1975 Honda CB 750 Conversion

[AdamNoel]

In my opinion, active balancing is necessary if you are using the same model of cells with a different age. For exemple cells that are salvage from different battery packs (which I would avoid). At the beginning of your thread, you wanted a battery with a continuous current output of 200A. Pushing a 220A (continuous) BMS at 200A (continuously) will probably reduce its reliability that's why I suggested the 400A one. If you want to pull 100A (continuously) then, the 220A BMS is perfect.

 

[BatteryManTakeMeByTh]

In my opinion, active balancing is necessary if you are using the same model of cells with a different age. For exemple cells that are salvage from different battery packs (which I would avoid). At the beginning of your thread, you wanted a battery with a continuous current output of 200A. Pushing a 220A (continuous) BMS at 200A (continuously) will probably reduce its reliability that's why I suggested the 400A one. If you want to pull 100A (continuously) then, the 220A BMS is perfect.

Ah, that makes sense on both counts. Thank you for clarifying. All my cells are the same age, so point one won't be an issue for me thankfully. As for point two, you're right, that was my original design. But, several people mentioned it's just plain more efficient to run at higher voltage, so I decided to follow that advice to lower current. Especially since I didn't want 1-2mm thick bus bars.

 

[BatteryManTakeMeByTh]

Hi again, y'all. Turns out the maker space I have access to at the moment doesn't have a battery welder that I can use, it seems. Or, at least, it would require me moving the whole pack up to the prongs every time as they were at a fixed location. So, I am looking to buy one. I have found the Glitter 801H, and it looks pretty good. I'm just wondering if I should get it from what seems to be the manufacturers website, or from Amazon or something. Any input would be great, both on the model of welder and on where to buy it.

I think I could probably get away with the lower-end models from Glitter, but I want one that I'm sure is going to last through like 420 welds (12V pack 3s4p, 44V pack at 12s6p, 110V pack at 28s12p) without having to get another one or replace anything. Does that seem like a reasonable expectation for this welder? I haven't used any of these before, so I'd like to spend my money somewhat wisely.

On a separate note: I've been reading other threads, and I was wondering about structural integrity of the battery with just the 2 sets of spacers and the welds holding them together. I don't want to rely on just that, give that the big battery will likely be 50+ lbs. My first thought was that my spacers fit far enough down over the cells that I could just layer 3-5 of them up the cells instead of just the 2 (top and bottom). This seems rigid, but workable. What do y'all think? I have limited-time access to the Prusa 5-headed printer, so I'd like to make the most of it if that seems workable. Otherwise, I've thought about using something like spray foam in between the rows of cells. This seems good on face because it doesn't come in pieces that might be too big, I can just spray it in between. Normal spray foam is highly flammable, being petroleum-based and all. But, there are fire-retardant foams like this one. I'd have to do a lot more research to find one that seems to fit my purposes, as the reviews on that one seem mixed including a noting of flammability, and others I looked at were easily several hundred dollars and clearly meant for a whole house. I don't really know what else I could put in between the cells to keep them in place in the battery. I'd also rather whatever is put in there is non-adhesive, which is a pain. Just don't want to rip the cell wrappers. Any ideas would be great. I'm leaning towards the extra spacers because it seems simplest, but they are plastic so they're still flammable.

 

[adsc]

Are the holes in your cell spacers just smooth bores? I would have designed them with a slight lip, so that the hole diameter is not the same at both ends, and the cell is stopped at the very end and can't slip through completely. And yes, maybe also make them encase a bit more of the cell, because there is going to be quite a bit of weight resting on those things at the lower levels.

 

[BatteryManTakeMeByTh]

Are the holes in your cell spacers just smooth bores? I would have designed them with a slight lip, so that the hole diameter is not the same at both ends, and the cell is stopped at the very end and can't slip through completely. And yes, maybe also make them encase a bit more of the cell, because there is going to be quite a bit of weight resting on those things at the lower levels.

