Decision making RE: My conversion project

[MidTNJasonF]

I am a nuts and bolts sort of guy. I can cut it, mill it, turn it, and weld it but electrical theory and calculation is relatively new to me. While I am fairly competent with a standard 12v electrical auto/moto system I lack knowledge in the higher voltage and amperage systems of an EV are a bit beyond me, especially when understanding system component needs/capacity.

With all that said I have fairly well defined goals and a few things already decided. In fact a few parts for my conversion are starting to trickle in.

Goals:
40 mile range (shooting for 50 with a margin of error for real world of 40)
Top speed of 60mph (again real world need is maintaining 45 with peaks up to 55)
I would like to do this with a 72v DC based system if I can since that seems to be a sweet spot for component availability and pricing without getting into higher powered car focused components.

My commute is 11 miles of curvy backroads with 35 to 45 mph speed limits and a few hills but nothing major. Realistically I could get away with a 25~30 mile range but I would like to be able to run an errand or two at lunch/afterwork if the need arises which would add another 10 miles or so in town.

I am going to make a restomod vintage electric motorcycle using components of one of my 1972 Honda CB 450 motorcycles. I may rob some components off one of my CB 350's as well since I have so many spares. The frame is beefy and steel so it should support a motor and battery pack well and be easy to weld, cut, or drill.

I am using a 10 Nissan Leaf battery modules in a 4.4kwh pack. I have read several build threads utilizing them and looked at the specs. They seem like an incredibly cost effective and well engineered solution for a setup like this. The only downside I see is since they are 2s2p in the aluminum case at 7.4v nominal/60ah a BMS solution will not be as cut and paste as some other solutions. I do not see an easy way to monitor each cell in the pack, only the module itself.


What I need help with is motor and controller selection.

I plan on using a mid mount DC motor driving a traditional chain and sprocket setup. I wanted to use Mark's hub motor to free up frame area for other components but honestly the cost is not in the budget for this build.

I am seriously considering the Agni 95R. I can get one at a pretty nice price and it looks to have the specs. I noticed this is a popular motor for racing applications but usually in pairs for high speed capability.
Is there anything undesirable about this motor in a single motor application that would limit me from using it?

Alternately I have looked at the Motenergy ME1003 from someone like EV Drives. Also cost effective and seems to have the specs on paper.

Also in consideration is the Motenergy ME4201 Brushless DC PM. Again it looks cost effective on paper but would probably require a bit more controller.


For Controllers I am considering the
Alltrax SPM-72400, the Kelly KDZ72401, or maybe even a Curtis 1221M-6701 or 1205M-6402.
The Curtis has the disadvantage or extra cost of needing a programmer or software and adapter cable. The Alltrax and Kelly seem to have less cost involved in the hardware and software for programming.

What I do not know is what peak and continuous amperage ratings I need to target for my setup. That would determine, in part, how much controller I need. If I could get by with 200a or 300a peak I could step down a bit in controller capacity but my reading seems to indicate that I would be better served in the 400a to 500a range.

Anyone have specific input on those particular controllers and motors or good alternatives to them that are economical?

 

[dnmun]

you can build a 24S leaf pack and use the 24S lipo D131 i have to balance it. that would get you to 100.32V DC, full charge, so you could find the controller to run up there to make that kinda speed.

 

[MidTNJasonF]

you can build a 24S leaf pack and use the 24S lipo D131 i have to balance it. that would get you to 100.32V DC, full charge, so you could find the controller to run up there to make that kinda speed.

No following you here. Are you talking about breaking the modules apart and using the cells in series or linking 12 of the modules in series for a 24s2p configuration?

With only one voltage sensing post on each module I fail to see how a 24s BMS will see anything but 10 voltage signals from a pack of 10 Leaf Modules. I have no plans to disassemble the Leaf Modules and configure the individual cells.
This is really may not be that big of an issue since most seem to be using them with a minimalist BMS treating each module of 4 cells as a single 7.4v "Cell".

Even at max charge 10 modules would give me roughly 84v which is within the capability of the controllers I listed (most being 90v max). Are you saying that 10 modules at 84v max charge is not going to hit my speed goals with an appropriate controller?

 

[Hillhater]

Doesn't the center "Voltage Sensing" tap allow you to monitor each 3.7 volt, 2p cell pair in the module ?
Paired cells will automatically balance each other, so it will be easy to set up a cell level monitoring / BMS for the pack.

 

[MidTNJasonF]

Doesn't the center "Voltage Sensing" tap allow you to monitor each 3.7 volt, 2p cell pair in the module ?
Paired cells will automatically balance each other, so it will be easy to set up a cell level monitoring / BMS for the pack.

It is a single M4 voltage sensing post. I do not see how it would read anything but module voltage at 7.X volts. That said I do not have them in my hands and do not know exactly how it is configured.

