Sunday, June 8, 2014

Out with the old...

I've been really enjoying the ElectroJeep with its new LiFePO4 cells.  So much so, that I decided it was time for the Volt914 to get the same treatment.  The AGM batteries are now nearly 5 years old, and their capacity is significantly reduced.  I plan on putting 68 cells in so the nominal voltage level will be 218V, roughly the same as the 216V nominal of the AGM batteries.  The cells arrived this week - CA100FI cells, 100Ah LiFePO4:

I purchased 75 of them to allow for a 10% margin of failure.  Also purchased were 75 of Clean Power Auto's MiniBMS modules and the associated head-end controller, as well as an Android EV Dashboard from Electric Motor Werks.  The ElectroJeep has both those systems, and they are working very well.

It was rainy yesterday, so instead of doing yard work, I pulled the old AGM batteries.  Here are all the old batteries, stacked up behind the car:

I discovered significant water damage after pulling the batteries.  First, the battery warmers in the rear box were destroyed by water (they were still moist even though the car has been in the garage over a month now):

Second, water has somehow gotten into the front compartment.  I suspect this ended up worse than it could have been due to previous battery acid spills:

Sigh.  I'll fix it real good this time!  In the meantime, here is the layout I'm working toward with the new cells:

I'm going to make sure that the rear box is completely water-tight.  I don't want a repeat of the water damage.

Sunday, May 13, 2012

Digital Battery Regulators

With the ElectroJeep going to Lithium, I had the opportunity to replace the Volt914's analog battery regulators with the Jeep's digital regulators.  At first, this seemed like a trivial task - just swap out the old analog regs, pop in the new digital regs, and off we go!  Unfortunately, the newer digital regulators have a slightly different component layout - specifically, their power tabs and Regbus connectors are in different places than the analog, so the old boxes I had built for the analog regulators would not work.

However, there was a silver lining to this cloud.  The older boxes were not very waterproof (I had lost 2 regulators to water damage).  Also, I never had put a good battery warmer solution in place.  So, I took this opportunity to do a minor overhaul to the Volt914's battery system while I was at it.

First, I had these nifty devices - they are called "Farnham Battery Heating Pads".  They are designed to take 120V AC and produce 35W of heat each (consuming, of course, 35W of electricity in the process).  In this picture, I have crimped insulated FastOn 1/4" tabs onto the terminals:

To better protect the regulators from water damage, I decided to restore the battery boxes to their original heights, and have the regulators sitting on top of the batteries inside the box.  Fortunately, I never throw anything away (well, my wife may disagree...) so I was able to retrieve the old tops to the boxes and attach them with mending plates (this part of the box is only under compression, so it does not need much shear strength):

For the rear box, I sealed the seam and most of the holes with really thick, sturdy outdoor tape:

For each box, I created a wiring harness for the heating pads.  This is the harness for the rear box.  The harness ends in FastOn connectors - one pair for each heating pad - and one pad per battery.  The other end of the harness is a WeatherPak connector - my favorite:

Here are two of the pads in place int he front box, with the harness connecting them:

And here are the three batteries in the middle box, with the pads underneath and the harness attached:

The last step was hooking up the original MetricPak connectors and battery interconnects.  Here is the rear box with all that wiring in place:

With all the prep work out of the way, it was time to actually do the part of the project which I meant to do in the first place.  I mounted the digital regulators onto 1/8" polypropylene plastic boards. This prevents them from moving around, and it also adds a margin of safety since the poly board will separate the regulators from the battery terminals:

Here is the rear box, all complete.  You might note some sheet-metal screws attaching the poly to the batteries - I was very careful to drill only into the "handle" portion of the AGM-1280T.  This adds further mechanical support to the regulators:

With all the regulators in place, it was time for a test.  The front box is the farthest from the charger, so, if its yellow lights come on when the "test" DIP switch is set on the charger, all is good. All is good:

Finally, I need some way to prevent the batteries from bouncing up and down in the boxes.  I have some very dense foam that I cut circles from - one for each battery - and double-stick taped in place (again, shear strength is not important, these are all under compression from the box top):

And the Volt914 is ready to drive again.  I have not yet attached the battery heaters to any kind of thermostat, so they are not yet plugged in.  Stay tuned - I have a plan which I hope to bring to fruition shortly...