They are, indeed, just smooth bores. I won't lie, that's partly because I'm a novice at fusion, so I had a hard time making any kind of lip I was satisfied with. However, I did try, and I took it off to have the most room available on the cells to weld. I figured extra tolerance for cell position would be good.

I can probably print them to be the full width, but I'm not sure if I'll be able to do that in a timely manner, as I'm losing access to the 3D printer I was using. I will likely get my own or use one at a future maker space. Until that time, do you think it'd be sufficient to have like 4 or 5 of em up and down the cells? The spacers are 5mm thick, iirc.

I do also want to ask again: Does anyone think the glitter 801H or the 801D is a good welder? I want one that won't crap out until at least 500 welds.

 

[adsc]

Maybe two at each end will be good enough. Hard to judge, though. Since your spacers are one complete piece, the weight should be better distributed than with single spacers that are clipped together.

I have no experience with spot welders, unfortunately.

 

[BatteryManTakeMeByTh]

Maybe two at each end will be good enough. Hard to judge, though. Since your spacers are one complete piece, the weight should be better distributed than with single spacers that are clipped together.

I have no experience with spot welders, unfortunately.

That's sorta what I'm thinking, but I'd really rather not rely on "maybe." Trouble is, I would also rather not have to print 16-24 more copies of my spacers to put them all up and down the lengths of the cells. I probably could get it done, still. But it'd be hard. I'm also more worried about lateral pressure on the cells than the bus bars or spacers bending. The spacers are pretty dang resilient (made of PLA at 15% infill), so I'm more concerned with the copper and the weld points than anything. But, I'd still rather be as safe as possible on all fronts. Recommendations would be great on any strategy to mitigate either lateral or vertical pressure on some cells and not others.

 

[adsc]

There should be no significant force acting on the long axis of the cells. Maybe a little during turns, but most of the forces will be up/down from bumps and forward/backwards from deceleration/acceleration.

 

[BatteryManTakeMeByTh]

There should be no significant force acting on the long axis of the cells. Maybe a little during turns, but most of the forces will be up/down from bumps and forward/backwards from deceleration/acceleration.

That makes sense. I just think that's the part that's least structurally sound. I think printing another 8 sets of spacers to add one in the middle for all packs might be enough for the back and forth or up and down forces.

 

[BatteryManTakeMeByTh]

Hi, again, all. It's been a very busy couple of months for me. I moved and then promptly broke my collar bone on an electric skateboard. Helmet on, thankfully, but still putting me off working on things. At least I can finally type with two hands again.

I grabbed a UF20B spot welder online, and I'm planning on building a 12V pack or two along with a replacement 42V pack for another electric skateboard.

Not much to update right now otherwise except I'm starting to design a temperature monitoring board for the big battery. The ANT BMS I picked only has 2 temp sensors, and I have 15 bus bars. So, I'm going to design my own PCB to measure, record, and transmit temp voltage. I will expand it at some point to measure various voltages and currents in the bike's electronics later, too. But, first thing is to get a working prototype. Then, I can design a board. Then, I can worry about further revisions. To work up to this, and because I *was* having a lot of fun with my electric skateboards, I'm also starting to design a simple power monitoring board for my skateboards. I'm planning on having a male XT60 connector on one end, a female connector on the other, and then simple hardware to measure and record data on an SD card or something. I want to make it small enough that it'll fit within the skateboard's ESC housing. I know this isn't exactly the thread for this, but would anyone else want the design if I make this? I didn't see anything similar online anywhere that was tiny and recorded data. Maybe I just missed the ones that do. Either way, I'm going to give this a shot because it seems fun.

 

[adsc]

Oh shit, I hope you have/had a good recovery.

 

[BatteryManTakeMeByTh]

Oh shit, I hope you have/had a good recovery.

Thank you, I'm recovering well. I can do electronics stuff, but I think battery welding is still off the table for another week or two. Doing PCB design in the meanwhile, and that's been fun. Definitely kicking myself about the injury.