Volkswagen Drops Liquid Cooling, Will Instead Air Cool e-Golf Battery


VW e-Golf

VW e-Golf

Back in November 2013, when the Volkswagen e-Golf made its US debut at the 2013 Los Angeles Auto Show, Volkswagen put out a press released containing this statement:

“The liquid-cooled lithium-ion battery accounts for 701 pounds of the e-Golf model’s 3090-pound curb weight. It is composed of a total of 264 individual prismatic cells, which are integrated into 27 modules (each with six or twelve cells). Collectively, the cells have a nominal rating of 323 volts, with an overall capacity of 24.2 kWh. A battery management controller (BMC) performs diagnosis and monitoring functions and also regulates the temperature balance in the battery junction controller (the interface to the motor’s energy supply). When the car is not in use or in the event of a collision, power from the battery is automatically cut off.”

VW e-Golf

VW e-Golf

After extensive testing, Volkswagen engineers say that “e-Golf has passed various long-term engineering evaluation milestones in desert temperatures and cold weather climates, without the necessity of a cooling system.”

News of this switch to air cooling comes via Darryll Harrison, VW US’s manager of brand public relations, who emailed AutoblogGreen.

In the email, Harrison writes:

“Generally speaking, regarding the system, it’s important to note that the e-Golf was designed with efficiency in mind. The battery pack utilizes ultra-efficient lithium-ion cells that deliver 25Ah per cell with an energy density of 59Wh per lb. The pack is comprised of 264 cells, packaged into 27 modules (of either 6 or 12 cells) delivering 323 volts and weighing in at 700 lbs. As it relates to battery temperature, VW has developed a Battery Management Unit with an intelligent thermal control that allows the pack to remain within an optimal temperature window, helping to maintain performance and range in a variety of temperatures. This system allows the e-Golf to operate, even in more extreme temperatures, without the need of a cooling system and without dramatic impacts in performance based on testing.”

“In terms of the battery pack, the engineering goal was to develop a highly efficient system as opposed to one that focused on charge-time or capacity (like some of our competitors). In partnership with Panasonic, VW utilizes a lithium-ion cells designed for gentle charge and de-charge during use which helps to reduce heat and energy consumption often associated with cells designed for rapid charging and de-charging. Our engineers refer to them as “marathon cells.” Additionally, without a cooling system weight savings are achieved which aides in overall efficiency of the vehicle. Due to the efficiencies achieved, minimal waste heat is created during operation (i.e. during fast charging) and is quickly directed by the battery metal structure into the chassis, away from the battery, helping to prevent extreme temperature conditions inside the pack.”

If liquid cooling isn’t needed, then VW made the right choice in eliminating the complexity of that system.  Air cooling, if adequate for the given type of battery chemistry, is far simpler and less costly than liquid (active) cooling.

We believe VW made the right choice here,  but do you?

VW e-Golf

VW e-Golf

Source: AutoblogGreen

Categories: Battery Tech, Volkswagen


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52 Comments on "Volkswagen Drops Liquid Cooling, Will Instead Air Cool e-Golf Battery"

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Only time will tell. Keep an eye on those in Arizona who lease/purchase this vehicle.

Exactly. It doesn’t matter what VW, Eric Loveday, I, or anyone else “believes”. What matters is what will happen after a few years baking in Phoenix. Then we will KNOW whether they made the right decision.

Most of the Golf’s sales are in cooler European countries. I doubt they sell many in Arizona, Spain, etc.

Cutting out a few percent of their market to take a big bite out of costs makes sense.

LOL Arizona isn’t the only place that gets hot. VW is vying to be the largest automaker in the world, not just a regional provider in Europe.

Arizona accounts for 0.085% of the world population. Why should anyone care about it?

Because they’re very vocal about their LEAF batteries quickly deteriorating in the hot sun. VW doesn’t need that kind of negative publicity, especially since they’re just starting their EV push.

Exclude Arizona from sales.

