Roast Me: Battery / Motor options for a Honda 175 Conversion

[RedFalcon]

My daughter and I are converting a 1969 Honda 176 SL Dual Sport.

We are making it street legal so she can get a motorcycle drivers license. There will be no highway use with this thing. School is 2 miles away, which will be the daily commute. But I'd love to get a 30 mile range with some street legal speeds up to 50 if needed so the the travelling diameter can be broader.

I've been looking at a drop in QS138 motor and controller kit like this to get us off the ground fast: https://www.electroandcompany.com/product-page/qs138-70h-v3-3000w-em-150-kit

I DO NOT want to hand build a battery if I can avoid it.

Question for the techno heads on this forum:

1. Assuming I use the Q138 and Votol EM-150 controller, are there any relatively plug and play batteries that will meet my needs?

2. Has there been any innovation in repurposing Sauron or e-scooter batteries in parallel for a more plug and play experience?

Total Noob here so let the roasting begin!

 

[amberwolf]

Some questions and thoughts:

Do you want it to have "safe" acceleration capabilities, or is it ok if it just toodles up to speed over a long distance? It takes more power to do the former than the latter, even though only for moments at a time. Gearing the motor low will get you torque that will accelerate quickly, but reduce the top speed available. Increasing voltage can fix that, or not changing the gearing but increasing current capability from the controller and battery to the motor. (you need the same things for hills)

Battery capacity and system power/current capability requirements: How far does it have to go at what speed, worst case, and under what conditions does it have to do this (winds, hills, stop/start traffic or continuous riding, etc)?

If you are interested you can do some power and power usage guesstimates on the motor and/or trip simulators at ebikes.ca, using the "custom" fields for controller, motor, battery, etc., to see how much power you need for worst case conditions, and how much capacity on average it may take to go each mile.


You can probably parallel smaller batteries for range, as long as they all have the same voltage and chemistry (identical batteries is better than otherwise). Paralleling them to get the power you need can work too, but it depends on their quality. If they're cheap and/or used, they may be made of poorly-matched cells that don't all have the same capacity or capability, so some of the packs may shutdown under load sooner than others, putting more of the workload on those still working, so they sag in voltage more and potentially also shutdown, and so on (a bit like a string of old xmas lights).

So...using packs that are individually at least mostly capable of running the system on their own is better than requiring all or most of the packs to be working together to operate it, as far as stress on them goes and as far as ride safety (since you don't want it to shutdown on you). Then they're paralleled together for capacity (range).

It might not be possible to do it that way, and you might have to depend on multiple paralleled packs to handle the load together.

Another option that is not quite as hard as building the whole battery yourself, but will probably perform better over time, is to take all the individual identical packs, and parallel each one's cell groups to the others, and use one BMS to monitor them all for LVC and HVC...but not run the power thru the BMS like the smaller packs do. Instead, the BMS just controls a contactor that actually handles the power, which also allows for other things like "easy" precharge of controller caps, etc. Charging can still be done thru the BMS FETs, or via the contactor if higher charging rates are needed. One of the BMSs from the packs can be reused for this, or you can buy a new contactor-based BMS to reduce the DIY of it all.



I couldn't find a bike or scooter or whatever named Sauron; did you mean Sur Ron? If so, those could probably handle the power needed by themselves, depending on which specific battery you use, and then parallel them for range.

For other escooter batteries, it depends on the specific battery.

 

[99t4]

I DO NOT want to hand build a battery if I can avoid it.
... are there any relatively plug and play batteries that will meet my needs?

Suggest you monitor Genuine Lithium Batteries for DIY Projects website (batteryhookup.com). Their selection changes weekly, if not daily. Many here have scored good batteries from them.

Calculate your V, A, and Ah requirements, and measure your spatial dimensions to make a suitable choice. Might require patience.

 

[calab]

I'd build around ev vehicle batteries, like a Tesla battery module, or better yet a battery module that is the most common of the day but be careful of the voltages, I dont know what the voltages are for the different modules, but thats what I'd look into. I'd go 48v, 52v, 60v, but I would think heavily going 72v and building around that voltage. Critical is to not stress the battery, get a big dishcarge battery, but limit with a programmable controller.

 

[gofastjuice]

I'd build around ev vehicle batteries, like a Tesla battery module, or better yet a battery module that is the most common of the day but be careful of the voltages, I dont know what the voltages are for the different modules, but thats what I'd look into. I'd go 48v, 52v, 60v, but I would think heavily going 72v and building around that voltage. Critical is to not stress the battery, get a big dishcarge battery, but limit with a programmable controller.

You're going to have a hard time fitting Tesla modules into a bike of this size. Even the older S modules, which are the smallest I've seen from Tesla, are too large according to EV West:
Height: 3.1 Inches
Width: 11.9 Inches
Length: 26.2 Inches
Weight: 55 Pounds
Voltage nominal: 22.8V/Module

The model 3/Y is even worse, with the packs in those cars compromising of only 4 modules permanently bonded together. Our friend Allen Millyard has the frame you need if you're set on these modules.

 

[jonescg]

I've always said, it doesn't matter what it weighs, if it won't fit, it doesn't matter.
The hub motor is definitely the winning option on a bike this size. You can probably get a battery of unique proportions made form cylindrical cells to fit inside the frame cradle, but it won't be very big. Probably big enough at least.