# Lg 4.4 ah 36 volt battery pack



## aquabiologist (Sep 8, 2017)

Found the answer myself

After some more digging found a list of lithium chemistry and battery codes here:
https://batterybro.com/blogs/18650-.../18880255-battery-chemistry-finally-explained

The lg 4.4 packs sold on ebay are lico chemistry. So no. Not safe for ev purpose.

Gesendet von meinem E5823 mit Tapatalk


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## Solarsail (Jul 22, 2017)

Series hybrid is the way to go, unless you have 200 kWh of EV storage. You have a very nice architecture: 4s45p10s2p

And the 2.2 Ah cells are cheap, about $1.30/cell as opposed to $3.25 for a Panasonic 3.4 Ah. At $164 /kWh they are the cheapest on the market. I have decided to go with the Panasonic at $266 /kWh for my 12 kWh pack, as it will be 35% smaller and lighter.

May I ask what motor and controller are you using?


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## Solarsail (Jul 22, 2017)

The problem with parallel cells I understand is that if one cell in a group or bank that is in parallel is underpeforming, it will be hard to find out which cell that is. And one bad cell can make the whole bank and pack useless by triggering underdischarge voltage protection.

I am surprised that you say the LCO chemistry is not safe for EVs. Isn't that exactly what Tesla has been using? Tesla is not using LMN. So why do you need to be safer than a Tesla?


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## Duncan (Dec 8, 2008)

$266 dollars a kWh??

I paid $1800 for a 16 kWh Volt pack - thats only $112 a kWh

And I got all of the fixing hardware, five contactors, the BMS modules, the main fuse and a current sensor all part of the package

The Volt modules are water cooled/heated and are capable of delivering oodles of power - I'm drawing 400Kw!! - for a couple of seconds


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## Solarsail (Jul 22, 2017)

That is a great deal Duncan. The price of the Panasonic drops with volume. The price I quoted was for a 1.3 kWh pack. For a 12 kWh pack, the consumer price will drop to about $230 /kWh. These are new cells under warranty. Also, it gives you a lot of flexibility on how to configure the pack, as I am building from scratch. And if I were to expand the pack, I can do that in increments, and need not find used auto packs. Availability is not an issue.

In my application, I don't need to draw a lot of power. 25 kW would be plenty.

Five contactors? Where these all in the power pack on the power main? Why would there be five contactors in a Volt power pack?


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## Duncan (Dec 8, 2008)

five contactors
two big ones were for the main HV lines 

Three smaller ones
One was for the pre-charge
One was for the heater for the water circuit (did I mention the heater - it was in the pack as well)
I can't remember what the third one did

If you are buying to make something and sell it - then you really have to buy new

If it's for your own project then buying something like a Volt pack makes a lot of sense - everything is made to automotive quality levels - a LOT higher than normal consumer levels


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## Solarsail (Jul 22, 2017)

I am just building for my own use.

Two heavy contactors for the HV line. Is that because the negative also has a contactor or is it that there are two modules and each has its own contactor? Why would the HV need two instead of one?

So the battery heater is HV. Yes, used EV batteries are a very good deal. I would love to pick up a used T3 pack with the 2170s.


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## Duncan (Dec 8, 2008)

Hi Solarsail

I think all electric cars break both the positive and the negative HV lines - for safety
The Volt also has a fuse/service plug that breaks the pack into two 

I know that is a legal requirement for Home builts in NZ to have a contactor in both lines

I was able to use one of the large contactors for my pre-charge but I draw too much current to use them as my main contactors and I had to pay money to get a pair of larger ones for my main contactors


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## john61ct (Feb 25, 2017)

How do the 3.2V prismatic cells compare pricewise? Just a bit fuzzy on the units conversion. . .

Say I can get them at $130 per 100AH (C/20 rating) delivered, how many of those would it take to get to 12 kWh?


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## Solarsail (Jul 22, 2017)

Hi Duncan - thanks for the info, it is very helpful.

May I ask what is your 400 kW application? Racing?

Can I ask why do you have to pre-charge the inverter controller? Does it have a huge capacitor? Are you using a microcontroller to manage the battery?

