Fried cap in charger while driving -- thoughts on why?

Do you own or run a Bedford CF Electric then this is the place for you to discuss it here.
Griffon
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Fried cap in charger while driving -- thoughts on why?

Postby Griffon » Wed Feb 11, 2009 2:35 am

Ok - question time for current or former CF electric owners, or anyone who knows something about them...

I have a Zivan NG-3 charger sitting in between the two front seats. I use that charger for the obvious purpose - to charge the traction battery pack. So far, it has worked just fine.

While driving my CF Electric (aka The Griffon) today, everything seemed to be running ok, but I started to sense an alarming smell of something plastic getting TOO HOT! I looked down at the controller (I have the "engine cover" off, but the controller cover on), but didn't see any smoke. I then happened to notice something moving around the charger, and a second look revealed white smoke issuing from one of the vent fan openings. Note that the charger was not plugged in to AC at this point (I was driving on the road), but the dc output was connected into the 216V system through the SIM as one would expect.

Smoke issuing from any part of your EV (save tires when drag racing) is alarming, and it is especially so when you are travelling down a street and the item smoking is right next to you inside the passenger compartment. Luckily, I was travelling down a a straight section of street, and there is a quick disconnect on the DC output of the charger. I reached down and grabbed the connector and pulled it free, isolating the charger from the 216V system. The rest of the short drive proceeded uneventfully.

It's very possible I always disconnected (isolated) the Zivan charger when driving the van previously. I've only really been driving it for a few days; the previous trips were just "round the block" test drives.

When I got home, I disassembled the Zivan charger and found the smoked component is (or was?) a 100 uF 450V electrolytic capacitor which parallels the DC output.

This is sort of what I expected to find, although I can't see any reason for it other than sudden internal failure of that capacitor -- possible, but unlikely. It would be more likely to fail when the charger has been running, heated up, and finishing the charge at it's highest output voltage (~ 320 V).

But wait... what if a high voltage ripple coming out of the battery side of the traction controller caused an overload of AC flowing through the capacitor?

At first, I'd think the batteries would "stiffen" the 216V system to where there wouldn't be much ripple from the switching of the controller. But maybe in this case, they don't. Maybe the ripple frequency is too high, or...???

Has anyone had a problem like this before? Any ideas?

I'm concerned something may be wrong inside my traction controller (Lucas Mk 4A). I don't want it to fry my DC/DC converter, which is currently working very nicely. The controller does make more noise than I'd expect -- it sounds like there's actually something in there vibrating, especially at low power (crawling along at low speed). I wouldn't expect that from a electronic controller (does anyone know what frequency these controllers operate at?).

I have not had the time to remove the traction controller cover yet for an inspection.

I have a smaller variac-based charger that I can use in place of the Zivan for now.

Any help on this would be greatly appreciated.

- John

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ChrisB
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Postby ChrisB » Wed Feb 11, 2009 9:32 am

Can only really comment on controller noise , mine when I had it certianly use to whine a fair bit, I think they are fairly low frequence switchers and hence the amount of whining they do, especially at ver low speeds

As for the controller I cant help as I used the orginal Chloride charger.

ChrisB
I reject reality and substitute my own !!!!!!

Griffon
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Joined: Wed Jan 14, 2009 1:41 am

Fried cap in charger while driving -- thoughts on why?

Postby Griffon » Wed Feb 11, 2009 3:56 pm

Chris,

Thanks for the reply. Mine does whine, but it seems to also make a low frequency chattering sound at very low speeds. Chattering is the best word I can come up with at the moment to describe the sound. It sounds a little more mechanical than a whine.

This may be a situtation of my not knowing quite what to expect. I've never been around a "known to be working perfectly" CF electric before.

On Friday I'll try to hook up a small microphone inside the controller housing and record a drive round the block, then post it as an MP3 you can download and listen to.

- John

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ChrisB
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Postby ChrisB » Wed Feb 11, 2009 8:51 pm

OK

Just a thought , check the field relays are behaving themselves.

Best thing is to hook the lid off the controller and have a looky about while getting someone to drive it slowly.

DO becareful though, you've got a good 200vdc floating about in there and if somethings not right and goes poof it will normally do it quite empressivily :shock: and the last thing you want is get covered in molten metal :cry:
Also 200vdc will burn you quite easily without you realising it if you get accross the supply so again be VERY careful in there.

