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

testing

Testing, testing, .. out road.

60_testingThe conversion of a petrol or diesel vehicle is the most sustainable and economical way of driving a perfect electric car. The main idea behind this, is to re-use all the vehicle´s components that have no impact in the internal combustion engine, and to substitute it with a full electric motor. Engine, radiator, petrol tank, exhaust tubes, alternator, etc will be removed, reducing the car´s weight. By having a chassis with all the necessary parts for driving, as interior, brakes, tyres, shock absorbers, etc, all effort is reduced to install and design an electric system with a motor and batteries.

61_testingIt is very important to choose a good design for the electric system, electric motor, battery pack and motor controller should have the same specifications in power and speed to the ones the car when it was originally designed. Too much power could damage the traction components or may not respond as well to breaking, and too little could cause the gears no to acquire the adequate speed.

Elektrun is a project that was born two years ago to probe the concept of transforming a city car to electric, ideal for short trips within the city.  We have chosen a Renault Twingo to build a prototype,  it is a vehicle with little weight and a reduced size, and after two years of design, test and experiments we have made it work.

62_testingThe main issue for this kind of transformation is the range the batteries will achieve. Now days there are cars that can drive 700kms in one single charge, in order to achieve that, it needs at least between 70Kw and 80Kw. Our prototype comes with a 7,4Kw.

 

 

63_testingThis prototype has an 15KW AC induction motor with a maximum torque of 80Nm, a battery pack of 72V and 100Ah, it has an 80V and 350Amp controller. This can speed the car to 90km/h in 5th gear.

The first tests shown the total weight didn’t affect at all in corners, the shock absorbers responded well as expected, and by removing the engine noise the driving was much more comfortable.

64_testingAn additional vacuum pump was installed to help the braking system. The braking was also performing very well as, it responded to hard braking and kept the car stopped in steep ramps.

 

65_testingA small display was installed in the interior to monitor, at any time, battery usage, current, motor temperature, state of charge, etc.

 

66_testingLights and interior accessories as electric windows, radio, air flow, window cleaner, etc were kept in the car.

This car takes 8 hours to fully charge the battery pack, although there are chargers that could reduce this time from 6 to 4 hours.

 

 

You can see a video about the first tests here:

Coupling_make_it_right

Coupling, make it right the third time.

This is one of the most, if not the most important and tricky mechanical manipulations you have to do when converting a vehicle into electric. Connecting the electric motor to the existing transmission is a big debate, as you can just connect both axis together with some sort a coupler or do it using a clutch.

 

50_coupling

Usually, both axis have different diameter, splines or are in C-fase (as they say in America), so you will need two different couplers, one for each shaft (motor and gear-box).

 

51_coupling

Now, those two couplers can be connected directly or with the original clutch (there is a big debate around this subject). In our case, we will follow the clutch design. The main reason is efficiency, as having the ability of changing gears, will give you more efficiency in all cases of the driving, such short, medium and long gears. Although this approach is a bit more complicated in implementing, as the flywheel needs to be adapted to the motor shaft, the driving of the car will be as similar as with the combustion engine.

The first part of this transformation is to have the adapter plate mounted in the motor so the flywheel attached keeps in the same position in relation to the gearbox.

52b_coupling

 

52_coupling

 

Then, we need to attach the flywheel to the motor with an adapter. You can use a steel coupler from Lovejoy or Rotex, machined exactly for the electric motor shaft. It is also very important to measure all the components including the clutch that will go inside the gearbox, so they all fit perfectly.

Once the flywheel machined and attached to the motor, it is time to screw the clutch to the flywheel. From that point on, the operation it is just a standard clutch installation.

 

53_coupling

 

54_coupling
Now, in the 1st attempt to install the clutch, it all went smooth a part from a little periodic noise from inside the gearbox. So, we had to dismantle the clutch again to see what happened. Our surprise was that the flywheel was touching very lightly inside the gearbox. That was the 1st problem easily solved by reducing the flywheel or by carving a bit the specific gearbox area where the flywheel was touching.

