If It Ain't Broke ... Part Deux

Since the new Volt/Amp meter was such a hit in the PorschEV, I ordered another one for the evTD. I failed to point out in my earlier post that this device, unlike some other Chinese wizardry, comes with documentation that is actually useful and even in color!

It will replace the trusty JLD404 that has served so well for the last six years. Like the EVIC, it became invisible in sunlight. The JLD404 has the logic contained in the display, so it needs to be powered on full time to retain the cumulative amp hour data. 

That led to several "bricking" incidents where the 12 volt auxiliary battery went flat. I designed a module to keep the 12 volt battery charged from the main pack whenever it gets low. The display of the new Volt/Amp meter will be turned off when not in use, so it will add less parasitic load.

This was a fairly straight forward like for like replacement, so the 1000 amp JLD404 shunt was swapped out for the 500 amp shunt/logic unit.

Similarly, the JLD404 mounted below the dash was replaced by the new unit.

Where the JLD404 displayed only one value at a time and had to be toggled from amp hours to run time to amps to volts, the new meter shows volts, amps, and run time simultaneously with the battery capacity gauge representing amp hours. Amp hour data can be seen on a detail view that also allows for configuration.

Postscript:

Discovered that the inverse display really is visible in direct sun! That's good news since the top is rarely up on the evTD ... too much fun open air motoring.

If It Ain't Broke ...

The patron saint of aging do-it-yourselfers, Red Green, said it best. After a summer with no break downs or other excitement, I was feeling the itch to make some "improvements". After all, projects like EV conversions are never really finished, they're just waiting for the next opportunity for skinned knuckles and sore backs. The internet presents all kinds of temptation, and I'm a sucker for amazing Chinese technology.

I found this little gem on Amazon and it seemed too good to pass up: a voltmeter/ammeter with simple amp hour counting to drive a battery gauge for a remarkable price and available in the US with free delivery for Prime customers.

The illustration shows a USB connection from the shunt/logic unit to the display, but it also has a built-in wireless link. The font is a nice size and can be reversed (black on white) for better visibility. While it caps at 300 amps it has a 500 amp shunt. I have never seen over 300 battery amps on either the MG or Porsche, so at 400 volts it should be just right.

You may recall that the PorschEV dashboard was build around an EVIC display for most of the system monitoring. As it turns out, there were several factors that have made it less than optimal as I lived with it for the last three years. First, it is very difficult to see in any kind of sunlight. The only time it's really visible is during night driving. Second, since I revamped the cooling system, the temperature read-outs have been largely irrelevant. If I need to check the temps, I can access the wireless GEVCU data from my iPhone. Third, while it accurately displayed the pack voltage, the amp hours and battery capacity display never worked correctly and for reasons I fully understand and accept, were not going to get fixed. Finally, after reconfiguring the GEVCU for full power, I learned that the Siemens motor had plenty of torque to essentially go direct drive. I wired in a switch for electronic reverse and simply leave the transaxle in fourth gear. That makes the rev counter display uninteresting. The net result is that the EVIC display was not adding much value to the driving experience.

The original dash panel was still gathering dust under my workbench, so a little fun with a hole saw made it a nice place to reconfigure the driving info center.

Black paint makes the base disappear. The speedometer was mounted in the center with the Volt/Amp meter on the right and the air conditioning control to the left. You may recall that I originally placed the AC controller on a windshield suction mount because there was no room on the dash. Now it's nicely integrated and in the line of sight.



You may also recall that I cobbled together a charging display for the rear of the car so I could keep tabs on charging progress. That required an extra contactor, a shunt, a couple of relays, and a box to mount the display and hide the spaghetti wiring. Oh, and it burned out pretty regularly. Not terribly expensive, but not the kind of reliability you'd want for a plug and play function. 

Since the shunt/logic unit supports multiple displays, I replaced all of that paraphernalia with a single piece. Wireless is very cool!

Neglect is the sincerest form of ...

Neglect is the sincerest form of saying "Everything's going great!" Sorry I haven't posted in such a long time, but there's not much interesting about just driving and enjoying the family fleet of EVs.

The Autumn season brings a couple of favorite car shows to display the conversions. First up was the Texas All British Car Day show in Round Rock. While the evTD is a mongrel: German chassis, Chinese Batteries, with US content being a body from South Dakota, motor from Illinois, and controller from Florida, most of the chrome is genuine British MG parts. It does personify the essence of British motoring so the show organizers let me in, but relegated it to the "Special Interest" class where we were surrounded by MGB's with monster V8 engines. Beautiful workmanship all around and I must say we were right at home and attracted a nice crowd to the outskirts of the show.

