About $750 shipped. I haven't had a chance to give it a real test yet. Rained all weekend, but will keep you posted. My only concern is the 150 amp Daly bms. I know Daly is higher quality than most Chinese bms, but it's still Chinese bms. It came with 6awg wire and that's not going to hold up to 150amps but for a few seconds. This is my only flaw I think. I'm going to give it a good run through some high grass and see how hot the 6 awg wire gets. The wires on the factory lead acid is 4awg.Wow, that looks great! Please let us know how it works out. I'm exploring my options on how to tackle this myself. I'll keep an eye on battery hookup. How much did you pay for the cells? Right now I'm considering the easy route of trying out the cheap 12V 100Ah options on Amazon (like Ampere Time or Chins).
I also put a layer on top before I screw the cover on it.
Don't want concentrated force on the terminals, if batteries bounce when hitting a bump. Not as likely for a mower than some other mobile applications.
The foam should help; terminals would press into foam, and form would hold batteries with other areas. Although, busbars would probably take a lot of that and apply force through terminals.
Did either of you consider these from Battery Hookup at some point? https://batteryhookup.com/products/new-battery-hookup-lifep04-32650-3-2v-5000mah-cells-1
They're cylindrical cells, and there's been some positive results reported. I can get 16 'cells' for $880. Not sure how they compare to prismatic cells in terms of durability, etc., but they're packed and stocked here in the US. Looks like I can get a very comparable price for prismatic cells from Amy Zhang, too.
Also, I was thinking of adding something like this for monitoring the battery: https://www.amazon.com/dp/B088RG27L...colid=HTUVLT52UC6V&psc=1&ref_=lv_ov_lig_dp_it. Bluetooth from the Overkill BMS is nice, but it would be nice to also have a physical gauge showing values at all times.
It's good to hear that your current peaked at 91A. Roughly how much current draw did you peg during flat straight lines? I saw that there is a 125A fuse built into the power line in the mower, which probably means the intended peak current is quite a bit below that.
They're rated for 100A continuous and 200A peak (10 sec). But with the 125A fuse in the mower, I feel it's more than enough.I honestly hadn't seen those cells! They look pretty neat and that's a good price. It doesn't look like they handle quite as much current but it's probably enough (1C). I noticed during straight lines something like 60A. With just the blades running and sitting still, it was around 20A. That meter looks pretty cool. Is it the same dimensions as the Ryobi by chance? Can you configure it for LiFePo? I might look into that.
They're rated for 100A continuous and 200A peak (10 sec). But with the 125A fuse in the mower, I feel it's more than enough.
I'm not sure if the meter is the exact same dimension as the one in the Ryobi but at 2in diameter looks very close. If I can't fit it in as a direct replacement then I thought I would 3D print a mount for it on the left side somewhere. It should work with any type of battery: you just connect it in line with the load and configure it when the batteries are fully charged (and you specify the capacity). Then, it just integrates current flow over time to determine SoC. At least that what I gather from reading some of the reviews.
I thought about the bouncing as well and while the cells are not compressed, they are quite snug. I added a thin piece of foam to the bottom of the batteries to provide some cushion for movement. It would take some serious holes/bumps to toss the batteries up. My next task just to provide some additional bounce support is design and print some clips to hold the sides. I also thought of a strapping mechanism, but afraid of tension and stress on the side of the cells. I don't want foam on the cells as it will insulate the cells, potential for thermal issue.Are you saying it's better to have them open @tentious? I don't see what keeps them from bouncing up and down except the weight. Do you think that's OK to have them exposed like that? I do like his terminal caps though. Those are pretty neat! The foam I used on the top was the slotted foam that the batteries sat in. So they are semi-open. Mainly because I had that left over. I suppose I could just make sure they stay within the cells so they aren't on top of the terminals. Is that what you mean?
Maybe easier, but a shunt would more accurately keep track of SOC vs voltage. You also get current, which I would be interested in seeing.
Something like this might be easier/better. Voltage based only and configurable curve for battery type. Can just hook it up to 48V and power on with the key.
That does seem more convenient. I wonder how well voltage-based SoC monitoring works with LiFePO. I'm so used to it being supper crappy with the SLAs in the Ryobi that I thought measuring actual current would be a much better way. But I suppose we can always calibrate as needed against the Overkill bluetooth data.
Something like this might be easier/better. Voltage based only and configurable curve for battery type. Can just hook it up to 48V and power on with the key.