telemetry

Telemetry confirmed good news.

We went to the speed track, in Cartagena, where we could use the track for some time. We thank you very much for their help.

70_telemetry

 

We decided to drive a non-stopping run at a constant current, to see how other aspects of the prototype (our electric Twingo), as range, temperatures, rpms..etc. . were affected.

 

Due to the amount of corners the track had, we couldn’t get a stable current consumption, but at least we could monitor it, and that was the result for 20 min drive.

71_telemetry

 

We can see an average of 120 Amp out of the battery pack most of the time. And also, around 210 Amp out of the controller.

72_telemetry

All this time we have consume around 3,3 Kw, which is a stoning 46% of the total capacity.

73_telemetry

 

But, ¿how this test affected to the rest of the components?. Well, we could see the controller a bit too hot, so that led us to think about an additional cool system for the controller. We saw a peak of 72ºC, which is the limit of a healthy temperature, so we are working in some system to dissipate faster the temperature of the heat sink controller.

74_telemetry

 

The motor also was a bit warm, but we could see a very healthy average between 40ºC and 50ºC, so no drama about it, for now.

75_telemetry

 

We can also see that we tried to get the motor at the stable revolution rate of 2500 rpm, which is the manufacturer  recommended rpm rate to get the maximum torque. Seeing that we did drive a maximum rpm efficiency it is also good news. So, Telemetry came ok at Cartagena´s speed track.

 

76_telemetry

 

So, a little video with a summary of the whole test can be enjoyed here. If you need a professional video recording work for your project, please contact:  Tecnoformavictor.aldaya@tecforma.com

77_telemetry

Bateries the big deal

Batteries, The big deal.

The batteries world is in constant change nowadays with the electric vehicles take off , the new and improved power storage, super capacitors, and the new kid on the block, graphene.

Lead batteries and AGM or gel are a thing of the past. We are now having the Li-ion present going to the new Li-air future.

The necessity of longer trips, fast charging times a better performance are a must in electric vehicles, and more and more, those demands are the big deal in EV.

Fresh air, still to come.

Till now, the obvious technology in the batteries department has been lithium-ion. But since some time ago, a new technology based in air is the real interest for manufacturers and EV developers. The new Li-air promises up to 10 times the energy density of their cousins li-ion. IBM´s project 500 has the aim of driving 500 miles in one single charge  in a family car using those new batteries. Although this has been achieved already by the Metron Institute (Slovenia) with LiFePo4 technology.

Li-air cells

The way it works is, a Li-air cell uses cheap carbon as a cathode (instead of cobalt), a molecule of a oxygen pivots through the cathode and gives the battery its name. But it has remained theoretical because of its big challenges. Among them: the other electrode in such batteries—the anode—is pure lithium metal, which provides a lot of energy but also ignites when exposed to water, carbon dioxide, or other contaminants.

Such is the challenge, that IBM and JCESR (Joint Center for Energy Storage Research) have decided to step back from the LI-air project, and IBM has turned his favour to a Lithium Sodium technology.

Li-Na cells

But with all these changes, a new development continues, and metal chemistries are also under development, in particular Aluminium-Air. An Israeli company (Phinergy), has claimed to solved corrosion, and recharging issues with a silver based catalyst. A prototype EV claimed to have 1600km range with Al-air batteries. However those cells cannot be electrically re-charged having to re-load them mechanically and topped up with water.

It smells sulphur.

Lithium Sulphur cells are another energy dense technology that could solve the needs for the EV in a near future. This new chemistry tends to solve issues like life cycle and stability. Based around a carbon based electrode, those cells are said they could go ahead Li-air technology.

Li-S cells

Many studies and research from Imperial College (London)  to German company BASF are putting their efforts into Li-S. They said this could be the 4th generation of batteries, expecting ranges of 400Kms in the next decade. Scientists at Lawrence Berkeley Labs (California) have introduced graphene oxide into Li-S cells that are said to deliver 1,500 charge cycles without deterioration.

Other researchers from ETH Zurich are working with Sodium-ion cells, stating that are much cheaper than Li-ion. But they have two major problems; they are three times heavier than lithium and tend to lose capacity when not in use.

Lithium Ion are here to stay.

Despite all the development in the power storage field, one thing is clear, most of EV at the moment go for Li-ion, and the fact that manufacturer are offering cheaper prices and even Tesla is building a new Lithium batteries plant, makes you think that in the long term this technology is here to stay.

