Motorcycle Sidecar Conversion

[Korto]

HI. I'm thinking about an electric motorcycle sidecar, and trying to work out if it's practical (I'll say 'practical' because when I say 'possible' I get people replying "Oh, anything's possible with enough money!", which isn't entirely helpful).

To set the scene, I currently have a 4 person motorcycle sidecar (2 on the bike, 2 in the cab), being pulled by a 1996 Suzuki VS1400. Total weight of the rig about 400kg, fully loaded including luggage probably around 750kg.
She handles it, able to do highway speeds (110km/h) in reasonable comfort, but she's a bit thirsty (10km/L) and is having increasing mechanical problems in her old age.

I was first thinking about converting the Suzuki to electric, but there was no obvious way to go about that (and would leave us without transport for what could be a long duration), so then I thought about picking up an old BMW from a wreckers and contacting these blokes, L.M. Creations, who make conversion kits for them.

A problem I see is the rig is much heavier, and so would need a lot more battery nd probably a bigger motor. They say 80km for their tank battery, but I'll probably be getting half that. Of course, there's more room in the sidecar so possibly a distributed battery, but this battery problem really becomes acute for long trips. I'd need at least a 200km, more like 300+km range, and I suspect that would be a very big battery, with a lot of weight, so it can't all go in the sidecar (very heavy sidecars create very unsafe handling), and that's a lot of weight when braking to all go on one little front wheel.

I do have an idea of a trailer carrying a "long trip" battery. The bike and sidecar would have enough battery for perhaps 100km, while the detachable trailer has another 200km in it. The trailer would have its own braking system hooked up to the rear brake (I vaguely remember reading about electric trailer brakes somewhere) so it won't overload the poor front brake, and for normal trips the trailer can just stay at home and save carting all that weight.

If I can Vehicle-to-Grid the trailer with our solar panels, it can act as a house battery, so it's not dead money.

Anyway, that's what I'm thinking at present, but I don't know much about it. Nothing's happening soon, as I'll only have the money after we inherit. Which will be sooner than we like, but still probably a couple of years.

 

[j bjork]

A problem will for sure be range. If you do 10km on 1L, that is pretty much for a car. Your engine might be a little less efficient than a car engine, but not much. So I suppose you can expect a car size battery if you want car range. Maybe 20kwh per 100km range or so?

 

[Korto]

Yeah, the sidecar really killed the range. Before, I was getting about 17km/L (online specs say 17.5, funnily, some other websites give 14km/L so I don't know what they're smoking), after, I'm getting 10. Of course, that's with double the expected people and a great big barn door hanging off the side, so it is what it is.
But, we want to use it (or its replacement) for roadtrips, and 100km range won't do it. The last trip was more than 300km one-way, with one stretch (Putty Rd, beautiful road) being 170km between petrol stations. Only managed it because I had a jerry-can with me. (The petrol tank on the VS is 10L + 3L reserve, so, ironically, 100km before reserve).
But a jerry-can of petrol is a lot cheaper and lighter than the battery equivalent.

But this bike does need replacing when I can; I mean, it's off the road again now (starter motor died), and I would prefer electric if I can reasonably manage it.

 

[scianiac]

Based on those numbers I think that range would only be possible with a pretty advanced build and some extreme changes. For instance if you dramatically modified the bike and sidecar to make them way more aerodynamic, battery would still be large and you would need to use very high energy density cells to keep the weight in a range the vehicle can even handle. Some other optimizations to efficiency could help a lot, simply lowering the cruising speed, more efficient tires, etc.

There is a very good reason that EVs focus so much on being as aerodynamic as possible, for highway or higher speed cruising it's necessary. Can we see a picture of the bike? I'm just wondering how aerodynamic or not are we talking and I wonder if some solid and easy aero improvements can be made now which will be very informative if it's possible, in addition to saving you gas. If you can improve the efficiency with the gas bike considerably in ways that also effect the EV that will go a long way to seeing if it's possible.

 

[Korto]

OK, see if I cn get this picture in...
Do remember I'm NOT in fact thinking about converting this actual rig, but I'm using it as a "placekeeper" to give me some numbers to work with. I'm hoping that if I then deliberately build something to be electric, it will be better, not worse.
For instance, it's a wide sidecar to fit 2 people side-by-side. If the the future sidecar seated people one behind the other, it could be narrower (possibly 2/3s the width)

But it does have the general aerodynmics of a brick.

 

[scianiac]

A brick is probably somewhat more aerodynamic. Yeah a sidecar that is 2 in a line would decrease the frontal area considerably which will help a fair bit. A bike with a fairing would help, although bike fairings are tricky as they start to increase the frontal area at some point so you go too big and they are worse for aero. Also cleaning up all the sidecar hardware so it's inside the body of the sidecar would help a lot.

I still worry the 4 people plus batteries issue may be an issue, like I don't know much about sidecars but what I do know makes me worried about that much vehicle weight. At some point you are just building a very unsafe car. Are two of these people small and are they getting larger at a rapid rate, based on the timeline that may be something of an issue.

I think at least you are looking at, starting with a sturdy but weight efficient bike, idk like one of those large touring bikes with an aluminum frame although that may lead to sidecar connection issues. Sidecar probably should be custom, partially to hold two people, but also to be aero, weight optimized, possibly battery optimized — to maybe but the battery inbetween? A custom sidecar probably can be made much lighter since it can be done with a more optimized tubular spaceframe and designed to fit the bike perfectly. It looks like that sidecar spends a tremendous amount of weight on adjustable brackets. I assume sidecars are sort of designed to be not too light for stability reasons so if you made it light and then added battery to get back up to a safe weight for insance. Battery is certainly custom to be energy dense and fit the space perfectly.

Like I see your vision but also, buying a car, EV or ICE converted to EV is probably way way more practical and cheaper.

 

[Korto]

The sidecar is all steel--body, frame and attachments to the bike--and weighs 140kg by itself so if someone (who wasn't me) was to use aluminium, it could save a lot of weight, maybe even enough to make 10kWh of battery (assume around 50kg) no net increase in weight (I don't know, I don't use aluminium).

If this bike was to be done, it will certainly involve a trailer carrying a battery, maybe something like this, 30kWh, reasonably compact. It will however add another 225kg, plus trailer.
So the assumption is 10kWh on the rig, with 30 on a trailer that can be attached for long trips.
Lets round the whole weight off to about 1 tonne, fully loaded.
On the bright side, the trailer weight won't be on the bike's suspension, and it can (WILL) have its own brakes, so the bike won't have to stop the whole 1 tonne, but it would have to pull it.

edit: Hang on, how much was that battery I linked? $2500 for 30kWh? That sounds...wrong. An order of magnitude wrong. Have I misunderstood something there?

 

[lnanek]

I've paid $300 for a 20Ah battery on one of my bikes before. That one is 9x the capacity, so sounds like you are getting a deal. It also has a CAN data port, water cooling hookups, resistive heaters - way more functionality.

I'm fortunate to live somewhere no heating is needed. Similarly I'd always just get a stronger battery or put two in parallel rather than putting together a water cooling system. And I prefer Bluetooth to my phone from the BMS rather than CAN bus. I can see why cars might use that stuff, though.