 A week later was the IBM Car Show held to promote the Employee Charitable Contributions drive. It was a gorgeous day with most of the cars owned by other retirees.

The spectators were largely current IBM employees, mostly of a technical sort, so plenty of deep dive discussions into the componentry and design specs of the PorschEV. Lots of fun!

Mechanical Stuff

Has it actually been over six months since my last post? Time flies when you're having fun. Not really a lot to talk about, just incidental nuisances with things unrelated to the electric nature of these cars plus a few minor electrical glitches. For instance:

The driver's side door handle on the Porsche broke. I mean broke as in "thirty year old metal fatigue". Replacements are available but a bit pricey. The good news is that it can be installed without disassembling the whole inner door panel. Unfortunately, no photos.

On the MG, the steering box was the only moving part that wasn't replaced when we did the conversion and it's become pretty obvious that it should have been. What started as a vague off center feeling in the steering became a scary lack of response to steering inputs. A new steering box was the order of the day and fixed that situation right away. It's nice to have the car go where you point it.

After I replaced the wonky steering box on the MG I was enjoying a test drive when I smelled a hot plastic electrical smell. Back in the garage I noticed that the Battery Management System had lost touch with a block of cells and after major disassembly found a burnt cell board and a main board that had oozed a bunch of silicone all over its housing. I know - Jack Rickard told me so - but after six years in service, I finally removed the BMS and bottom balanced the GBS pack.

Burnt Terminal

Bleed charge off with PowerLab 8

Final trim with home made resistor

After six years, the GBS pack is still at full capacity and reasonably well balanced. So now, BMS free one day at a time.

With all that done, it was time to tackle a two year old problem with a broken transaxle mount. This is the second time that the forward mount has broken, this time not as a result of drag racing, just every day use. The car remained drivable but made an annoying "Bump-Bump" noise as the rear of the motor bounced off of the rear cover whenever torque was applied. Since the mount was broken and could be removed in two pieces, we were able to do the replacement with the motor and transaxle in place.

The new mount has no rubber buffer and is a solid piece welded up from quarter inch steel. It's sold for "off-road use only". I suspect it would be pretty harsh with the old VW boxer motor but smooth as silk with an electric, and with any luck significantly more durable. It raised the rear of the motor enough to cause interference with the tachometer sensor on the tail shaft of the motor, so I had traded "Bump-Bump" for "Screech-Scratch". Simple fix for that is cutting a clearance notch in the rear valence.


The MG now has the drivability issues sorted out just in time for Spring weather outings.

CHILL!!!

Man, has it been hot here in Austin. With highs approaching 110F, temperatures in the garage are in the low 100's during the day, so working on the Porsche has been a sweaty endeavor. We installed the Benling Air Conditioning compressor in the car early in the build process, but there were some things that needed to get done before it could be put into service. The car's cooling system, radiator and fans, needed to be uprated and I had to figure out how to mount and wire the controller. So here we are after almost two years on the road, finally ready to put a freon charge in the compressor and enjoy some cooler motoring.

New compressor in place.

Sadly, after doing the freon charge the compressor just sat there, inert and stupid. Can't know for certain, but I suspect that it was a victim of a known issue that I failed to account for in the initial installation. That makes me inert and stupid. Here's Jack Rickard's explanation in the first twenty minutes or so of this video from August 13, 2010. In short, the compressor's input capacitors work their little hearts out trying to run the car's motor! Except mine never blew a fuse, just burned out the inverter that's built into the compressor after two years of unprotected exposure to the traction pack. Expensive lesson learned.

New A/C contactor hiding under the two red cable boots

Thanks to Jack Rickard and Bill Bayer for shipping my replacement so quickly! This time I may have erred on the side of excess caution, but I completely redesigned the A/C circuit to include a spare contactor I had in a box of stuff and a 400 volt 100 amp diode to prevent any outbound current from the A/C unit. Since the compressor and charger share an input line from the battery pack, both are protected. 




The new compressor also came with the newer design controller which is not quite as ugly as the original. One of the delay factors in bringing the A/C online was my attempt (without success) to use the original dashboard controls to manage the compressor. I hate to chop holes in the dash or otherwise bastardize its classic look, so a suction windshield mount for an iPhone did the trick. I also added an on/off switch to the console in an existing hole to power the compressor contactor and controller simultaneously, keeping them both out of harm's way when not in use.

Speaking of harm's way, I had to crawl deep under the dash to pass the wiring through the firewall. I had fished some of the earlier wiring for the charger and dash gauges through without doing the contortionist routine and noticed that they were dangling in the path of the accelerator pedal mechanism and in some cases showed signs of chafing on the insulation. Another complete rework was in order and that slowed things down considerably. I'm happy with the results and especially happy that this time the compressor fired right up and pushed cold air through the vents as it was meant to.