 

55_coupling

Another and second problem was the flywheel, even that was correctly inserted into the splined motor shaft; it wasn’t properly screwed, so that centrifuge force could cause the flywheel to move forwards touching the gearbox shaft. So apart from soldering a coupler in the centre of the flywheel, we asked for a whole too to be able to screw and stop the flywheel.
Now this modification caused to move the block flywheel-clutch forwards 6 mm, so we had to cut the gearbox shaft 7 mm.

 

58_coupling

Also we discovered that the flywheel wasn’t properly turning flat respect the axis, so we sent it to a machinist to rectify that tiny difference and also to reduce the diameter of the flywheel, with that we solve 2 issues. Removing mass of it, so it would had less inertia and also avoid touching the gearbox inside.

 

56_coupling

The final result was this 3rd attempt, where the flywheel was turning flat against the clutch disk, was fitted to the motor shaft, the diameter was much smaller, so it wouldn’t touch inside the gearbox and had less mass, so less inertia and better performance. It needed to be balanced (to have the same mass radially so it wouldn’t vibrate at high rpm) , but as the flywheel was already balanced when manufactured, we trust it would still be balanced after the rectification. The gearbox shaft was also cut 7 mm to receive the motor block. And once all modified it all fitted as a glove.

 

57_coupling

 

 

The final result fitted quite well. Tested at high rpm and ahd no vibrations at all.

 

59_coupling

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

que-coches-se-pueden-convertir-a-electricos

How to convert your car to electric?

quien mato el coche electricoWhen I had the idea of converting my own car to electric, I had two goals in mind. To be able to drive a novel car, that wouldn´t make any noise and the cost for the fuel be little or nothing.  The other goal was to stop once for all contributing to dirt our environment and be able to tell the rest of the people “Yes, we can”, now days you also can have an electric vehicle exactly as it was at the beginning of the 20th century in New York (See the documentary “Who killed the electric car?” ).

Little by little, this idea was more and more real, asking other people, researching on the net and other countries where this was already a reality, I started the project of building an electric car.

Choosing a donor car.

The first step, once everything is clear, was to choose a cheap car and appropriate for the project The best cars are old vehicles o classic cars. The reason for this is because they are not complex in their design and electronics are not playing an important role in the car functions.  There is no need to be afraid at this point, nothing anyone can overcome reading a bit about the chosen car.

01_renault_twingo_elelectricAnother important requirement is the car to be light in weight, less than 1000 Kg is more than adequate, and 800Kg is ideal.  The reason behind this is the resistance the car has because of the friction in the roads, the more resistance, the more electric energy it will need to drive.

There is also other elements that a high speed affects the performance as the Aerodynamic coefficient, but this will leave it for the time being.

The old Renault Twingo is a car that weights very little, it doesn’t depends much on electronics (it doesn’t come with power steering or automatic gearbox). So I decided to get a cheap second hand Twingo and I spent 500€.

 

 

And now, the motor.

The motor is something you need to spend some time researching on it to take the correct decision. By choosing a small car, the motor doesn’t have to be very powerful, so a 7 to 15 Kw motor can be just perfect. There are two kinds of motors:  DC motors (direct current) and AC motors (alternating current). The first ones are cheaper, more accessible in second hand markets or scrap yards, but they are less efficient. The second ones are more expensive; they weigh less and are more efficient. Then according to other technical aspects are synchronous motor and asynchronous, also other with permanent magnets, which supposed to be top of the list. As examples, there are 7 Kw motors from China that cost less that 1000€, while in Europe or USA you can have 15 to 25Kw motor between 2000 and 4000€. I decided to go for an Slovenian 14 Kw motor, branded Letrika. I knew this provider at the electric car fair EVS27 in 2013.

Motor electrico

Motor electrico

Lets go to the motor controller.

This is one of the main components, it is also one of the most expensive and it goes paired with the motor for two reasons: One, it is the one in charge to convert the batteries electric power to the correct voltage necessary for the motor, and the second, to regulate the speed of the motor, so the controller needs to be designed for it. As with the motor, there are DC controllers and AC controllers. The good news is that most of the motor manufacturer they also do the controllers, and if the don’t, normally the motor can be configured for generic configurable controllers.

