Drivetrain options for threewheeler - goldenmotor, motenenergy, batteries oh my

[evolknuj]

Greetings all!
I am building an electric cyclekart imitation of a 1935 Morgan F2 three wheeler. Basically an historically themed, small scale, big wheeled go kart. Here's my build thread if you're interested in more details: https://www.cyclekartclub.com/forum/custom-karts-forum.6/morgan-f2-threewheeler-electric-cyclecar.37863/

I've been reading and lurking on DIY EV sites while building, but I'm very near the point where I need to pull the trigger and order motor, controller, and battery and would appreciate advice.

To get solid advice on parts to buy, you must provide the following info.
Desired max speed on level ground:
35mph
Desired max range at what cruising speed.
15 miles at 25mph (with hills involved)
Preferred bike wheel size, or wheel size of bike you want to convert. Most common kits are for 26" wheels.
Rear drive wheel is 12" pitbike rim (overall diameter with street tire probably 8" greater)
Brake type of motor wheel. Disc or not.
Disk
Rider weight.
220 lbs rider + 30 lbs dog + ~250 lb chassis (guessing on chassis, trying to keep it light)
Terrain. Exp: mostly flat, some short hills under 20% grade, I want to climb mountains, etc., etc.
Hilly (hill country outside Austin TX)
Budget.
~$2000 for drivetrain: motor + controller + batteries + wires + throttle/switches

As you can see above, I don't have any great need for speed and likely it would scare the poop out of me to go over 30mph in my deathtrap. But I'll need enough power to go uphill, and want to be able to go faster than most golf carts. NEV, not highway.

I'm started by looking at the 3 and 5 kw kits from Goldenmotor. The 3kw model is certainly easy on the budget, however I have concerns that it would not provide satisfactory power. The 5kw kit would seem to give enough power, but at that price range... it's not a lot more to instead get a ME0909 based kit from thunderstruck-ev or evdrives, either with an Alltrax SR 48300 or Sevcon Millipak 4Q (regen & reverse), especially since these non-GM kits typically include a PB-8 throttle and wiring harness etc. The GM pieces dont even seem to have a separate contactor? And I'm worried by the general quality, keep finding quotes like "with GM something will go wrong eventually"

But I'm saying a lot of names that I don't really know -- I don't really know the pros/cons of Alltrax controllers vs Sevcon controllers etc, or whether the fact that the GM controllers don't need (?) contactors is a problem, so I would appreciate advice.

Finally for the battery, hopefully the above would help inform those more experienced than I determine sizing. I think I need a 48v 20 aH pack, and am strongly considering the Goldenmotor LFP-4820M, but I don't know if its max continuous discharge rate of 40A would be overly limiting. In general I'd prefer to have a motor/controller capable of more and be able to add battery in the future if I need more range/power than to have to start replacing components completely.
I haven't been able to find many obvious pre-built alternatives to the goldenmotor batteries in the 20ah range though. Luna seemed to have one, but it's no longer available. Anywhere else I should be looking? I don't think i'm up to building my own first time.

Thanks for reading (assuming you got here, sorry I'm long winded)!
Paul

 

[amberwolf]

First, if you haven't already seen it, I recommend looking at http://ebikes.ca/simulator , reading the entire page, and then playing with various systems and slopes and throttle settings, etc., withyour expected vehicle weight and aero, to see what it will really take in power to do the things you need it to do.

Second, this may be unimportant for your needs, but keep in mind that generally it will take more power to launch quicker, so if you want low speeds but high torque for quicker takeoffs (also useful for hills), it may take more motor (and/or controller and/or battery) than otherwise.

(for example, my SB Cruiser doesn't actually need all that much power, maybe 1500w, to just ride around under 20MPH even with winds...but for acceleration (especially with a dog or cargo onboard, not to mention a trailer full of either) that's quick enough to be safe in traffic, I need at least two to three times that much power (more as the load goes up). At least your dog is only 30lbs, about 1/5 of one of mine, of which there are four. :lol: )

YOu may want to look at successful builds around ES and DIY Electric Car forums that are similar ot yours in size and specs and usage needs, to see what they used for battery, motor, controller, etc. It should help in some decisions (but it is probably a lot of poking around and reading).

Regarding controller differences...best way to see which have features you're after is to look at builds using them, where they talk about the features they use and why. Based on threads I've seen around here, Sevcon, if not already programemd to do exactly what you want, is a PITA and requires a specific programmer and software to do it, as well as significant knowledge of how to do it. Alltrax I don't know their programming, but it is at least a standard serial connection, and probably just needs their software. May be straightforward (there are threads with sections poeple have done that here on ES). There's a lot of kinds of controllers out there, including various ones for sale here on ES, and DIY controllers like the Lebowski variants that can be very powerful but you have to build your own. :/ Incememed has a sensorless BLDC (I'm beta testing one) that seems pretty good but I'm not sure if it will do what you want yet, but we're testing out different firmware and settings changes. (when it will do what my trike needs, it'll probably work on yours).