As you are in Kiwi, can I ask you if you have experience with e-drive for cats? That is the purpose for my 100 kWh project - to put it on a cat with solar panels (100m2). Do you know of people doing this? If I do this, it will most likely be based in Brisbane (only 13 hours from Vancouver).


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## Solarsail (Jul 22, 2017)

john61ct said:


> How do the 3.2V prismatic cells compare pricewise? Just a bit fuzzy on the units conversion. . .
> 
> Say I can get them at $130 per 100AH (C/20 rating) delivered, how many of those would it take to get to 12 kWh?


I believe you mean LiFePO4 prismatics. My understanding is that they are more expensive, because their unit capacity is less. Assuming the prismatic is 1S, then energy is 320 Wh/cell. You will probably need at least C/4, so the capacity probably drops to 280 Wh/cell. That is 3.5 cells/kWh or 455 $/kWh. This is almost twice the price of 18650 LCO.

You would need 12K/280 = 42 cells or $5,500 per 12K pack. Problem is that these cells are such huge capacities that it will limit you to the voltage that you would get. 42S1P will give you 134V. 21S2P gives you 67V. So you can only get 33V, 45V, 67V, and 134V. If you want to get 96V or 192V, you have to greatly increase the capacity to 17 kWh, or drop it to 8.5 kWh for 96V.

My argument is out of billions of 18650s in laptops, how many have recently caught fire? And note that laptops don't have microfuses. Do you hear of laptops catching fire anymore? And when they did, it were just a few, and probably related to the Sony problem. All these millions of smartphone portable chargers, 1 cell and 4 cells, etc. are they catching fire? I have done nail tests on loaded 18650s, and I don't get a fire. When my batch of NCR18650Bs arrive I will do some more tests.

Can you please give me the size and weight for this prismatic?

I think the 18650s mentioned by Aquabiologist in this tread is a much better deal than the prismatic. Or as Duncan has said, a used EV module.


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## Solarsail (Jul 22, 2017)

I am not sure if the test attached (Panasonic 3.4Ah 18650) indicates there is a puncture of the shell or if the pressure release valve has been activated. The 18650 survived an impact. Temperature rose to 170C.


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## Duncan (Dec 8, 2008)

Hi SolarSail

My car has a Paul & Sabrina prototype 400 v - 1400 Amp controller with great big disc shaped capacitor
I'm using 340 v and 1200 amps in - Duncan's Dubious Device
http://www.diyelectriccar.com/forum...dubious-device-44370p15.html?highlight=duncan

You will find that all controllers have and chargers have decent sized capacitors so there is always some form of pre-charge system to avoid a huge inrush current when you switch them on

Mine is purely manual - I switch the 12 v power on which switches one of the main contactors on - then switch the pre-charge (I'm using a kettle element as a pre-charge resister) then when I reach about the right voltage I switch the second contactor on

You get the same with the charger - you need to couple it through a resister until the voltages get close or you get huge surge currents and your contactors welding together


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## Solarsail (Jul 22, 2017)

Thanks for the link. That is one cute hot rod you got there. At 400 kW, that would be equivalent to (400/.74)*1.5 = 800 HPe? I am told ICE HP is 50% exaggerated when compared to electric, due to torque curves and very tight optimal operational window for an ICE.

Have you thought of putting in a 2 speed gearbox, to get better starting acceleration, and lower end run RPM? How about a planetary gear set, a lock, and electronic synchronization? Let's say the planetary gearset is 2:1 ratio. The universal gear is locked to ground (stationary) by a stationary solenoid (#1). This will be low gear. To change gears, the solenoid #1 retracts and releases the universal. Motor RPM goes to half which will synchronize the universal with the planets. Another solenoid #2 that is bolted to the universal locks the two, so now you have high gear. To go back to low, lock 2 opens, motor doubles its RPM (in relation to the planets) so the universal becomes stationary and lock 1 closes. No clutches needed, no synchromesh needed, and you get the benefits of a planetary gearset. Is this easy to build?


