Those 24kwh BMW/Chargepoint CCS chargers

In doing research on lithium ion batteries, and correctly recharging them, one charge rate factor keeps coming up... a C/1 charge rate, not to be exceeded, for longevity of battery life of Li Ion celled batteries.

A C/1 charge rate means a charging capacity to charge the battery fully to it's max capacity of Kwh in a 1 hour charge time window.

A C/.5 charge rate means a charging capacity to charge the battery fully to it's max capacity of Kwh in a .5 hour charge time window.

A C/10 charge rate means a charging capacity to charge the battery fully to it's max capacity of Kwh in a 10 hour charge time window.

Trickle chargers for car batteries are normally a C/20 rate ... 20 hours or slower, to fully charge.

What does this mean to you and me, as e-Golf owners/leasers? That no matter the size or kwh of the battery pack, you don't want to, in the current case with 24kwh battery packs, want to DC fast charge from a low battery charge state in under 1 hour.

The BMW chargers, in conjunction with the size of the battery in the I3 being rated at 22kwh, is at or just under that 24kwh Dc fast charger rating.

The 50kwh Big kahuna's that cost $10 a charge with 50kwh capacity and charge to 80% in 20 minutes... are not the best for the longevity and life of a LiIon battery like in our e-Golf or a BMW i3. Probably not good for a Nissan Leaf with CHAdeMo 24kwh or 30 kwh battery either.

Until Li Ion battery manufacturers start making recomendations for battery chemistry that can be charged at a C/ 0.5 rate, or fully charged in a half hour not affecting battery life, waiting 50 minutes to an hour to quick charge should be the gold standard for those with e-Golfs with 24kwh batteries.

If I am going to DC charge with level 3 at all, I will seek out those 24kwh chargers, or just hang in there with 240V 30 amp level 2 charging stations as being "safe" for the long term health of the battery in the e-Golf I own.

Obviously, this is more a concern when doing longer trips /long range travel that exceeds normal range and battery capacity to get by on one charge, round trip.

http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/mag/504PET23.pdf


Far too often, the battery-charging system
is given low priority, especially in
cost-sensitive applications. However,
the quality of the charging system plays
a key role in the life and reliability of
the battery. To develop an optimized charging system
for lithium-ion (Li-ion) batteries, designers must be
familiar with the fundamental requirements for charging
these batteries. Designers also should be aware of
the tradeoffs of linear versus switch-mode charging
solutions.
The rate of charge or discharge often is expressed
in relation to the capacity of the battery. This rate is
known as the C-rate and equates to a charge or discharge
current and is defined as:
I=M Cn ⋅
where I is the charge or discharge current, expressed
in amperes (A); M is a multiple or fraction of C; C is a
numerical value of rated capacity expressed in ampere-hour
(Ah); and n is the time in hours at which C is declared.
A battery discharging at a C-rate of 1 will deliver its
nominal-rated capacity in 1 hr. For example, if the rated
capacity is 1000 mAh, a discharge rate of 1 C corresponds
to a discharge current of 1000 mA. A rate of C/10 corresponds
to a discharge current of 100 mA.
Typically, manufacturers specify the capacity of a battery
at a 5-hr rate, where n = 5. For example, the battery
mentioned previously would provide 5 hr of operating time
when discharged at a constant current of 200 mA. In theory,
the battery would provide 1 hr of operating time when
discharged at a constant current of 1000 mA. In practice,
however, the operating time will be less than 1 hr because
of inefficiencies in the discharge cycle.

JoulesThief said:

... that can be charged at a C/ 0.5 rate, or fully charged in a half hour ...

Click to expand...

Small nitpick: At least when talking about R/C (remote control models) LiPo batteries, the charge rate is usually written as 1C, 2C, 0.5C, etc. so on the e-Golf 24.2kWh battery, charing at 1C would require ~24.2kW of power into the battery. Charging at 2C would be 46.4kW, etc.

kirby said:

JoulesThief said:

... that can be charged at a C/ 0.5 rate, or fully charged in a half hour ...

