Corbin's Treehouse - Corbin Dunn, Santa Cruz, CA
Plug Bug

Archive for the 'Electric Bug' Category

Plug Bug: charger repaired; back on the road

The bug is rolling again! About 39,800 electric miles. I asked Manzanita Micro why it failed and what I could do to prevent it from happening again. They said it “was something in the negative side of the rectifier bridge. possibly something in the ground.” — I’m not sure what that exactly means. For now, I’m going to limit charging the car at 20 amps. I had previously been pumping it up to the full 30 amps, hoping to get the rated 6kW of power out of it. I think that makes it have trouble…but I can’t say for sure. 

Here’s a picture from today while I was charging at Apple:

IMG 4642

I always open the hood to let the charger get some extra cooling. It tends to overheat and starts blinking its LED when I keep it shut. 

Bug down! Charger broken (again – 3rd time)

Sadly, the electric VW bug will be taking some time off the road. Last time it was the transmission, and this time it is the Manzanita Micro PFC-30 charger. I didn’t even get a 1000 miles before another problem came up. I was really hoping to hit 40,000 miles and it is nearly there hovering a bit over 39,700 miles. 

Last Sunday I was charging the car and pulling about 27 amps. The charger should be able to pull 30, but quickly goes into a limit mode due to temperature. This happens no matter what the temperature is, and is just a flaw in the charger. It might happen due to the voltage of the car: the car runs at 154 volts, but charges somewhere higher, like 170V – I’m not sure as the exact voltage as the charger has no measurement for this and you turn a dial to adjust it. So, it is stepping down the 220v input to 154v. And, I know the charger is only about 80% efficient, so the extra energy has to go *somewhere*, and that somewhere is heat dissipation. 

The charger has failed several times:

First time: May 2011 – Charger Not Charging — Manzanita Micro repaired it (out of warranty) for $170. I wasn’t quite clear on why it failed.

Second time: September 2012 – Charger Failed again. – $213 to repair it, and they said the reason was from corrosion on the cables.

This time, I’m seeing the same symptoms as the first time; the charger is causing a ground fault, and flipping the circuit breaker that my EVSE is hooked up to (50amp breaker).

I opened the box..I think the bad part is underneath where I can’t see. It smells like magic smoke. 

I don’t have much choices for a replacement charger; it is by far cheapest to just get this one repaired, so I’ll send it back and have them fix it again. The EMW charger looks nice; it outputs 12Kw, and is a decent price ($2300) — but I can’t fit the 12x12x12” dimensions in my current location. And I don’t want to pay $2300 for a new charger, when I can get the current one repaired for a lot less.

IMG 4513

chargepoint energy stats for my bug

Since July of 2011 I’ve been using chargepoint for charging at free charging stations, and at work. Prior to my work getting J1772 stations, I would use a dryer plug outlet that was provided for EVs. Here is a screen shot of the stats for my use:

Screen Shot 2015 07 22 at 7 57 39 PM

10,673.912 kWh used in about 4 years. Mostly with the bug, but some with another EV (Jan/Feb ’15). This also doesn’t include other J1772 stations I’ve used that aren’t charge point (i.e.: the free stations downtown Santa Cruz), and it doesn’t include charging at home. 

The large gap from August to January was when the bug’s transmission was broken, and I was forced to drive another car for a while. The shorter gaps were probably vacations.


Plug Bug: You are only as strong as your weakest cell

I had known for quite some time that I had a weak cell in my battery pack. My electric bug’s battery consists of 48 lithium iron phosphate cells. I use the eLithion battery management system with a custom display I fabricated along with some custom ardiuno code to show cell info from the CAN bus. I would routinely see one cell (number 9) sag heavily under load. 

One day I left work work (a 20 mile drive) with my pack at about 50% charged. At about five miles from work my low battery warning buzzer went off telling me that I had one cell that was fully discharged. That was my bad cell number 9, and I was only at 30% SOC once I arrived at work:

IMG 3918

The cell was down to 2.07v, which is well below the nominal 3.20 volts, and the “fully discharged” value of 2.7 volts. I had ignored the low voltage buzzer, and continued to drive car, taking more energy out and over-discharging it. I knew this might destroy the cell, but I was okay with that as I had a spare cell at home. 