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## brian_ (Feb 7, 2017)

Solarsail said:


> How about a planetary gear set, a lock, and electronic synchronization? Let's say the planetary gearset is 2:1 ratio. The universal gear is locked to ground (stationary) by a stationary solenoid (#1). This will be low gear. To change gears, the solenoid #1 retracts and releases the universal. Motor RPM goes to half which will synchronize the universal with the planets. Another solenoid #2 that is bolted to the universal locks the two, so now you have high gear. To go back to low, lock 2 opens, motor doubles its RPM (in relation to the planets) so the universal becomes stationary and lock 1 closes. No clutches needed, no synchromesh needed, and you get the benefits of a planetary gearset. Is this easy to build?


No, I don't think it is easy to build, to work reliably and handle significant power. As far as I can find so far, there are no solenoid-shifted two-speed transmissions (planetary or otherwise) currently available... although there are many transmission companies which are quite capable of designing the product and manufacturing the components.


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## Solarsail (Jul 22, 2017)

But you see, there is no load on the solenoid. It is not moving gears or shafts or rings or clutches. All it does is to lock the universe gear to either ground or to the planets. Even a 12V 1A solenoid could do that. And multiple solenoids can be used for each lock. With a strong traveler, the lock can handle lots of torque, I think, as long as it can overcome the centrifugal force in high gear. A brush would be needed to deliver power to lock #2. The #1 lock is stationary so no issues there.

It would be best to put the lock#2 on the planetary set. Less centrifugal force and also can use the same ribs on the universal gear as lock#1 uses for latching.

I think the Volt already uses electrical locks (and a clutch) in its very complex transmission, which I understand is based on one or two planetary gearsets.


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## Duncan (Dec 8, 2008)

Hi Solarsail

I can spin my tires from stationary - and I just don't have the space for any gearbox at all

As far as top speed is concerned - for the 1/4 mile it would be handy but for the road the overall speed limit is 100 kph - and I can do over 140 kph

For the motorsport they are quite sensible here - the faster the sport the more safety is needed
For the basic stuff I do they make sure we stay below about 100 kph

To go up to the next level I need a license and a lot of other stuff


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## brian_ (Feb 7, 2017)

Solarsail said:


> But you see, there is no load on the solenoid. It is not moving gears or shafts or rings or clutches. All it does is to lock the universe gear to either ground or to the planets. Even a 12V 1A solenoid could do that. And multiple solenoids can be used for each lock. With a strong traveler, the lock can handle lots of torque, I think, as long as it can overcome the centrifugal force in high gear. A brush would be needed to deliver power to lock #2. The #1 lock is stationary so no issues there.
> 
> It would be best to put the lock#2 on the planetary set. Less centrifugal force and also can use the same ribs on the universal gear as lock#1 uses for latching.


I'm not sure quite what mechanism are meant by "locks", but in practice they would be dog clutches if they are going to handle any significant torque. There are bicycle transmissions which use pawls (such as the Pinion series, and similar to what is normally used as a park mechanism in an automatic or an EV gearbox), but in the bikes that's a one-way drive (no regenerative braking) and these transmissions only handle a few hundred watts of input power (although at significant torque).

There are transmissions intended for electric vehicles which shift gears, such as the GKN two-speed eAxle, used for the front axle of the BMW i8. GKN runs synchronizers with a motor which slides a conventional shift fork (like a traditional manual transmission) to slide the moving part along the input shaft... and that's in an integrated drive system, developed in close cooperation with major auto manufacturer for their most technically advanced model, boasting "a complex GKN shift control software which combines eMotor control with a precise synchroshift control using advanced sensor and actuator technology."



Solarsail said:


> I think the Volt already uses electrical locks (and a clutch) in its very complex transmission, which I understand is based on one or two planetary gearsets.


The Volt transaxle is mechanically pretty simple (compared to a modern automatic), like other similar hybrid transaxles (such as those in Toyotas). It does use a planetary gear set, although as a power splitter rather than as a shifted reducer. It does have shifted elements to change modes; they are shifted by engaging and disengaging multi-plate hydraulically actuated clutches, just like conventional automatic transmissions.