Li-ion cells

Li-Ion developers, Bosch, GS Yuasa and Mitsubishi, claim that the could reduce the prices to half in the Li-ion filed, and double the capacity, that would make EV much more approachable to normal consumers.

There are also many new promising developments with carbon, but the gap between the lab and the factories is too big to stop producing Li-ion for EVs.

graphene cells

The magazine “Electric & Hybrid Vehicle Technology International” writes in their July 2014 issue about the carbon:

“The real deal?. A new type of dual-carbon battery technology that could potentially be a game changer for EVs has been launched by a Japanese R&D company. Called Ryden, the new battery is said to offer energy density that’s comparable to Li-ion products, but over a much longer functional lifetime with far improved safety and cradle-tocradle sustainability, says Power Japan Plus, which will begin production of the cells later this year at its manufacturing facility in Okinawa, Japan. The Ryden battery makes use of a completely unique chemistry, with both the anode and the cathode made of carbon. “Power Japan Plus is a materials engineer for a new class of carbon material that balances economics, performance and sustainability in a world of constrained resources,” says CEO Dou Kani. “The Ryden dual-carbon battery is the energy storage breakthrough needed to bring green technology such as electric vehicles to mass market.” Kani says that the Ryden battery balances a breadth of consumer demands previously unattainable by a single battery chemistry. In terms of performance, the new battery is not only energy dense and operates at above four volts, but also offers a charge time that’s 20 times faster than that of current Li-ion designs.

dual carbon cellsThe Ryden technology has been created so that it can slot directly into existing manufacturing processes, requiring no change to existing manufacturing lines. Furthermore, the battery enables consolidation of the supply chain, with carbon being the only active material used. As a result, manufacture of the Ryden battery is under no threat of supply disruption or price spikes from rare earth materials, rare metals or heavy metals. According to Power Japan Plus, its technology is the first high-performance battery that meets consumer cycle-life demands, being rated for more than 3,000 charge/discharge cycles. The breakthrough also eliminates the unstable active material used in other high-performance batteries, thus greatly reducing fire and explosion hazard. Furthermore, the new battery experiences minimal thermal change during operation, eliminating the threat of a thermal runaway. Finally, it can be 100% charged and discharged with no damage. Adding to the sense that the Ryden battery could be a key moment for EVs is that it is 100% recyclable, vastly improving the cradle-to-cradle sustainability of battery technology. As an add-on to this, Power Japan Plus is testing the battery with its organic carbon complex material, working toward the goal of producing the battery with all-organic carbon in the future. Made of naturally grown organic cotton, the carbon complex exhibits properties not seen in other carbon materials. By controlling the size of the carbon crystals during production, Power Japan Plus can engineer the carbon complex for a variety of applications.”

que_coches_son_mejores

Which vehicles are best to convert to electric.

There are hundreds of thousands of cars out there waiting to be converted. The best cars to be converted to electric are small old cars. The older is de car, the less electronic components it has and the easier will be the conversion.

As the batteries are still the big issue in a conversion project, regarding the weight and the price, the only way to minimize this aspect is by installing the less battery modules possible, and this can only be achieve nowadays by using a donor car that needs little electric power to drive, therefore it will need few batteries to run.

Another advantage in this philosophy is financial cost in the project. An old car will always cost you less than the equivalent two years old car. The Mini may be the exception in this case, but hey, it is a Mini.

Here are some examples or perfect old cars easily convertible, and examples of their prices in the second hand market.

o    Renault twingo

 30_renault_twingo30_renault_twingo_precio

o    Fiat Punto

31_Fiat_Punto

31_Fiat_Punto_price
o    Citroën AX

 32_Citroen_AX

32_Citroen_AX_price

o    Ford Ka

39_Ford_ka

39_Ford_ka_price
o    Mini

33_mini

33_mini_price
o    Nissan Micra

 34_nissan_micra

34_nissan_micra_price

o    Open Corsa

35_Open_Corsa

35_Open_Corsa_price
o    Peugeot 205

36_Peugeot_205

36_Peugeot_205_price
o    Seat Ibiza

37_Seat_Ibiza

37_Seat_Ibiza_price
o    Volkswagen Polo

38_Volkswagen_Polo.jpg

38_Volkswagen_Polo_price

adapter_plate

The adapter plate

One of the key aspects of a conversion is how to connect the existing gearbox to the new electric motor. This is normally done by an adapter plate that fits in both sides, the old gear box and the new motor.