Regarding contactors--if you're using brushed motors, you should have some kind of guaranteed cutoff, as brushed controllers usually fail full-on. The higher the voltage the pack is, and the higher current the system, the more cotnactors will be better than simple power switches, both because it's easier to deal with precharge (to prevent contact destruction) and because switches get large and expensive (and are not as reliable to break a circuit under load) at high votlages / currents.

Motors...you could even use a hubmotor (QSMotors and others make motorcycle-sized motors with bolt-on rims that would probably end up the same size as your existing rear wheel). But it is easier to change the gearing on something that runs a chain or belt drive to the wheel, so if it doesn't perform the way you want at first, you could change sprockets to make it faster or slower, lower or higher torque.

Which motor...that depends on the kind of system you want. Do you want a brushed system? (simpler, but less efficient) Or brushless (more complex, but more efficient, and has no stuck-on-failure-mode).



Battery--it's not about the Ah, first. First, it's about the A(mps) it can output. But before you can pick a battery, you must first decide:
--how much power you need, to do what you want.
--This determines how much motor you need.
--Once you pick which motor to use, then you pick the controller to be able to run that motor at the power level you need.
--At this point, you now know what voltage and current will be needed, and this lets you begin picking a battery.

But you also want to know how many Wh/mile your system is expected to use. YOu can make guesstimates on that based on other builds similar to yours, if they report it (many don't). I would guesstimate in general that yours will probably take around 100wh/mile or more, probably more on hills. This will let you determine how many Wh the battery must be, so you can pick the battery with enough Ah to give you the range you need, with enough to spare for detours, wind, pack aging, etc.

So, assuming you needed 100wh/mile at 25MPH, and use a 48v pack, then 15 miles x 100wh/mile is 1500wh. 1500wh / 48v is 31.25Ah. So the minimum you'd need at that efficiency/usage level is 31.25Ah. If you used a higher voltage pack, you'd need less Ah for the same Wh.


Keep in mind...pack ratings by vendors are not always reliable, both in Ah and in A capability, so you should probably derate what they say by anything up to 25% or so (or more) to guarantee that the battery will run the system to let you do what you want (especially as it ages).


Where to buy batteries...I don't know anything about GM's batteries, but their motors/etc are about like most of the other common Chinese ebike/etc stuff: not the best quality, not the worst. There are known good vendors; the only one I have that came from one is an EM3EV unit, it's pretty old but it still does what it's supposed to (with some capacity loss from age); everything else that's any good I built from used EV cells (EIG NMC), the Luna pack I have I wouldn't consider good but it's old and they've probably improved (you can search the forum for people's opinions on that). There's other threads about where to buy batteries, too.



BTW, you should check the MC legal requirements in your area to be sure there isn't a requirement for it to be able to go a certain speed, etc., before you pick your motor and gearing. (I suspect there isn't one, but...you don't want to build it all and be unable to register and use it just because it can't go fast enough, even if you will never use that speed...or whatever other silly requirements the bureaucrats thought were a good idea).

 

[Dui ni shuo de dui]

OMG, those things are way too awesome!
I wish I could build one, but there is nowhere I could drive that where I live...

Anyway, here are my two cents:

Apparently you're building a 3 wheeler so that's a good thing. Because if you want to, you can use a hub motor. With a 4 wheeler that would have been almost impossible, you'd have to go with a transmission.

Using a hub motor will allow you to considerably ease the whole construction, and keep the cost and time to completion down. The only drawback would be that you cannot change the gear ratio, but that's not really an actual concern since you don't seem to be the kind of guy who likes riding at insane speeds, so you just have to size your motor for a good acceleration, you will always be able to tweak the top speed later with your controller. A hub motor can and will give you enough torque to do burnouts if you plan ahead your windings KV correclty, so don't worry about power, it will have plenty enough, much more than you expect.

To answer your concerns about hub motors:

Just as expensive: not if you factor in all the other stuff you need: axles, chains, sprockets, brackets, wheel, etc... It can add up pretty quick. And your time is valuable too, building all that stuff will take you considerably longer.
5kw hub motors... probably aren't really 5kw: indeed, they are way more than that. Take a QS motor, they are reliable and very powerful. A 5KW rated motor can deliver more than 20KW reliably. I have a 3KW motor on my bike and it has been running at 16KW everyday for 2 years, no problem whatsoever. My good ol' 2000W is running at 11KW for now 5 years on the scooter, still runs fine too! That will be way, way more powerful than any of the other lawnmover engines cars the other people are building in your awesome forum, that's for sure!
unsprung weight: Doesn't really matter in practice, you just need a good gas shock, really. We're not talking about Formula one performance here, a good shock will do the job just fine.
no possibility to re-gear for more torque/speed as dictated by weight: yes, BUT: you can size your KV low enough to have a great acceleration, then use flux weakening to get more speed if you need to. So in the end it it about the same.
limit wheel choices as they must integrated into the rim (will a 5kw hub motor fit into a 12" rim? unclear!): Hub motors exist in 12 inches and the rim is already integrated with the motor so you don't even have to buy one. No brainer. The disc braking system is also very easy to integrate.

