Now i was trying to figure out how to fit more batteries into the same space so i am sketching in freecad a system where the cells are stacked vertically and side to side with each other. Is more complicated but a very efficient way of using the space.
Oh...that's what doing it right looks like! That is so cool, thanks for sharing. I can see now that having a 3D printer would be fun to play with.
I am not sure that is 'right', but it works for me. I made a thread asking members of the forum if they could see things i needed to improve and they helped me a lot with some details.
how would you do differently?
Is hard to describe with just words, but i would stack the 16 cells packs vertically, side to side with each other with the terminals facing in the front.
Is that so you could stack more packs vertically in the same space you are using horizontally for the packs you have?
Oh eBay not amazon. Got it.
Yes and not only that, i would change the position of the busbars too making it much better. Right now they are vertical at the center, i could change them to horizontal right above the battery packs and under the inverters. I would look so much better and be more efficient. Also it could be much easier to build an enclosure for the batteries.
Thank you for sharing your design and making video of Poron flammability, I'm actually going to use Poron 5mm spacers between cells- besides heat insulation they should allow cells to expand 'in place': designs with springs apply pressure from the sides and when cells expand due to charge they would need to physically move adjacent cells in the string - or be compressed more than intended.I don't use no stinking springs.
Springs will compress and allow the cell center to deform over time.
I don't use no stinking springs.
Springs will compress and allow the cell center to deform over time.
The idea behind compression fixtures is to hold the cell in the original form with minimal expansion in the middle which could damage the jelly roll. I use foam. I started the original foam thread, it was my very first post and they haven't been able to shut me up since.
I use threaded rod as a hard stop with 3mm Poron sourced from Ebay. Originally I used neoprene in the house bank but switched to Poron. One member mentioned lately the seller will cut it to size for you. I just use a paper cutter like you used back in school.
from the 314Ah cell doc posted here: "The product generates expansion force during use, and the expansion force is about 60000 N when the cell capacity attenuates to 60% under the test conditions of 15 mm steel plate + 0.0 mm GAP (the space for cells to expand). Customers shall consider the reliability of structural strength in the product design process, and it is suggested to reserve 2.0 mm ~ 2.5mm expansion space while grouping the cells." So I'd go with thicker than 3mm Poron based on that paragraph. I also think for springs to work as intended the cells between the plates would have to be able to move freely as their combined expansion can only be absorbed by the springs. Since that is not likely to happen the cells would get over-compressed.
LF280K
they also require not to exceed 10,000N force (39psi) to avoid cell damage. I understand it the cell squeezed between 2 hard surfaces that won't move is capable of developing self destructing expansion force during charge.
Looks amazing. Also looks like you built 5 packs and decided, "I give up - I'm buying pre-built!". That is an amazing setup. Security camera too. Is this a business of some kind? looks like you're adding a 4th inverter wow.
4701-40 3mm seems like the sweet spot, pretty difficult to get them to dangerously high pressure levels, so plenty of safety margin as the cells age.
I bought the 3 server rack batteries first and then decided to diy them for half the price.
