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by john61ct
Jan 14 2021 9:06pm
Forum: E-Bike Technical
Topic: What kind of torque arm for 1000 watts 48v mountain ebike?
Replies: 3
Views: 89

Re: What kind of torque arm for 1000 watts 48v mountain ebike?

Likely need very rigid steel forks there, never heard of any aluminum being strong enough to be safe

Were you thinking of doing regen?
by john61ct
Jan 14 2021 9:03pm
Forum: Battery Technology
Topic: Design help?
Replies: 17
Views: 687

Re: Design help?

I was not in any way suggesting you use LiPo. My point was, if those C-rates are not practical from LiPo units that are head and shoulders above normal LiPo that should make you realize you need to go back to the drawing board with cylindricals. If you can't reduce the continuous power needed - and ...
by john61ct
Jan 14 2021 2:34pm
Forum: Battery Technology
Topic: Design help?
Replies: 17
Views: 687

Re: Design help?

Those really just aren't realistic ambitions if you want any longevity at all

Here's an example of true experts discussing the upper limits of LiPo performance

which wrt to power density are light years beyond cylindricals.

https://www.rcgroups.com/forums/showthr ... p=46317309
by john61ct
Jan 14 2021 11:47am
Forum: Items for Sale - New
Topic: New Original LG 21700 5000mAh Cells
Replies: 5
Views: 185

Re: New Original LG 21700 5000mAh Cells

What assurance that they are genuine?

Have you run your own cap tests?
by john61ct
Jan 14 2021 11:42am
Forum: E-Vehicles General Discussion
Topic: Emax s110 scooter with 60v lithium batterie
Replies: 4
Views: 97

Re: Emax s110 scooter with 60v lithium batterie

Likely a low voltage cutout, sagging under heavy load or at lower SoC

then recovering a bit, then dropping again, etc
by john61ct
Jan 13 2021 12:03pm
Forum: Resources & EV Related Parts and Services
Topic: Custom axle
Replies: 2
Views: 60

Re: Custom axle

Cromotor? https://www.electricbike.com/cro5/

@spinningmagnets ?
by john61ct
Jan 13 2021 8:41am
Forum: Battery Technology
Topic: Need advice on BMS24
Replies: 15
Views: 546

Re: Need advice on BMS24

Voltage while in use is hopeless at SoC% guesstimation. At rest isolated for an hour is better but very very rough, needs a calibrated table, and that tale changes for each cell model and as the pack ages. Counting coulombs is a bit better, but I doubt any chea BMS does it with accuracy better tgan ...
by john61ct
Jan 13 2021 8:17am
Forum: General Discussion
Topic: project e-trailer w solar charging
Replies: 13
Views: 613

Re: project e-trailer w solar charging

10-sec googling
https://www.atomiczombie.com/cyclebully ... -diy-plan/

Then use this

site:endless-sphere.com CycleBully

to find past discussions here
by john61ct
Jan 12 2021 12:09pm
Forum: General Discussion
Topic: project e-trailer w solar charging
Replies: 13
Views: 613

Re: project e-trailer w solar charging

I've seen commercially sold motorized e-trailers that push the bike, said to work quite well.

Likely they put in better quality professioal design / engineering than what most DIYers can manage. . .
by john61ct
Jan 12 2021 11:55am
Forum: Motor Technology
Topic: True FOC: definition and examples
Replies: 77
Views: 5157

Re: True FOC: definition and examples

Comments on why Kunteng and TSDZ2 projects are not true FOC

viewtopic.php?p=1610791#p1610791
by john61ct
Jan 12 2021 4:29am
Forum: Motor Technology
Topic: True FOC: definition and examples
Replies: 77
Views: 5157

Re: True FOC: definition and examples

aha, thanks for clarifying
by john61ct
Jan 12 2021 4:27am
Forum: Battery Technology
Topic: In case of fire...
Replies: 8
Views: 283

Re: In case of fire...

Step zero

never have them anywhere unsafe to just let them burn out
by john61ct
Jan 12 2021 4:25am
Forum: Battery Technology
Topic: Need advice on BMS24
Replies: 15
Views: 546

Re: Need advice on BMS24

Such a low charge rate is not dangerous on its own

but depends on the stop-charge algorithm you use.

