What are the sturdiest bike frames that could check into luggage if I build them with a removable battery?

glennb said:
You said Sabvaton 72V. That’s 20S. Tool packs are 5S.
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5 times 5 is 25, no? 5 times 4 is 20. I legitimately just assumed I was wrong for several minutes while I tried to work out the nominal voltage of these packs versus the declared voltage and came to the same conclusion of putting 4 of the packs in series. You managed to confuse the heck out of me for like ten minutes, which is honestly impressive.

future proofing (‘cos tool batteries are transitioning to this cell format).
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This is possibly the most convincing thing here. I'm still not willing to walk into federal law enforcement scrutiny with blatantly deceptive intent, but I appreciate your concern. When I can no longer find 5Ahs as they die, I'll make the transition.
 
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Sorry, yes, that benefit is only applies for equal current, in the 6P Vs 6P comparison.
 
Gotcha.

I'm currently staying at the top of a hill. About 300 ft above the main road at a fairly steep grade. This might be a silly question, but if I fully charge my batteries before I leave, how seriously do I have to worry about regen overcharging my batteries?
 
Not sure regards regen, not something I’ve investigated, sorry. A search should turn up plenty of discussion on it, it’s a real concern.

You said you want ten years out of this bike. The batteries won’t last that long. They’ll fail one at a time, and you should very much want them to be near enough identical. To that end, you’ll want to select cells and/or specific packs that are likely to be available in years to come. High power 18650s are already obsolete. When pushing cells hard, the limitation is thermal, and the larger cans come in to play.

You’re lucky to get 200 cycles from 5Ah 18650 tool packs (used in tools), particularly with fast chargers. You might get even less, given the hammering you’ll be giving them to achieve the 45mph you want.

Any cycle life data you find for cells is likely to be a a poor approximation for you, because it’s highly unlikely anybody will pack them together at 2mm spacing, fail to control the ambient temperature, discharge at anything like the rate you’ll be subjecting them to, nor charge above the 0.5C rate that you’re in all likelihood going to.

FWIW, another benefit of 21700s is the larger positive electrode, which permits wider nickel strip.
 
Afterthought … it’d be sensible to use a regular pack for regular use, and reserve the tool batteries for aeroplane trips. If you don’t travel more than once a month, and keep them in the fridge at storage voltage, you should get your ten years no problem.
 
That's probably a good idea, yeah. Maybe the LiGo 10X will come out before my next trip lmao.

If I go 4s4p I get better range on the bike and ease the discharge at the cost of damn near completely filling my personal item. Then again, I, like many men before me, am shameless enough to find a jacket a bazillion pockets to put the stuff that would normally go in my personal item and literally only use it for airports. Can't move the drill batteries to the jacket though, since I gotta build a neat block to put 'em all into.

I wonder if there are ways to control (lower) the charge rate. I might be able to find a charger that's designed to slow charge power tool batteries, but I dread having to reverse engineer and modify one. I could also maybe somehow design the panniers to let air through the front and rear faces of the battery block? Take a filter off a PC case or something. But the *rain*.
EDIT: These things. Label says 1 Amp, a review complains of slow charging. 0.2 C is exactly what I'm looking for. Hopefully it comes with a sensible cutoff voltage if it's bothering to drive LEDs and shit.

Contractors are always going to need to be able to fly, so it's hard for me to believe that 18V 5Ah batteries will just completely disappear unless TSA regulations change (in which case so do my design constraints). As my 18650 5Ah drill batteries start to lose capacity, what's stopping me from replacing one battery pack from each parallel group with the 21700 5Ah batteries that will inevitably appear in their place? I could get my multimeter out and compare voltages after arriving somewhere to bin batteries by how far they've discharged so I'm replacing a quartet of similar batteries. As long as I keep track of which ones are the newfangled 21700 ones and make sure I don't put them in the same parallel group, what's the worst that could happen?
 
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AreYouSeriousMan said:
I'm currently staying at the top of a hill. About 300 ft above the main road at a fairly steep grade. This might be a silly question, but if I fully charge my batteries before I leave, how seriously do I have to worry about regen overcharging my batteries?
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Not a silly question but: Don't overcharge the batteries. Avoid it by either not fully charging them before the steep descent; or not using regen until they are sufficiently discharged to safely accept regen current.

Do you have questions on whether overcharging causes serious damage or not?
 
99t4 said:
Not a silly question but: Don't overcharge the batteries. Avoid it by either not fully charging them before the steep descent; or not using regen until they are sufficiently discharged to safely accept regen current.

Do you have questions on whether overcharging causes serious damage or not?
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Ughhh, my brake pads...

No, it's just the only way I can see myself getting a partial charge out of this setup is plugging a 1amp charger for each of the parallel groups into a power strip, putting one drill battery from each parallel group onto each charger, plugging the power strip into a kitchen timer, and plugging the kitchen timer in once everything's set up in hopes that they charge uniformly. Then I'd have to come back with a multimeter and possibly... probably make manual adjustments.
 
AreYouSeriousMan said:
No, it's just the only way I can see myself getting a partial charge out of this setup is plugging a 1amp charger for each of the parallel groups into a power strip, putting one drill battery from each parallel group onto each charger, plugging the power strip into a kitchen timer, and plugging the kitchen timer in once everything's set up in hopes that they charge uniformly. Then I'd have to come back with a multimeter and possibly... probably make manual adjustments.
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Seems like a tradeoff in compensation for hitting your other (more important?) priorities.

Did you know there's ways of reducing a charger's ultimate top voltage by splicing a diode into the output.
 
AreYouSeriousMan said:
No. I'll look into that. Not an experienced tinker by any means.
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It's cake. Different diodes have different forward voltages (amount of voltage drop across the diode) and different current capacities. Also they might need heat sinking to dissipate the required amount of energy. But it's not a hard problem to solve.
 
Regarding replacing packs, ideally you wouldn’t.

You’d instead buy four more than you need, use a numbering system, and rotate them in and out of circulation (FIFO) so that they’re all wearing equally.

When one fails, take it out of circulation. By the time four have failed you can be confident that they’re all on their last legs and the whole lot need replacing.
 
Regarding charging, there’s dozens of possibilities for doing it. You’ll need to specify your requirements and preferences in more detail before that subject’s worthwhile discussing.

It’d be tempting to travel with a single or double dock rapid charger and cycle the packs through it. You have plenty on your plate with the rest of the build, and might as well start with this approach, because charging is in the critical path and conjuring the “ideal” charging system will inevitably delay the whole project.

As to airflow for the packs in the panniers … yes, of course that would be best. They don’t need the full 45mph windblast though. Venting the panniers will be one of the more trivial aspects of this project.
 
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