ChrisB
I reject reality and substitute my own !!!!!!

john
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BEDFORD CF

Postby john » Wed Feb 11, 2009 9:45 pm

the lucas controller used on the cf choppes the armature current at variable hz and mark space ratio up to 30 mph at this full volts are
applied.
to go faster the field is reduced by a chopper circuit .
the cause of the filter cap. blowing up is the ripple accross the battery
pack exceeds the rating of the cap.
the cure fit a relay to disconnect charger whilst driving shunt contacts
with a 10k 10w ww resistor to precharge filter cop.JOHN CRAYTON

Griffon
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Postby Griffon » Thu Feb 12, 2009 4:15 pm

Thanks for the info and suggestion, John. A relay is probably the end solution for this problem, but I never would have thought that the controller would create so much ripple on the battery side. I do notice that Lucas did not put any bulk capacitance across the input to controller, maybe due to the cost and size as well as safety concerns along with the fact that it "worked fine" without it. They weren't really thinking of the possibility of someone using an "aftermarket" charger and leaving it connected while driving.

I have tomorrow off work, so I'm going to open up the controller (I've only looked inside my spare mk 4a controller, not the one actually in the van). If I don't see anything visually suspicious, I'll make the audio recording I mentioned earlier. It could be it's working just fine, but I'd be glad for someone with CF Electric experience to listen to the recording and say either "Yes, that sounds like mine did" or "No, that sounds strange, you might have a problem."

I'll probably go to the trouble tomorrow of swapping out the existing controller with my spare unit just to see if it makes the same sound. Also would be a good check that the spare is actually functional... have never tested it although the previous owner said it was good.

- John

Griffon
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Joined: Wed Jan 14, 2009 1:41 am

Fried cap in charger while driving -- thoughts on why?

Postby Griffon » Sat Feb 14, 2009 6:36 pm

Just wanted to post an update on the status of my CF electric. I have not made any audio recordings yet. Yesterday, I decided to spend the time working on swapping the controllers. That's no 10 minute job.

My spare controller does work, once I replaced a blown commutation fuse (90 amp). Stupidly, I did not bother to check the fuses while I was cleaning up and visually inspecting the controller prior to installing it. I'll never be sure if it blew when I first pressed on the accellerator, or if it was blown all along (I'm suspecting the latter). The controller logic must have sensed a fault and cut the main contactors in the SIM -- the resulting arc caused a bit of smoke to come out of the SIM, but I don't think there was anything damged. When I found the blown fuse and replaced it (lucky I have several spares!), the van was drivable.

Took a quick test drive. This controller doesn't seem to make the same level of noise (it's a little quieter), but it still makes the same sort of noise. Keep in mind I'm driving with both the controller cover and "engine cover" off, so I'm hearing much more than one would in normal driving with everything in it's place.

The regen seems better on this controller. The regen worked on the other one, but this one seems to "feel" better -- I can feel the mechanical resistance increasing as I press the brake pedal further down (but before the hydraulic brakes kick in).

I'm probably going to run on this controller for a while and see how things go.

I'm finding the current meter I mounted on the dashboard isn't meant for use in a vehicle. The movement is too "light", or undamped. The needle bounces around too much, so I have to visually average the reading, which means I have to watch it for several seconds at a time. But I don't want to do that, 'cause I'm driving!

Will be working today on a data logging system that will hopefully simultaneously record battery voltage, motor current, vehicle speed, one audio channel for a microphone.

- John

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Flying John
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Postby Flying John » Sun Mar 29, 2009 10:41 pm

I think its a little silly leaving the charger side connected while driving. The original chargers had a loop to stop you driving with the charger connected and my CF, with a charger built under the pax front seat, also had a disconnect under the bonnet to make sure you didnt drive with it still connected to the charger.

As for the regen and the amount of braking required - this is set up by adjusting the potentioneters that sit just under the bonnet on the drivers side. there is a set up instruction in the manual and you can adjust it to bring more (or less) regen on with different degrees of brake application.

The whinning is normal as others have said two choppers both on armature and the field. However another noise to be aware of is the chattering that the chain drive gearbox makes if the tensioners are too loose.

John
.

Griffon
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Joined: Wed Jan 14, 2009 1:41 am

Postby Griffon » Fri Apr 03, 2009 2:19 am

Thanks for the reply, John.

It's interesting that you mention the noise made by the chain drive. I've made an audio recording using a small microphone placed near the chain drive case. The recording was made during a ~20 minute drive over various conditions -- long stretch uphill, long stretch downhill, higher speed on flat highway, etc. I need to get this recording converted to an MP3 and posted somewhere where anyone can download and listen to it.

I'd be very grateful if you could listen to at least part of this recording and tell me if the noise you hear is normal for a CF electric, or if it sounds like something is worn out. It seems to make a lot of noise to me... I have not yet taken the cover off to visually check out the chain, tensioners, etc.

I'll probably post the recording this weekend. I'll start a new thread in this forum when I do.

- John (aka Griffon)


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