Once I got to work, the BMS wouldn’t let it charge! It thought the under voltage condition was an error where it shouldn’t let any energy in (which is strange). Luckily, I could easily unplug the BMS connection to my charger, and let it charge for a bit:

 IMG 3920

This pulled the voltage up to 2.70 volts, and let it normally charge:

IMG 3919

At this point, I knew that 30% state of charge (SOC) was my real world “battery empty” point. This one particular cell has lost 30% capacity in the 4+ years and 39,000 miles that I have been driven the car. I know the other cells aren’t as bad, as they don’t sag under voltage load, but this one bad cell is the limiting factor of my pack. If I continued to discharge it below 30%, it would cause the cell to die. That in itself wouldn’t be that bad, but I heard dead cells can sometimes reverse the voltage and suck energy out of their neighbors. I would also have to bypass it in my BMS, as it wouldn’t let the car drive with a dead cell.

I continued to drive the car for a month or so, and just didn’t let it get that low again, and it worked fine. But I really wanted that extra bit of range and capacity “just in case”. Plus, I had two spare good cells for this very reason.

Last weekend I finally did the work to replace the cell. I had previously used a volt meter to find out which cell it was (the numbering doesn’t seem to be related to anything I can figure out). It was a cell in the front trunk of my car, so I pulled out the module for it:

IMG 4297

I snapped the green strapping wires apart, replaced the bad cell, and then strapped the module back together.

This time, I used my engine hoist to pull the module out and put it back in:

IMG 4298

It was so much easier than trying to pull it out by hand (which I had done when I originally installed the modules!). 

The bug now has a bit over 39,100 miles. The transmission is leaking a bit of oil from the main shaft seal; I’m afraid it will eventually fail again.

Now, I need to do another capacity test with the pack and see how the other cells are doing. 30% loss over roughly 4.5 years isn’t that great…the cells forecast an expected 20% loss after 10 years of use when discharging to more than 20% SOC. I always did this, but I also always charged to 100% SOC (indicated by roughly 3.6 volts per cell). I think always charging to 100% has reduced the capacity. If I were to do the project again, I would write some smarter charger controlling logic to limit max SOC to 90 to 95% for most charging sessions, and only charge to 100% on the days I knew I would really need it, or would use the energy right away. Sitting at a high SOC for a long time isn’t good for the cells.




Plug Bug: Killing Chargepoint Charging Stations

Well, my bug wasn’t killing the charging stations, but it was giving them an internal error. It seems that the newer charge point stations with a large display weren’t compatible with my car’s J1772 port for some reason. There are rows of them at my work, and I’d plug in and it would give an error: 

IMG 2387

Error Code #303-RSC, RELAY STUCK CLOSED. I couldn’t find any information on this error, and both phone calls and emails to ChargePoint went unanswered. The phone people just assumed it was a problem with the station, but I told them my car caused it and I wanted to know WHY it happened. Still, no info.

So, I really wanted to use the closer chargers at Infinite Loop instead of walking across the street to the older style. I started poking around and discovered the two pins were leaking voltage to ground. The ground is the 12v ground of the car, and I had known about a ground leak for quite a while. Pack voltage is usually isolated from the car’s normal ground system and chassis. On cars, the chassis is used for the 12v negative side (the ground). Yet, if I compared the plus side of an amp meter to my negative most terminal on my pack, I would read almost my entire pack voltage!

I knew this. It went away when I unplugged the controller/motor, and I assumed it was the brushes in the motor and not a big deal. Sometimes dust builds up in the brushes and causes a leak (or so I’ve heard). 

I figured this might be causing the charging station issue. It was easy to test; I drove to work, unplugged my controller/motor (it is on a BIG anderson connector), and sure enough — it worked!

When I got home I had to figure out where it was leaking. If I disconnected just the motor the leak still happened. I finally traced it to the controller. The Netgain controller has two high voltage “pre charge” wires. They are orange wires from the controller. They go to the contactor that the controller controls. One goes to the pack voltage side, and the other goes to the other side of the contactor that is “on” when the contactor is closed (providing power to the controller). The controller does some type of voltage check on both sides to pre-recharge things.  For some reason, the side on the non-open side of the contactor caused the problem; disconnecting it fixed the problem — well, almost, as the leak was only 2 volts or so. It was leaking “out” for some reason from here, and it is some problem in the controller. Swapping the orange wires didn’t matter (they were interchangeable). If I removed the pack voltage side wire, then of course, the leak went away entirely.