Tuesday, August 3, 2010

500 miles at 216V

This weekend, I passed 500 miles in the Volt914 with its new 216V pack.  It is staying very well balanced - the Rudman Regulators are doing their jobs well.  And, with quite a few trips in it, I'm able to assess its efficiency at the higher voltage and with the new charger.  Take a look at the miles vs. kWh plot:
As you can see, the least-squares fit line shows that a good approximation of wall-to-wheels electricity use is a 910 Wh fixed overhead per charge, and about 280 Wh per mile.  This is wall-to-wheels, so it accounts for all the efficiency losses of the AC-DC conversion process as well as the reverse DC-AC conversion for driving.  Not too shabby!  And, much better than the old 144V floodies with the Zivan NG-3 charger, which were giving me 1,230 Wh fixed overhead per charge and 380 Wh per mile wall-to-weels efficiency (!).

Edit: Forgot to mention, at my current cost of 7.5 cents per kWh, I spent  about $14 for the electricity for those 500 miles, at an average cost of 2.8 cents per mile.  Which compares to 3.7 cents per mile with the old 144V system - a 25% reduction in cost.

Of course, I will soon be paying essentially *nothing* for the electricity my cars use:

This is a 5 kW array, which will generate about 7,000 kWh per year.  Between them, the Volt914 and the Electrojeep use about  2,000 kWh per year, if I drive both of them every work day.  Which I don't.  But I could :-)

Sunday, April 25, 2010

Out with the old, in with the new

I finally got around to replacing the ammeter that came with the kit. For some reason, it was a -50 to 50 amp meter. The controller generally draws more than that except in economy mode. So, I got a -150 to 150 amp meter, along with a 150A 50mv shunt. Removing the old shunt was a little bit of a pain, but fortunately I had mounted it high enough that I could access it without removing the battery boxes.

Here are the new shunt (on the left) and the old shunt next to each other:

Notice the discoloration and warping on the old shunt? Here is the same area from below:

Definite heat damage. It's not clear to me whether there had been a loose connection at some point (generating extra resistance == heat), or whether the 50A rating of this shunt was just exceeded too often, but it is clearly damaged. I'll monitor the new shunt for damage frequently for a while.

Driving with an operational ammeter is extremely useful. For one thing, I can see that my "normal" and "economy" modes indeed are not different - which I had *felt* but not proven. Both pull 50A max. I'll tweak that at some point. It would be useful to have something in between 50A (economy) and 150A+ (performance)...

Addendum: this is very similar to damage that Randy Pollock suffered (although not as extreme):

We have the same shunt, in the same system, and had the same failure. I don't think this is a coincidence.

Tuesday, February 23, 2010

Of Mice and Men

As in, "the best laid plans of." Or, while I'm on film allusions, how about "The Remains of the Day:"

But I'm getting ahead of myself. The car has been running very well - except for the nagging fact that the battery warmers have not been drawing any amps except for the first day they were plugged in. And the batteries have not been kept warm - instead, I've been keeping the car in a heated garage ($$$$). So, tonight I decided to start with the middle battery rack - the one with 3 batteries. It's the easiest to access. So, I pulled the batteries out and pulled the warmer out. Another allusion, "What Lies Beneath:"

And what a mess it was that lay beneath. The clear plastic around the thermocouple was discolored and clearly burnt:

Dissecting the clear plastic, it is obvious that the nicrome wire got too hot and simply vaporized:

Seeing this, I decided to pull all the warmers out. Each one had similar damage. And, in fact, some of them had burn-throughs in the middle of the cable:

Even when the cable had not burnt through, it is clear that the cable produces too much heat for the foam insulation. Here is one of the dual-sided pieces, melted all the way through:

Which brings us back to the pile of stuff at the beginning of the post. I'm very fortunate that no other damage occurred. So, it is back to the drawing board for battery warmers. I'm considering some of the battery heating pads, or other options. Stay tuned.

Saturday, February 20, 2010

Misc Saturday

It is snowing today. Grr. I won't drive my car in the snow - too much of a risk of someone crashing into it. So, I decided to get the heater working again. As mentioned here, the Crydom solid state relay was stuck closed. I happened to have a Tyco EV200AAANA contactor lying around. It handles 500A of current, so it is way overkill for the 3A or so max needed by the DC-DC converter. Oh, well. Here is the new contactor in the place of the Crydom relay:

I installed it, hooked up the cables, and turned the heater on - voila! Heat! So now, when it is cold but not snowy, I can drive around. I put a clamp-on ammeter around the HV cable, and measured 10A when the heater starts up, which decreases to around 5A as the heater warms up and the resistance increases (V = IR, after all, and V is constant). The updated PDF of the wiring diagram is in the usual place (nothing major changed, just replacing the Crydom with the contactor).

