OK I'm confused!

How do you store and manage your electricity?
Post Reply
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

OK I'm confused!

Post by Paul9 »

Hi people,

I have been charging with a new KPS 2000 charger which is fairly obviously a 2kw charger. 2kw divided by 240 volts means a roughly 8.33 amp draw. I then noticed my 10 amp extension lead was getting very hot. I bought a power meter and took some measurements. According to the power meter the charger was drawing:
1,787 watts,
236 volts and
10.28 amps.

Of course 10.28 amps x 236 volts = 2,426.08 watts which is nowhere near what the power meter read - 1,787 watts.

At the same time my TBS-Pro said the charger was puting 12 amps at 141 volts DC into the battery bank. Equals 1,692 watts. With an inefficiency factor of about 10 - 15% this figure of 1,692 watts is what I would expect from a 2,000 watt charger.

I assumed the power meter was defective in some way as 1,787 watts divided by 236 volts gives a amp draw of 7.572 NOT 10.28 amps.

So I bought another power meter from a different manufacturer in case I received another defective power meter.

The new power meter said the charger was drawing from the wall as follows:
1,771 watts
235.7 volts
10.20 amps.

These figures agreed almost exactly with the first power meter! And the TBS-Pro figures agreed with the first power meter readings.

My confusion stems from how can two different power meters come up with almost exactly the same figures and both be wrong? I wonder if maybe the amp reading is correct (as the lead gets very hot) and the wattage reading is wrong?

Could somebody please explain what I am missing?

Thanks in advance
Paul
User avatar
brendon_m
Senior Member
Posts: 742
Joined: Sat, 28 Oct 2017, 11:00
Real Name: Brendon McCarrol

Re: OK I'm confused!

Post by brendon_m »

What's the power factor? It is probably reading in Watts and you are working out kVA
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

By power factor I assume you mean the inefficiency of the charger. The charger normally sends 85 to 90% of the power it receives into the battery bank.

My confusion is with the readings on the power meter itself before the power even gets to the charger.
antiscab
Senior Member
Posts: 2706
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: OK I'm confused!

Post by antiscab »

power factor is a measure of how much the AC amps are in phase with the AC voltage.
you can have a very efficient charger (watts out/watts in) with a very bad power factor (watts out / AC amps x AC volts)

you just have a cheap charger with no power factor correction
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
User avatar
brendon_m
Senior Member
Posts: 742
Joined: Sat, 28 Oct 2017, 11:00
Real Name: Brendon McCarrol

Re: OK I'm confused!

Post by brendon_m »

I have a charger here that draws 8A @240V which makes it close to 2000W but it's not actually 2000W it's closer to 1000W. Its power factor is woeful so it's not 50% efficient its actually 90% efficient and the amps are lagging behind the volts. Ie the 8 amps are not flowing when the voltage is at 240V. When the line voltage is at 240V there is only a few amps coming out of the wall then as the voltage starts to drop off as it goes through the cycle the amps keep flowing and peak at 8A. So overall there's ~ 1000W of energy going into my charger but the peak amps and the peak volts are not simultaneous.

As a side note the amps peak can come first and then the voltage peak or the other way round. It just depends on whether it's an inductive load or capacitive. A resistive load would have the amps and volts peak at the same time
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

Ok guys I think I understand. It is not simply volts times amps equals watts? There is more to it than that?
antiscab
Senior Member
Posts: 2706
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: OK I'm confused!

Post by antiscab »

Paul9 wrote: Thu, 12 Mar 2020, 14:58 Ok guys I think I understand. It is not simply volts times amps equals watts? There is more to it than that?
for AC yes, there is more to it than volts x amps.

If you do volts x amps on a microsecond basis, and add it all together, you get the real power.

https://en.wikipedia.org/wiki/Power_factor

your charger should have near perfect displacement power factor (amps should peak at the same time as volts).
The problem is the amps waveform is not sinusoidal (doesn't match the voltage waveform in shape).
basically the charger only draws AC amps when the AC voltage is above the DC bus voltage, which generally only happens when the AC voltage is near the peak of the curve (above 300v)
This is the case for all powersupplies with a rectified DC bus.
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
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

Thanks guys I am starting to understand.
User avatar
coulomb
Site Admin
Posts: 4403
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Re: OK I'm confused!

