Talk to me like I'm stupid- Tesla Supercharger

[roma258]

Can anyone explain to me (in relatively simple terms) why a Tesla supercharger can charge at 440 miles of range per hour and Level 2 J1772 takes 3.5 hours to charge an Empulse with a mixed range of 80 miles? I understand some basics (takes longer to "top off" the battery), but I guess I'm wondering how transferable the tech is, now that Tesla has apparently released all of its patents.
http://insideevs.com/tesla-model-s-charging-440-miles-per-hour/

[benswing]

Charging speed is measured in kilowatts (kW). 

The J1772 plugs charge at a maximum of 6.6kW (30 amps at 220V, or 7.2kW 30 amps at 240V).  The J1772 "plug" is actually an outlet and provides alternating current (AC), so your vehicle must have a converter to change that to direct current (DC).

The Tesla Superchargers charge at a rate of 135kW.  They work using direct current, so you don't need any onboard converters, it just injects the electricity into your vehicle battery.

Using the Tesla 85kWh battery as an example:

Ideal time to charge 85kWh with 6.6kW: 13 hrs
Ideal time to charge 85kWh with 135kW: 38 minutes. 

As you mentioned, batteries need to be charged more slowly as they get close to being fully charged.  So those ideal times are not accurate, but they are a good starting point.

[roma258]

What's stopping Brammo from charging at, let's say 25kW?  Is it a matter of expense (higher spec components)?

[littlefreak3000]

It would require batteries larger then the ones in the Empulse and a high power battery charger that is tuned to the specifications of the Empulse batteries. So in turn a really expensive charging station that's worth more then our bikes.

[Shinysideup]

OK. Talk to ME like I'm stupid...

Knowing Zero's batteries can be charged faster with multiple chargers, in the best case scenario, how much straight DC power (in kW) could the Empulse's batteries take on from a hypothetical Brammo fast charger?

What mods would have to be done to the bike? Another plug bypassing the onboard charger and being wired directly to the batteries? What would that cost? What would be the cost of such a best-case fast charger?


And would such a setup have any time and/or cost advantages to using multiple AC chargers as Zero does? Remember, I'm stupid!

[benswing]

Right now the only commercially available charging system that uses J1772 plugs (the electric car charging stations) is a 2.5kW charger.  With a Zero there are 2 ports into the battery, so you can set 2 up to charge at 5kW.  (Also, you can add the onboard adapter for 6.3kW of charging power.)

A guy in Quebec made a charger that works at 6.7kW, but it isn't waterproof.  So you can charge faster.  It's my understanding that you generally don't want to charge much faster than the # of kWh in your battery.  So with the Brammo 10kWh battery, you probably don't want to charge faster than 10kW.  (Otherwise you can overheat the batteries and damage them.)

Ideally both Brammo and Zero would have ChaDeMo adapters available so you don't have to carry around chargers and you can just pull up to a ChaDeMo station and slam your battery full of electrons!

[Chocula]

One of the issues with Zero's CHAdeMO port is that many of the chargers did not support the lower voltage (~100V vs ~400V) needed for the Zero.  Brammo also uses a lower voltage battery pack.

Additionally there is the maximum rate of charge the cells can withstand without damage which can be further hampered by needing to dissipate heat generated from charging.  Zero's site quotes 95% in under an hour.  This equates to about 1C which most lithium chemistry batteries can handle with no ill effects.  I don't think I would want to charger faster than 1C without the manufactures blessing that the batteries can take it with out degrading.

I for one would much rather Brammo have an option for a 2nd on board charger wired in parallel or replace the existing one with a 6.6KW charger using the existing J1772 plug.  Maybe not quite as fast as a DC quick charger, but there are plenty of J1772 charging stations that support 30 amps and DC Quick chargers are much less common and are frequently more expensive to use.

Heck, have an external 6.6kw charger mounted in a removable saddle bag with its own J1772 connector and you can achieve a 1C charging rate just by finding 2 J1722 plugs next to each other (1 for the on board and 1 for the removable charger).  That is way easier than finding a CHAdeMO or CSS DC charger.


Chocula

[roma258]

I for one would much rather Brammo have an option for a 2nd on board charger wired in parallel or replace the existing one with a 6.6KW charger using the existing J1772 plug.  Maybe not quite as fast as a DC quick charger, but there are plenty of J1772 charging stations that support 30 amps and DC Quick chargers are much less common and are frequently more expensive to use.

Heck, have an external 6.6kw charger mounted in a removable saddle bag with its own J1772 connector and you can achieve a 1C charging rate just by finding 2 J1722 plugs next to each other (1 for the on board and 1 for the removable charger).  That is way easier than finding a CHAdeMO or CSS DC charger.
Chocula

So is there a reason why a 6.6kW charger wasn't used in the existing plug in the first place? Once again, cost of components?

It's my understanding that you generally don't want to charge much faster than the # of kWh in your battery.  So with the Brammo 10kWh battery, you probably don't want to charge faster than 10kW.  (Otherwise you can overheat the batteries and damage them.)

So this basically means that as things stand, you can't fully charge your battery in less than an hour?

[frodus]

The size of a 6.6kw charger is not something that would fit easily on the bike.... And would cost another couple grand to the customer. Plus it's extra weight.

[benswing]

So is there a reason why a 6.6kW charger wasn't used in the existing plug in the first place? Once again, cost of components?

It's my understanding that you generally don't want to charge much faster than the # of kWh in your battery.  So with the Brammo 10kWh battery, you probably don't want to charge faster than 10kW.  (Otherwise you can overheat the batteries and damage them.)

So this basically means that as things stand, you can't fully charge your battery in less than an hour?

Size, weight & cost are the inhibiting factors.  Doctorbass, up in Quebec, has a shoebox-sized 6.6kW charger, but it gets hot and needs fans, so it isn't waterproof. 

The only person who has charged his battery in less than an hour is Terry Hershner, and he breaks the rules because he knows what the battery can handle so he pushes the limits.  Without an electrical engineering degree, I wouldn't try what he does.  Certainly a manufacturer isn't going to give consumers the ability to do what he's done. 

Some of the ChaDeMo stations haven't been built to spec (50V-500V), so some of them don't work with the voltage that Zero or Brammo motorcycles need.  Quite a few work, but it seems Zero doesn't want to sell a (fairly expensive) ChaDeMo adapter that doesn't work sometimes, even though it is no fault of theirs.

[kingcharles]

It is a choice Brammo made. They selected to use an off the shelf charger.
Another option was to integrate the charger in the motor controller. Like the Mission motorcycles or Renault Zoe.
But it would mean that the motor controller also no longer is an off the shelf item thus driving up the cost again.

I am sure that in a few years every bike will use this architecture because it saves weight, requires less space and reduces cooling complexity.

In fact Zero might do this for 2016. They need to improve their charging capabilities and with their own motor design it wouldn't surprise me if they were already working on an integrated approach.

But maybe Brammo will beat them to it with their recent round of funding!