I also installed a goody I got from Electro Automotive. This was supposed to have been part of the original kit, but got overlooked somehow. They were gracious enough to send it to me gratis. It is a combo regen enable/disable switch along with a 3-position rotary "ECONOMY / NORMAL / POWER" switch. It hooks up directly to the 4 wires that have been dangling in my cabin for 2 years. I attached it where the radio would normally go:

Finally, I got around to attaching the door sills and speaker grills - these are what holds the carpet in place. I'd been frequently pulling the carpet back into position, and got tired of it. It took me about 10 minutes, I don't know why I put it off so long:

Also, earlier this week, I put a new rear-view mirror on. The original Porsche mirror would not stay stuck to the glass, so I went with a traditional after-market metal "button" and rear-view mirror combo. Works very well:

P.S. - this is post #100 to this blog. I never thought it would go on so long when I started...

Monday, February 15, 2010

On the road again!

The big news of the day is that the Volt914 is an automobile again! I drove it a total of about 12 miles today. But I'm getting a little ahead of myself...

The morning started with a large, immobile lump of steel, lead, glass, and plastic sitting in my garage. Turning the key did not result in the proper effects. So, I went after it with my digital multimeter. I found that I had swapped two wires - the keyed +12V and the "lower interface terminal block" wire. Fixing that resulted in all the right things - the oil pressure light came on, etc. The 12V system was alive!

However, all was not ready for driving. The Crydom relay seems to be stuck closed - it is always transmitting full HV regardless of the control inputs. As a temporary workaround, I used the heater contactor to control the DC-DC converter and voltmeter. I had to extend the wires to reach the contactor lugs:

With that set up properly, I made sure the DC-DC converter was properly wired. That yellow block is a 60A 12V fuse (the DC-DC converter is rated for 55A). Before hooking it up to the fuse, I verified that it is putting out the 13.3V it is supposed to (it is a battery-charging DC-DC converter):

With that taken care of, it was time to seal everything up. Here is the front compartment with all the wiring in place - it will get neatened up a little more some time later, but for now, it is operational:

And here, for the first time in months, is the front hood closed:

I then hooked up a computer to the controller and tweaked the necessary parameters to convert it from 144V nominal to 216V nominal. For the record, here is what was tweaked:
  1. EE2AccelBatRamp - 16 (was 12)
  2. EE2NoAccelBat - 189 (was 126)
  3. EE2RegenBatRamp - 18 (was 34)
  4. EE2NoRegenBat - 240 (was 160)
  5. EE2BatVLoMem - 0.018 (was 0.0122)
  6. EE2BatVHiMem - 0.018 (was 0.0122)
  7. EEXMinAccelPower - 10800 (was 9609)
  8. EEXNormAccelPower - 21600 (was 24000)
  9. EEXMaxAccelPower - 32400 (was 36000)
I had previously tweaked the EEXNormAccelPower and EEXMaxAccelPower variables in an attempt to get more power out of the 144V system. It did not really work. It will be interesting to see how the power selector switch from ElectroAuto works - it should arrive later this week.

I took two drives today. The first was just over 4 miles "around the block" (never more than a mile away from home in case of breakdowns). It feels peppier than it used to - losing 180 pounds of lead probably helps. The regen brakes have the "pulsing" effect again - I will need to tweak the RegenBatRamp variables some more. The very good news is that the combo of the new DC-DC converter (rated at 55A) plus the massive 4-gauge cable I used for a main 12V bus have made it so there is never any voltage drop, no matter how much 12V stuff is happening.

The second drive was to my local AutoZone, where I snagged stick-on letters to put a "VOLT914" sign on the back:

I charged in between the drives, and at the end of the second drive. Mostly to try to get the timer adjusted properly. It was reading 6A when it cut off the first time, so I increased its time by 30 minutes (from 45 to 75 minutes). It was reading 3A the next time - I probably need to tweak it up another 30 minutes to 105 minutes.

After playing with the charger some more, I hooked up the rear fans. This involves a relay box and stringing various wires:

Here is a diagram of the rear fan control. The DPDT relay is there so that when the key is not turned on, the fans are being driven by the AC-DC power supply when plugged in (this keeps the charger cool). When the key is turned on, they are instead driven by the car's +12V:

The PDF may be found here. Regarding range, it is a little early to get a good read, but the second drive was 7.6 miles, and consumed 3.1 kWh, for a net 408 watt-hours per mile (from the wall). This correlates very favorably with the 144V / Zivan system, which consumed about 4.0 kWh for the same distance - so at first blush, the Manzanita charger and new batteries are about 25% more efficient.

I also made a little chart based on Concorde's own data, showing the SOC versus voltage for my "216V" pack:

And that's all for today. I'm exhausted. This week - mostly just test drives, but I may have the opportunity to show the car off for some government big-wigs on Friday - stay tuned.