This has to be designed and fabricated with high precision, as the geometry of the whole transmission is under jeopardy if there are errors. There are already manufacturers with already made adapter plates designed and proven to be working perfect. The other option, will cost more time, but it may be cheaper, is to design yourself. That was my case, as so far none did a conversion for a Renault Twingo yet.

So, I decided to design it myself, and give the machinist an sketch of the actual plate.

The plate needs to be made out of a material that needs to be strong, light and cheap. The perfect balance between those 3 variables is aluminium, that is why 99% of the adapter plates are done in such material.

The thickness for the adapter plate depends on the torque and power for the electric motor. For a 14 Kw motor I was recommended a 17mm plate, but my local supplier only had 10mm or 20mm (a paradox working next to Alcoa), so I went for 20mm, that would not add much more weight and it would improve how strong the joint would be.

I started to disassemble the gearbox, and making a template based on a front picture.

20_adapter_plate

After having a proper front picture, I edited with a photo manipulation software (The Gimp) to have just the shape of it.

21_adapter_plate

Once I have a shape of it, I started taking measurements from the centre to the screw holes, between them, and so on, to have a real measurements of it. As in this procedure, error needs to be near zero, I recommend to use a good calibre.

22_adapter_plate

Once all measure have been done (double check and triple check), I draw that template into a 2D CAD software (LibreCAD), and draw many references within the same distances, all the centre points of the pin holes and the actual centre.

23_adapter_plate

Then, when I finished drawing all the circles and, I measured within the 2D CAD software all lines and compare with the real measurements. Surprise, surprise..I had some minor errors.

24_adapter_plate
After double checking the real measurements and the positions in the 2D draw, I printed out in paper 100% sized, and I could see all the wholes were in the exact position, so I gave the design pre- green light.

I took the final design to the machinist as ask him to fabricate a 1mm cheap copy just to try all the screws. They have a super-sized kind of plotter/cutter that can cut  2 cms aluminium as it was butter.

25_adapter_plate

I tried the 1mm template and I fitted like a glove. Just one small 8mm was a bit miss-aligned (about 0.5 mm), the rest all fitted perfect. So I gave the 100% green light and I asked the machinist to cut it in a 20 mm aluminium plate. Even though it took some time as the were out of stock, finally I had it and connect both, gearbox and motor like a charm.

26_adapter_plate

La bomba de vacío y los frenos

The vacuum pump and the brakes.

Mostly all cars use a braking system with power brakes and this system needs to be left as it is in a electric converted vehicle. If the weight is bigger after the conversion because of the batteries, then the brake system should have at least the same braking capacity or even more.

Working brakes are very important with an EV since one way of emergency braking (engine compression, the one experienced when you downshift) is gone with an EV, you get no such thing from an electric motor, unless you have a regenerative braking system.

The difference between the braking system in a electric converted car and a petrol car is not the actual brakes, but the system on how the vacuum is generated to the brake booster. In a converted car this has to be done with a vacuum pump.

The vacuum pump is the same device as an air compressor, but the air valves are reversed so instead or throwing air it sucks it. In a standard car. De level of vacuum pressure needed for the brake booster is around 16” Hg to 18”hg (inches of mercury), that is about 54000 Pa (Pascals) or N/m2 (Newton/ m2), so this level of vacuum pressure is the one the vacuum pump should maintain.

There are electric vacuum pumps in some diesel cars as Volvo or vans whose diesel engine do not vacuum enough pressure for the brake booster. Those electric pumps work with 12V and they consume around 6 or 7 amps. You shouldn’t use the vacuum pumps designed for the door locking systems, as those do not provide enough vacuum for the braking system.

11_reservoir_enSometimes a long braking push in the pedal ma use all vacuum pressure in the braking circuit, so the pump would need a few seconds to make the needed pressure level again. To avoid this situation a vacuum container (what a paradox, a container  that holds emptiness lol) can be installed between the pump and the brake booster to keep some more time this level of pressure. Note that the bigger the container, the longer the braking capacity, that means, you can brake more times till the pump started again to generate the level of vacuum again.

 

12_vacuum_switchNow, for the container to work, a vacuum switch needs to be installed to keep the vacuum pressure level above the given value, in our case around 15” Hg. Those sensors have a valve associated that opens or closes the brake circuit for the pump to maintain the vacuum.

13_vacuum_pumpThis pump and components are very popular in conversion in the USA (SSBC pump), and the Hella vacuum pumps. I did order one for about 200€ plus 60€ of delivery. The surprise was when I received the package after paying some additional 90€ for customs tax, and saw the pump was Made in Spain.