Check here:
https://www.qsmotor.com/12-inch-scooter-motor/

They can custom build the motor for you if you give them your specs and your goals.

I see no real objective downside using a hub motor, the pros and cons are largely in favor of a hub in your case. Many people ditch the idea because of subjective reasons, they just "don't like it". If you were building a 4 wheeler, then yes, hub motors would be impractical, but in your specific application that's what makes the most sense.

Regarding battery: You don't want crazy speeds, but you want good acceleration. There are two ways of doing that:
-The usual way is to use a "standard" motor, with normal KV. In which case, a low voltage but high current setup works best.
-In your case, I would suggest you to ask the motor manufacturer for a low KV motor, and use a higher voltage in order to lower the need for current.

So basically, I'd go with at least 60 or even 72V, depending on your motor KV, and either 20 or, ideally, 30Ah. I can't really estimate precisely how much battery current you will actually need since that will depend on what motor you choose, but I assume that for a nice acceleration it might be around 150A battery, so you will need to find cells capable of 5C discharge continuous if you go for 30Ah. Thats not too difficult to find.
It seems like you live in the USA, so you're lucky to have access to these battery packs which are, in my opinion, the best bang for the buck ever:
https://www.ebay.co.uk/itm/28s2P-A123-AMP20M1HD-A-Prismatic-Pouch-Cell-for-electric-vehicle-3-6-kW-hr/143114951981?hash=item215250dd2d:g:mPEAAOSw5xhcVo7b

If you can fit one of those in your car, then it's a no brainer, go for it. It will happily take any kind of power you'll throw at it.
For a 72V 40Ah pack, the weight is 25kg and dimensions are 42x16x25 cm.
Of course, go for lithium if you can, but if you have some lead acid layin' around you can still make your first tests with that.

About controller, it's a bit early to discuss it now, but at least the basic features should be:
-flux weakening, to be able to tweak the speeds if needed
-At least 80A battery draw 150A/phase but the acceleration might be a tad weak, 150A battery draw 350A/phase if you want some really impressive acceleration (if you expect that to be weak you might be surprized )
-I don't think you'll need variable regen, but it's up to you to decide
-Reverse, but they almost all do that

Anyway, that's an awesome project, looking forward to see it completed, keep us posted!

 

[evolknuj]

It seems like you live in the USA, so you're lucky to have access to these battery packs which are, in my opinion, the best bang for the buck ever:
https://www.ebay.co.uk/itm/28s2P-A123-AMP20M1HD-A-Prismatic-Pouch-Cell-for-electric-vehicle-3-6-kW-hr/143114951981?hash=item215250dd2d:g:mPEAAOSw5xhcVo7b

If you can fit one of those in your car, then it's a no brainer, go for it. It will happily take any kind of power you'll throw at it.
For a 72V 40Ah pack, the weight is 25kg and dimensions are 42x16x25 cm.

I've "heard of A123", but I don't quite understand. The link is to an ebay listing (with questionable spelling/grammar) for a battery with "Dimentions are 500x245x160mm". Where can I find a 72V 40 Ah pack with the above weights and dimensions? Would it have BMS etc? Or are you referring to building my own pack from individual A123 cells? I'm hesitant to try anything like that for my first attempt at DIY EV

 

[evolknuj]

Ok, give me enough time for it to sink in -- 500x245x160mm ~= 42x16x25 cm, it is the same pack you're talking about. And you're right, $1k shipped for a 72V 40Ah seems like quite a good deal, especially when it can deliver around 120 A continuous. Compared to the same price for a 48V 30Ah battery with 60A continuous rating... does seem like a no brainer. I'm going to think on it for another couple days, but highly likely I'll be ordering one of those -- my vehicle can take it.

Thanks! And if you have any pointers to detailed instructions about how to set up a BMS for it, I'm all ears/eyes!

 

[evolknuj]

I'm new to this, so hopefully someone can chime in as to whether this is obvious or not. If I get the A123 pack off ebay, it doesn't have a BMS. So I would need to get a BMS myself and add it -- several places in the forum the ANT bluetooth BMS (especially 300A version) is recommended, which I think is something like this: https://www.aliexpress.com/i/32827394534.html ? I'm a little not sure because it doesn't say "ANT" anywhere -- is that supposed to be a brand name?

