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1975 Honda CB 750 Conversion

adsc said:
With that big of a battery I would consider using the BMS only to activate a contactor, and not route the load through it. Could probably use two cheaper 16s BMS like this.
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I agree with that, though I don't know exactly what I'm looking for BMS-wise in that regard. Are there specific models you know of that do that, or would that be a self-fab thing?
 
adsc said:
Self-fab. Here is a good thread about it: BMS-controlled contactor for high-amp discharge
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Just triggering contactors on BMS power on makes sense to me. Shouldn't be horrible, though I will need to look for contactors rated for 120Vdc at 100A. Any idea which ANT BMS I would want to look at to find one with some kind of LV power supply in it that I could tap? I didn't see a huge variety of options, so maybe there's only one or two.
 
You can use the BMS P- connection to control the ground of a regular contactor's 12V coil. The positive on the coil is connected to the positive bus of the 12V system of your bike (usually a DC-DC converter constantly charging a regular/small 12V battery). When the BMS has a problem, it will disconnect the coil's ground and the contactor will open.

With this setup, it doesn't matter what BMS you use, as long as it can do 28S. But regarding the BMS, if you want to use an onboard charger, you might want to get one with CAN communication.
 
Makes sense to me. I was mostly wondering if there was a controller out there that just had a simple digital or toggled power supply I could tap for ease. Not too hard to just get a converter, though. What do you mean by onboard charger exactly?
 
I guess it's possible that some higher end automotive BMS have a built-in DC-DC converter for 12V output, but I don't know any. I think some motor controllers have it, but afaik Fardriver doesn't.

An onboard charger is just a charger for the battery that is permanently attached to the bike. If you want to charge at public charging stations, you need a reasonably powerful charger, and those things are not small and light, so not really something you're gonna carry in a backpack or in saddle bags. But if you're fine with slow charging and/or charging at home, you can keep it external. Personally, I decided to put a 3.3 kW TC Elcon charger on my bike and make a small charging logic with a Type 2 plug, so that I can charge my battery in 2 hours on a public AC charger.
 
adsc said:
I guess it's possible that some higher end automotive BMS have a built-in DC-DC converter for 12V output, but I don't know any. I think some motor controllers have it, but afaik Fardriver doesn't.

An onboard charger is just a charger for the battery that is permanently attached to the bike. If you want to charge at public charging stations, you need a reasonably powerful charger, and those things are not small and light, so not really something you're gonna carry in a backpack or in saddle bags. But if you're fine with slow charging and/or charging at home, you can keep it external. Personally, I decided to put a 3.3 kW TC Elcon charger on my bike and make a small charging logic with a Type 2 plug, so that I can charge my battery in 2 hours on a public AC charger.
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That makes sense. I'll look around, but I'll probably be going with Fardriver if I can.

So, the onboard charger is the power electronics to utilize car charging ports out on the road? I do want that eventually, but I think I will start with just charging at home so I can get a working prototype to iterate on. Plus, my initial use case is just riding this bike about 10 miles a day on week days and a bit for fun otherwise. I don't really need it to charge quickly. I definitely would like to charge on public chargers eventually, however. Two hours is still a while though. How much capacity do you have? 6.6kWh doesn't sound that large if you're maxing out the 3.3kW speed.
 
Also, as an update, I just got this back from WellGo to confirm their design before manufacturing. How we lookin on bus bars? I think these look pretty good, but I always like hearing from others. 1774616687673.png
 
Man. I keep doing this. Glad I sat on it for a minute. I sent them the right model, too. I'll have to update them before giving them the go-ahead. You're a lifesaver once again.
 
BatteryManTakeMeByTh said:
So, the onboard charger is the power electronics to utilize car charging ports out on the road? I do want that eventually, but I think I will start with just charging at home so I can get a working prototype to iterate on. Plus, my initial use case is just riding this bike about 10 miles a day on week days and a bit for fun otherwise. I don't really need it to charge quickly. I definitely would like to charge on public chargers eventually, however. Two hours is still a while though. How much capacity do you have? 6.6kWh doesn't sound that large if you're maxing out the 3.3kW speed.
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Yeah, I guess you could also make an adapter for a portable charger to charge on public AC charging stations, but portable chargers usually have like 10 - 20 DC A max, so it would take many hours to charge a decently sized battery. My first battery has 72V and 105 Ah, so it will take even longer than 2 hours to go from 0 to 100, but that's not what you're gonna charge usually, if you're at a public charger.

