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4s4p LiFePO4 Build Log

Thank you for sharing all the details of your project. I'm thinking about buying the same batteries but like you've already said, finding a big enough tool box / container is a problem.
You're welcome -- it's also to keep me motivated between project time (day jobs are such a drag :))

The batteries are gorgeous but they aren't as easy to work with as prismatics, where the leads are on the same side. I'll have more details of my box in a few weeks as I start the fitment process.

If looking for containers: total length of the battery is about 320mm. 280mm + 20mm of leads on each side. And 60mm diameter of course.
 
Those breakers are something else I have been looking at some that I would like to connect between my inverter and MRBF fuse. Want it mainly for the compact size of having a disconnect.
They make battery disconnect switches that are pretty compact and enclosed. If you use it a lot that might be a more durable option. Search for "mini battery cutoff switch"
 
They make battery disconnect switches that are pretty compact and enclosed. If you use it a lot that might be a more durable option. Search for "mini battery cutoff switch"
Yeah I have been doing some image searching and at the 300amp mark they do offer some decently sized. Still do not seem as small as some of those circuit breakers. But would feel better with an actual switch used.
 
Everyone: LiFePO4 batteries have a very flat voltage curve

Me: Yep, sounds good. My batteries are pretty close to full so I'll just top balance with this dinky charger instead of wasting time reassembling the pack.

6 days later.... finally starting to get near 3.5 volts.

Adding an open circuit voltage chart I found, and wish I had before I started!
 

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Looking good, I was thinking of buying these or the 100ah packs that are made from their 32650s.
Any idea what one of these cells weigh? It's not listed on the site.
 
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Looks good just got done building mine.
 

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Why the hate on that breaker? I've got a 40a and 50a in my van.
Only replying to agree with others.

Those things are bad and shouldn't be trusted. Popping early is one thing but they also like to simply not work at all, or add a ton of resistance to the circuit and get hot.

I've had my share of them when I was a dumb kid doing car stereos. Installed a dozen of them before I started learning first hand about their issues.
 
Looks good just got done building mine.
Awesome!

I like the way you did your bus bars, lots of flexibility.

I’m in the middle of moving so my project is on hold for a while :(
 
Awesome!

I like the way you did your bus bars, lots of flexibility.

I’m in the middle of moving so my project is on hold for a while :(
I used 1/8 by 1.25'' aluminum sanded real good with paste. Learned a lot from yours. thanks
 
I’M BACK!

The hardest part about projects is picking them up again after a long break. The second hardest part is cutting holes in new equipment.

Due to vehicle changes I no longer have to fit the Renogy unit inside the box. Everything will run off a single Anderson 120 plug built into the box, basically like what BigBattery does.

I still haven’t figured out the internal support structure, but happy to be making progress again!

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I needed the battery for a trip, so was forced to do things quickly which was great for bypassing perfectionism.
  • Shifted the battery to the right
  • Added a slot-in wooden spacer to hold the cells in place
  • Added protective sleeving to the BMS balance wires
  • Added squishy rubber strips between the cell groups
  • Added a 150 amp ANL fuse
  • reorganized BMS cabling
  • Dangly nylon strap for ease of removal
Everything is secure inside, and has been working great for the last several weeks. I ran my shop vac (1300 watts) for extended periods of time and nothing in the box was even warm.

Most tasks from here on would be cosmetic:
  • add anchor point for main negative cable
  • Secure ANL fuse better
  • Add plexiglas inserts on top of bus bars for protection and looks
  • Add a switch to Bluetooth module so I can turn it off when not in use (since it’s completely unsecured)
  • Clean up the rubber padding between cells
  • Add a pad to the inside of the lid
  • Find something to put in the extra space on the left (snacks maybe)
I would consider the battery “done”. I’ll make another followup post if I ever get to the rest. For now, happy it is now in working service.


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