Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[kensiko]

For the same capacity you can't take or put as much amps with cells in series. In parallel the current is split between the cells.

[Burton]

Is that right? Why is there an energy loss when cells are connected in series compared to cells connected in parallel? (Seriously - I'm asking - I'm curious and I want to know!)

Lets say you have two power sources. Both are 50v and 100amps.

If you put them in series you get 100v @ 100 amps or 10000 watts

If you put them in parrallel you get 50v @ 200amps or 10000 watts

Now if you give them each a motor which requires their respective voltages which do you think would last longer? A 100amp battery pack or a 200amp battery pack?

[Doug S]

"We are confident that the new line will exceed expectations and look forward to seeing how the motorcycle world responds."

So, it seems like the obvious question is "what are our expectations that they're confident of exceeding"?

I'm going to speak only about the S and SR since I don't ride off-road. Here are what I'd consider a reasonable list of expectations for them:

1) Lower price. This is by far the biggest factor still limiting electric motorcycles to a niche market, and Zero should be focusing at least 80% of their energy on getting prices down across the board. The bikes are already competitive head-to-head with just about any ICE bike except in terms of price and range. I'm hopeful they can do at least as well as they did last year and bring the price of the S down $1000 or more, even if they make improvements. If they can get the base price down to $10,000 in a few years' time, I think the bikes become much more of a real mainstream option for people.

2) More range. Of course more range is always better, and this is the one area other than price where the S/SR have a clear disadvantage to ICE bikes (I think top speed is adequate for 95% of riders 99% of the time). But my commute is 50 miles per day mostly on the freeway, I get home daily with at least 30-35% SoC still left, and some people will ALWAYS whine that you can't refill the tank in 5 minutes. If I had to guess, I'd say that they may somehow contrive to offer a 20-25% larger battery pack, in addition to keeping the power tank option, but I hope any larger batteries remain optional. Keep lower price as the top priority.

3) Charging options. Obviously there are options available already, and as long as they stay optional I'm all for more. A factory J1772 option with more powerful charger than the onboard one would be great for people who aren't as willing to go off the beaten path as Ben, Terry and Doc are. But in favor of the first priority, I'd stick with the 115VAC onboard charger as the base option.

4) Overall quality improvements. I'm not expecting to see Marzocchi or Brembo parts on our bikes, and I don't think that's necessary...the components are pretty serviceable as they are, for presumably a much better price than the high-end components. Incremental improvements can improve performance and perhaps reduce the price. Small improvements like cruise control, reverse and better motor cooling would be very welcome and cost very little if anything.

5) Performance improvements. Honestly, I don't think I'd spend any energy on trying to improve the performance. The SR is already a torque monster that can show a Hayabusa its rear tire from a standing start, and I just don't think top speeds well into the triple digits have much value on a street machine. I think the battery/motor/drive belt/rear tire package is pretty much maximized at this point, and significantly improving the performance would require redesigning ALL that stuff. Mission and Lightning are discovering there's just not that much demand in the hyper-performance market.

So how do I think Zero intends to exceed my expectations? My guess would be in battery capacity, which is fine with me as long as it remains optional, and a base model still with "only" 70 freeway miles' range is still available, at a lower cost.

[protomech]

Is that right? Why is there an energy loss when cells are connected in series compared to cells connected in parallel? (Seriously - I'm asking - I'm curious and I want to know!)

Lets say you have two power sources. Both are 50v and 100amps.

If you put them in series you get 100v @ 100 amps or 10000 watts

If you put them in parrallel you get 50v @ 200amps or 10000 watts

Now if you give them each a motor which requires their respective voltages which do you think would last longer? A 100amp battery pack or a 200amp battery pack?

oobflyer is basically right. Arranging cells in series instead of parallel would increase the pack voltage, decrease its amp-hours, and not change the capacity.

***

Burton:
Let's use Zero's existing modules. ZF2.8 module = ~100V 25Ah (2.5 kWh).

You could put two modules in series for ~200V 25Ah (5 kWh).

You could put two modules in parallel for ~100V 50Ah (5 kWh). (This is Zero's ZF5.7 pack)

Let's say you hook up a motor and controller to the pack and draw power out at 1 kW. Both packs will supply the power for approximately 5 hours; the series pack is supplying 200V 5A to the motor controller, and the parallel pack is supplying 100V 10A to the motor controller.

