Tuesday, October 18, 2011

Vehicle Speed Calculator Mark 2–Now with possible acceleration calculation

Here is a nice little EV speed calculator…




Tyre Types should be entered using their standard notation (For example: “P175/35 R14”), or you can enter the numbers manually. Gear and Differential ratios are entered in standard x:y ratio format.

All estimates here are absolute perfect-world best-case scenarios. You WILL NOT get these performance figures, this is merely a (very optimistic and simplistic) estimate. 0-100KMH is 0-62MPH, give or take a few thousands.

If you have any problems with it, drop me a line in the comments, and let me know what browser you’re using.

Sunday, September 19, 2010

Converting a vehicle... What to start with?

I want to convert a vehicle to an EV, but the question is, what vehicle?

In theory, something slim and sporty would be best, for aerodynamics and efficiency. But sports cars have a few drawbacks:

  • Not much in the way of room to store batteries
  • Not a lot of weight capacity for carrying batteries
  • Expensive to buy.

I'd love to convert a Citroen, with their hydropneumatic suspension system making for a silky smooth ride, along with being able to carry the load. However:

  • Rarer than solid gold rocking-horse excrement here in Canada
  • Mechanically complex
  • incredibly hard to get parts for.
  • In pre-XM models, the hydraulic pump has to be powered too.

So, what will I do? The answer may surprise you.

A pickup.

Yes, that's right, a pickup truck. A small one, like a Chevy S10 or a Ford Ranger (Not a Dodge Ram or an F1/2/350).

"Why on earth would you do that?", I hear you ask.

There's a few good reasons.

  • They're cheap to buy
  • They have a high carrying capacity
  • You can use the masses of dead space under the pickup bed to store your cells
  • They're cheap to buy
  • They're usually rear-wheel drive, so making a Direct Drive pickup would be fairly easy
  • With Direct Drive onto the rear differential, the entire engine compartment would be virtually empty, more space for cells
  • They're cheap to buy
  • Replacement, and custom, parts are very easy to get hold of (and relatively cheap)

Yes, I know, I'm a cheapskate. But when you're broke 90% of the time, it's to be expected, really.

So, what am I going to put into this thing?

Hopefully the local ReStore has an ACIM I can snag for dirt cheap and use, and when PaulMHolmes gets his finger out and gets his AC controller plans working and available I'll grab those and make myself a controller for it. Then it'll probably be a matter of getting some 12v cells until I've stashed enough to splash out on a LiFePO4 pack (or something better – Kokhams maybe, or A123s?)

Saturday, April 17, 2010

DC Vs. AC – The Next Generation

It seems there are some new developments in the home conversion EV field, and I thought it would be a good idea to chronicle some of them.

DC

Paul and Sabrina’s EV Open-Source controller, the “ReVolt” (Warning: Massive thread!) has come on leaps and bounds, and is now capable of massive voltages and (perhaps more importantly) amperages, and now has a nicely modularised design so you can build and use your own custom power section to the standard controller board. It runs with both MOSFETs and IGBTs, and can be extended quite a bit. It also features real-time data readout and parameter adjustment.

AC

Not content with building a fantastic DC controller in the ReVolt, Paul and Sabrina are at it again, this time coming up with a 3-phase AC controller. It’s in the early stages at the moment, but the thread there also seems to be becoming a stopping off point for everyone making their own AC controller, which is good news! With this new controller, cheap AC motors already designed for EV use (Like the surplus Ford/Siemens motors out there, or a Toyota Highlander Hybrid axle).

Conversions of note

Gavin Shoebridge (AKA KiwiEV) may just be on the brink of starting KiwiEV 2, and I for one am rooting for him all the way. And if you haven’t already, you too can help! Not only is Gav’s e-book informative, it is practical and entertaining, with videos accompanying his experienced advice. He did a great job with KiwiEV 1, and you can learn from his mistakes. And when he does start KiwiEV 2, I will be following him every step of the way.

My own EV conversion

Erm… Yeah. If/When the Saskatchewan Government decides to finally take our old Chevy Corsica, and give us the $350 that’s promised under the “Retire your ride” scheme, I’ll have $350 (maybe) towards starting an EV.

“Why not use the Corsica?” I hear you ask (Well, I would if you did… you know what I mean…). Well, here’s an abridged list of things that need to be fixed on the Corsica before it’s really road-worthy:

  • New springs/shocks/struts all round
  • New brakes discs and pads, front and rear
  • New transmission (Automatic, if converting to EV, will need to be switched to Manual)
  • New power steering pump/lines
  • New engine (Not applicable if converting to EV)
  • New exhaust system (Also not applicable for EV conversion)
  • New tyres (and possibly new rims)
  • Patched/repaired bodywork
  • Lots of rust removal
  • New drivers seat mounts
  • Underbelly patching

With this LONG laundry-list of faults, it would be considerably cheaper just to ditch the car and start anew with something else. So what is my ideal setup?

  • Lithium Ion (LiFePO4) cells for main power storage
  • Super/Ultracapacitor pack for load smoothing, improved regen and acceleration
  • AC direct-drive system
  • 400+V system voltage, handling peak power loads of 3,000A (Mainly from Ultracap pack)
  • 260Ah capacity (minimum)
  • Battery heating/cooling system (‘cause it gets MIGHTY COLD here in the Great White North)
  • Optional demountable genset (For long distance travel, preferably diesel)
  • 240V AC charging, at as high an amperage as I can get here, with the option of 110V opportunity charging (Block heater plugins, for example, would be a great way to sip some capacity as you shop)

I haven’t mentioned chassis, mainly because I am torn in that regard. On the one hand, something like an S10 would be easy to convert, and while it’s not the most aerodynamic of vehicles, it would certainly get the job done. On the other hand, something like a Mazda 3, or a Pontiac Wave, would be good for carrying capacity (Large dog + crate = need for fairly large “cargo” capacity) combined with light weight for better range. Though for sheer bragging rights, finding a Lotus Elise glider, or an RX8 to convert would just be too sweet, but unfortunately also too limiting (2 seats, and virtually no cargo area makes it difficult to justify), even as a daily driver. Where would you put the groceries, after all?