Click to expand...

Small nitpick: At least when talking about R/C (remote control models) LiPo batteries, the charge rate is usually written as 1C, 2C, 0.5C, etc. so on the e-Golf 24.2kWh battery, charing at 1C would require ~24.2kW of power into the battery. Charging at 2C would be 46.4kW, etc.

Click to expand...

Tried to clarify it for you above, hope that helps. I am not that familiar with the R/C terminology.

Ahh of course, the notation is just algebra!
C is a value, 2C is twice that value, C/0.5 is just a different way to express 2C. I should have seen that earlier.

kirby said:

Ahh of course, the notation is just algebra!
C is a value, 2C is twice that value, C/0.5 is just a different way to express 2C. I should have seen that earlier.

Click to expand...

The 0.5 is basically a time factor, a full charge in 0.5 hour or half an hour quick charge rate. Preferred charge rate is not in less time than 1 hour. 2 hours is even easier on the battery pack and perhaps VW feels that 7.2 kw an hour is ideal for their 24 Kw battery capacity with 240 Volts at 30 amps.

JoulesThief said:

The 50kwh Big kahuna's that cost $10 a charge with 50kwh capacity and charge to 80% in 20 minutes... are not the best for the longevity and life of a LiIon battery like in our e-Golf or a BMW i3. Probably not good for a Nissan Leaf with CHAdeMo 24kwh or 30 kwh battery either.

Click to expand...

Having just used an EVGo 50kW charger for the first time last weekend, I was more concerned with all of the warnings on the charger about accidental death and injury.

But, TBH, 35 minutes for a complete charge is much more civilized than L2 and while I don't plan to use it often, it is very nice to have that feature.

Here's hoping that the technology improves to where this is the default, and not the exception.

However, it would be nice to be able to select charge rate for the 50kW connection. IIRC the eGolf makes use of up to 42kW of the 50, and the charge rate is non-linear based on initial state of discharge. You seemingly can't set the rate from the phone app or the charger station.

Geoff

Nope. You have no control over DC Fast Chargers. It just pushes in the maximum current that it can based on what the car tells it that it can handle.

HighTestElectrons said:

Here's hoping that the technology improves to where this is the default, and not the exception.

Click to expand...

I don't hold out much hope.

Our house has 200A service - where we live, that's all you can have nowadays. If you wanted more, you'd need to get three phase power, and I'm not sure how you'd get that in a residential neighborhood reasonably.

That's 48 kW of power.

And that assumes that you black out the whole house just to charge your car.

CCS chargers that can do 50 kW have three phase connections and probably need upwards of 70 kW of input power to do it (they need to convert AC into high voltage DC, which is not an amazingly efficient process).

That's the arithmetic that makes me dubious about a future of universal all electric transportation. I don't see how the energy delivery infrastructure scales. People talk about increasing battery capacity, but they're missing the larger problem. Filling a gas tank at the pump is an instantaneous energy flow of something like 5-10 MW. Even if you give EVs a discount for being 4 times more efficient, that's still an order of magnitude or more power than a Tesla Supercharger - the current world champion of retail electrical energy delivery.

Unless EVSEs come with a Mr. Fusion, that's not going to be possible.

nsayer said:

Our house has 200A service - where we live, that's all you can have nowadays. If you wanted more, you'd need to get three phase power, and I'm not sure how you'd get that in a residential neighborhood reasonably.

That's 48 kW of power.

And that assumes that you black out the whole house just to charge your car.

CCS chargers that can do 50 kW have three phase connections and probably need upwards of 70 kW of input power to do it (they need to convert AC into high voltage DC, which is not an amazingly efficient process).

