mux wrote:Somebody has done this before, like a dozen times: replacing the old 24kWh cells with new ones. The BMS just adjusts to the new cells.
I've seen where they've put 24kWh cells in a 24kWh battery. But what if the cells (or combinations of cells in parallel) contain more than 24kWh? Has this been done? Let's say you do fit 50kWh of cells in the original battery box. Are we sure it will work?
mux wrote:Ah, yeah, cost is a logical reason to go for something specific... NKON.eu, probably the largest consumer-facing bare cell vendor in Europe, and it's like 70 miles from where I live. They have excellent prices on bulk, about 1.2-1.3x wholesale prices (typically $150-200/kWh). Although for my temporary extender pack I'm using second hand Yuasa LEV50s for about $100/kWh, but that's cheating. I don't think second hand cells are acceptable for permanent installation in a vehicle, unless you have a really solid BMS.
I'm glad you can find new cells at that price. Like jkenny23 mentioned
jkenny23 wrote:Best current value for automotive scale batteries is ~$135/kWH for [used] Volt modules...
Here in the USA it is hard to find new cells that aren't $15 for a pack of two 18650's, which is more than $1 per Wh, or $1,000 per kWh, (so a 24kWh extender or replacement comes to about $24,000 USD), although there are those Fire cells for cheap, but we all know that they aren't worth a thing.
So used cells may have to be the way to go here in the States. However, there are overstock cells that pop up every once in a while, like the ones sold by Alarmhookup on eBay: 100 LG 18650's $150
His cells come to about $215 per kWh if you include the shipping into the price. However, many times they are in limited supply. So if you can get his cells, you might be able to build a 24kWh battery for as little as $5,500. But you can't if he only has 5kWh of cells available, meaning that again, used second hand cells end up looking like the way to go.
One thing I've even contemplated starting a hobby of harvesting old laptop batteries. I'm quite scared of using generic brand cells, even more than using used second-hand name brand cells, and by harvesting laptops you know you are getting name brand cells. If it's truely Sony, LG, Samsung or Panasonic, new or used, I'd be willing to put those into my car. But still, there are a lot of counterfits out there too. I've never heard of Yuasa brand cells or batteries. Hopefully they are rebranded name brand cells. When I see deals for $0.50 per kWh for some Fire brand cell on Alibaba.com I'm sure it's too good to be true.