First build: 1980 CB125

[asa]

I have been lurking here long enough and I'd like your feedback on my draft part list for my first build!

The donor bike is a 1980 Honda CB125 S. I would like to be able to get up to 65mph (105kph) if needed, but will mostly be riding in town at ~30mph (48 kph). I don't need more than 20 miles of range. But I am thinking of building a removable second battery to extend my range on longer trips.

Here is a link to the parts list (photo below):

EV CB125 parts

docs.google.com

 

[harrisonpatm]

You're looking at about 1.5kwh for your battery. You might get 20 mile range off that.... but itll be cutting it close every charge. 2p would be better; even though it'll be double the weight, it should make up for it with range. Especially since you're getting used cells, they may not have the capacity you expect them to have.

For a contactor, check out TE Connectivity EV200AAANA 500a 0-900vdc Tyco 12/24v

For your DC/DC converter, 600w is going to be way overkill, if it's just lights and horn. Which is fine. Just a note. If you found one you can afford at 600w and have physical space for it, go for it. You could always add 12v floodlight and speaker system later!

Apologies if you already have it covered, but the engine was a stressed member of that bike. By removing the engine, you've also removed a structural component of the frame. If you actually plan on going 60mph, get it reinforced so it doesn't buckle in half when you hit a pothole at that speed.

 

[asa]

Awesome thanks!

Yes–– I will for sure need to re-enforce that gap at the bottom and attach the foot pegs and kickstand. The gearbox was attached at two points in the back––at the very bottom and a bit higher. You can see the eyelets in the photo. Do you think I'll need to re-enforce across both points or just the bottom?

The 600W DC-DC is coming from the onboard Kelly charger. Open to swapping it with something else!

 

[harrisonpatm]

The gearbox was attached at two points in the back––at the very bottom and a bit higher. You can see the eyelets in the photo. Do you think I'll need to re-enforce across both points or just the bottom?

Just to make sure we're on the same page. You need to reinforce between where the engine attached at the forward section of the bike, and where the gearbox attached at the rear section. Does that make sense? Your bike currently has only a spine. Give it a ribcage.

2002 Harley Davidson Softail Electric

2002 harley fatboy all electric Trying to figure out to mount Rear hub motor when the axle is too short https://youtube.com/shorts/NjZrfg-0-D4?feature=share https://youtube.com/shorts/NjZrfg-0-D4?feature=share

endless-sphere.com

Kawasaki Ninja 250 build

QS8kw v4. 17"/3.5"hub motor. Fardriver controller 96850. Looking for Chevy volt modules/2 96 v. Charger for same,low power? Not sure about bms? Need DC to DC converter.

endless-sphere.com

 

[asa]

Yep, same page!

 

[scianiac]

Having bought the 8ah SPIM cells from battery hookup awhile ago I would recommend buying more than you need and selecting the highest capacity cells, mine had quite a range of capacities, those may be better but hard to know and they go out of stock often so you may not be able to order more if you have a few low capacity cells (that will limit the entire capacity of the pack of course).

 

[asa]

Thanks! Do you remember what percent were bad? How much should I overbuy?

 

[scianiac]

Well it's not that any were "bad" they just had variable capacities, they all were perfectly functional but some were over the 8ah spec and some were like 5-6, I never ended up using them for the bike since they are also huge for their capacity but I think I bought 14 and it looks like 10 are around 7-9ah. The 3 lowest capacity I used for a 3S battery spot welder. I would say you should look at the SPIM cells and their weight and size compared to your battery needs and compare them to other cells. They are amazing at discharging tons of power but at the cost of not amazing energy density so if you don't need that power density then higher energy density cells may be a better choice. Obviously assembly is another thing so may be easier to just go with them instead of spot welding a battery from 21700s and same goes for cost.

 

[amberwolf]

Keep in mind any pack built from cells that aren't identical in all their properties isn't going to remain balanced on it's own; the greater the differences in properties the greater the imbalance will become during every usage.

If that's not a factor, then dont' worry about it, but just thought I'd bring it up in case it matters for your use case.

 

[asa]

[..] I'd bring it up in case it matters for your use case.

Thanks! What do you think? When should that matter? Just for longevity or something else?

I am using a BMS of course and will top balance before connecting.

 

[amberwolf]

It matters for performance and longevity, and for charging times. How much it matters depends on the amount of difference between the cells, and what you're going to ask of them relative to their capabilities.The harder they are used, the more difference the differences make.

With cells that are all equal in properties, you get the full capacity of the entire pack, and the full capabilities of the entire pack, and they don't need balancing, because they will all charge and discharge equally, until eventually (usually years later) they age enough to begin becoming different.

With cells that are different, you only get the least-capable cell's capacity and capability, so one with the highest resistance will sag in voltage the most, limiting power output and cutting off output due to LVC under load sooner, and the one with the lowest capacity will limit the range by cutting off output due to LVC even when not under load sooner. Depending on the amount of cell difference, they could need balancing on every charge cycle to get sufficient capacity and capability from them. The differences will only grow worse with time, so balancing will take longer and do less and less to help the system (this is also true of cells that start out the same, but they will take much longer to reach this point).


It's very difficult to actually get matched cells, so it's likely that any pack you build will have some degree of mismatch...but the closer you can get them, the better the pack will perform, for a longer part of it's lifespan.

 

[mazzola]

@asa have you fit the QS273 motor to your bike yet? I was wondering if the axle fit into the dropouts/swingarm just fine or if you had to do some modifications.