Archive for February, 2011

LiPo – Batteries Terms Explained

Electronics, technology | Posted by admin February 28th, 2011

I came across a great article on LiPo batteries on the RC Helicopter web site.  These guys have been using LiPo batteries with a lot of sucess.   Click here to read the full article.  Below are the highlights translated into values which are more to our using.

Below are some of the values you need to look at when designing a pack.

148 volt LiPo pack = 40 cells x 3.7 volts

Ah – Capacity indicates how much power the battery pack can hold and is indicated in amp hours (Ah).

C –How fast a battery can be charged or discharged. A battery with a discharge rating of 2C would mean you could discharge it at a rate 2 times more than the capacity of the pack, a 3C pack = 3 times more, a 20C pack = 20 times more, and so on.

Let’s use our 100 Ah battery as an example; if it was rated at 2C that would mean you could pull a maximum sustained load up to 200 amps or 200 amps off that battery (2 x 100 amps = 200 amps). The higher the C value the higher the cost usually.  What this means to an EV though is how much power you can effectively use.  If the C rating is low, you are going to have to use more cells to increase the voltage so that you use less amperage.  My car can easily pull up to 1000 amps at 168 volts if I am racing.  Taking off from a stop at normal driving speeds can easily require 200 amps.  Many cells will allow you to pull at a higher C rating for a short period of time without damaging the battery.  If the cell is drained too fast, this usually results in heat which can damage the cell.

Internal Resistance – Most decent higher discharge rated LiPo cells will have roughly 2 to 6 milliohms (0.002 to 0.006 ohms) of internal resistance when brand new. To calculate the total internal resistance of a series wired pack, you would then add these numbers together so a 148 cell pack with each cell having 4 milliohms of resistance will show a total internal resistance of about 592milliohms (0.592 ohms).

As packs age, the internal resistance goes up and the warmer they run. Lower discharge rated packs will generally have higher internal resistance readings.

Palm Beach Supercar Supershow

car shows | Posted by admin February 27th, 2011

Feb . 26th Palm Beach Florida – West Palm Beach Super Car Super Show

My son Andy and I and the  EV GT-40 attended the Palm Beach Super Car Super Show along with Andrew Roddy and his electric E-Box.  We were joined at the show by Paul Little and his electric conversions.  In all we had a total of 8 electric cars at the show and took up a pretty nice area right in the center. We made a great impression as we sat in among the ultra expensive and iconic super cars. (Yes, if you are paying attention, there were three Andys.)

Flagler Drive

Cars Lined up on Flagler Drive

Builder Andrew McClary with the EV GT-40 Electric Car

Andy McClary with the EV GT-40. He gets his license next year and already has his eye on the car

The EV GT-40 was a big hit and drew a lot of crowds.  The major parts of the car was labeled up along with illustrations to show how an electric car works.  Andrew Roddy had his electric E-Box with and AC Propulsion Systems motor and controller right next to the EV GT-40.   The cars drew larger crowds than the Ferrari and Lamborghini which was sitting next to it.  This I think caused some disappointment to the owners of those cars which were a lot more expensive than my electric Gt-40 replica.  By the end of the day both myself and Andrew Roddy were horse from talking all day to people with questions.  They all had questions and a real interest in the cars.

EBox and EV GT-40

Andrew Roddy and his E-Box along side the EV GT-40

Checking out the car

Motor controller and Charger

Everyone had questions

EV GT-40 Electric Car

People spent quite a bit of time inspecting the car

EV GT-40 Electric Car

Car enthusiast looking it over

The E-Box all electric car by AC Propulsion - Andrew Roddy owner

An Electric Lamborgini Replica

Notice the EV Logo

12" Warp 9 in the Lamborgini Replica

2005 Ford GT-40

Ferrari

Dual 12" electric motor Porshe - Paul Little

280HP x 2 - All Electric


Cars lined up along Flagler Dr.

Exotics and Race Cars

Dancer gracing the grandstands


Drag Racing Rolls Royce

One FAST Rolls Royce

Leather Covered Nitros Bottles

A very good showing of electric cars

Even speed boats

Very Cool Looking Chair

Porsche

A Local Dance group takes the stage

Drag Racer

Lotus

Lotus Interior

Lamborgini

GT-40 Replica

Performance Power Racings GT-40

Parts of an EV

Restoring and Building | Posted by admin February 26th, 2011

Pricing out a Lithium Ion Pack

batteries | Posted by admin February 7th, 2011

Calculations for a new battery pack using Thundersky Lithium Ion (lifepo4) Cells

40 ah cells

3.5lbs each
$50 each

112 cells in pack
392 lbs
358.4 volts
14.32 kwh
43 miles expected range*
$5,600 total

60ah cells

5.51 lbs each
$75 each

72 cells in pack
396.72lbs
13.84kwh
41 miles expected range*
$5,400

90ah cells

7.05lbs
$112.50 each

72 cells in pack
230 volts
507.6 lbs
20.73kwh
62.81 miles expected range*
$8,100

100ah cells

7.72lbs each
$125 each

56 cells in pack
432 lbs
179.2 volts
17.92 kwh
54 miles expected range*
$7,000 total

200ah cells

16lbs each
$250 each

56 cells in pack
896lbs
35.84kwh
108 mile expected range*
$14,000

* .33kwh per mile with current configuration, with lighter pack this should be even less

The other added expense that has to be considered is a high quality BMS (Battery Management System).  Its not an option. Without this it is easy to destroy a good set of very expensive batteries.