Of course, being in a rented house, in the hood, with a barely-1 car garage, and with a distinct lack of tools or experience, makes this all very pie-in-the-sky thinking at the moment. But you never know, if we get that lottery win, who knows what might happen?

Monday, May 25, 2009

Getting the power to the road

Having thoroughly discussed wheelmotors on here, I think it’s time to change subject completely and talk about wheelmotors.

Yes, you did read that right, and no I haven’t lost it.

Several home-built EVs, especially ones done for-cheap (For instance, Forkenswift), they’re done with DC motors taken from old forklift trucks. Usually the “drive” motor is used, and all is well. But flicking through the Princess Auto catalog a little while ago (What else do you do at 2:30am when you can’t sleep?), I came across a few interesting things, not least were some small, but reasonably spec’d Hydraulic motors. (I can’t link to them, their website is stupid – If products have the same name, you can only see one of them!) A little more digging, and I find a set of things called “Inline Axial-Piston” motors, which have great characteristics (Torque up to 83 ft-lbs (each!), top speeds of 3-4000 RPM). So my thinking is that, perhaps, one could take the “Pump” motor from a forklift, hook up some high-pressure hoses, and have the basis for a very space-efficient vehicle. With no need for drive shafts at all, it gives all kinds of space for batteries, and if you were custom-designing your vehicle, you could have a flat floor with the batteries inside (Using thin cells like LiFePO4 laid on their sides, for example), a small “Engine” compartment with the motor, controller and hydraulic splitter, and just some high-pressure hoses going from there to the wheels. Driving the motors in series/parallel would give reliable performance with behaviour like a limited-slip differential, and the difference in displacement between the pump and motors will act as the gearbox. And the units themselves are reasonably small and light, which completely throws away the whole “messes up the handling” problem.

But I’m no hydraulics expert (Heck, I wouldn’t know where to begin, to be honest), so ideally what I’d really like is for some hydraulics guru to take a look at this and tell me if I’m nuts for considering it. I know hydraulic drive is used in some low-speed vehicles (dump trucks, forklifts, that kind of thing). So why not high(er)-speed situations like this? We don’t need all 3000 RPM (heck, with 15” wheels and average tyres, you reach 120KPH (75MPH) at 1185RPM! 1500RPM would suit perfectly (give a little leeway for the racers out there :) )), but we do need the torque and power. Ideally, this system should also drive backwards. Not only for reversing the vehicle, but to be able to drive the motor ‘round, giving the option of regenerative braking too.

So, someone who has an idea what to do with these pipes and things, drop me a line and let me know if this’ll work or not.

Wednesday, May 20, 2009

Wheelmotors (yet again) and the Eliica

Yes, I’m going to talk about wheelmotors again. Mainly because I recently saw a video on the Japanese Eliica project. This uses 8 (yes, 8) custom designed and custom manufactured wheelmotors. Which, again, are not available for purchase anywhere. And this was debuted way back in 2004. Over 5 years ago. According to Wikipedia (Not the most reliable source, but it’ll do for this case), there are only 2 in existence, and while they’re fast (370 kph, or 230mph for you old-world proponents), and have a decent range (200km/120miles for the “Speed” version, 320km/200miles for the “Street” version), no-one is anywhere near touching them, or the technology they’re made from.

Just what is happening with the motor industry? It’s obvious the technology exists out there – all my previous posts here show it’s around. All we need is someone to take these disparate parts, put them together into one working shell, and float it on the market. Tesla is leading the way, but we need more. And while Obama’s plan in the US to incentivise EV production may also help the home converter, there’s still a lot of hurdles needed to jump before any kind of EVs really make it into the mainstream. And when the media stops with the whole “Look at this insane person – he took a working car and turned it into a high-speed golf cart” angle, and move closer to “covers all local commuting, costs $0.10 to ‘fill’, built by a novice for less than $5,000, will last for 10 years”, they might start getting the public more interested, and less amused.

On the subject of frozen metals

I have been reliably informed that LiFePO4 batteries will actually warm themselves in use (The internal resistance generates a little heat). This means, with a well-insulated battery box (and plenty of fresh-air cooling for during the summer), using and charging the batteries will keep them nicely within their operating temperature.

Of course, another idea would be to funnel “exhaust” air from the cabin through the battery box on it’s way out of the vehicle, too. As LiFePO4 are sealed, there’s no need to worry about gassing (As you need to with PbA). And at –40, you can bet the cabin heater will be running!

So then all you have to worry about is when the vehicle is sitting idle and not charging, say at a place of work with no available outlets. Then you really do have a problem, and it might be an idea to fit some kind of “command start” system for remote warming, or a temperature monitoring device, to ensure the cells don’t get too cold. And I believe it would be quite simple to repurpose a system for ICE cars (yes, they have them – keep your car nice and warm while you pop into the shops, it just idles the gas engine while it waits. Talk about inefficient!) to do a similar task for a battery box.

So, it seems, for Canadian conditions, LiFePO4 cells are the best bet. For now, anyway.

Monday, May 18, 2009

EV Speeds Calculator

Here is a nice little EV speed calculator…



Tyre Types should be entered using their standard notation (For example: “P175/35 R14”), or you can enter the numbers manually. Gear and Differential ratios are entered in standard x:y ratio format.

If you have any problems with it, drop me a line in the comments, and let me know what browser you’re using.