suppliers, deciding on options, selecting busbar/wire sizes, deciding on BMSs, and building a case. Not sure the ROI makes sense unless you do this a lot, which fortunately I will.

2. There is always a better way to build your battery, but it's not always worth it, nor is it a one-way door (you can update later on if you want). I was considering flexible bus bars to allow for expansion/contraction, so many ways to compress/not compress the batteries, etc. At one point, I just decided to make decisions and stop churning, knowing that if there are better ways to do this, someone else will post and I can always change my design.

3. These cells are extremely compact and save a ton of space. I love Battleborn, but these cells take up less than 50% of the space of equivalent Battleborn batteries.

I'll post updates as we install these into our latest build.
 

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DJSmiley

Solar Addict
Joined
Aug 13, 2020
Messages
584
Nice build!

As for the BMS: You can flip them and add some spacers. There are 6 holes with M3 thread. Using spacers allows for airflow and the wires not to bend too much (directly from the pcb)

That way you can screw them (drill a hole in the acryl and put in a small bolt, allowing to go through the acryl, spacer and screw into the threads in the BMS)
 

Isaac-1

Solar Enthusiast
Joined
Nov 4, 2021
Messages
88
Looks nice, one thing I would consider changing is mounting the acrylic spacer below the aluminum L channel instead of on top, that way if it should ever fall it can't short out the battery terminals. Just thinking of a situation like dropping the entire battery, or if the van were in an accident. Adding a disconnect breaker on the case itself might also be a nice feature.
 

bryn

Solar Enthusiast
Joined
Nov 4, 2021
Messages
89
Looks good, I’m building a similar system with 304ah eve cells for my camper.

in regards to how you paralleled your packs, are you drilling another hole in the centre of the bus bars you made to allow for an equal draw on the packs?

im using fusing studs on mine, but with a 3 way isolated to isolate a pack if it fails on the road.

please let us know the real world draw on that RTX2000 AC, i would a fitted one of these when I built my van, if they were available 4 years ago.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
6,062
Location
Rural NE Ontario Canada
This is a very well done assembly and well thought out. I do have to agree that a spacer between the bottom face of the BMS and the Arcrylic is prudent as the FETS on the bottom would be affected by reduced airflow. I really like the busbar setup using the base with upgraded bars but I am wondering why that was not extended to include a 3rd 3/8's for the battery terminal out leads, I would not want to double up on the terminals as it can be easily avoided. I don't recall you mentioning if/how you will put a top over that but I'd go with the clear acrylic but like this below using similar aluminium L Braces with the acrylic on top of the side pieces.
1639743488920.png
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
Nice build!

As for the BMS: You can flip them and add some spacers. There are 6 holes with M3 thread. Using spacers allows for airflow and the wires not to bend too much (directly from the pcb)

That way you can screw them (drill a hole in the acryl and put in a small bolt, allowing to go through the acryl, spacer and screw into the threads in the BMS)
I had no idea what size these threads were! I'll buy some M3s, add spacers, and lift the BMSs. Thank you!
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
Looks nice, one thing I would consider changing is mounting the acrylic spacer below the aluminum L channel instead of on top, that way if it should ever fall it can't short out the battery terminals. Just thinking of a situation like dropping the entire battery, or if the van were in an accident. Adding a disconnect breaker on the case itself might also be a nice feature.

Great idea. Never thought about these coming down shorting the battery terminals. Flipping the acrylic should be a fairly simple change!
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
Looks good, I’m building a similar system with 304ah eve cells for my camper.

in regards to how you paralleled your packs, are you drilling another hole in the centre of the bus bars you made to allow for an equal draw on the packs?

im using fusing studs on mine, but with a 3 way isolated to isolate a pack if it fails on the road.

please let us know the real world draw on that RTX2000 AC, i would a fitted one of these when I built my van, if they were available 4 years ago.

My current plan is to put the positive terminal on one of the studs and the negative on the other, similar to what you'd do in any regular battery system, but the bus bars are so short I'm not sure it matters? I'd love to know if it does though.
 