Regardless, if I follow this idea of getting the A123 pack and adding my own BMS, what that really means is that I need to open up the battery pack case, and somehow attach a skinny wire off the BMS to each side of each cell in the battery.

That sounds hard -- my research says the A123 cells have short aluminum tabs that are hard to attach to, and that's a ton of little wires to route and make sure don't get tugged, dislodged, pinched, etc every time I remove the battery from the vehicle to charge it (yes I plan to remove the battery to charge/store it in my back yard 'bunker' rather than in the garage next to flammable stuff).

Am I right in my understanding of what getting the very-reasonably-priced A123 pack and a separate BMS would involve?


I think I need something more 'turnkey' as this is my very first EV project. The goldenmotor battery packs are 60A continuous at 48V, which should be 2880W -- not enough for a 5kw motor. A 72v pack at 60A continuous would be 4320W, which is more like it... or a 48V pack at 90A continuous. I've not had a lot of luck finding something prebuilt like that however... but this morning, I found this:
https://lunacycle.com/blog/luna-announces-a-monster-52v-battery-for-ludicrous-builders-/
14s10p, 48V (52V), 90A continuous, 25Ah/1300Wh, 'smart bms', a nice aluminum case with handle for transport and handling, and a sub $1000 price including charger. Shipping probably not included 8) .

This obviously isn't as high spec as the A123 battery in the Ah, continuous amps, or voltage ratings... but is also half the weight and ready to use out of the box, and sounds like it would be more appropriate for my scenario and skill level.

 

[Dui ni shuo de dui]

I'm new to this, so hopefully someone can chime in as to whether this is obvious or not. If I get the A123 pack off ebay, it doesn't have a BMS. So I would need to get a BMS myself and add it -- several places in the forum the ANT bluetooth BMS (especially 300A version) is recommended, which I think is something like this: https://www.aliexpress.com/i/32827394534.html ? I'm a little not sure because it doesn't say "ANT" anywhere -- is that supposed to be a brand name?

Yeah it seems to be the same. Don't really bother with the name, I don't think it really matters.

Regardless, if I follow this idea of getting the A123 pack and adding my own BMS, what that really means is that I need to open up the battery pack case, and somehow attach a skinny wire off the BMS to each side of each cell in the battery.

That sounds hard -- my research says the A123 cells have short aluminum tabs that are hard to attach to, and that's a ton of little wires to route and make sure don't get tugged, dislodged, pinched, etc every time I remove the battery from the vehicle to charge it (yes I plan to remove the battery to charge/store it in my back yard 'bunker' rather than in the garage next to flammable stuff).

It sounded hard to me too at first, but it's actually very easy. There are just a few torx screws to access the battery tabs, then you just have to solder the BMS wires on each. Really easy, no need to be worried about this step if you have basic soldering skills.

This obviously isn't as high spec as the A123 battery in the Ah, continuous amps, or voltage ratings... but is also half the weight and ready to use out of the box, and sounds like it would be more appropriate for my scenario and skill level.

If you're that concerned about the BMS installation, maybe you can ask the battery seller to install it for you. Just send him the BMS and ask him if he can install it for a small additional fee. But really there's no need to panic, it's pretty much straight forward.

 

[Dui ni shuo de dui]

Ok, give me enough time for it to sink in -- 500x245x160mm ~= 42x16x25 cm, it is the same pack you're talking about. And you're right, $1k shipped for a 72V 40Ah seems like quite a good deal, especially when it can deliver around 120 A continuous. Compared to the same price for a 48V 30Ah battery with 60A continuous rating... does seem like a no brainer. I'm going to think on it for another couple days, but highly likely I'll be ordering one of those -- my vehicle can take it.

It's actually much more than 120Amps continuous. Those cells can deliver 10C continuous, so in this case it's 40Ah x 10C = 400A...
We've run those at 600A peak on a motorbike and they are still doing very good.

That's what's nice about this battery, it won't limit you. You'll have any choice of controller or motor you want without being afraid of frying your battery. Plus it's supposed to last a long time and it can take deep discharge cylces without being damaged. It also have a very low self discharge, which means that it won't die if you forget to charge it for a few months (which is important I guess on cyclekarts, since you probably don't drive them very often).

 

[evolknuj]

I did end up going with the lunacycle battery in the end -- was still scared of doing the BMS. Finally got my Morgan working enough to finally test it out last weekend (has brakes now, one anyway!). Driveway only, but acceleration is great so far. I'll be looking into instrumentation (suitably analog for aesthetics) to tell me how many amps I'm pulling at any point in time etc, but I think the luna battery will work out for me. It's nice not to have to worry about that part of the build too much and just focus on the dimensions and driver comfort. See my cyclecartclub link above for more details, pics, vids.