And Texas and Florida and California and etc where the LEAF owners are having issues…

I’m pretty sure LEAF issues are largely due to their chemistry choice.

The Panasonic batteries that VW is going to use probably aren’t as temperature sensitive. Panasonic made a presentation several years ago showing cells that can do 3000 cycles (seemingly half depth) at 50 deg C with < 15% capacity loss:

And while you’re at it, exclude Texas, New Mexico, California, Mexico, Louisiana, Alabama, Florida, Georgia…and what of those infamous Northeastern summer heat waves? Might as well count for dismal range
in winter cold snaps…

When Nissan claims that gen 2 LEAF will also be air-cooled, and VW follows this path, it makes BMW and Daimler look smart, and that’s not something you’ll hear from me every day.

“Arizona” has been an environmental EV engineering banchmark since the Leaf Battery Stories first came out.

Good to know VW is willing to play Thermal Russian Roulette with their BEVs, for a never-stated increase in range or reduced cost of manufacture. We only know what it weighed with an active coolant system…

Thanks VW. My list of prospective EVs with hardy environmental and seasonal versatility just got shorter…

No I don’t think they made the right choice. They are behind the curve. Who want’s a “gentle charge system” on an EV. If their chemistry is so heat tolerant why isn’t Nissan using it.?

There are various engineering/cost pay offs with batteries and heat. You can use more heat/fast charger tolerant battery chemistry but then you loose energy density (think i-MIEV). Similarly you can go to a bigger battery pack and generate less heat because the charge/discharge rates stay largely constant for a car of a set size and weight so the load on each cell in the battery goes down with pack size. Water cooling systems also add weight and expense so maybe you go to a bigger battery pack (say a 28 kWh) and only sell it as a 24kWh. Lots and lots of pay offs and options. I am not saying that VW won’t make a bad call but I’d be surprised after what happened with the Leaf if VW delivered a car that couldn’t handle the heat or fast charger.

Does this indicate that fast charging will not be available for this vehicle?

It’s also designed for gentle acceleration. 0-60 in 10.5 seconds.



Dr. Kenneth Noisewater

When it comes to EVs though, VW is vigorously sucking.

Pure EVs, yes. But PHEVs are getting a bit more support at VW Group than almost anyone. Golf GTE, Passat, Panamera, Cayenne, A3, A4, A6, and soon after the A8, Q7. Probably others, too.

I’m guessing they figured they have so few HEV sales that they might as well go headfirst into PHEV. Plain HEV really makes no sense nowadays, as the marginal cost to become PHEV is just batteries and a charger. Even at a pricey $400/kWh premium, they’ll pay for themselves in 3-4 years.

Dr. Kenneth Noisewater

AFAIK they don’t have a single EREV planned, where the electric motor is more powerful than the gas engine. And their PHEV batteries are pretty poor from what I’ve seen.

Aside from megabuck exotics, I guess.

All EV battery chemistry is not the same so it is a bit of a loaded question. Some historical data though.

GM Volt was the first to offer a genuine 8 year 100,000 mile battery warranty with their liquid cooled thermal management. In fact, no one else offered such a warranty, not even Tesla. Limiting the access to only part of the 16.5 kWh battery has seemed to be a good approach for the time.

Liquid cooled is the choice of Tesla and most current technologies.

The weakest design, or at least giving more access to the degradation is found in the air cooled LEAF pack.

Has VW found a break through? Maybe, the industry is changing rapidly. Call me old school, but for this snap shot in time I will hold on to the liquid cooled thermal management just a while longer.

What does the VW warranty look like? That might be more telling than the specs.

Exactly. What does the warranty look like. 100,000, or 150,000 in the CARB states, is only as good as a manufacturers definition of normal capacity loss. I’ve personally experienced VW not standing behind legal minimums, for emissions related equipment, and don’t have much faith in the brand.

24kwh is similar to the i3, and like the i3, I don’t think it works without an engine. We already have enough 18-24kwh “short” BEVs.