As I mentioned many are not concerned with this due to:
A) the relative high quality of the cells in the modules and the initial OEM automotive QC levels.
B) as you state the cells in the module should stay balanced in the modules baring an actual cell failure within the module.
C) the relatively low cost of replacing a single module if one begins to show poor readings.
D) an occasional manual balance would go a long way to solving any issues with the pack.

I am guessing a simple voltage cut off style or AH monitor management system would prevent over charging and over discharge situations thus prolonging the life of the modules sufficiently for their relative cost.

I am using the leaf modules regardless. I can figure out battery management later down the road. I really need to get the controller and motor selection ironed out before I worry about secondary and monitoring systems.

 

[John in CR]

The center tap on the modules plus the positive and negative poles gives you all the access you need to monitor and balance the 2s module. There is no need to monitor the individual cells in parallel, because they are electrically the same as one 60ah cell. For a motorcycle you're on the right track with either 10 or 11 modules, because going to 12 modules for a 24s pack puts it right at the 100V limit of components in those controllers. Those who get away with running 24s packs are running slow relatively low power bicycle hubmotors, and they push their systems to the limits in an attempt to get speed with results that would be unacceptable for a motorcycle.

My main suggestions for approaching an emoto build are to:
1. Build it as light as possible while retaining the strength and rigidity needed. Power-to-weight is everything and it's easy to get great performance with a bike that weighs 200lbs or less, but as you get higher things get much more expensive and the added weight means you need even more battery to power it.
2. After weight, aerodynamics is the next most important thing unless your rides will be relatively long at speeds of 40mph and up, in which case aerodynamics is THE most important thing.
3. Forget any ideas you may be entertaining about using a multi-speed transmission. It's just unnecessary weight, space, and efficiency loss, because electric motors have such a wide torque band. Tesla's cars are single speed systems, as are Zero's electric moto's. Brammo uses a single speed on it's race bikes, but puts a tranny on it's commercial emotos just for rider familiarity, but users typically just ride around in 1 gear.

 

[MidTNJasonF]

My main suggestions for approaching an emoto build are to:
1. Build it as light as possible while retaining the strength and rigidity needed. Power-to-weight is everything and it's easy to get great performance with a bike that weighs 200lbs or less, but as you get higher things get much more expensive and the added weight means you need even more battery to power it.

My starting bike weight is 412 lb (187 kg) (dry). I can not physically lift the engine and gear box assembly by myself easily. When I had to lift it out of the back of my van I thought I might have herniated something. It is easily north of 200lbs, probably nearing 250lbs.

With the weight of my cells (8.3775 lbs (3.8 kgs) each X 10) at 83.8lbs and the proposed motor at 24 lbs I am doing pretty good so far. The Controller an associated wiring would be mostly off set by the weight of things like the carburetor and air box. The weight of the charger would be offset by the weight of the exhaust (the headers on the original were double wall, chrome, and heavy).

Eliminating the original harness and creating a new minimized 12v chassis harness would save a bit along with using smaller LED based lighting as opposed to the large reflector and automotive bulbs originally used.

Honestly with all that said in all my years of racing weight has been one of the most over rated areas of focus. I have seldom met drivers/riders that would not be served better by eliminating 10lbs off themselves before they spend cubic dollars try to shave 10 lbs of their car or bike. You can design intelligently but seeking further weight reduction for a street driven motorcycle under 500lbs does not come with a high rate of return.

Weight balance on the other had greatly effects real world riding dynamics. If a rider can't feel a difference in balance between the your ICE powered bike with a full tank vs a near empty tank that may not make as much sense to them. COG and front/rear weight balance have a greater impact on bike handling dynamics than overall weight (within a reasonable weight range).

Don't get me started on suspension setup... :lol:

2. After weight, aerodynamics is the next most important thing unless your rides will be relatively long at speeds of 40mph and up, in which case aerodynamics is THE most important thing.

Again in my opinion aerodynamic concerns are overrated for a street application. If I was concerned with aerodynamics I would be building a high speed stream lined vehicle, most likely a low COF car. Motorcycles, even modern sports bikes, have very poor aerodynamics.

It is completely impractical to ride in a full tuck behind a fairing and frankly there is nothing much I am going to do with my 6'3" broad shouldered body behind the handlebars. That would be like trying to hide a road side billboard behind a rain umbrella. I ride upright, seated chair style. That is what works for my 40+ year old back, shoulders and bad knees. Diverting a little air around the front of the bike with a fairing does nothing to the massive low pressure area behind my back where most aerodynamic concerns should be focused.

Again could some small gain be had with a vintage GP style race fairing, sure but the gains should not be oversold especially at the sub 50mph speeds we are talking about. Rolling resistance however is worth addressing.

3. Forget any ideas you may be entertaining about using a multi-speed transmission. It's just unnecessary weight, space, and efficiency loss, because electric motors have such a wide torque band. Tesla's cars are single speed systems, as are Zero's electric moto's. Brammo uses a single speed on it's race bikes, but puts a tranny on it's commercial emotos just for rider familiarity, but users typically just ride around in 1 gear.