Go back and read what I wrote, see if you can write it out in your own words
by john61ct
Jan 11 2021 11:50pm
Forum: Motor Technology
Topic: Advice - 18 FET Controller Mods for More Power
Replies: 10
Views: 539

Re: Advice - 18 FET Controller Mods for More Power


amberwolf wrote:Per-phase current sensing is not required for sinusoidal control (though it is for FOC)
Q posted in "True FOC" thread
viewtopic.php?f=30&t=105139&p=1610716#p1610716
by john61ct
Jan 11 2021 11:48pm
Forum: Motor Technology
Topic: True FOC: definition and examples
Replies: 77
Views: 5157

from amberwolf in another thread

From Amberwolf, elsewhere and closely paraphrased:

Per-phase current sensing is required for FOC

though it is not required for sinusoidal control

_____
but I thought true FOC was possible completely sensorless?
by john61ct
Jan 11 2021 8:34pm
Forum: Battery Technology
Topic: Need advice on BMS24
Replies: 15
Views: 546

Re: Need advice on BMS24

When you find you do need faster charging, anywhere up to 150A is perfectly fine as far as the cell longevity is concerned. If your charge termination is just voltage based HVC thus CC stage only, and 15A being dangerously low 0.04C Best to set the cutoff a bit lower, say 3.42Vpc If you did use say ...
by john61ct
Jan 11 2021 8:27pm
Forum: Battery Technology
Topic: Need advice on BMS24
Replies: 15
Views: 546

Re: Need advice on BMS24

Many if not most vendors have no clue about what they sell, just distribution in & out. From China the tech side is often outsourced, rarely available to the sales staff, hardly anyone speaks English, and asking Qs loses face, you and your boss. Can't trust spec sheets need to test yourself. Or ...
by john61ct
Jan 10 2021 11:06pm
Forum: Vendor Relations Corner
Topic: Battery Clearing House
Replies: 11
Views: 863

Re: Battery Clearing House

So long as capacity is 90+% of rated Ah, ideally 95+% then resistance should be fine too.

I would not bother with SoH lower than that, IOW no to worry too much about ESIR in your go/no-go factors.
by john61ct
Jan 09 2021 3:03am
Forum: Motor Technology
Topic: Advice - 18 FET Controller Mods for More Power
Replies: 10
Views: 539

Re: Advice - 18 FET Controller Mods for More Power

I don't see any images--if you have them on an external site, they're not visible to me here for whatever reason Show up fine here, I believe you determined it was a fault in the ISP of your neighbor or something? https://i.ibb.co/5TJ582k/20210108-211419.jpg https://i.ibb.co/n09rzM5/20210108-211435...
by john61ct
Jan 08 2021 8:55pm
Forum: Battery Technology
Topic: Need advice on BMS24
Replies: 15
Views: 546

Re: Need advice on BMS24

selecting a charge profile that is used for displaying SOC Those two are not really related. I would get a dedicated Battery Monitor for SoC guesstimation if you want reasonable accuracy, but set that aside for now, get everything working for now just using at-rest voltage, as read by a confirmed a...
by john61ct
Jan 08 2021 3:19pm
Forum: E-Bike Build Threads / Photos & Video
Topic: Another full suspension build
Replies: 272
Views: 4144

Re: Another full suspension build

Always educational man!
by john61ct
Jan 07 2021 11:36pm
Forum: E-Bike Technical
Topic: Please help with BMS to fix the BIKE
Replies: 11
Views: 266

Re: Please help with BMS to fix the BIKE

The controller is inherently power limiting. That is its function, fundamentally. For this reason, I prefer to use a battery and a motor that are both rated higher than the controller. I can run at full power until the battery is depleted without anything getting hot or going awry. Yes, but for fut...
by john61ct
Jan 07 2021 10:20am
Forum: E-Bike Technical
Topic: Please help with BMS to fix the BIKE
Replies: 11
Views: 266

Re: Please help with BMS to fix the BIKE

Something has to be the limiter to protect the battery if your brain+throttle hand cannot. A fuse / CB can do it but that's a very blunt instrument. Some BMS just burn when overloaded, others are protective and just shut down. A good controller can be programmed to do it. Or a CAv3 can be added to d...
by john61ct
Jan 06 2021 12:33pm
Forum: Battery Technology
Topic: 2020/21 What's the best 100A Peak Pack?
Replies: 56
Views: 1549

Re: 2020/21 What's the best 100A Peak Pack?

That's some crazy risky experimenting there! I actually want to "productize" a generic current limiter for exactly that use case plugging large depleted sub-packs back into the Full "mother bank" in parallel. I have my eye on these: https://a123batteries.com/a123-systems-3-7-volt...