Any conventional automatic transmission controls planetary gear sets as you are describing, but they use multi-plate hydraulic clutches (although long ago they used drums and brand brakes). There are a very few dog clutches used, although ZF has resorted to them in the HP9 transverse transaxle to save space... and they actuated hydraulically, just like the multi-plate clutches.


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## Solarsail (Jul 22, 2017)

Thanks a lot. I'll study this and get back ...


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## Watt Neon (Jul 23, 2017)

I am sure you have all seen and known of the zombie 222. He uses an electrically engaged overdrive unit that is a 2:1 ratio. I am not saying it will work for any specific build but he is throwing a ton of tq through them. Sometimes he runs a few of them is series for top speed runs. 

Sent from my SM-N910V using Tapatalk


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## Solarsail (Jul 22, 2017)

Hi Brian - this is the best I could draw it. The blue gear (sun) goes to the motor. The red gear ring (planets) go to the reducer that then goes to the differential. The black gear (universe) can free wheel. The diagram shows the state in high gear 1:1. Since the blue is half the radius of the black, the reduction will be 2:1. The locks (electrical solenoids) are two sets (I think you call them clutches, but I always thought a clutch can slip). Set 1, green, are grounded (attached to chassis). Set 2 are attached to the red ring, but do not interfere with the gears. There may be as many locks in a set as is necessary to handle the torque. I have drawn 2 of six in each set.

Now, there are these "catches" that are metal strips welded to the black gear, to the side of the gear, so they do not interfere with the red gears. The catches populate the whole side of the gear - I have drawn only 9 of them. You can think the catches as being a dog clutch, but to one side of the black gear. They act as a dog clutch with the solenoids.

To shift into low gear, the red locks pull in and the black gear freewheels, the motor is sped up so that the speed of the blue gear is exactly twice that of the red gear. This will render the black gear stationary. When this happens, locks 1 (green) can engage and catch the black gear and ground it. This puts the gearbox into low gear. 

The reverse happens in order to go back into high gear. Advantages:

All shifting is electrical and easily controllable
No slipping clutches or synchromesh are needed
No gears, clutches, meshes, or shafts have to slide which would need hydraulics
No grinding of gears or clutches, always engaged
Fully concentric, symmetric loading, and reduced load on bearings
Only one set of electrical brushes are needed for the red locks
Once locked, power can be reduced to the solenoids

Disadvantage:
Probably needs custom solenoids to be able to handle significant torque

Update: By putting the solenoids on the black gear, they can act two-way and either engage the red ring or ground. This way, half the solenoids can be eliminated. See second image below.

I hope this design makes sense. If the clutching could be improved, would this not be superior to the BMW i8 box?


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## Solarsail (Jul 22, 2017)

Of course good torque handling could be accomplished by two dog clutches, one between red and black (or red and blue), and the other between black and ground. But that would make the thing heavy and need a bit of mechanism to engage and disengage them.

Regarding the Pinion, they have a nifty product, but as for e-bikes, they are better off ditching the gearbox and installing a generator (which would need a small single speed gearbox) for the biker to charge the battery. A lot lighter, more efficient, and more control. It also allows the biker to pedal downhill to charge the battery for a long uphill. And also allow the biker to use the battery for other purposes like lighting during camping, even cooking, charging phones, running a tablet, etc. A serial hybrid instead of a parallel hybrid.


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## brian_ (Feb 7, 2017)

Solarsail said:


> ...
> I hope this design makes sense. If the clutching could be improved, would this not be superior to the BMW i8 box?


Essentially you're proposing radial rather than axial teeth for the dog clutch, so you can run it will solenoids that don't need to slide anything axially. Pushing of of these locking elements into place is essentially like pushing the key into a keyway while the shaft is turning... not from the end of the shaft, but inward from an extra-deep slot in in the part surrounding the shaft. It can also be compared to engaging the parking pawl (the moving part) into the cogwheel (the rotating part) of the Park feature of an automatic transmission or an EV transaxle. If you look at the size of the dogs (teeth) of a dog clutch (from a non-synchronized transmission) and the width of the spaces they plunge into, you'll get an idea of how sturdy these locking elements need to be if they're going to survive and how much space they need to have a chance of getting in while everything is spinning at different speeds.