So, I was hoping I could put this pack voltage wire on a relay that comes on only when the key is on. This way, the charger works when the key is off.

I found a good relay on DigiKey and Mouser, and a better price on Amazon (especially with free Amazon prime shipping):

This is an Omron MKS1XT-10 DC12 relay. The details on Amazon are poor, and Mouser’s specs stated: 10 amp contact current (more than enough for that wire thickness), 220 VDC switching voltage (my pack is 154V nominal, and way less than 200V ever), and the relay runs of 12VDC (or 24VDC). Perfect! Amazon says $20 now…but it was $26 when I bought it (d’oh!)

I also got a terminal mount for it, so I could easily mount it in the car:




 So, for about $40 I’d be good to go! I got them, tested it, mounted it in the car, and the car’s controller still worked when I was doing this switch. I was afraid the controller might pre-charge on key-on *BEFORE* the relay kicked power to it, but it seems to work okay.

And, now it works at the charging station without having to unplug the main battery pack. Excellent!


Plug Bug: Transmission / motor removal in an electric conversion

I was still having trouble with my transmission. My last post talked about how I got it back in — this was months ago, in October 2014. I drove the car about 20 miles, and while coasting in 3rd downhill it made some bad grinding noises, so I put in the clutch (which didn’t stop the noises) and pulled over on the notoriously dangerous Highway 17 by Scotts Valley. The transmission was spewing oil everywhere! I had to get towed home. I wasn’t sure what was wrong, and I took the motor/transmission back out. Oil was everywhere in the clutch, and I had to clean it out really well with brake cleaner. It seems to have spewed into there from the “main shaft seal”. I had no choice but to mail it back to MOFOCO. It took a while, but the mechanic Roy Henning sent me this picture back:


I asked why this would happen and he said it may not have been filled with gear oil, or it was low on oil. I trust these guys; they have been doing bugs for longer than I’ve been alive, but I know I put a few quarts in it (I forget how much at this point – it was too long ago). But, I may not have filled it enough; I do recall filling it while it was on the jacks, and the instructions say to fill it when level. Maybe that was the problem…I don’t know.  He said he would fix it for free as a courtesy, but wasn’t happy about it. So, I offered to pay the shipping costs to help offset the difference. This ordeal made the transmission cost way more than it would have if I would have bought it local (but I did get to keep my old transmission — there was no core exchange required).

So, I waited for him to fix it. A few weeks go by, and I ask how it is going. He said it has been done for a while and was waiting for payment for shipping — however, I didn’t get any ship notification (I checked everything — spam folders, etc), and as soon as they sent the request for reals (via PayPay), I got it. So, I think they simply forgot to bill me. I got the transmission back in late December. When it wasn’t in the car, and I rotated it, it didn’t sound quite right; sort of a odd non smooth noise every now and again. But, I figured they knew what they were doing, and they said they did test drive it before they mailed it to me. 

The car had been sitting idle for a few months at this point, and I was frustrated with it. So, I had ordered another EV replacement for a while, and put the bug project “on pause”…this gave me less stress about getting it running again to have an EV to drive; I wanted a reliable car — even though the bug has been quite reliable, it still occasionally has “old car” problems that need to be dealt with (like the tranny, the brakes, and the steering).  I got the transmission back into the car in December on my break, and did a test drive the day before Christmas. After 45 miles, it was leaking a bit of oil again out of the drain hole from the flywheel. I feared it was going to have the same problem again. So, I emailed Roy at MOFOCO and he said he had no idea, but did offer to take a look at it again for free. At this point…I didn’t feel like dealing with it, and I just parked the car and drove my new EV.

Roll around to last week, and I decided to get it going again. The car sat for five months, and I missed driving it. If It wasn’t driven the batteries would just deteriorate over time, and I wanted to get use out of them. This time, I documented pulling the transmission, in case anyone else needs to do it sometime. The video is below, but be warned, it is 20+ minutes long!


One thing I had heard on The Samba was that it could be the main pilot bearing not seating right. That might cause excessive vibration, and cause the main seal to leak. It turns out my pilot bearing was pushed a bit far into the adapter, so I machined a little ring to push it out to what I think is the proper location. I’m hoping this fixes the problem…so I put it all back together.