Thundersky Lithium Cells 3.2 Volts Each - 4 of the ones in my hand are a little more than a single AGM currnetly in use.

A Trip to Greenshed Conversions

Restoring and Building | Posted by admin February 5th, 2011
I

Loaded ready to transport to Fort Pierce

I was having some problems with my battery pack and needed some expert help.  To get that help I traveled to Green Shed Conversions to get the help from Steve Clunn.  Green Shed Conversions in Fort Pierce, Florida is the home of Steve and Audrey Clunn.  Steve has been doing conversions and putting together electric cars for more than 15 years now.  He has a wealth of experience and knowledge on electric cars.

Unloaded and ready for inspection

Steve Clunn looks over the EV GT-40

Steve's Volt Meter with multiple inputs

Batteries wired to Steve's meter

Once we had the car all wired up, Steve and I took a ride in the car.  While I drove, Steve carefully monitored the suspected batteries.  Sure enough, upon acceleration two of the batteries were dropping to less than 7 volts and creating a lot of resistance in the pack.  These few batteries were pulling down the whole pack.   The issue seems to be that the batteries were not being charged at a high enough amperage.  Over time they have developed higher resistance which prevents them from giving up their charge.  To fix this, these batteries were charged at a very high amperage very quickly.  After driving the car a second time, they were showing at least a 10 percent increase.   The process is going to need to be repeated a few times before they come back up to 100% efficience.

Steve had a number of battery packs at his shop.  We tooks some time to look at the Thunder Sky Lithium Ion batteries and compared them in size and capacity to the AGM batteries I was currenlty using.  The battery I have in my hand has about the same energy capacity as the large AGM battery.  The Lithium battery weighs about 8 lbs. verses the 80lbs of the AGM.  Though expensive, the price on lithium batteries is coming down.  A pack with almost half the weight of my current pack could easily deliver four to five times the capacity.  My current pack has about 8kwh of capacity and weighs about 1,000 lbs. .  A 24kwh pack could be done in lithium ion batteries with a wieght about 400lbs.

60 ah Lithium Ion Battery. 4 of these has more usable energy than Hawker Odyssey AGM. The 4 cells would weigh about 24lbs vs. 80 lbs for the AGM battery.

100 ah Lithium Ion vs AGM with about 50ah usable

One of the dangers of lithium batteries is that they are not very forgiving to abuse.  Without a proper battery management system a pack could be killed pretty quickly by allowing them to drain to 0 volts or over charging.   The pack below was removed from a car that was used by an owner who let them all drain to 0 volts.  Steve is going through them trying to revive some of the batteries, but 80 percent will end up unusable.

a killed battery pack

Steve and Audrey’s property is filled with all kinds of electric experiments and projects like the motorcycle below.

Electric Motorcycle

Zap Electric Car

Zap Electric battery pack and controler

Electric Bike

An electric Lamborgini

Electric RAV 4 - This is Audrey's daily driver

I want to thank Steve.  He is one of electric vehicles heroes and was gracious enough to spend the day with me to find the problem in my pack.

Nissan Leaf Test Drive

technology | Posted by admin February 1st, 2011

Got a chance to visit the Nissan Leaf test drive event in Fort Lauderdale. Nissan had a really nice display which was like a small village they setup out in the Sawgrass Mills parking lot.

The main tent was for registration and also had a number of video displays that helped educate people about electric cars.

After they had a group ready, we were escorted into the next tent which housed a display with the Leaf’s battery pack. The pack is a very nicely organized system of 24 prismatic flat lithium ion modules. Each module houses 4 cells. The total pack is 24kwh of energy.  I don’t know how hard it is to actually get into the pack when it’s on the car, but it looks like it would be pretty easy to change out a bad module if you can get into the pack.

The next tent we were escorted to was a display on the range and iPhone system monitoring and control. For those that don’t have an iPhone there is also a web site. From your phone you can read battery charge and a lot of other car functions. One nice feature is that you can turn on the AC or heat remotely. So if you car is plugged in charging in the garage, you can turn on the AC and the car will cool itself off the garage power and be cool when you unplug it to drive.

From here we were lead out to the cars to drive. We first went through a little course setup in the parking lot with cones and then out on the street. The car performed real well. There is an econo mode which we also tried. In this mode acceleration is really sluggish and the regen is a lot heavier. You can really see how driving in this mode would lead to better economy, but for the average driver, it’s no fun.

The back seat was easily large enough to fit 3 adults, so it really is a 5 passenger car. There was even a nice sized trunk.

Charging the car can be done in two ways. There is the new standard j-1772 connector which can be plugged into a public charging station. The car comes with a cable with one of these connectors and a 120 volt standard AC plug. They recommend having a 240 volt charging station put in your house though. This is around $2k. These methods take from 6-8 hours to charge fully. The other method of charging is through a special high speed charging port which can handle a lot higher voltage and amperage. This would be used by fleet vehicles such as Taxis. This high speed port would allow the car to be charged in as little as 30 minutes.

Overall I was very impressed. Nissan seems genuinely committed to making this technology work. As a side note, all of the dealerships will have charging stations. I wonder if they will be kind enough to share a few electrons with other EVs who come to visit?