That's the arithmetic that makes me dubious about a future of universal all electric transportation. I don't see how the energy delivery infrastructure scales. People talk about increasing battery capacity, but they're missing the larger problem. Filling a gas tank at the pump is an instantaneous energy flow of something like 5-10 MW. Even if you give EVs a discount for being 4 times more efficient, that's still an order of magnitude or more power than a Tesla Supercharger - the current world champion of retail electrical energy delivery.

Unless EVSEs come with a Mr. Fusion, that's not going to be possible.

Click to expand...

I have a 400A panel with 320A service on a home built in 2012. PG&E had no reservations about provisioning that. They even upgraded the transformer feeding my house and my two neighbors without any cost to me. In any case, 10kW is enough to recharge any EV that's used for personal transportation during overnight hours. If you look at the Tesla Supercharger network, they only power about 10% of the miles travelled by the cars that use the network. That's a free network. Normal BEV use going forward will use 3-10kW overnight charging and occasional 20-150kW public fast charging. Fast charging for non-Tesla vehicles will be less because they will not be free or unmetered. There will be some local bottlenecks that will require grid upgrades, but overall, EV charging will not require significant changes to the electrical grid. If there is a real case that requires more than 150kW per vehicle, they can use local batteries to buffer the effect on the grid.

nsayer said:

I don't hold out much hope...Unless EVSEs come with a Mr. Fusion, that's not going to be possible.

Click to expand...

I hear what you are saying but Musk has already said that decentralized power storage is what will allow the infrastructure to keep up, and the power wall product is that idea in reality.

Serializable 7.2kW bricks that can be used to store base load electricity and feed it back as necessary. Wiring several houses together you could have enough power to charge a few cars, and replenish the batteries off hours. The assumption is that PV and other secondary sources feed this mini grid which can both augment the primary grid, offload consumption during peak times, store energy for later use or isolate their storage for other uses such as high capacity charging.

It will take a different way of thinking, but the capacity is what you make it.

.02

Geoff

It'll be a while before Powerwalls come down in price enough for me to justify buying one. A long while. Solar panels would come first.

Actually, if your utility offers ToU metering, you probably could have a powerwall pay for itself in only a few years by performing ToU arbitrage.

Buy low, sell high.

nsayer said:

Actually, if your utility offers ToU metering, you probably could have a powerwall pay for itself in only a few years by performing ToU arbitrage.

Buy low, sell high.

Click to expand...

Living in the house full time, during the day, retired, with AC running daily, does not make ToU economical with where I live. I am usually happy with 80F and a fan blowing, the lady turns it down to 76F. You can imagine what that does to the electrical bill from June through October most years, in So Cal.

JoulesThief said:

It'll be a while before Powerwalls come down in price enough for me to justify buying one. A long while. Solar panels would come first.

Click to expand...

As with most of these technologies, both the rate of incremental improvement and limited lifespan of the electronics tilts the economics in favor of leasing. This is what Tesla and SolarCity are pushing: a guarantee that they can beat or equal your current electricity charge or fraction thereof with an equipment lease that puts you slightly ahead. That includes sellback to the utility, so it's a closed-end calculation based on your available footprint.

Where powerwall will be pushed is an option for EV charging, where 80% of your home's capacity will be dedicated to charging the car 30KW approximately, while you run your house off the battery for a few hours. If the battery costs an extra $50 per month ($6k amortized over 10 years), I think a lot of folks would spring for it.

Geoff

Looks like ChargePoint added another one of these along Interstate 5 in N. California, at Williams, at the Carls Jr. Restaurant.

http://api.plugshare.com/view/location/79148

and Redding

http://api.plugshare.com/view/location/73333

but it's a long stretch still to Yreka

http://api.plugshare.com/view/location/75901

I used my first CCS DC charger today with the eGolf. The charge rate was 20KW. This is a big improvement over the 7.2KW charger and allowed me to do 180 miles today in 30 degree weather.

Does anyone know what the max charge rate is with the CCS charger? Was the car limiting it to 20KW?

I checked the manual and cannot find anything that specifies the max rate the car will accept.

