After-build add-on Power Factor Correction

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Johny
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After-build add-on Power Factor Correction

Post by Johny »

For those who may have used chargers in their EV that are not PFC (Power Factor Corrected), I thunk a thought.

Since most of our chargers are switch mode and would accept DC input (consider carefully before trying), and PFC doesn't apply to DC, it follows that if an AC to DC device that supplied, say 340 VDC and a couple of kilowatts would immediately give you a PFC charging system.

So I searched for one.
Emerson make an 85 ~ 264VAC in, 380 VDC out (with adjustment down to 75%) that handles 4.2 Amps. (Model number AIF04ZPFC-01L)
Two of these in parallel (yes they are designed for this) would nicely give my cheap chargers PFC rating AND (maybe) local electrical authority rating at the same time.
Unfortunately the cheapest I can get them (digikey) is US$251.
Digikey link
Anyone know a less expensive alternative?

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coulomb
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After-build add-on Power Factor Correction

Post by coulomb »

Johny wrote: I thunk a thought.

Your thort provoked a thorny thort that has pricked me for a while.

Your scheme would have two switch stages; a PFC stage and a buck stage. So there would be an efficiency hit compared to some arrangement where you had just one switching stage.

But it's my belief that most PFC chargers are exactly like this anyway; the PFC stage produces some 400 V or so, which gets bucked to the battery voltage. All the smarts are at the back end (how much voltage and current to give the battery, for how long); the PFC stage just tries to maintain the DC bus voltage.

There is such a thing as a buck-boost converter. Suppose you have a 144 V pack charging at about 150 V; that's about the middle of the mains sine wave. So for about half the sine wave, you want to be boosting from low mains to battery, and for the other half, you need to be bucking down to the battery voltage.

I never seem to hear about this being done. Is it because it's inherently inefficient that way? And if it is, is it more inefficient than having two stages? There would also presumably be a cost benefit to having half the switching silicon and iron/ferrite.

Maybe it's because it's difficult to arrange for isolation this way, though it still seems possible to me. Besides, some chargers aren't isolated anyway.

Maybe it's because it's tricky to combine the needs of the front end (getting the current waveform the right amplitude and shape for maximum power factor / minimum distortion) and the back end (needing more or less current and/or voltage). But surely that's "just software".

Maybe this makes more sense with a higher voltage pack, so that the PFC stage is always boosting (so the pack would have to be over about 350 V, even when heavily discharged, or about half this figure for those parts of the world using 120 VAC). At this battery voltage, I don't see much difference between having the PFC stage maintaining 400 V across a capacitor bank, or maintaining 400 V across the battery. Of course, it needs to be a lot more precise about the voltage if charging the battery directly.

My apologies if this has been answered already; I could not find it in a quick search.
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Tritium_James
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After-build add-on Power Factor Correction

Post by Tritium_James »

Coulomb, a buck-boost converter has poor switch utilisation, making the silicon more expensive (around double) compared to a buck or a boost. This may be negated by the single stage instead of two.

An isolated buck-boost is a flyback converter. These have poor transformer utilisation (unidirection core excitation) so aren't any good for anything more than 50-100W.

antiscab
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After-build add-on Power Factor Correction

Post by antiscab »

Vicor Megapac modules usually convert 95-265vac to 400vdc

getting a big enough one cheaply enough is the real trick however.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
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bga
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After-build add-on Power Factor Correction

Post by bga »

The first question answer would have to be "Why bother?"
- It's only one EV charger.
- Do the utilities really care about one little ~2kW load that looks a lot like a few PCs?
Then after that,
Would a passive capacitor or inductor network work as a retrofit?

I bought a couple of Elcon chargers (two needed for 500+ volts), and the Elcon chargers are supposedly power factor corrected, although there have been a few negative comments about its effectiveness.


Here's a golden marketing opportunityImage
-----------------------------------------
Sell a box with likely looking (and cheap!) components in it to power factor correct your home. Just plug it into any 240VAC outllet and it magically reduces your electricity bill. Don't forget the flashing LED and never mind 3-phase or improbability.

The only trouble is that there are already several of these on the market and they'll sue for stealing their 'revolutionary' tricknology.

The tricknology would be would be how to zap the saps, thus proving P.T. Barnum's maxim that there's a sucker born every munite.

Some other Barnum quotes:
"Every crowd has a silver lining"
"Without promotion something terrible happens... Nothing!"
"Money is a terrible master but an excellent servant"




It's not the end of the world, but I can see it from here.

antiscab
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After-build add-on Power Factor Correction

Post by antiscab »

depends upon how many amps you are able to pull from a powerpoint.

the line impedance at the house I'm renting is 1.5 Ohms (single phase connection)

The ute chargers draw 2000W and 13.5A
the voltage at no load is 250V

raising the PF to 0.95 would drop the amps back to ~9A, or would allow me to draw more.

out of curiosity - what have you measured the PF of the Elcon chargers to be?
Mine have been 0.99 according to all my meters.
The RMS amps and volts look right for the power used:
on my Vectrix:
241V @ 5A is converted to 147V 8A

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

bga
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After-build add-on Power Factor Correction

Post by bga »

I haven't got them running yet.
I haven't even hacked for my application.

