Onfe's "Slimline" 5kWh build

[Onfe]

Hey all, I'm putting together a pair of 24v packs based on the 105Ah EVE cells from Shenzhen Luyuan (via @Amy Wan (Luyuan) ). I thought a few elements of this build may be of interest to some people and it only seems fair to give back for all the information I've gathered from the people on this forum.

Context​

I'm working through the process of converting a van into a tiny home, but with the used van market being pretty wonky right now, I'm still looking. In the meantime, I've got started on the aspects of the build that I can, such as the battery bank for the electrical system.

Given the space constraints and my mind's habit for wanting to try the unknown, the battery bank is ideally going to live in the space under the kitchen cabinetry (toe-kick, plinth, etc.), so keeping it slim in terms of height is the goal. I've got a second location in mind that would fit a more standard style pack if this doesn't work out.

I'm building two independent 24v packs to aid in weight distribution compared to a single heavier pack. The 105Ah cells also seem more robust and less prone to the slight swelling people talk about on the 280Ah cells.

Specs​

I'm going to be building two packs each with:

8 x 105Ah EVE cells in series, giving a 24v nominal pack
1 x DALY 8S 24V 150A common port BMS
1 x 125A MRBF mounted directly on the +ve terminal

Each pack will also get a ~100A mega fuse on the main busbar, "backed-up" with the MRBF due to its higher breaking capacity so I hopefully don't end up having to pull out the packs too often from under the cabinets. I don't intend to ever push more than 100A from each pack.

Each pack should have around 2.5kWh usable capacity, giving around 5kWh in total.

What's next?​

The cells arrived a few weeks ago but due to some deadlines, I've only just started the top balance. While they sit there with the charger whirring in the background I'll write up the next post detailing how ordering the cells went, what I paid and how they arrived.

Once I've got my hands on a van I'll start a more general thread about the whole system if there's any interest.

 

[Onfe]

Cells​

As mentioned previously, I decided to go for the 105Ah EVE cells from Shenzhen Luyuan. They're supposedly a bit more resilient than the 280Ah cells and given they'll be in a van and probably end up mounted sideways that's a good thing.

I decided to contact Amy after browsing this forum and seeing quite a few happy customers. She was very polite, informative, and quick to respond. In the end, the price seemed right and the communication was really good so I decided to go forward with ordering.

Ordering​

I contacted Amy back on February 26th and requested quotes for a few different variations of cell capacities, quantities, shipping and taxes. I also mentioned that I'd found her through this forum. She got back to me the same day and by March 1st I'd got enough information to make a decision on the 105Ah cells. I paid through Alibaba and Amy confirmed receipt of payment within the hour.

I paid $1021.60 USD for 16 cells, shipping and customs (DDP), double busbars and welded studs.
- 16 x $47.80 per cell.
- 16 x $1.50 for welded studs per cell.
- 16 x $0.8 for extra busbars.
- $220 for DDP shipping and taxes to my door.

If you're put off by the shipping price, make sure you "request a quote" as the shipping estimate by Alibaba was way off.

Dispatch & Delivery​

Amy dispatched the cells 15 days after payment, and she sent photos of everything before they were sent. She apologised for the delay in getting them dispatched and kept me in the loop with what was going on. Once the cells were dispatched there wasn't any tracking or solid indication of when they'd get to the UK.

I contacted Amy on the 15th of May as I hadn't heard anything from DPD (the last mile courier chosen). She checked with the shipping company and it turned out they'd been stuck at UK customs, which isn't a surprise given Brexit has completely mucked up the waiting times for customs, but annoying nonetheless!

I got notification from DPD that they'd got my parcel on May 19th, and they were delivered the next day.

Packaging​

Cells were packed in boxes of 4, with cardboard separators and plenty of foam. The stud terminals were pushed into the foam and a further piece used to secure the entire set of cells from moving about (not shown in the photo).



The busbars were split into two boxes, in a plastic bag and a foam separator between them and the cells.
Two boxes of four cells were combined in a larger cardboard box, so what arrived on my doorstep was two boxes containing 8 cells each.

Quality​

This is my first time handling these aluminium cased cells, but overall I'm impressed. The wrapping around the cells shows no damage and all the vents look just fine to me. None of the QR codes was scrubbed or damaged. The printed "CE" sticker on the cells is obviously a bit suspicious.



The laser welding on the studs is OK, tightening things onto these terminals feels a lot more certain than it would do into the aluminium terminals. The welding does take up some surface area on the terminal so the actual contact patch for a bus bar is reduced.
As you can see in the photos, the welding does discolour and wrinkle the terminal plastic somewhat. They're M4 sized and just long enough for two supplied busbars, the washers and a crimped BMS cable.



The hardware included contains washers, split washers and nyloc nuts. I might leave off the washers and use flanged nylocs instead to gain more space for a thicker busbar. The busbars included are tinned copper, 2mm thick, 12.5mm wide, and annoyingly only long enough to connect side by side not edge to edge.

Summary​

I'm happy with my purchase, although the shipping was slow I expected that (it's why I ordered in Feb despite only needing them in June, after all!). I'll be ordering some copper bar to make my own busbars it seems, though if you're making a more standard 8S pack they'd probably be fine.

I'm going to get on to top balancing these cells and then I'll let y'all know how that worked out.

edit: Added size of studs (M4) and fixed a few typos.

 

[OzRhys]

Looking forward to seeing how you progress. I have 120ah cells on the way and I'd like to make a slim configuration as well but 12v.

 

[Onfe]

As per usual life got busy but oh well - In other exciting news, there's a van sitting outside now!

I've been balancing these cells in batches of four and with a 20 amp supply they take about 16 hours to hit 3.5v, so can just about do one set of four a day.
The Riden DPS5020 I picked up on Aliexpress is holding up surprisingly well, even pumping its full 20a rating. Gets a bit warm then the little fan on it kicks on and off. I've got it hooked up to a trashy 12v supply I had lying around and the fan on that is awful.

I've just got one last set of four to do then I'll stick all 16 in parallel and bring them up together the last little bit to 3.6v, hope that doesn't take too long. I'll make sure I take pictures when top balancing that last set, too.

A meter of 16x4mm copper bar fell through the letterbox today so that's the busbars sorted. Mentally it's all coming together - just need to sift through the 'net and buy the bits!

 

[Lumenbeing]

Any updates on this?