So far, I’ve got about 120 miles on it this way. It is still leaking a tiny bit of oil….but I think I’ll ignore it for a while. It might be the main shaft seal was blown out, and not replaced. I’m just going to go with it as is and hope it is okay. It seems to drive pretty well again, but the transmission is still the noisiest part of the car.




Plug Bug Videos

I made a playlist of all the videos I have on YouTube to more easily find them. Here they are:

Electric Bug: Running Again!

So, I got my new rebuilt transmission from MOFOCO. I put it back in the car and buttoned up the rear end entirely. I then attached the shifter…but, it wasn’t shifting! So, I posted on and the guys there said something might be wrong w/the nosecone setup. I had to drop the transmission/motor combo again. This time I decided to make a better cradle for it:


These pictures are mainly for my future reference so i can remember how it goes. The strap holds it on pretty well.


I popped the nosecone off and it was definitely shifted into a gear. It didn’t seem like it was shifted into two gears at the same time…but it definitely wasn’t working before. I pulled the three things below so they were all aligned, and put the nosecone back on. I could then shift it by hand, as I should have been able to do in the first place. Excellent!


Then it went back in the bug…and it seemed to be doing okay. I put it all back together…and did a quick test drive. Success! Back to electric driving. I’ve been missing it.

Final drive ratio in an electric conversion car

So, I’m getting a new transmission for my VW bug (number 3), and probably buying it from What drive ratio should I get? They can do a few different options.

My bug is/was currently running the stock stuff for a 69 bug:

Screen Shot 2014-09-04 at 6.10.30 PM.png

I have 165R15 coker tires, and the diameter was calculated via: &

The ratios I got from the VW manual, and the screen shot is from my Numbers spreadsheet (email me and I’ll send it to you).

Here are my current speeds for a given RPM and a given gear. Max motor RPM is around 5000 (maybe 5500, but that is pushing it), so I have to shift before then. I don’t use first; it is pointless (I have enough torque to not need it), too jerky, and would have to quickly shift.

Screen Shot 2014-09-04 at 6.12.07 PM.png

I always start in 2nd, shift into 3rd at about 40mph, and 4th at 65mph; this keeps me under the 5,000 RPM limit. I have a top speed of a bit under 100mph, based on the RPM.

So, the diff ratio is 4.375 (also called 4.38); also known as the “ring and pinion” gear ratio. What if I get a freeway flyer 3.88 ring and pinion? Dropping that into my spread sheet gives

Screen Shot 2014-09-04 at 6.19.11 PM.png

So, if I did this, I would: start in 2nd, shift to 3rd at about 45 mph, and shift into 4th at about 75 mph. I rarely go 75 mph; the car starts to shake a bit at high speeds, and it just isn’t designed to do that. The lower ratio would probably make the car less torquey, so I’ll stick with the standard ratio.

Electric VW: Transmission Killer

In my last post on the bug, I had mentioned that I replaced my brushes, hoping it would fix some noise I was getting in the transmission/motor area. It didn’t help, and I then replaced two CV joints, as one was worn pretty bad. That also didn’t help.

So, I bit the bullet and removed the transmission/motor. This isn’t fun; I have to remove some of my cells in the rear seat area as they cover the hatch that lets me undo the transmission from the shifter. It isn’t too bad; I simply undo the red hold down strap, disconnect the BMS and cell wires, and then pull out the center set of cells.


The hardest part about getting the rest of the stuff out is to remember how to do it. I had made a motor mount thing that I used to slip under the motor and get it out, but I forgot that it doesn’t work anymore (for some reason), and I simply use a piece of plywood under a jack to lower the motor/tranny combo. I have to first remove the “ears” on the transmission to get it to do this; it is a pain. Once I remembered all the tricks, it slid right out (this took a while).


Now, here’s what failed. The bearing that holds this shaft in place is blown (not the throw out bearing, but the bearing on the case itself):


The shaft wiggles like mad, and the bearing has clear damage that I can see, and it is obviously leaking when it shouldn’t leak from there.

So, time for a new one. Last tranny was from Bugformance in San Jose, CA. I’m going to try this place next: which means waiting a few weeks…

(c) 2008-2015 Corbin Dunn

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