A few of us have commented that dog clutches should work, but if companies such as GKN (the supplier for the i8) can't do it, it's obviously a serious challenge. The radial version would be even more difficult to control and to make strong enough.


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## brian_ (Feb 7, 2017)

Solarsail said:


> Regarding the Pinion, they have a nifty product, but as for e-bikes, they are better off ditching the gearbox and installing a generator (which would need a small single speed gearbox) for the biker to charge the battery. A lot lighter, more efficient, and more control. It also allows the biker to pedal downhill to charge the battery for a long uphill. And also allow the biker to use the battery for other purposes like lighting during camping, even cooking, charging phones, running a tablet, etc. A serial hybrid instead of a parallel hybrid.


Logically this makes sense, except that in reality both the generator and the motor are far too inefficient for the overall system to be acceptable; they're also too heavy. These are the same issues as with series hybrid cars, but much worse because weight and efficiency are more critical.

To be fair, there are series hybrid buses and a very few series hybrid cars. The Chevrolet Volt runs as a series hybrid some of the time, the Honda Accord Hybrid runs as a series hybrid at most speeds, the BMW i3 REX is a plug-in series hybrid, and the Nissan e-Power system (only in Japan so far, in a variant of the Note) is a purely series non-plug-in hybrid.

By the way, even with a parallel hybrid bike, the controller could be programmed to allow the rider to pedal downhill, against increased regenerative braking. The motor/generator doesn't care what's driving it.


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## Solarsail (Jul 22, 2017)

Brian, thanks for your replies, which is very educational for me. I had to tend to other matters, so was unable to respond to you in time.

I have redesigned the planetary gearbox and made it simpler, by eliminating the commutator - i.e. now its brushless. Please note the application I have in mind is e-bicycle hub motor. The amount of torque is very low as compared to an automobile. But hub motors need a reduction gear, and thus by this planetary reduction gear, one also gets the option to reduce at two different ratios, with a simple addition to the planetary reduction gear.

I still think an optimized generator instead of a gearbox or a chain and sprocket system will be superior. The weight is basically a small generator plus a one-speed multiplier. I cannot see this to be any heavier than a 6 speed gearbox and chain and sprocket.

Hub motor regeneration is not very efficient as generators like to run at higher speeds and also can be optimized to the task. Thus if a hub motor regeneration is only 60% efficient, I think a pedal generator will be 90% efficient.

Furthermore, the cyclist can generate even if the bike is stationary, like on a ferry or in a cabin. Not easy to do with hub regeneration.


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## Solarsail (Jul 22, 2017)

brian_ said:


> Essentially you're proposing radial rather than axial teeth for the dog clutch, so you can run it will solenoids that don't need to slide anything axially.


The new design does away with the actuator clutches and uses one-way clutches or pawls. Electronic synchronization may still be needed. There is no actuator on the planet or universe gears, and thus no need to transfer power through a commutator.

In the figure below, what we have are two sets of planets of different radius on the same ring, and two universes (or rings). Red sun connected to motor, blue planets to wheel, and the two universes are free wheeling with the pawl.

There is only a single pawl and it is ground connected. So it does not rotate. If it latches to the inner orange ring, you get the high speed, and when latched to the black outer ring, you get low speed. The ratio between the ratios is 1.6 in this diagram.

By using one-way pawls, latching becomes easier. Although zero-way parking pawls could be used, they are unnecessary for the orange ring. For regeneration the black ratchets must become a parking ratchet.

What do you think of this design. It can be fit into a hub motor. Even maybe for a low-power automobile. It provides both reduction and two speeds. Hub motors should be geared. I wonder if this can be further simplified.


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## brian_ (Feb 7, 2017)

*hub gearing*



Solarsail said:


> ...
> In the figure below, what we have are two sets of planets of different radius on the same ring, and two universes (or rings). Red sun connected to motor, blue planets to wheel, and the two universes are free wheeling with the pawl.
> 
> There is only a single pawl and it is ground connected. So it does not rotate. If it latches to the inner orange ring, you get the high speed, and when latched to the black outer ring, you get low speed. The ratio between the ratios is 1.6 in this diagram.
> ...


