Thursday, December 17, 2009

Seeing the Nissan Leaf in Person

Things have been nuts this week, but I did get a chance to see the Nissan Leaf come to Portland today. It arrived at OMSI this morning and the OEVA got a private session with the Leaf this afternoon.

Here's Nissan's spokesperson who graciously answered all our geeky questions about the car. The Leaf boasts a 100 mile range on a 24KW battery pack. I have a 14KW battery pack and I only get about 20 miles when going on the freeway. The 100-mile range of the Leaf is based on a profile called LA-4 which is mostly stop-n-go city driving around 25 MPH. Nissan did say that commuting on the freeway at 60mph would probably yield a range of 75-80 miles instead.

Here's the requisite photo op with the Leaf showing the charging plugs at the front of the car. The one on the left takes a 440V 50A input while the plug on the right takes the standard J1772 plug that the EV industry has been trying to settle on for years.

I'm still weighing in on giving up on my homebrew Civic-EV and just buying one a Leaf. I still have a few more months to decide.

Monday, December 14, 2009

When Things Fall Apart

Yesterday was not a good day. My landline and internet connection went dead on Saturday and the lamp globe for my ceiling fan broke apart above my bed, putting glass shards in the covers.

This gave me an excuse to get off my computer and drive over to Home Depot yesterday (Sunday) to try and find a new globe for the ceiling fan. I had recently installed the PakTrakr system, so I cleared out the serial logging attachment and started collecting data. On the way to Home Depot, I missed my exit and ended up going another two miles to the next exit. I knew I had gone farther than my battery pack should have handled, especially in the cold, so I stuck to city streets and slowly drove home.

Halfway home, the battery gave out. I crawled into a Taco Time and asked if I could plug in. The manager pointed me to an outlet outside the building but he didn't think it worked. It didn't. After that, I walked a block away and found an auto parts place that was kind enough to let me plug in. After the car sat for 20 minutes, I had enough juice to get to the auto parts place. I also collected the serial data log on my laptop from the PakTrakr for later analysis.

After plugging in, my friend Ruth picked me up and dropped me off at home. I had an appointment last night near the auto-parts place. My plan was this: have a friend drive me to pick up the Civic (after four hours of charging), drive to my appointment, plug in there for an additional three hours and hopefully have 40% charge left to get home.

We'll, I picked up the car from the auto-parts place, drove to my appointment and plugged in. Three hours later, I came out and realized that the charger hadn't given the batteries any extra charge. After poking around under the hood, I also found a critical resistor that enabled the DC-DC converter had broken off. Without the DC-DC converter to charge my 12V battery, my car would die quickly with the headlights on at night. It was rather moot because I still had little charge in my batteries. It looked like the charger had given up the ghost on me.

I got a ride home from another friend (it's good to have friends when you own a home hacked EV) and called a tow-truck this morning through BWC (the environmentally friendly alternative to AAA). I felt rather sunk all night because the car is basically useless without the charger and the batteries will degrade rather quickly if they sit in a discharged state.

I got the car home later this morning, fixed the resistor for the DC-DC converter and tried the charger again. To my surprise, the charger actually started up. My batteries seemed to be quite out of balance and the charger just wasn't putting much amps into the batteries, even with the shunts not active yet.

I still have to analyze the system more, but here's what I think is happening: The charger can only generate about 175 volts because it gets it's input voltage by rectifying the 120V AC line. When cold, AGM batteries need a much higher charging voltage. If I look at the datasheet for the LifeLine batteries, I actually need to charge each battery up to 14.90 volts at 40 degrees F to get to 80% charge. Let's see, 14.90V x 12 is 178.8V, which is higher than the charger can actually put out. The battery shunts were actually working properly and only shunting the batteries when they reached 14.9V. Since the charger couldn't reach that level for all batteries simultaneously, only a few shunts kicked in before the charge current dropped precipitously, leaving an unbalanced pack.

In short, It doesn't look like the Belktronix charger can actually charge these particular AGM batteries under cold temperatures properly.

My next task was to look at some of the PakTrakr data I gathered. The serial log was heavily garbled, so I couldn't just load it into a spreadsheet. I had similar noise issues with the 914EV here, but adding a 100 ohm series resistor didn't clean up the issues.

I did find that under massive current draws that at least one battery was getting yanked down to 7.2 volts (ouch!). Either that battery is undercharged or I perhaps hurt it over this past year and it's (probably) damaged. It's too bad that the best battery data comes under a high current draw when the serial data is the noisiest.

This being the wintertime, it'll probably be a few months before things heat up to where I can effectively drive the car again. In the meantime I'm going to check out Nissan's Leaf this week and think about ditching all this unreliable homebrew stuff to buy a commercially engineered EV...

Happy Holidays!

Sunday, December 6, 2009

Replacing and Saving the Aux Battery

Well, the car's back on the road again. Yay! I replaced the 12V auxiliary battery (a group 30 motorcycle battery) and got a 2 year warranty on it just in case.

I remember in the past, I fully drained my 12V accessory battery at least twice by accidentally leaving the headlights on. In fact, I almost did it again yesterday when driving the car over to a friend's place. The car is a bit older and doesn't have an alarm when you leave the headlights on when turning off the ignition.