Isn’t this exactly what Nissan said about the Leaf battery? As for heat during charging being the culprit for loss of capacity, the DOE study, in which they fast charged two Leafs and slow charged two others, found that heat during charging was not a factor in the degradation of the Leaf cells. Hard to believe the VW cells will be that different.

Anything is possible but the likelihood is that VW is blowing smoke because they either don’t have the technology for liquid cooling/heating ready or the technology is too expensive or they need the space which you have to dedicate to a heating/cooling system.

I will believe it when I see it.

Living in the northeast US, my concern is not with heat, but rather the degradation of battery range in cold temps.

A liquid temperature management system could have been used to keep the battery relatively warm while plugged in – now that option is not possible.

Hopefully the VW uses a different battery chemistry than my Honda Fit EV, which suffers a 50% range degradation in cold (<32F) temps.

They don’t even need a liquid system . . . simple little electric heating pads should be able to do the job. Or a system that uses the cars cabin heater could also be devised.

With the right battery chemistry, you can probably get away with little thermal conditioning. But if you live in a very cold or very hot place, it would at least be nice to have an option for cold weather or hot weather package. I live in a very temperate area where I really need pretty much no thermal management (Northern California).

*sigh*… when will they learn?

I can just imagine what will happen after people who live in hot climates fast charge their car often.

Volkswagen: “Oh…well… we didn’t intend on people actually using our car… We thought this was just a silly trend with EV’s”


Dr. Kenneth Noisewater

Maybe they don’t intend to sell them outside Europe or CARBifornia? Those places are relatively mild..

Can’t someone build an air-cooled system that uses the same heating/cooling system that heats/cools the cabin? I think Coda did something like this. Just have some separate valves that direct conditioned air to the battery space. Have it automatically turn on/off to condition the battery when plugged in.

This seems like a way to do it for the least amount of money since you only need 1 heating/cooling system that handles both tasks and just some automatically controlled valves.

The i-MiEV (equipped with the CHAdeMO fast charger) does this.

It appears the Renault Zoe uses the heat pump to cool the battery.

Normal real world use probably voids your warranty on this ‘gentle marathon chemistried’ EV… :p

The repetition of the cell / pack stats tells me nothing about how much weight was removed and what the resulting range increase and MFG cost savings was… Surly it was large enough for VW to economically justify letting some packs fry on hot days?

It looks like it went down from 701 lbs to 700 lbs with the removal of liquid cooling.

“water” cooled thermal management is not that expensive. It can be done with a gallon of water. The main issue is that (as NASA discovered), air is a very inefficient thermal transfer media.

I placed water in quotes because the chemical mix used to cool modern cars is not just water.

The e-Golf can charge in Germany just on 1-Phase with 3,7kw or 16A. This is gentle as described. But what ist with CCS ? Charging with 50kw is gentle as well ? I dont understand this. Or is CCS not allowed every day ? And what about accelerating and braking ? This is also discharging and charging over 3,7kw. Doesnt make sense.

“…minimal waste heat is created during operation (i.e. during fast charging) and is quickly directed by the battery metal structure into the chassis, away from the battery, helping to prevent extreme temperature conditions inside the pack.”

Sounds like they are using the car as a big heat sink with no fans. Seems like passive cooling to me.

Also, I think the term is “dis-charge” not “de-charge”. I don’t think this guy knows what he is talking about.

He said they are using a battery designed for gentle charging and dis-charging, then he goes on to say that minimal heat is created when fast charging. Using fast charging on cells not meant for it seems a little “off”. I will believe it when I see it.

We carefully reseached that other big mfr that offered EV’s in Arizona with no cooling for the batteries….. they seemed fine whats to worry about? and we all know lo resistance cells dont heat up much when pushed hard (when new) but when you stick em in a sealed sardine can over a 130f parking lot? then hit the DCFC?

The e-Golf has several features that are hopefully going to be adopted by all other EV’s:

* they have separated the regen scheme from the drive mode

* the regen scheme includes free-wheel coasting (with no regen) as on of the choices

* they (apparently) have a direct heating electric defroster.