If instead of drawing a fixed power, you draw a fixed amps - say 10A from both packs - then the 200V pack will supply twice the power (200V 10A = 2 kW, vs 100V 10A = 1 kW) for half as long (25 Ah / 10A = 2.5 hours, vs 50 Ah / 10A = 5 hours).

***

oobflyer:
The reason why Zero probably configures their packs with modules in parallel for higher amp-hours, lower voltage instead of in series basically comes down to component availability and design cost.

Component availability
A higher-voltage battery means that you need a higher-voltage charger, motor controller, and motor.

The motor is pretty easy to make - and Zero designed their own motor for the 2013+ bikes.

The motor controller is supplied by Sevcon, and Sevcon's low-cost line of Gen 4 Size 2/4/6 motor controllers are only available up to about 150V, and (I recall hearing) even that was only available recently. Zero needs access to part samples in order to build prototype bikes; if the part samples don't exist then they can't use them. Maybe Zero will build their own motor controller someday; but an OEM-quality motor controller is very expensive to design.

Sevcon does make a high-voltage motor controller in the Gen 4 Size 8 and Size 10. They're very expensive, multiple thousands of dollars. Harder to build a bike to a price point. Other manufacturers make OEM-quality high-voltage controllers, but again they're very expensive.

The charger isn't too difficult to design for higher voltage - the 2013 Zeros just used Meanwell LED supplies in series. (2 series, 2 parallel for the S and DS). They could double the voltage by using 4 LED supplies in series. However, the same thing about component availability applies; Zero's either gotta use whatever they can get samples of or they've got to build their own. $$$

Design cost
Basically comes down to safety. Making things safer takes more time, which means more money.

Luke aka liveforphysics is an electrical engineer that works for Zero, and he's very active in the electric bike builder community. He's written several rants (rant 1, rant 2) about the dangers of high-voltage (700V) systems.

As you mentioned, it's the current that does things (including killing you). Voltage accomplishes nothing useful other than enabling current to flow. The more voltage, the more things that didn't let current flow before start flowing current. This includes things like almost invisibly scuffed motor winding enamel (that may never have arc'd catastrophically at 350v), the humidity collecting from thermal cycles under your insulation boots over lugs, the tiny solder flux residue impurities that didn't get entirely cleaned off before the conformal coating was applied, the silicon jacketed balance tap lead that was bent sharply once, internally tearing the jacketing leaving a thin place that may never have arc'd and exploded at 350v, etc.

In this case he was talking about a 700V battery; but it's still true that a 300V battery and powertrain requires more design safety than a 100V battery. From the battery perspective it simplifies things if they stack their modules in series instead of parallel, since they can design and validate a 100V module .. but the overall battery is more expensive (for 300V with 3 100V modules, you have 3 BMS instead of 1, or you have 1 BMS with 3x the number of taps) and any type of failure is more expensive (both in terms of human life and in terms of PR damage).

[oobflyer]

Thanks Protomech - makes sense!

[oobflyer]

Disappointed!

Yes, the improvements are nice, but - the charging! What happened to the charging??
As a life-long long-distance motorcycle rider - I was really hoping that Zero would continue on the path of faster charging so the bike becomes as practical as a gas bike for longer rides. 185 miles of city driving? Who drives 185 miles in the city?? At the very least there should be a J1772 - 220V charging option. It seems lilke an obvious huge step in the evolution of the electric bike to be able to take advantage of the J1772 charging stations that are becoming ubiquitious.
Brammo has J1772 charging at 220V
Mission has J1772 charging at 220V - and Fast DC charging!
Lito Sora has optional fast-charging
The Saietta charges at 200V...

OK, I'll stop my whining and complaining now... I'm sure it won't be long until someone figures out an aftermarket solution - as Harlan and Terry and Ben and others have for previous models.

[benswing]

For the next year it will be up to us to set up faster charging, but I'm pretty sure Zero has their eye on this since we have been asking for it lately.  I'm also a little bummed they are giving up on the ChaDeMo for now, but they have their reasons. 

Whoever can make fast chargers at the lowest price will certainly help us out in the meantime!

[Burton]

For the next year it will be up to us to set up faster charging, but I'm pretty sure Zero has their eye on this since we have been asking for it lately. 

In a couple weeks I should have a quick charger build up with great detail so others can reproduce it.