Yes as I stated in my original plan I would have liked to go with EnerTrac Hub motor but for budget concerns I am going to go with a simple frame mounted motor with a chain and sprockets set up for direct drive to the rear wheel. Probably have to get a larger sprocket or two made for the rear wheel to get the gearing correct but sprocket specialists can take care of that.


I think I am going to pull the trigger on the Agni 95R. No one has commented on it but it looks to have the specs on paper. Probably select the Alltrax SPM72400 or the Kelly SPM72400.

I know regen is more difficult with PM DC motors than it is with AC motors but I would like to see if I can get some just for the engine braking effect. I am a momentum rider. I prefer to stay off the brakes and not use the throttle hard. A little engine braking goes a long way when finding a nice rhythm and corner entry speed on a winding road. The Kelly is available with regen control I need to dig into the specs of the Alltrax to see if it has that capability as well.

 

[John in CR]

On street bikes weight and aero don't make that much difference, because you don't need to worry about efficiency since a 6lb gallon of gas contains almost 34kwh of energy. I built a slow pig heavy electric moto as my first journey into electrics. I'm not saying worry about grams like cyclists do, or even that 10-20lbs will make much difference, but if you're starting with a 400lb moto, then there's lots of weight to be saved...maybe start with trading the donor bike for something much lighter as a starting point.

WRT aero, I didn't mean to suggest that it's essential to take it to the extreme and force an uncomfortable ride, but our electrics don't require the same amount of cooling air flow, so there's a lot of opportunity for small changes that can have a significant effect. That in turn can significantly affect range. It won't matter if you just hot rod around with very short trips, but if you cruise at steady speed the difference is worth some effort.

Take lots of pics of the build process. We all love to see everything we can to borrow ideas from, and with your experience I'm sure you'll have plenty that can help others.

John

 

[MidTNJasonF]

On street bikes weight and aero don't make that much difference, because you don't need to worry about efficiency since a 6lb gallon of gas contains almost 34kwh of energy. I built a slow pig heavy electric moto as my first journey into electrics. I'm not saying worry about grams like cyclists do, or even that 10-20lbs will make much difference, but if you're starting with a 400lb moto, then there's lots of weight to be saved...maybe start with trading the donor bike for something much lighter as a starting point.

John

You do realize that almost no modern motorcycle from the major manufacturers makes it to the street under 400lbs right?

A relatively modern 600cc or 1000cc sport bike is in the 385 to 420 lbs range, heck even the featherweight Ninja 250 was just south of 400lbs, 380's if I recall. I will actually have an easier time taking weight off my donor bike than I would off a modern sport bike. The weight of the CB450 motor I am removing is probably in the neighborhood of 35 to 45% heavier than a modern 600cc japanese inline 4 cylinder and more than double the weight of the ninja ex250 twin. I can just about tuck one of those under each arm since they are about 95lbs.

If people are discounting older motorcycles as donors because they percieve them as heavier they are missing out. The heavy bits are the ones you strip out to make an EV out of it. The battery pack and motor will come in just over 100~110lbs saving over 100lbs right off the top of that 412lb start weight I mentioned earlier.

Anyway I certainly do not indend to come off as argumentative but I probably sound that way. I plan on scaling as much of the components of the motorcycle as it is built.

I was presenting the project to some friends in my local Maker group yesterday eand got a few people who are very interested in having a hand in the project. Several of folks have experience professionally with automotive electrical harness design and manufacturing. One of them even has some experience putting together large industrial controls cabinets so that will be a nice help when it comes to wiring things up. I may like vintage stuff but I am no Lucas fan, I prefer to keep the magic smoke in the wires. I have an interesting story about being in a '59 bugeye sprite, in a thunder storm, with only plastic side curtains, and roughly 2 inces of water in the floor pan (hint that is where the main harness is) but that is a story for another time and thread.

 

[MidTNJasonF]

Doesn't the center "Voltage Sensing" tap allow you to monitor each 3.7 volt, 2p cell pair in the module ?
Paired cells will automatically balance each other, so it will be easy to set up a cell level monitoring / BMS for the pack.

So after some more digging the voltage sensing (middle) post reads the voltage of one of the two pairs of cells in the module. Depending on where you measure that voltage across will determine waht that reads. You can monitor the other pair of parallel cells as well if you hook things up correctly and have a BMS capable of reading series connected cells. something like this http://minibms.mybigcommerce.com/minibms-4s-cell-board/
configured something like this:


This would be a 4 module 8s pack. For a 10 module pack as I have planned it would require an additional two boards and the head board they all feed to. The voltage from C1- to C4+ will be 15.2V (or 4x whatever cell voltage). The board subtracts the other readings, so if C1- to C3+ is 11.4, then it will figure out that cell 4 = 15.2 - 11.4 = 3.8V.

I am starting to wrap my head around the BMS layouts now and I have a pretty good handle on some of the basic power, current, and capacity calculations so things are pregressing well for my old brain.