Post by coulomb »

Paul9 wrote: Thu, 12 Mar 2020, 11:49 I then noticed my 10 amp extension lead was getting very hot.
That's why power companies hate poor power factor: it heats the cables without delivering the goods!

Better quality chargers will have a "Power Factor Correction" stage. That's a bit of a misnomer, but it does make the charger draw 0.99 or higher power factor, But it adds cost: a PFC chip, one or two MOSFETs or IGBTs, a high frequency inductor and a handful of small components. So the cheaper chargers skip that stage and just use a $2 diode bridge. Smaller chargers can get away with that (except in Europe), but 2000 W should really be unity power factor.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

Thanks coulomb
The chargers I use are KPS (KingPan) but it is not because they are the cheapest I could find. They are half the size and half the weight of the Elcon chargers of the same wattage. Size and weight are both important factors when fitting components into a small Suzuki Swift.

The KPS chargers are also open at both ends. One end has large exhaust fans and the other end has open vents to allow air into the charger. This keeps the KPS chargers much cooler than the Elcon chargers of similar power ratings.

I have also blown up more than one charger! I would rather blow up a $500 AUD KPS charger than an $1,800 AUD Zivan charger.

Thanks to all you guys.
Cheers
Paul
User avatar
Bryce
Senior Member
Posts: 415
Joined: Sun, 13 Jun 2010, 16:54
Real Name: Bryce Gaton
Location: Melbourne

Re: OK I'm confused!

Post by Bryce »

Hi there - I would also check the conductor size in your '10A lead'. They have been downsized over the years as manufacturers cut costs to the nth degree.
You need at least 1.0mm2 conductors to carry 10A continuously for a long period of time (preferably 1.5mm2), but many so-called 10A leads are now as low as 0.75mm2.

Cheers
Bryce
Current EV drive: 2019 Kona electric
Also in family: 2019 Renault Zoe
Past drives: 2011 Blade Getz, 2011 Leaf, 2001 Citroen Berlingo conversion
Past Conversions: DC Berlingo, AC Berlingo, AC Sprinter
antiscab
Senior Member
Posts: 2706
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: OK I'm confused!

Post by antiscab »

the new elcon chargers are about 1/4 the size now.

The zivans also have pretty bad power factor.

How have you blown up chargers?
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
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

Thanks guys

I have tried the new smaller Elcon chargers, Neither worked. In a previous thread back in August 2017 I listed some of the problems I had with the new Elcons. i quote it here so you don't have to go hunting for it:

"First problem is that the connectors are 4 pin, pin and socket connectors. The female connectors do not fit snugly onto the male connector - they wobble!

Secondly the female lugs that go into the female connector don't stay in. If you turn the female connector upside down the lugs (and any wire attached to them) fall out of the connector. These lugs are also very thin. Less than 2mm in diameter. Don't drop them on the garage floor as, if your garage looks like mine, you will never find them. And TC only give you 8 pins in total - no spares.

Thirdly, neither the female connectors nor the lugs that go in them are available in Australia. I have tried some online stores suggested to me by "Coulomb" and they have advised they do not have them.

Fourthly the User Manual is less than clear in regard to which hole in the female connector receives which wire. Emails with "Coulomb" and a number of emails to TC in China have, I think, cleared this up.

As a result of the above I managed to blow one of the connectors up (the DC OUT connector). A loud bang accompanied by a large shower of sparks and melted lugs was the result. Despite being very careful that the right wire went in the right hole, I may have stuffed up my connecting somewhere, so I am not laying all the blame necessarily on the charger. End result is one stuffed $1,000AU charger.

I have been told persistence is a virtue so today I got out the other new charger and wired it up without the female connectors and insulated the living daylights out of all the wires. I powered the charger up and it just sat there. The fan didn't spin and no LED lights. But I had achieved something - no explosion! About the same reaction as if I had wired up a house brick."