Controllers are also classified according to the maximum current they can feed, the more current and voltage, the more powerful l the motor will be. There are several brands as Brusa, Curtis, Sagem, ..

 

03_curtis_controllerI got a Curtis controller, medium range for AC motor, the Curtis controller 1236. Most of the controllers are programmable, so you can adapt it to your own motor. You will have to study a bit about variety and features of the controller best suits you.

 

 

And we get to the batteries, the queens.

Batteries are the most important element in a electric vehicle, as they will define how much power and how much range the electric car will have. I hope one day this element will be the less important, but for the time being, this technology is more complex than we may think. The appropriate batteries bank is conditioned by the maximum distance the car will drive in one single char and also the charger and the BMS (Battery Management  System).  Not all kind of batteries can be charged or discharged in the same way, if you don’t follow the manufacturer requirements and limits, batteries can be affected and their life span be reduced.

There are several technologies in the market right now, but in practical terms we can talk about 3 or 4 types. Lets start by the cheap ones.

04_lead_batteryLead Batteries. They are the cheapest ones, but the least suitable  ones because its design, as they are not design to provide a constant current all the time, but to provide a very strong one in one go, and this is not what a controller for a electric motor needs. The good news for a budget car, is that even dead, you can re-acconditionate them or de-sulphate them. This is a delicate process as the content inside the batteries is sulphuric acid, so if you are a bit un-sure of what you are doing, better not to try. I have done it being very careful, and following all the security precautions and using protecting gloves, glasses and mask (in an open environment), at the end you need to neutralize the acid with sodium bicarbonate before wasting it to the sink. You can also buy them to avoid all this hassle. They are very heavy, but can be charged with any standard charger.

 

05_72V_agm_batteriesAGM or gel batteries.  Those are deep cycle batteries, they are lead batteries with more efficient electrolyte gel. They are a bit more expensive but they are designed for electric cars. They are very heavy too, and there are manufacturer that assure up to 1000 cycles before losing charge capacity. The charger has to be specially design for gel batteries to follow a correct charge parameters for gel or AGM. They are not very expensive, I bought 6 of them, 12V at 100Ah for about 900€.

 

06_lithium_battery Lithium batteries. This already more expensive, but they weight about half and they have double capacity. Those are the standard option for electric cars. They use to come in 3.7 cells, so you have to get many of them to achieve the desire voltage. Another VERY IMPORTANT issue is that lithium batteries need to be managed (charged and discharged) by a BMS (Battery Management System). The reason is that these batteries cannot be charged or discharged outside the recommended limits by the manufacturer. As an example, 18650 lithium cells can only be charged at a maximum of 4.1V and discharged at a minimum of 2.5V.
–    Pyrophosphate batteries (LiFePO4). They are the most expensive of all but also they have the more energy capacity.

comparacion_densidad_energia

Enough batteries for now..

 

07_dc_dc_converter_72vAnother very important component is a current converter for high voltage to 12V.
When we remove the IC engine (Internal combustion), one of the components that also disappears is the alternator, the one in charge of keep the battery always at the proper voltage (in this case we could call it the auxiliary battery) for lights, electric windows, radio, etc. So, as the alternator is missing, we need a system have it always charged, for example, a DC converter  72V to 12V.

 

 

 

Well, that´s it, isn’t ?. No, still something important, the brakes.

For the brakes, you need to supply the vacuum that the IC engine use to make for the brake booster. So we need to install a vacuum pump in order to replace the missing one in the IC engine.

08_iruna_vacuum_pump

Then you need other small components, but equally important as a pedal accelerator, a contactor, some relays, fuses, etc.

09_pot_fuse_relay_contactor

Those small components are as relevant as the big ones, because even with the motor and controller, with no cables, there is no use. Also, you need to see the high voltage requirements that the motor manufacturer recommends. Also the signal cables are also important in following no just the diameter but the isolation.

Now the adventure starts… just install everything in the car.

10_full_assembly

 

If you are interested in converting your car to electric and need more information, support, documentation or just someone who share your hobby, you can contact with us by clicking here.