[drivin98]

My Leaf has a 500V system (I have no idea how many cells or how they are connected).

Electricity is fascinating - wish I knew more about it.

Your Leaf more likely has a 364.8 volt system.
http://avt.inel.gov/pdf/fsev/fact2011nissanleaf.pdf

[ultrarnr]

oobflyer,

I understand your dissappointment about no J1772 charging on the 2015 Zero's. But where would you put it? It may be possible for Zero to put a L2 charger where the Power tank goes but what would the output be? 3Kw maybe? That is not nearly enough for long distance trips. When you look at the size and weight of the 2500 watt Elcons you really see the challenge that getting L2 charging integrated on a Zero presents. I think for the near future if you want L2 you will have to be mounting Elcons in side cases or a top box configuration.

[protomech]

ultrarnr:

Maybe something like this:
http://www.electricmotorcycleforum.com/boards/index.php?topic=3941.0

A 3 kW charger in an hour of charging will basically restore about as much energy as a Power Tank holds. So more charging really is only a win vs additional battery if you plan to charge for more than an hour, though the charger would be lighter and less expensive.

A smaller L2 charger does give you some peace of mind that you won't get stuck if you happen to run short on range in typical riding around town.. but I agree it's not ideal even for short rides beyond the range of the bike. Even a 5-6 kW charging setup like yours is really the minimum reasonable for planned rides beyond single-charge range.

Without changing their design and using no new technology, Zero could make a 6 kW charger that could fit in a saddlebag mount. You could pair them for the larger S bikes, giving you pretty reasonable touring capability with dual J1772 inlets. And then you could remove the chargers for regular around-town riding.

With the biggest battery S (ZF15.3?), a 200 mile trip would take about 4 hours of riding and 1 hour of charging at 55 mph, or about 3 hours of riding and about 1.5 hours of charging at 70 mph. That's pretty reasonable IMO, and it'd really unlock the "electrics are for commuting only" myth.

However, Zero seems to be content to leave charging solutions to the aftermarket. Probably they won't release a faster stock charging solution until they shift to 200+ V.. 2016 or 2017.

[kensiko]

Fast charging is probably:
- Complicated to be compatible with every fast charger
- Costly.

I assume this is why it is not added to the Zero 2015 yet. Maybe 2016? Another year to wait.

[Richard230]

I am pretty sure that Zero is always watching their dollars.  They are not about to spend a dime if there is not a large enough demand for a product to make a profit.  And right now, what with the limited available charging infrastructure, the expense and size of large chargers, the even greater expense of fast-charging technology, relatively low battery density, cheap IC motorcycles and gasoline, a relatively small market for electric motorcycles world-wide and the limited space available for anything on a motorcycle chassis, I have to agree with Zero that keeping the Level 1 charging system is the way to go for now.  Electric motorcycles are still not yet mainstream and the number customers that would want to take long trips on them are very limited.  Designing the bikes for commuting and for day trips at this point in the technology revolution would seem to be the best way to market the bikes and make enough money to stay in the electric motorcycle manufacturing business - and not be forced to go into the consulting business to make money.   

[Doug S]

I've said it before and I'll say it again: I agree with Richard, Zero should stick with only level 1 charging on the base models. Additional charging options are great, and I'm all for them, but don't make them standard equipment. Many of us who mostly just commute are very happy with our cheap solution; don't make us all pay for any of the other options.

The two remaining obstacles to much wider adoption of EVs are range and purchase price...particular price, in my opinion (since so many of us put on so many commuter miles). Purchase price needs to be brought down as fast as humanly possible to expand the market.

[Richard230]

I agree that the prices need to be lowered (you could say that about any product, of course).  But while we are considering that, notice that the prices of all established IC motorcycle brand models are increasing at a fast rate every year.  It seems like it won't be too long before IC and EV prices are much closer together than they are now.  It will just take a larger EV market and the corresponding economies of scale to bring down prices.  Right now that is tough to do considering the low production volume and the limited EV components available on the market to a small manufacturer.  (Think I read recently that Zero sales this year were somewhere around 2000 units.  That would hardly get the attention of most major motorcycle (or anything else) manufacturers.)

Sales would really take off in the U.S. if the gas prices were as high as they are in Europe and the UK.  But with current gas prices approaching $3 a gallon here, there is not a lot of incentive for the general public to invest in EVs to reduce the cost of transportation.