One-way pawls are common in bike transmissions. For instance, this is what Pinion (which I mentioned earlier) does for their bike transmission, with two differences:

Pinion uses spur gear gets, rather than planetary (the Pinion transmission is not packaged in a wheel hub), and
Pinions pawls are placed on an inner shaft, acting on teeth in the inside of the spur gears, rather than on the outside of ring gears.

Two-speed geared hubs have been available for bikes since 1896, three-speeds since 1903, and starting in the 1980's more ratios have become common, with the current planetary geared hub ratio maximum being 14 (in the Rohloff Speedhub 500/14). I'm not very familiar with the details of the mechanisms, but common three-speed hubs appear to use internal pawls (both to engage gears with a central shaft, and to lock ring gears to the case), and even the Rohloff Speedhub exploded view shows both internal pawls like the Pinion, plus an arrangement of teeth on gear side faces engaged by balls; they have a page explaining how it works: Gear steps 1-14, plus one detailing how each gear set functions: planetary gear system.



Solarsail said:


> ... What do you think of this design. It can be fit into a hub motor. Even maybe for a low-power automobile. It provides both reduction and two speeds. Hub motors should be geared. I wonder if this can be further simplified.


Power capacity with any of these simple pawl systems is extremely limited, so automotive applications seem very unlikely. The other issue in an automotive application is the lack of back-driving for engine braking (in a conventional engine-driven vehicle) or regenerative braking (in an electric or hybrid with the motor connected through the transmission).

This is a well-explored design path, so a novel application at much higher power levels seems unlikely to be successful.


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## Solarsail (Jul 22, 2017)

I think a two-speed gearbox for an EV is essentially mandatory, in particular with hub motors, that already have a planetary reductor. It also improves regeneration efficiency. Whether Tesla will adopt that, I don't know. It seems they got really burnt by their experience with the Roadster. But they should get more acceleration - which is a big deal to them, more top speed - higher efficiency and less wear and tear on the motors, and more passenger comfort. The differential can be integrated with the planetary gearset.

The Volt 2 has a pawl and also a pair of clutches. So the matter of clutching is settled for automobiles. In fact they could have vastly reduced the complexity and amount of metal in the Volt 2 by going serial - and could have eliminated the need for split powering. There is no reason why the pawl cannot be replaced with a clutch in the planetary design, for an automobile. The design is certainly a vast improvement over the GKN two-speed gearbox with a pair of old-fashioned slot rings rotating at engine speeds. (I believe the syncing is electronic and not slipping rings?) What were the GKN people thinking? Re-inventing the model-T? In German culture, creativity and risk taking is not rewarded well. There are too many vested interests in a technology that they want to experiment and take risks with a new design. But Kudos to BMW for being the first European EV producer.


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## Solarsail (Jul 22, 2017)

*Re: hub gearing*



brian_ said:


> Power capacity with any of these simple pawl systems is extremely limited, so automotive applications seem very unlikely.


I beg to differ. The Volt Gen2 has planetary gearsets and both pawls and clutches. So why do you believe what I have drawn, which uses the same mechanisms as the Volt, cannot be used for an automotive e-drive?

As noted above, if the black pawl clutch were to be converted to a parking clutch or a Volt clutch, then regenerative braking becomes possible. IMO, the i8 should have used Volt's planetary and clutch technology, according to my design above, to arrive at the required two speeds for the motor. Would have saved a lot of weight as compared to the GKN, and the synchronization would not have been so critical as the clutch allows for slippage when needed. And unlike the GKN, there will be no gear changing moving parts in rotation.

