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 built 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.