I blew up two chargers (one Elcon and one KPS charging simultaneously) at a public charging station but was doing my shopping when this happened and therefore cannot tell you the cause. The new Elcon above blew, I suspect, because the negative and positive pins are so close together that there may have been a short between the two pins(?)

And just recently my mate was re-arranging wires on a KPS 2000 and heard a bang and got smoke from the charger and it hasn't worked since.

I think it is just me and chargers don't get along!

Thanks
Paul
antiscab
Senior Member
Posts: 2706
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: OK I'm confused!

Post by antiscab »

good grief.
I had a similar experience with the connectors from 3.3kw TC Charger. - I had 2 of the wires transposed, and thus shorted.
fortunately I picked this up due to failed pre-charge, and was able to fix it without incident

the 6.6kw chargers have different connectors - jonescg how did you find those?

Oh - Paul you can re-use the PFC front end from dead elcon/TC Chargers for use with other chargers.
The PFC front end is dumb, it just tries to hold the DC bus at 390vdc or so, no matter what.
If you're keen you could harvest it
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
User avatar
jonescg
Senior Member
Posts: 3706
Joined: Thu, 21 Jan 2010, 23:05
Real Name: Chris Jones
Location: Perth, WA.

Re: OK I'm confused!

Post by jonescg »

Yes the new TC chargers are good. The connectors are high quality Amphenol kit and they work well.
Liquid cooling is well worth it, if you can plumb it into the car.
AEVA National Secretary, WA branch chair.
T1 Terry
Senior Member
Posts: 1173
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: OK I'm confused!

Post by T1 Terry »

This is one of those strange things I've discovered over the yrs. Inverters and generators that put out a modified sine wave (that often isn't much better than a square wave) seem to work very well with dumb non power factor rectified chargers. Before DC to DC chargers came down in price, we often used cheap 1000w modified sine wave inverters powered from the vehicle battery with a cheap 12v charger plugged into that to charge the caravan battery while driving. The chargers were marked as 40 amps, but they often put out 50 amps or close to it from the cheap inverter, yet maybe 38 amps when plugged into the mains or a quality generator like the Honda inverter range.

T1 Terry
Green but want to learn
Paul9
Groupie
Posts: 293
Joined: Mon, 20 Apr 2009, 02:10
Real Name: Paul Coggiola
Location: Sydney

Re: OK I'm confused!

Post by Paul9 »

Ok people I am about to sort of hijack my own thread.

Since I blew my first charger I have had an idea as to how chargers may be made more reliable. I always dismiss this idea until I blow my next charger and the idea resurfaces. It appears to me, from my own experience and comments made by other people, that chargers are the most frequently failed components in a DIY EV. I remember “bladecar” responding to comments in another thread of mine that one of the main reasons he stopped producing his cars was because of the unreliability of chargers.

So I wondered if it would be possible to build an “Australian” charger by starting with a Chinese charger and replacing the most commonly failing components with parts available in Australia?

I assume you know about the Pareto Principle or the 80/20 rule? It applies to businesses wherein 20% of the products account for 80% of the sales. Or sports teams where 20% of the players account for 80% of the points the team scores. The rule applies in many areas of life. The same rule may apply to battery bank chargers?

What if roughly 20% of the components in a charger account for 80% of the failures? I have absolutely no idea of the answer to that question but I am sure there are people on this forum who are well qualified to answer that question?

If the above is true (?), what if replacing the most “unreliable” components increased the cost of the charger by, say, 40%(?). If true, then I would have a charger that cost 40% more but is 5 times more reliable. Sounds like a good alternative to the chargers I have been buying over the last 10 years!

The above contains plenty of “what if”s and question marks. I readily admit I do not know whether any of the assumptions I have made above are valid.

I also have ideas as to how the above may be achieved if all the assumptions are correct but I will leave that until I learn the validity of the above?

Thanks
Paul
Post Reply