Regarding the Pinion 18 speed system, please note that the thing weighs 2.7 kg. Add to that two sprockets and a chain, and you are now close to 4 kg. On the other hand, a simple one speed spur gearbox can be only 0.3 kg, while a small high speed generator can be as little as 1 kg. I don't think a parallel e-bike hybrid that weighs 2.7 kg more than a serial hybrid would be superior? The pinion gear and chain's efficiency is probably not better than 90%. With the act of shifting, and having 8 pawls idling, it would be even less. While the optimized generator/motor pair on the serial would be 80% to 90% efficient. The cyclist can set the generator to a certain torque, and pedal with constant speed that suits the cyclist, and not have to worry to continuously shift to find the sweet spot, when climbing and descending. Furthermore, the cyclist can set the e-bike speed to a constant speed, while with the Pinion, the e-bike is subject to acceleration and deceleration as per the gear speed, which can reduce efficiency.


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## Solarsail (Jul 22, 2017)

Thanks for the pointer to Rohloff. It is just amazing what can be done with planetary gearsets, and in their case with slipping rings. As far as e-bikes are concerned, the first quality manufacturer that can do away with chains and gear sets (except for a 2-speed hub motor), and deliver a serial hybrid, I believe will have a major product hit. Unfortunately it may very well be the Chinese who will do that, but due to lack of quality, probably reflected in low efficiency, the serial e-bike hybrid will get a bad rap, which will discourage the Germans or Americans do develop one for a while. If generators can be 98% efficient (industrial quality), there is no reason why this cannot be done.


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## Duncan (Dec 8, 2008)

There is not and never will be a generator/motor combination that is anywhere near as efficient as a simple gear reduction

So when efficiency is really important - as in a pushbike - a generator/motor will suck


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## Solarsail (Jul 22, 2017)

Too early to say that. Industrial generators are 98% efficient. So there is no theoretical limit to efficiency. If the generator is geared to run at a high speed, it should easily approach 80 or 90%. If it reaches 90% it would be equivalent to the energy lost in mechanical sprockets and chain and guides and gear changes in use today. Besides, no electrical engineer will allow a mechanical engineer to claim they are better in something!


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## Karter2 (Nov 17, 2011)

I suspect that any pedal driven generator would require a geartrain/sprocket and chain to produce an efficient rpm for the generator from the average humans 50-100 rpm comfortable pedaling speed.
But.on an Ebike,.it is very common to have a direct drive hub motor, front or rear, and a single speed pedal gearset, as the input from the human is trivial in comparison To a well matched hub motor (power, torque , speed) 
The added complexity, weight, and cost , of a generator and multispeed gearing , are all unnecessary disadvantages to a properly designed Ebike.


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## Solarsail (Jul 22, 2017)

A two speed gear internal to and for a hub motor is essential, IMO. So no matter what kind of hybrid (serial or parallel), it would be needed.

And yes in a serial hybrid, there will be a single speed geared multiplier from pedal to the generator. The amount of load on the pedalist can easily be controlled by the pack charger, which is user selectible.

In an e-bike, the pedalist may wish to charge the battery because the trip or hill climbing exceeds the pack's range. In particular when commuting or cruising. In a parallel hybrid, the only way to do that is through regeneration (which is notoriously inefficient). So now you will need multiple gear speeds for the pedalist, in order to charge the battery or travel when the pack is empty. Thus we are back to the old chain and multiple sprocket system.



> The added complexity, weight, and cost , of a generator and multispeed gearing , are all unnecessary disadvantages to a properly designed Ebike.


There will be no extra weight, because you will eliminate the chain and sprockets and guides and mechanical controls. There is no extra complexity because you already have a battery pack and hub motor controller. A charger is not complex. Cost may be an issue, but you save by eliminating the multi speed sprocket system. You also gain many advantages, such as when camping you have power for lights or to charge your electronics, by pedaling while stationary. There will be no multi-speed gearing needed because the motor controller and charger acts as your gearbox.


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## Karter2 (Nov 17, 2011)

But the generator and hub gearing will add weight. ?
And the sprocket drive to the generator will negate any efficiency gains from the lack of mechanical connection to the wheel.
Its a well known and proven fact with ebikes that if you think you need more range, the best solution is to increase battery capacity, or to simply to pedal more.
There are litterally millions of Ebikes with non geared, direct drive, hub motors that work perfectly well even with low (250W) motors.
The US legal 750W ebike motors definitely need no gearing for normal use


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## Solarsail (Jul 22, 2017)

Karter2 said:


> But the generator and hub gearing will add weight. ?
> And the sprocket drive to the generator will negate any efficiency gains from the lack of mechanical connection to the wheel.


