Johny's Electric Vogue

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Johny
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Johny's Electric Vogue

Post by Johny » Fri, 26 Jul 2013, 23:20


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Johny's Electric Vogue

Post by Johny » Wed, 04 Sep 2013, 17:15

The eVogue likes this warmer weather.
A typical hill on the way to work, where I draw around 50 battery Amps for about 30 seconds saw the pack sagging to 570 VDC during the colder months (5 deg C).
Now at about 18 deg C, the same hill at the same current sees the pack staying above 600 VDC.

My estimated range has increased too. I am now arriving home, after 30kM travelled, with an estimated remaining range of around 48-50kM (to 80% DOD). In the colder weather it was often down to 40kM remaining range after my daily commute.

In the work car park this morning.
Image

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Post by Johny » Fri, 27 Jun 2014, 15:43

I am in the process of repairing my most-recent failed battery charger. There are 12 chargers in the Vogue each rated at around 59V at 3A.
This last one has shorted turns in the high frequency ferrite transformer. I can get into details of how I know that but just assume I know.
So last night I soaked it in DOT4 brake fluid for a couple of hours (ahh the cross discipline of EV DIY) and dissasembled it.

I documented each set of windings and insulation carefully.
What I found is a tad confusing.
Here is a circuit of the final drive and transformer then output.
Image

The primary is 40t.
There are two secondaries. the 12t centre tapped is for the +20V output for the PWM controller. No DC choke so it acts as a peak detecter so is largely stable regardless of the PWM duty cycle.
The main secondary is 56t centre tapped. Keep in mind that the maximum DC voltage required is around 60V.

Let's assume the charger was designed for 220 VAC.
The confusing bit is if we are feeding the primary with around 300 V P-P - why does the 12t centre tapped secondary only give us 20VDC. 12t centre tapped with a two diode full wave rectifier gives the same OP as 6t with a bridge (minus diode drop). So I would have expected about a 7th of the primary excitation. 300/7=42V. Instead I get about 150/7=21V.

Anyway the bigger issue is that I also I think there are way too many turns on the main secondary. It's almost as if they use the same transformer for a higher voltage charger.

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Johny's Electric Vogue

Post by weber » Fri, 27 Jun 2014, 16:13

It's because it's not a full bridge driving it, only a half bridge and a capacitor, so the primary only sees +- 150 V.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Post by Johny » Fri, 27 Jun 2014, 16:24

weber wrote: It's because it's not a full bridge driving it, only a half bridge and a capacitor, so the primary only sees +- 150 V.
I agree +-150 = 300V P-P. So where am I wrong (and I am).
Last edited by Johny on Fri, 27 Jun 2014, 06:25, edited 1 time in total.

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Post by weber » Fri, 27 Jun 2014, 16:40

So on each 6 turn winding you get +-150 * 6/42 = +-21 V and when that's rectified by a single diode you get +21 V. The second 6 turn winding still only gives you +21 V but with the peaks 180 degrees out of phase.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Post by weber » Fri, 27 Jun 2014, 16:45

I'm guessing the apparent excessive turns in the main secondary are because a 1 uF cap in series with the primary is kind of pathetic and causes significant average (but not peak) voltage droop under load, so the extra turns are needed to compensate.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Post by Johny » Fri, 27 Jun 2014, 16:49

weber wrote: So on each 6 turn winding you get +-150 * 6/42 = +-21 V and when that's rectified by a single diode you get +21 V. The second 6 turn winding still only gives you +21 V but with the peaks 180 degrees out of phase.
Thank you. My think was was weird so I'll just ignore my first thoughts on this. That makes sense.

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Post by Johny » Fri, 27 Jun 2014, 17:12

weber wrote: I'm guessing the apparent excessive turns in the main secondary are because a 1 uF cap in series with the primary is kind of pathetic and causes significant average (but not peak) voltage droop under load, so the extra turns are needed to compensate.
This part of the design is almost identical to most non-PFC PC power supplies. The two dismantled PC supplies I have skunged parts from both use a 1uF so it's pretty typical.

There would also be effective voltage drop from the choke.
looking back at my PFC experiments on these chargers I see that they couldn't deliver 3A at 60V when the primary dropped below 200V VDC.
Based on that, it looks to me like I could drop the main secondary back to 22+22 turns without any issues. I can try it before varnishing so it's easier to rewind again.

The way it was wound was:
20t primary
28t bifilar secondary
6t bifilar secondary
20t primary

First layer of insulation removed.
Image

6t bilfilar.
Image

I'm also thinking to drop the 6t bifilar to 5t in keeping with the idea that the charger was really designed for 220VAC. I don't have room to increase the primary turns (given the wire I have access to).

The PC transformer I followed a blog on had the primary totally wound (2 layers) then the secondaries. If I do it that way I can unwind the main secondary (make it the last set) and rewind with little effort.

I've always disliked magnetics - a little ungrateful from someone who gets to work and back with a rotating magnetic field.

Thanks for the help weber. Always appreciated.

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Post by Johny » Fri, 27 Jun 2014, 18:17

The disassembled transformer.
Image

Tape and wire in a 2 litre Ice Cream container.
I won't use brake fluid again - I had to wash it and me a dozen times.

My coding system is primary wire in a figure 8. 6t+6t sec. in an oval. 28t+28t in a big circle. I think it;s all the same size but I'm yet to measure it.
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Post by Johny » Thu, 30 Nov 2017, 07:27

I seem to only post here with problems but that's just because the Vogue has now done over 35,000km and never stranded me - or missed a day of travel.
The chargers are pretty much my only ongoing issue.

I had a spectacular charger failure a couple of months ago.
The Vogue has 12 of 59V 3A chargers - one per sub-pack.
I've had about six failures and usually it's because the charge current has drifted up from 3A to 4 or even 5 Amps (probably vibration even though I have siliconed the ten turn trimmer pots) - the switchmode transformer isn't even rated for 3A so either the power transistors fail or the transformer cooks.

I've been able to repair the chargers in most cases, even rewinding 2 transformers (crappy job) but this one....
IMAG3910.jpg
IMAG3910.jpg (326.55 KiB) Viewed 1161 times
It looks like vibration cracked the solder jount on the 60V DC side inductor (the toriod) and a plasma arc took out the PCB. The inductor wires are usually a nice golden colour. There is NO enamel left on the wires.
IMAG3911.jpg
IMAG3911.jpg (336.45 KiB) Viewed 1161 times
You can see the fan is coated with soot.
The curious thing is that the boot of the Vogue stunk of burnt wiring the night before - I checked everything and all the chargers were operating. I figured - well when it fails I'll find it. I'm still getting rid of the smell 2 months later and the charger is wrapped up in two plastic bags in the garage and still stinks (it's not allowed in the house).
I'm hoping the transformer is usable as I have no spare charger at the moment and the one under repair (for the past year and a half) needs it's transformer rewound.

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Re: Johny's Electric Vogue

Post by T1 Terry » Sat, 23 Dec 2017, 10:41

I have a number of these in the 12v version if they are any good to you for parts. Drop me a PM and we can organise postage etc if they are useful

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Re: Johny's Electric Vogue

Post by Johny » Mon, 25 Dec 2017, 12:21

Thanks for the offer Terry but I think the effort getting them to 60v would be a bit too much. I have recently bought a charger rated to 5 Amps and dialled down to 3 as a replacement to try and I think it'll be massively more reliable. I may just replace them as they fail and stop repairing the old ones.

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