I don’t understand the first feature – what do you mean that “the regen scheme is separate from the drive mode.”

As far as I know, free-wheel coasting is not a good idea. It has not been proven to be more efficient. In fact, Tesla recommends the higher regen setting in their manual specifically because it is more efficient than the lower setting.

I think what Neil is saying is very accurate, free wheel coasting is much more efficient than constant regenerating. And while you’re at it, why not give the driver the option to set his regen on the fly which will maximise charge recovery?

VW has got the user interface absolutely bang-on with the coast function and driver selective regeneration. This is where all EVs ought to be moving towards.

Tesla’s advice is because the brake pedal simply engages the friction brakes. So a low regen setting means decellation will have to be achieved by using the friction brakes more.

The Model S is not like other hybrid and electric cars that do a finely tuned regenerative/friction braking dance when pressing the brake pedal.

Big mistake.

Just look at the problems the Leaf has had in Arizona.

Liquid thermal management doesn’t just cool batteries, it can warm them in cold weather to keep them near their optimum temperature.

Voltswagen… hahaha!

If you don’t trust the battery, don’t buy or recommend the VW.

Unless you have the money for a Model S, my recommendation, based on driving a 2011 Leaf, is to wait. The current batteries are too expensive, too heavy and limit your options because of their low density.

And, please don’t tell me the average drive each day is less than 40 miles. That’s a PR red herring to explain current battery technology shortcomings.

It’s not PR – it’s a fact, and a great selling point for multi-car households.

Unless you’re some genius who took a job with a two-hour commute, most people live within 15 miles of every place they go during the course of a typical day. As a result, the average person drives about 30 miles per day.

For day-to-day driving (which is perhaps 90% of the driving done annually for a lot of people) an electric car with 80 miles of range is more than sufficient, and can save them thousands of dollars a year on gasoline.

I guess the geniuses need those jobs in order to play for all their gasoline.

On their official website they give 30 minutes charging time to 80% of battery at a 40 KW CCS DC charger.

And a 30 000 km inspection interval for the motor.

And they also mention a 10% reduction of motor power for every 1000 meters above sea level.

Isn’t it weird for an EV? maybe they just forgot to delete it from all those ICEs they sell?

Bottom line – it’s cost cutting, and that is that.

In the long run it is totally bad for ev reputation as a whole, and the car companies that cut corners in the near to mid future.

I love my Volt and it’s maker’s cautious and robust approach at over- engineering it’s battery pack. The recent story found here re: the 142,000 mile Volt reinforces that stance, and builds upon alleviating potential ev buyer anxieties.

Having air flowing around the cells or a non conductive liquid is not that much different in complexity. On the other hand a liquid can carry 1000 times more heat away by volume and therefore the system can be more compact. Liquid cooling will also allow a heat reuse somewhere else in the car like for cabin heating. Liquid cooling in closed loop will not cause dust deposit or external contamination. A liquid also has more thermal inertia which is essential to avoid local heat accumulation points.
A last advantage of a liquid system is its versatility since it will allow a car to operate on Mars as well as on Earth.

There are some disadvantages though. The extra weight of the liquid, the leak risk and the cost of the said liquid.

I’m surprised to see people suggest not selling the car in Arizona or point out how few people live there. Wow! I thought we wanted 50 state cars and spread EV adoption? I hope this doesn’t end up putting a bad name on EV’s.

Some people rightly pointed out that there are other states that get hot, where LEAF owners are also having problems. I would add we should be thinking about Central and South America, Africa, Asia and Australia.

It would be one thing to say we think they can make it work in hot climates. It is another to say its ok if it doesn’t because you can just exclude sales in AZ as a good solution.

I guess people must not travel much, or think about other communities in the world. Weird that’s the case on this site though.

To the folks that say just don’t sell in AZ, here is some evidence that VW thinks about electric vehicles outside the 2 continents you’re most familiar with..