Electric Earth said:
My first thought on the battery would be to build a custom triangle pack that's basically permanently mounted. Then I'd dress that up to look like a frame-bag for bikepacking. To me it's more of a hassle than I want to deal with constantly connecting and disconnecting a battery and carrying it into every place I go to. I'd just use a Big lock like the highest rated Kryptonite or something. I wouldn't leave it out overnight or anything, and don't live in a city, so I think it would be OK.
without the theft issue, but with cold like you're talking about, you might want to reconsider that, unless you can insulate it really well, and maybe build heaters into it that you can leave plugged in in the worst weather.
it depends on how cold the pack would actually get, and that's something you would have to test under the conditions you have there. you could build a box with the right dimensions, and pack it with a similar thermal mass, and put some electronic thermometer sensors in there in various places (or just one and move it around over a number of test sessions).
but to be accurate, that testing would have to be done under the cold conditions, and you probably don't have as much of those at the moment, or as bad, as you will in the winter.
I've read up on cold whether usage some and know you have to let it come up to room temp before charging. I thought riding the bike with a freezing battery was bad for it. Good to know that using it cold won't damage it. I doubt I'd ever ride too much below freezing. Once it hits mid-20s, I'd probably just take my truck. WI get really windy too when it's cold, and it's just miserable and tempting frost bite to ride in it. I'm not That committed to being 100% electric.
if you're not going to be in deep cold, then as long as you're riding it the battery will warm itself up to some degree, and if you insulate the entire enclosure, like say with 1" styrofoam sheets, or the 1" foil-covered foamboard insulation available at home improvement places, the heat it does generate will stay in it.
but you should still bring the battery inside with you whenever it is possible to do so.
if you *have* to, you could add the heaters. if you use regular reptile heaters, the flat rubber mats, they run off 110vac normally, and have no thermal controls, etc. they're just always on. so you could install those between the insulation sheets and the battery, and then wire them to a switch that connects them to the battery pack. if the pack is a 48v, then they will run at less than half the power they were designed for, but it would still be enough to keep a pack from freezing, if ti's that cold (especially windy). just don't leave them connected to the pack, bms or not, when you're not actually present, or you could forget and they could drain the pack completely dead, even if the bms shuts off the output (because many of those don't *completely* shut off the output, so there are still leakage currents if it's left long enough (days, weeks, etc)).
you also want to be sure the heaters cannot *overheat* the pack, just keep it from freezing, or getting so cold that voltage sag is so great under any load that it doesn't operate the way you need it to.
As for two motors, I'd still be limited to ~20mph with a 500w motor, right?
it's not just a 500w motor anymore when you have two of them used at the same time.
it's effectively a 1000w motor, and it would actually be able to sustain greater continuous power than a single 1000w motor, because it has more surface area and more thermal mass to radiate / absorb the waste heat.
so if your speed limit is simply not enough power at a single 500w motor, then two would increase the limit to whatever that supports under your conditions.
the major things that limit speed (other than power vs load / air resistance) are wheel size vs motor rpm at a specific max voltage. the motor rpm at voltage is a function of it's kv (rpm per volt) and it's gearing ratio (for geared motors, either geared hubs in a wheel, or motors not in the wheel that drive it by chain, belt, etc).
i would go to http://ebikes.ca/simulator , read the entire page so you know what everything is and how it works, and then experiment with different setups. it can simulate two separate systems at the same time, either to compare them, or to add them together for 2wd. even if they don't have the motor listed that you want to use, you can still use it to see how the system will change with one vs two motors, or different controller current limits, battery voltages/etc, and different situations (higher winds, hills, low vs high weight, etc).
