determining the over/under voltage capability of motors?

[mindgames11]

Discerning the peak voltage for a controller seems more straightforward to me by looking at the voltage ratings on the caps and checking the spec sheets for the output semiconductor devices.

However for the motor... since no one actually provides even an index card of truly useful information about their devices, I'm much more at a loss.
My understanding is that Power handling for motors is limited by heat- overall temperature increase from current, friction, whatever; and by breakdown of the dielectric shorting out the windings.

I'm considering a mid drive. Likely a 48v 750w BBS02. Can these be operated with 36v batteries?

I have a 250w 36v Kuo + A2B that I recently purchased and am about to put on the road. I'm likely going to run it at the suggested 36 volts, although I'm likely to swap out the controller at some point, whether it craps out, or whatever. The battery connector is a 5 conductor, so if I want to connect one of the other 36V batteries that I converted from their proprietary BMS to "ordinary" "here's the charge wires, here's the power out wires", so I'm going to need to figure out how to modify the battery connector dock on the bike (or splice/add positive and negative wires from the controller and circumvent the battery dock).

I have a few other E bike and scooter motors with 36 and 48 volt ratings. I'm wondering how I can make educated guesses as to if I can feed the 36v motors 48, and what I should be attentive to and what types of caution I should exercise when operating the motor on a vehicle.

some unrelated questions that I may make postings for provided I can't find suitable answers, but will include here in the hope that I can get more input:
1: What's the best way to add an on/off switch to a battery?
2: I have half a dozen 10s3p (iirc) batteries with nice, genuine LG INR MJ1 cells. If I end up really liking this 36v Kuo folder (I've come to not mind the insane weight of the DD motor in the rear wheel of the 28 inch wheel bike equipped with a 52v pack that was my first purchase into the electric vehicle world. I've got a serious chain and U lock combo and it lives outdoors in the city since the size and weight made hauling it up even one flight was irritating) a 10s6p battery might be a superb option to have if I want a longer range, not to mention the better ability to supply power (although again, I don't know what the 250W rating is, continuous or peak;if it's a conservative rating, etc.) I have some battery testers. two four cell devices and four one cell devices. Since it's kinda a pain to make new packs, would be be wiser to set up some kind of a dual-battery draw system, or just bite the bullet and pull apart a few of these packs and find if there's two packs with the cells close enough together in spec that I can use them in the same assembly?
3: has anyone used a hub motor for a scooter on an E bike, or a scooter hub motor or e bike hub motor as a mid drive, or a side mount drive?
Years ago I wished that I could add a lightweight system that I could add to a 20 inch bmx that once I pedaled up to speed (twenty-ish mph), I could engage it and have it keep me at the top end without my having to keep high cadence and instead leaning down low for aerodynamics and ability to give more attention to traffic and road surface conditions.

 

[DABANSHEE]

Have a look inside the controller, odds on it has 63v caps. If it does it means you should get away with a 52v battery.

 

[amberwolf]

Hmm...year-and-a-half-old thread, but in case it's useful to future readers that don't want to look up the answers in the many other ES threads talking about these things::

However for the motor... since no one actually provides even an index card of truly useful information about their devices, I'm much more at a loss.

There is no under or over votlage for a motor.

Motors have a kV, or RPM per Volt, that will help you figure out how fast they'll spin at full throttle on a particular battery voltage. Since most ebike motors don't state that kV, you can guesstimate it by finding the RPM at a certain voltage, which you can either test or if the seller states a speed and a wheel size and a battery voltage, you can figure out RPM from the speed and wheel size given with various online calculators.

The wire used on them has an insulation breakdown voltage, but since you don't know what magnet wire they used, you'd have to look up magnet wire insulation breakdown voltages and guess that they used the cheapest stuff they could find, and guess that it has the lowest voltage rating you see for wire of that kind.

I'm considering a mid drive. Likely a 48v 750w BBS02. Can these be operated with 36v batteries?

There are threads about the BBS02 that talk about that sort of thing, but it will depend on the firmware you have, and whether it's LVC is low enough to let you use 36v, since a 36v full battery is about where the LVC for a 48v battery would start.

I have a 250w 36v Kuo + A2B that I recently purchased and am about to put on the road. I'm likely going to run it at the suggested 36 volts, although I'm likely to swap out the controller at some point, whether it craps out, or whatever. The battery connector is a 5 conductor, so if I want to connect one of the other 36V batteries that I converted from their proprietary BMS to "ordinary" "here's the charge wires, here's the power out wires", so I'm going to need to figure out how to modify the battery connector dock on the bike (or splice/add positive and negative wires from the controller and circumvent the battery dock).

If those systems use proprietary comms to activate the system via their OEM battery, you'd probably have to reverse engineer those comms and duplicate them, or at least record them and play them back, to use a different battery.

If they don't use comms, and just work as long as you have the right battery voltage provided, then nothing to worry about.

There may be info in the various A2B threads that can help. not sure if there are threads about the Kuo.

I have a few other E bike and scooter motors with 36 and 48 volt ratings. I'm wondering how I can make educated guesses as to if I can feed the 36v motors 48, and what I should be attentive to and what types of caution I should exercise when operating the motor on a vehicle.