With the ambient temperature showing 100 degrees F, at 50% compressor speed (which master mechanic Keith Jordan says shows ideal line pressures) the inside temp dropped to 94.1 in the first minute and 92.8 in the second minute. 

Probably more important, the chilled air blowing through the vents felt very comfortable and made the car a lot more civilized. The compressor is almost inaudible when running and its sound is masked by the radiator fans. In this short test, the motor and inverter temperatures held at around 39C, so the heat exchanger in front of the radiator didn't seem to have any effect on the running gear. Tomorrow we'll stress it a bit more and mix highway miles with some local traffic. It's forecast to be another 110 degree day, so we'll get a good sense for what it can do.

The PorschEV is inching towards completion and all-weather everyday use.

New Speedometer in the PorschEV

I chose an Intellitronix digital GPS speedometer for the Porsche conversion mostly because it complemented the blue theme on the Andromeda EVIC display. Click here to see that post. After it was installed and the car was on the road, I began to have second thoughts. It took a long time to lock in on a satellite and begin registering at all, and there was a significant lag in the display when accelerating or decelerating. It was mostly good at reporting speed if you kept it steady, sort of suggesting an average.

A couple of months ago, it gave me an excuse to replace it. First one and then another LED disappeared from the right digit. That made it a little hard to read, but with some imagination you could guess. Twos and fives are a challenge, though. Reading the online reviews, I've learned that this is a common problem.

I have used Speedhut custom gauges in both the eBugeye and the evTD and they have been superbly accurate and reliable. They're custom built and you can configure a huge number of variations; font, text, needle, and background color, even custom logos. I toyed with the idea of a blue palette, but instead opted for a look that's pretty close to the original Porsche gauges.

Even though both our Prius and the Leaf have digital speedometers, I still prefer an analog display with a needle that tells at glance both what speed you're doing and the rate at which it is changing. The Speedhut speedometer locks onto the GPS satellite quickly and registers speed in real time. It's actually quite satisfying and works simply and with no fuss. I consider it an upgrade and don't miss the old one a bit.

COOL!

Last summer I was complaining about the undersized cooling system in the PorschEV and how it would send the inverter into thermal limiting, usually at the most inopportune times. How does sudden loss of power at highway speeds sound? The good news is the inverter protects itself from heat damage, but it's pretty disconcerting when it happens.

The cooler was a dual core Derale with one coolant loop for the motor and charger and the second for the inverter. With two Pierburg pumps and a 10" electric fan, it was adequate for the cooler months, but this is TEXAS and in the Summer (that's 2/3 of the year) it just didn't cut it.

A bit of Googling turned up a higher capacity aluminum replacement for the stock Porsche 924S radiator that was bundled with two 10" electric fans. Unfortunately, those fans  didn't fit so I wound up ordering a pair of 9" fans that did the job. I also found silicone 90 degree Elbow Reducer hoses that connect the 1.5" radiator outlets to the rest of the 5/8" system.


Here's a comparison of the two coolers. We're clearly adding capacity with the new system.

Mounting the new radiator had its own set of challenges. Long story short, the lower 3" of the radiator support was cut off at some point in its lifetime, so the original radiator was sort of dangling, held in place by some creative application of zip-ties. I devised a more secure if equally creative support involving angle iron and eye bolts. It feels secure and at least it's all metal.

The plumbing went together fairly easily using what was already there and rerouting the hoses so the pump output goes first through the inverter, then through the charger and finally through the motor before it passes through the radiator and then back to the catch tank for the pump.

One pump and catch tank was removed (set aside for the next project) and I think I'll use the space for a windshield washer fluid reservoir. Only one change was needed to attach the inverter output to the charger input. With everything on one cooling loop, I hope there is enough capacity to keep it all cool calm and collected.

The first short test is encouraging. With ambient temperature in the low 100's F (up to 104 in the sun on the road), a short 5 mile run around the neighborhood had the inverter steady at about 46C while the motor showed anywhere from 50 to 90C. At stop lights, the temps dropped to about 43 for the inverter and 48 for the motor, well below the 55C max recommended input temperature.

We're checking off the list of annoyances little by little. Next item is to get the air conditioning charged and working. How did we ever get along without it?

Update: 6/28/2017

I had experienced some coolant overflow on charging with the old system, so I was anxious to test it on a full charge starting at 366 volts. I have the fans set to run during the charge process and the temperature held at 34C (93F) with an ambient temperature around 33C (91F) in my garage. It's noisy but cool with no coolant loss. Happy times!