The comment was from a blog I read some time ago.
I probably won't investigate this unless it looks to be an issue.

0.99 is pretty good. -- is the solution to replace the ute charger with one of these?

For my own setup, I was thinking of running a 2.5sq mm out to the carport for a 15A outlet. This sould result in an approx 5V drop for a 15A load. Part of the plan is to also charge off a solar charged battery inverter so that pure solar power electrons can be used.
I have a Latronics 3KW inverter that seems to be very tolerant of lousy PF loads (it's an H bridge and big toroidal TX - very heavy) . I've only had it trip once in a couple of years -- and that was 200 watt fan that did it.
It's not the end of the world, but I can see it from here.

antiscab
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After-build add-on Power Factor Correction

Post by antiscab »

bga wrote:
0.99 is pretty good. -- is the solution to replace the ute charger with one of these?


unfortunately the voltage doesn't go high enough - max 417V

If I spend $1000 on two, I get a 3kw charger that I can't use in some places, at a charge rate thats too high for what I want to do.

I may use a cheaper chennic one and tap the DC bus though.

current plan is to use 12 x 60V e-crazyman chargers.

Matt

Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

bga
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After-build add-on Power Factor Correction

Post by bga »

I thought about this problem....

I opted for 2 x ELCON at 312V so that I could add some extra cells if needed. The 2000 watt was very close in weight and price to the 1500, so I went for the extra power.

The 2 Elcons should be able to draw 4000 watts on a cool day with suitably aligned planets. (312V each for a split charge of the battery)

This is obviously too much for a 10A outlet and slightly above the limit for a 15A outlet.

The Elcon chargers have an input line, unfortunately referenced to the negative battery output terminal, that can be used to control the device. Driving a voltage into this pin causes the charger to charge with linear region between 5 and 10V, I think, where the output current is proportional, so a POT can be used to control the charger.

The battery equalisation system I am using requires that the charge current be reduced to less than 800mA to allow the bypass shunt resistors to effectively remove fully charged cells from the charge circuit.

This is where the hack comes in.

In a floating multi-charger envionment, dealing with -ve lead referenced controls is hazardous to both fiddler and battery charger, so an opto-isolated interface that allows the control inputs to be referenced to chassis ground is needed.

At the lowest end, relays sense the contact closures and switch various resistors/POTs in to control the charger.

The intent was to make the car-side wiring simple with switch closure inputs to control the charger, probably as follows:
a) Global enable (start charging) - to BMS / clock
b) Force Low current (750mA output) - to BMS
c) High/Low set (15A / 10A input) - to charger plup

Maybe the RS232 control input on the Elcon can be wired (thru a microcontroller?) to allow real time control and monitoring of the charger. ???

It's best inside the charger, but in a box on the side is also OK and makes the charger easier to swap.
It's not the end of the world, but I can see it from here.

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After-build add-on Power Factor Correction

Post by bladecar »

Maate,

When you mention Vectrix, are you talking about the electric scooter? If so, can you rabbit on about it a little please with your thoughts, including the status of the company? If not, apologies to all. Greg

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After-build add-on Power Factor Correction

Post by antiscab »

yep, the electric scooter,

I have a few videos floating around:
http://www.youtube.com/playlist?p=PLCFDD8780E3FBEFD5

Lithium conversions are straight forward and relatively cheap
I can do up to 50Ah, 70Ah is possible soon (my own uses 60Ah cells).
only scooter I can get to do 100km @ 100kmh

the company was bought by gold peak, the battery manufacturer
they now manufacture lithium versions if you are willing to part with your first born.

Vectrix Australia vaguely exists, but not as part of Vectrix corp

visforvoltage.org is a gold mine

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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bladecar
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After-build add-on Power Factor Correction

Post by bladecar »

Hey Matt,
I have a second-hand Vectrix. It doesn't have a centre stand. It needs 2 tyres. Does yours have a centre stand? Who do you get to replace the tyres. It seems that it will not be easy. Any info will be good :)

Also, I'm not sure how to lock the steering (possible the steering lock is slightly stuffed or there's something I don't know about it. Thanks Greg

antiscab
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After-build add-on Power Factor Correction

Post by antiscab »

Hi Greg,

The centre stand was never released, Mik has bought one from overseas though.

It's not a standard feature though

Your local bike tyre place should be able to change the tyres,
I used tyres for bikes in Vic park for mine,

The front is straight forward enough,
for the back they looked at it and figured it out.

basically you unbolt the side that doesn't have the motor, once that cover is off you can take the wheel off the gearbox.


Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

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