Prefersdirt

Solar Addict
Joined
Sep 28, 2019
Messages
330
total cost was ~$1,400 ($0.20 pWh vs Battleborn at $0.67 and SOK at $0.42

Love the box. Much more than the ones I built for mine. I really love the numbers as I am looking to greatly expand our battery bank and our wallet just keeps running and hiding as I do so.

Very elegant build. if life ever slows down (ha ha) I will redo mine that way
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
This is a very well done assembly and well thought out. I do have to agree that a spacer between the bottom face of the BMS and the Arcrylic is prudent as the FETS on the bottom would be affected by reduced airflow. I really like the busbar setup using the base with upgraded bars but I am wondering why that was not extended to include a 3rd 3/8's for the battery terminal out leads, I would not want to double up on the terminals as it can be easily avoided. I don't recall you mentioning if/how you will put a top over that but I'd go with the clear acrylic but like this below using similar aluminium L Braces with the acrylic on top of the side pieces.
View attachment 76060

My original design was to build an acrylic case, extend the busbar and bend 90 degrees out the top of the case, and these would be my single positive/negative terminals, but couldn't get a clean bend in my busbar. I decided to simplify with the 2 studs to simplify the design.

Is there a reason to not double up on the terminals? Still learning here and would love to know so I can change my design.

For the acrylic case, I decided against doing the case. It will be enclosed in a cabinet where there is no exposure to anything that could get to it (I'll post another picture once I have it installed). I still may add it for redundancy, but I like your idea of angle iron on the top. Thanks!
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
Yes. Hopefully you have a cover. And a fuse.

👍 I'll add a fuse to my positive terminal and it will be enclosed in a cabinet. I'll post a picture of the installed system, likely this weekend.

Do you have any recommendations for fuses?

I used a blue sea systems block fuse in one of my systems and it failed. It created so much resistance that it started to melt and cause a large voltage drop, tripping the inverter any time you used >1800w of power. I swapped to a Mega fuse, but it's further from the battery terminal than I'd like (~12 inches). Does the distance really matter?
 

Carson - Vanlife Rentals

Carson, I build and rent campervans
Joined
Oct 12, 2021
Messages
25
Location
Seattle, Washington
Love the box. Much more than the ones I built for mine. I really love the numbers as I am looking to greatly expand our battery bank and our wallet just keeps running and hiding as I do so.

Very elegant build. if life ever slows down (ha ha) I will redo mine that way

Maybe I should adjust the learning to "nothing is a one-way door, but it's probably good enough since you'll never find time to go back and fix it" 🤣

My main goal was really space saving and I am concerned about longevity/performance (the electrical system for our vans is a tier 1 service. If it fails, the trip fails and we can't have that). The cost savings was really just an added benefit as the large campervan builds are quite costly as they are - although the savings allowed us to try out the new 12v domestic AC (a $3k unit) which we are excited about.
 

Prefersdirt

Solar Addict
Joined
Sep 28, 2019
Messages
330
Maybe I should adjust the learning to "nothing is a one-way door, but it's probably good enough since you'll never find time to go back and fix it" 🤣

My main goal was really space saving and I am concerned about longevity/performance (the electrical system for our vans is a tier 1 service. If it fails, the trip fails and we can't have that). The cost savings was really just an added benefit as the large campervan builds are quite costly as they are - although the savings allowed us to try out the new 12v domestic AC (a $3k unit) which we are excited about.
what is the AC unit? I can see many uses for such a thing.
 

Blackhat

Solar Enthusiast
Joined
Dec 3, 2021
Messages
45
Love the build. Very clean! Inspiration for sure as I'm considering a build to fit under the seats of my 4 Runner. The hacked up plastic cutting board is a great material source.

I think it's a shame the space savings of a DIY battery isn't discussed more. It's probably because most are using the low cost of the cells to build huge stationary banks that sit in a shed or utility room where space isn't critical. If that's your situation then buying a tote from Home Depot and throwing the cells in there works fine. But if you're handy with wood, metal or plastic you can use non-typical layouts that fit a huge amount of energy in a much smaller or oddly shaped space, and that can be a game changer in a vehicle build.
 
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