To prevent leaving on the Civic headlights, I installed a piezoelectric buzzer from Radio Shack with an inline diode.

Here is the buzzer with two fast-on connectors and the inline diode with the positive (red) buzzer lead. The anode of the diode is crimped to the fast-on connector and the cathode is crimped to the positive lead with a red crimp jumper. I probably could have soldered this and added heatshrink tubing, but this was faster.

The reason for the diode is that I only want the buzzer to be on when the headlights are on and the ignition is off. In the event that the headlights are off and the ignition is on, I don't want any current flowing backwards through the buzzer, possibly damaging it.

Here is the buzzer installed to the testpoints on the fuse block. I had already figured out this fuse block in an earlier post, so I knew which ones to tap into. The tachometer is gone, so I can tap into the fuse block where the tach light input was connected.

The second testpoint from the right goes to 12V when you turn on the parking lights or headlights. That gets connected to the positive buzzer wire through the diode. The third testpoint from the right is the ignition signal which goes to 12V when the key is on. The buzzer only activates when the ignition key is off and the parking/headlights are on.

I hope this saves me a lot of headaches with the new auxiliary battery. With temperatures dropping quickly, I don't know if I can get to work, but at least I can cruise around town with a heavy sweater on. (still no heater in this machine... :)

Happy Holidays,

Saturday, December 5, 2009

Comparing Conversion Costs with Paul

Paul Pancella (see link at right) put together a great spreadsheet comparing his Civic conversion costs with mine. There are a few minor updates, but things are very close for the most part. The only things that have changed on the Open Source Civic are the MES vacuum pump for the brakes and the fact that I ditched the custom tachometer and pillar pod. Even with these differences, the prices only change about $100.

Thanks for assembling this list, Paul!


(click on the picture below to get a full size version)

Hints from Paul on Paktrakr Installation

I'm just cleaning up my e-mail this morning and found a message from Paul Pancella about more installation issues regarding the PakTrakr system:

I can share my experience with the PakTrakr if you want. Ken Hall was very helpful, but the device itself was a little disappointing. The main thing is to be very careful with installation. The directions mention it, but it can't be emphasized enough, the remotes are easily destroyed if the ring terminals contact any battery terminals out of sequence. Depending on your physical setup, this can be hard to avoid during installation, since long wires are provided for each input. I'd recommend taping over all the ring terminals except the black one before getting near the car, then untaping individually as you install.

The temperature data from the remotes can be very useful, but the calibration on my units is at least 10 F degrees off. This was on my list of complaints when I twice sent the units back to Ken, but he was either unable or unwilling to do anything about it.

The individual module voltages are reported to 0.1 V precision, but again at least in my case, a few channels have offsets larger than this (up to 0.4 V). This magnitude is obviously significant in terms of balancing, so you will want to check every channel against a meter after installation. The offsets appear to be stable, so they can be accounted for if known.

I assume you will still have the Link-10? The PakTrakr has a "fuel gauge" function, but I'd guess the one on the Link-10 is a lot better. It will be interesting to compare them. I think mine is not very useful, maybe in part because it gets fooled by big voltage swings with regen. The whole system probably works better with lead acid than NiMH anyway.

I just wanted to pass this information along to all of you.


Tuesday, December 1, 2009

Installing the PakTrakr, Dead Aux Battery

Hi All,

The Civic-EV blog has been slow due to my bad batteries and being swamped at work. I got the recalibrated PakTrakr back a few weeks ago and finally had some time to install it tonight.

I've heard of some other folks blowing up their PakTrakr modules, so I tried a few tricks that seemed to work quite well in preventing spurious voltage spikes from killing the modules.

First of all, I needed to install two modules with six batteries apiece, so I split the battery pack into two halves. This does two things: it makes sure there is no current flowing in the cables and it isolates the two halves so that the PakTrakr modules don't see large voltage spikes when removing cables from the battery terminals.

Second, I put all the PakTrakr terminal loops in a plastic bag and only pulled one out at a time. This prevented the loops in the plastic bag from touching anything like the chassis or a battery terminal that could have provided a significantly higher/lower voltage.

Third, I installed each PakTrakr terminal loop from the lowest voltage up to the highest voltage and tightened the battery terminal at each step. This insured that each block of six batteries didn't get split up and introduce wide voltage variation.

The last trick involved connecting the two halves of the pack back together. Since I had to re-install a high current cable onto the battery lug, I removed the PakTrakr terminal first, touched the high-current cable to the battery lug (not to the Paktrakr terminal!) and then attached the PakTrakr terminal with a screw to the fully connected setup. Again, the intent of this was to prevent large voltage differences from blowing up the PakTrakr.

On a sadder note, I must have had a large leak in the system or a bad accessory battery, because it measured 2.9 volts after sitting in the car for a few weeks. This battery has probably been bad for awhile because one of the cells was bulged out, perhaps from the DC-DC converter dumping 40 amps into it. After some wrestling, I wiggled it out and will get a new one by the end of the week.

With the PakTrakr installed, I now have a good tool for seeing which batteries are dying first. Since I ran the car on a rather empty and unbalanced pack, I suspect I killed a battery or two. All batteries are at a nice 13.0-13.1 volts at full charge, but I suspect that some have significant loss in their capacity. We'll see...