If the motors are just motors, not with controllers in them like some do (like some of the A2B Ultramotor systems), then you can feed them whatever voltage the wiring is rated for--at a guess, at least a couple hundred volts.

As for cautions, we'd need specifics on what exactly you're worried about, or how exactly you'd be "operating it" so we could figure out if there are any things beyond the common ones you'd need even at the OEM-specified ratings.

1: What's the best way to add an on/off switch to a battery?

Depends on what you want it to do.

--physically disconnect it from the outside world entirely?

--just turn it's output "off"

--??

2: I have half a dozen 10s3p (iirc) batteries with nice, genuine LG INR MJ1 cells. If I end up really liking this 36v Kuo folder <snip> a 10s6p battery might be a superb option to have if I want a longer range, not to mention the better ability to supply power (although again, I don't know what the 250W rating is, continuous or peak;if it's a conservative rating, etc.)

If the 250w is just a label on the motor, it's not relevant to the battery draw.

If it is a rating on the *controller* that multiplies it's voltage by it's current limit, then if the current limit is less than the 3p pack version is easily capable of (not near it's max), then making it 6p doesn't really cahnge the power-supplying-ability of the pack, relative to what it's operating.

I have some battery testers. two four cell devices and four one cell devices. Since it's kinda a pain to make new packs, would be be wiser to set up some kind of a dual-battery draw system, or just bite the bullet and pull apart a few of these packs and find if there's two packs with the cells close enough together in spec that I can use them in the same assembly?

I don't know what you are really asking.

If you are asking if you shoudl just parallel two of the packs directly, then my answeer would be "yes", just connect htem directly at both main + and - and at every parallel group, after you ahve made sure every group is the same voltage as every corresponding group in the other pack. Then install a bms to monitoro and protect the entire pack as a whole.

if they already have bms on them you want to keep, then if they are commmon-port types (defined in many threads here) you can just parallel the main + and - of the packs as a whole. if they're dual-port then you'll need to disconnect those while charging. and disconnecxt the charge ports while discahrging (other posts define why)

Saem if you want to parallel more than two of them.

If you disassemble the packs you then have to be able to reassemble them, and that requires the equipment and materials and skills to do so, and that can cost more than just buying the packs you wanted in the first place.

3: has anyone used a hub motor for a scooter on an E bike, or a scooter hub motor or e bike hub motor as a mid drive, or a side mount drive?

Yes, there are many threads about many versions of this.

 

[amberwolf]

Have a look inside the controller, odds on it has 63v caps. If it does it means you should get away with a 52v battery.

It's not just about the caps.

Every part connected to the battery bus must be able to handle the battery full voltage, *and* the voltage spikes that occur on the system running at that voltage, which will be higher than on a lower voltage, and still have margin for safety.

it also depends on whether the controller has an HVC that prevents operation above a certain voltage (some do, some don't).

 

[DABANSHEE]

It's not just about the caps.

Every part connected to the battery bus must be able to handle the battery full voltage, *and* the voltage spikes that occur on the system running at that voltage, which will be higher than on a lower voltage, and still have margin for safety.

it also depends on whether the controller has an HVC that prevents operation above a certain voltage (some do, some don't).

Of course, even the thickness of the wires in the harness can be a limiting factor, but its sort of a guide to what the designers wanted their safety net to be.

 

[amberwolf]

Of course, even the thickness of the wires in the harness can be a limiting factor,

Thickness of the wires doesn't have anything to do with the voltage the system is capable of.

It *does* have an effect on the *current* it is capable of.


Thickness of the *insulation* on the wires would have to do with the voltage capability, but that will be far beyond any voltage any of the parts inside can handle, as most of the insulations are rated in the hundreds of volts).


(if it did, you could look at thickness of wire and tell what voltage something should work at, but that doens't work even a little bit--try comparing the thin wires in high-voltage fluorescent backlighting, and comparing those to the same thickness wires in logic-level devices, etc--same thickness of wire, completely different voltages).

 

[amberwolf]

<scnip>the thickness of the wires in the harness <snip> but its sort of a guide to what the designers wanted their safety net to be.

Wiring (thickness or other characteristics) isn't, by itself, any real indicator of or guide to a "safety net" choice or intent. It can indicate part of a pattern of margin choices, given a specific use case intent for a device or system, but it doesn't say anything useful on it's own.


Parts tolerances, specifications, etc., could be, if you go with the *lowest capability* part, and the slimmest-margin specification.

But even that doesn't really tell you what the designers *wanted*--you would have to actually ask them to find that out , since there are various schools of thought on what margins should be, and reasons for having different margin amounts (mostly about cost). It does tell you what the company / dev team / budget control team as a whole chose to do, but not what they actually wanted.

For cheap stuff, designed to a cost-level, margins are generally very slim, or nonexistent, by the demand of the price point.

For stuff that must be 100% reliable, margins have to be greater, and how great those will be depends also on the price point, but they have to be large enough to completely clear all of the worst-case possible scenarios and use-cases for that particular device or system.

And there is every level in between those.