There are also 6.6 kW TC Elcon chargers, but unfortunately they don't go low enough on their DC Voltage to be used with my battery. Plus I've checked local laws, and it's not even allowed to draw more than 16A on a single AC phase here to avoid skewed loads, so that's not really something I could do anyway. The only way to get faster charge speed would be to add multiple chained units to draw from multiple phases at the same time, but they are kinda heavy and bulky, so not really something I'm keen on at the moment. A compact 3 phase AC/DC charger with a DC voltage between 60 and 120 V seems to be something that doesn't really exist on the consumer market at the moment.

So really, 3.3 kW charging is the best I was able to get at the moment. Should be okay for getting half a battery charged in a little more than 1h. I also ordered the control unit to be programmed so that the charger is only drawing 10A on the AC side if the control pins of the Type 2 plug aren't connected, this way I can plug it into a normal house outlet and charge more slowly. Some houses here still only have 10A fuses.
 
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adsc said:
Yeah, I guess you could also make an adapter for a portable charger to charge on public AC charging stations, but portable chargers usually have like 10 - 20 DC A max, so it would take many hours to charge a decently sized battery. My first battery has 72V and 105 Ah, so it will take even longer than 2 hours to go from 0 to 100, but that's not what you're gonna charge usually, if you're at a public charger.
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That all makes sense to me. I was assuming 10-20A charging overnight most likely, or while at work during the day.

Do you usually charge 20-80% while out in public?

adsc said:
There are also 6.6 kW TC Elcon chargers, but unfortunately they don't go low enough on their DC Voltage to be used with my battery. Plus I've checked local laws, and it's not even allowed to draw more than 16A on a single AC phase here to avoid skewed loads, so that's not really something I could do anyway. The only way to get faster charge speed would be to add multiple chained units to draw from multiple phases at the same time, but they are kinda heavy and bulky, so not really something I'm keen on at the moment. A compact 3 phase AC/DC charger with a DC voltage between 60 and 120 V seems to be something that doesn't really exist on the consumer market at the moment.
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Not that surprising since we still don't really have that many EVs on the market. If there comes a time where there are enough on the market and the road to have aftermarket parts, maybe we'll have that kind of converter.
 
Yeah, charging slows down above 80% or so, which is why it's not worth it anymore with my setup.

The battery I have is built from simple LFP prismatic cells at the moment. The idea was that if the bike project fails, I can still use the cells for a solar home battery. If the bike is somewhat successful, I can still make a 96V NMC pack and switch the controller. Maybe I'll have even enough space for a second onboard charger.

But first trying to get that one on the road. Making it road legal will probably be the most difficult problem.
 
I hear you with road legality. It sounds like MI doesn't care much, but I'm not itching to find out if that's true or not.

How much did the prismatic cells run you total? I was wondering about those.
 
€ 690 including shipping from nkon.nl

But it's not ideal making a battery with them, because of cell size and discharge rate. Cell size means you only really have space for 24s1p, and then discharge rate is not very good with 100 A continous / 150 A peak. Could probably push them to 150 continous and 200 peak with good cooling. Or try to find smaller cells that you can do 24s2p with, that have better discharge than 1C. But with LFP it's usually just 1C.

Maybe I could also fit a 32s1p pack, but connections then probably become a bit of a hassle, and BMS is another issue, would probably have to use two 16s BMS. 24s1p with big prismatic cells that have screw terminals is pretty nice mechanically, though. Only need one special busbar, to connect the two 12s halves, the rest comes with the cells. Am a bit worried about screws getting loose over time, but we'll see.

Nkon also has/had large round cells (EVE C40 40135) with screw terminals and 3C discharge rate, which I originally wanted to use, but I was not able to design a pack with good geometry that would fit into my frame. Maybe if the current battery turns out to be too weak, I'll give it a try.
 
Yeah, I had heard about some of the challenges of working with them, which is why I just opted for the simpler option of the Molicel P42As. 45A peak from a single 21700 cell is pretty good, and with 12 in parallel, I should never be coming anywhere near that limit.

How heavy is it at 24s1p? I do like that the cells have the connections built in. Welding 336 cells is gonna be a pain.
 
Yeah, that's more or less what I was expecting. I think mine will end up being similar if I remember right.

Also, hopefully the last revision here:

1774959500311.png


I'm pretty sure it's right this time. That looks like 12p to me, not 28p. And, I count 14 groups per block. Am I going insane or can I send it?
 
Looks good. The little tabs are for the balance wires, right? If so, the start, middle and end bars with only one column of cells should probably also have one (only one on either of the middle ones).
 