I think we are talking apples and oranges. The hub gearing is unrelated to the issue of serial or parallel hybrid. My understanding is that all e-bike hubs have some sort of reduction gearing. The standard 500W hub motor cannot give you the power you need to go on even a slightly positive grade. 

I have a kick scooter with 5" hub motors, rated at 300W, but can push to 500W for a while. It can't go up a 7% incline (moderate incline). How can a 500W motor on a 28" wheel do that?



> The US legal 750W ebike motors definitely need no gearing for normal use


Would that not be equivalent to 750 * 5/28 = 134W on a 5" wheel? If 300W cannot do 7%, then 750W on an e-bike cannot do 7*134/300 = 3.1% approximately. That incline is barely noticeable.


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## Karter2 (Nov 17, 2011)

Your understanding is wrong,
Ebike hub motors come in several types..different power rating, different winding configurations, different speed ratings, etc
Typically a 750 W motor would have a max rpm of 250-300 , direct drive, litterally the spokes are laced onto the magnet housing (we are talking 3 phase , brushless , DC, "Outrunner" configuration.)
Enough torque to flip bike and rider over backwards if careless !
Maybe you need to test a few Ebikes before you start redesigning one.


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## Solarsail (Jul 22, 2017)

OK, my confusion between torque and power was in error.

300W can't do 7%. But 750W might do that, especially if well constructed. Maybe my German made 300W 5" hub is not of the necessary quality.

"3 phase DC"? Wouldn't 3 phase imply an AC motor? The input may be DC, but it is being inverted inside the hub, and is an AC induction motor. 

I have tested an e-bike. It failed miserably on a 7% incline. I believe the motor was 300W nominal or maybe 500W. It was not that it was going up too slow. It was that it came to a stop. All of that energy turned into heating the coils.


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## Karter2 (Nov 17, 2011)

As i said, there are many different "configurations" of Ebike hub motors...even if you only consider the 250w lower power versions.
Different winding and pole count, different magnet materials, even different controller (inverter) designs, make huge differences.
That is why i said you should test "a few" different ones.
For steep hills or heavier loads there are "geared" hub motors, where the motor is a higher rpm construction in the hub center, encased in a planetary gearbox to boost the torque to the wheel. Externally you cannot tell the difference when assembled in the bike wheel.
A small sample..
https://endless-sphere.com/forums/viewtopic.php?f=3&t=4892
Most motors now are 3 phase BLDC (magnetic, brushless DC) with a separate inverter/controller .(.not strictly AC)
Some motors are also 6 phase and even 9 phase , with phase switching (why/delta) to alter speed/ torque characteristics on the fly.
Recently there is a tendency away from in wheel direct hub drive motors , towards "mid drive" motors driving onto the pedal crank such that the traditional bicycle chain drive and gearing can be retained.
This actually reduces the overall weight since smaller, high rpm motors can be used, cutting down on the weight of magnets and copper in the package whilst retaining the torque at the wheel.


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## Solarsail (Jul 22, 2017)

Thanks Karter2. As the picture in the link shows, the hub motor can contain a high ratio planetary gear. So the motor can be high rpm and lightweight. The only advantage of a mid drive is therefore that it can benefit from the chain and sprockets speed changer. There appears to be no other benefit. In fact for the motor to drive through the chain, will create more friction loss, and reduce performance. The mid drive motor will still need its own reduction gear, so no weight advantage there.

But if a second planetary gearset is put in the hub motor with an electrical clutch, then it is possible to get two speeds out of the hub motor, and that will wipe out the advantage of a mid motor.

The other debate of serial vs. parallel says in the case of a hub motor, if the chain drive is replaced by a gear multiplier and a high rpm pure generator of 90% efficiency, there should be no net gain in weight, but lots of gains in usability, such as a CVT, noiseless operation, and accessory power.


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## Karter2 (Nov 17, 2011)

This may interest you..
https://endless-sphere.com/forums/viewtopic.php?f=3&t=58490&hilit=2+speed+motor


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