Stretch2727 said:

I used my first CCS DC charger today with the eGolf. The charge rate was 20KW. This is a big improvement over the 7.2KW charger and allowed me to do 180 miles today in 30 degree weather.

Does anyone know what the max charge rate is with the CCS charger? Was the car limiting it to 20KW?

I checked the manual and cannot find anything that specifies the max rate the car will accept.

Click to expand...

A C/1 charge rate, as provided by a 24 kwh charger to a 24.2 kwh battery, should be just fine. It's the C/ .5 charge rate or putting in 24 kw in 1/2 an hour with a 50 kwh quick charger, that is hard on the traction battery, and your owners manual recommends it "be done sparingly".

In the above equations the denominator is a time factor, based in hours. .5 is 1/2 an hour, full charge, 1 is 1 hour to full charge 4 is 4 hours to full charge. Since your battery is a 24.2 kw battery, a 24 kwh charger should be fine. Not the best, like a 3 to 4 hour recharge, but certainly not as damaging as a 80% charge in 20 minutes, or a 90 to 93% recharge in 30 minutes. Hence the term "sparingly". My definition of sparingly is less than 5% of all recharge cycles. YMMV.

http://batteryuniversity.com/learn/article/ultra_fast_chargers

We won't know what the maximum charge rate is until there are CCS chargers that have higher power available. I posted the charging curves of the higher power chargers from BTC and ABB which are called 50kW chargers. You can see those curves in this thread. Even though they are called 50kW chargers, they top out at about 38kW on the e-Golf. The real limitation is how many amps the charger can deliver. I think the ABB will go up to 110 amps and the BTC will deliver up to 100 amps. The smaller chargers that are called 24kW are usually limited to 60 amps DC. I think the maximum rating of the current CCS connector is 125 amps, which would probably result in a peak rate of about 44kW at the e-Golf's voltage of 350VDC at 80% SOC. That voltage is significant because that is the point where the car tells the charger to ramp down the current.

Stretch2727 said:

I used my first CCS DC charger today with the eGolf. The charge rate was 20KW. This is a big improvement over the 7.2KW charger and allowed me to do 180 miles today in 30 degree weather.

Does anyone know what the max charge rate is with the CCS charger? Was the car limiting it to 20KW?

I checked the manual and cannot find anything that specifies the max rate the car will accept.

Click to expand...

The dealer mentioned 42kW is the max it will pull from a CCS line. The rate of charge is dependent on the state of depletion when the charger is connected and will reduce over time to what is appropriate for that state of charge, tapering as charge approaches 100%.

The 50kW EVGo combination CHAdeMO/CCS charger near me is rated at 385V and 130A. Unsure if CCS runs at full power.

Geoff

HighTestElectrons said:

Stretch2727 said:

I used my first CCS DC charger today with the eGolf. The charge rate was 20KW. This is a big improvement over the 7.2KW charger and allowed me to do 180 miles today in 30 degree weather.

Does anyone know what the max charge rate is with the CCS charger? Was the car limiting it to 20KW?

I checked the manual and cannot find anything that specifies the max rate the car will accept.

Click to expand...

The dealer mentioned 42kW is the max it will pull from a CCS line. The rate of charge is dependent on the state of depletion when the charger is connected and will reduce over time to what is appropriate for that state of charge, tapering as charge approaches 100%.

The 50kW EVGo combination CHAdeMO/CCS charger near me is rated at 385V and 130A. Unsure if CCS runs at full power.

Geoff

Click to expand...

Pretty sure that the e-Golf throttles back the amount of amps and voltage available. If you have 22.1 kwh available, and you've used 20 kwh out of the battery, with 10% left in the battery, you need 18 kwh and it will fill to 90% SOC in about 30 minutes, 80% SOC in 20 minutes... you'd actually be adding 70% of 22.1 or about 15.5 kw, in 20 minutes. That works out to about 45 kw in an hour. Those rechargers are rated at 50 kw/ hr.