Yeah, I was wondering about that. I was thinking it probably wouldn't be a big deal to attach to the bus bar anyway. But, the more I think about it, the more annoying that seems. I think I'll ask them to add that and then send it. Thanks for all your help, once again
 
Alright, I'm back again. My bus bars have arrived, so now I need to learn how to well a pack lol. My plan is to use a bunch of spare 18650 cells I have, some 0.15mm copper, and 0.15mm nickel strip to weld a 12V pack for the low voltage systems in the bike. Mostly I think this will be a backup, but I'm thinking about trying to integrate it into the main circuit between the 120->12VDC converter and the high current relays too.

I am going to get as much practice as I can before ruining my nice prefabbed bus bars. So, I'm also going to shoot for a 43.4V pack after making and testing a 12V pack. I have an electric skateboard already (Wowgo 3 from like 2019 or 2020, got it from a friend), and the OG pack died on it riding after a rain. I salvaged most of the cells and bought a replacement that isn't very good. I'm thinking I'll at least take the spare cells, order a 43.4V BMS, and try my hand at replacing my skateboard battery too. I feel like that'll be a good simple test run for putting the bike's electrical together.

Any input on these plans would be great. I'm going to a maker space to user their battery welder for now. I'm moving at the moment, but I do plan on getting (or making) a battery spot welder once I'm settled again. I've seen some tutorials, and it looks like it'd be fun to make a spot welder. Definitely lots more research before I want to commit to that though. Probably a post-bike project since I don't want to have to implement and test computer timing control before making the bike. Again, input welcome. Thanks for all the help so far. I'll attach bus bar pics later.
 
Good welds are really important, both because of resistance and mechanical stability. It sucks when you have to take apart the pack again because of a few bad welds that broke during riding the bike or that develop hot spots and deplete faster than their neighbours.
 
Exactly my thinking. I want to get the energy and timing settings down beforehand, and I want to have had a few practice runs to figure things out the hard way at least a bit. Safety first, of course.

This is the BMS I'm looking at, ANT 21-30s, 220A continuous, 500A peak. My only real concern is that the balancing is passive. It's a fairly hefty pack. Any chance that's going to be an issue?

Speaking of BMSs, I was also looking at ones for the smaller trial-run packs. For the 12V one, there seem to be a lot of options on amazon. Any issue with these? For example, this one? Seems like it shouldn't need to really be high current or anything special. Bluetooth could be nice I guess, but I intend it to be a backup for the 12V systems if anything every causes issues with the main battery.

Then, for the 43.4V BMS, I found this. I haven't done much looking on this yet, but there do seem to be a fair amount. I had 30A current, I'd like more. Happy to upgrade the space for the battery too.
 
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BatteryManTakeMeByTh said:
Exactly my thinking. I want to get the energy and timing settings down beforehand, and I want to have had a few practice runs to figure things out the hard way at least a bit. Safety first, of course.

This is the BMS I'm looking at, ANT 21-30s, 220A continuous, 500A peak. My only real concern is that the balancing is passive. It's a fairly hefty pack. Any chance that's going to be an issue?

Speaking of BMSs, I was also looking at ones for the smaller trial-run packs. For the 12V one, there seem to be a lot of options on amazon. Any issue with these? For example, this one? Seems like it shouldn't need to really be high current or anything special. Bluetooth could be nice I guess, but I intend it to be a backup for the 12V systems if anything every causes issues with the main battery.

Then, for the 43.4V BMS, I found this. I haven't done much looking on this yet, but there do seem to be a fair amount. I had 30A current, I'd like more. Happy to upgrade the space for the battery too.
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If your cells are new, the passive balancing is not a problem. My 2 ANT bms are working really well for balancing the cells of my battery packs.

For the BMS size I would suggest the 400A continuous one, if you have space. https://www.aliexpress.com/item/100...c_item_bridge_pc_main__QZKEkRc__1774015446783
 
AdamNoel said:
If your cells are new, the passive balancing is not a problem. My 2 ANT bms are working really well for balancing the cells of my battery packs.
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I will be using all new for the big battery, so that's good to hear. Any idea how old they have to get before passive is no longer good enough?

Also, any particular reason for the 400A continuous? Doesn't seem like much of a price difference, so I don't mind. Just wondering. I'm definitely looking for overkill, so it seems like a decent idea. Only thing is that I'm looking to top out at 10kW roughly, and with a 110V pack, that's only 100A. I dont think I spec'ed the bus bars thick enough for much more than 200A at 0.8mm thick. Even that seems like pushing it to me.
 
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