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  #651  
Old 07-01-2012, 10:05 PM
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Default Re: 10kW / 60A DIY charger open source design

Last picture for awhile...

This gives a better idea of the overall design. It's meant to "stand up" like this with the fans blowing up. Dimensions of the enclosure are 7 1/8" x 10 1/4" x 10 9/16". The maximum dimensions with buttons, terminals and feet will be 8" x 10 1/4" x 11" (different shape but smaller in volume than a 4kw Elcon)



There will be about 1 1/2" between the fans and the bottom of the battery box where this will be mounted. Hopefully that provides enough airflow using a pair of 75-100cfm fans.
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  #652  
Old 07-02-2012, 06:35 AM
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Default Re: 10kW / 60A DIY charger open source design

Just mulling something around in my head here. Wouldn't it be possible to build the charger with a pfc front end for single phase and a rectifier / filter for 3 phase? Best of both worlds. Just feed the dc input of the buck stage from either source.
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  #653  
Old 07-02-2012, 07:29 AM
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Default Re: 10kW / 60A DIY charger open source design

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Originally Posted by jackbauer View Post
Just mulling something around in my head here. Wouldn't it be possible to build the charger with a pfc front end for single phase and a rectifier / filter for 3 phase? Best of both worlds. Just feed the dc input of the buck stage from either source.
Sounds ok to me, except you'd need a large switch, and you'd want to make sure that you never switched the high DC voltage while under load. So really for the few percent of efficiency that you gain, it would be easier to have the PFC stage there all the time, with six diodes on the input, and just feed into any pair of 3-phase inputs when you have single phase.

Huh, maybe you could put the six 3-phase diodes after the PFC stage, and arrange another diode so that DC doesn't get fed to the output of the PFC stage when you are using 3-phase. You'd want to be careful that you don't have a 3-phase plug of some sort that you could get a shock from when using single phase input; in theory the diodes would prevent current at the 3-phase inputs, but I'd bet there would be enough current from leakage and capacitance across the diode junctions to give a nasty shock.

The three phase filter would be between the 3-phase input and the 6-diode bridge.

So there are some safety / practicality issues to think through, but it might be doable.
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  #654  
Old 07-02-2012, 09:00 AM
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Default Re: 10kW / 60A DIY charger open source design

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Originally Posted by rwaudio View Post
Last picture for awhile...

This gives a better idea of the overall design. It's meant to "stand up" like this with the fans blowing up. Dimensions of the enclosure are 7 1/8" x 10 1/4" x 10 9/16". The maximum dimensions with buttons, terminals and feet will be 8" x 10 1/4" x 11" (different shape but smaller in volume than a 4kw Elcon)

There will be about 1 1/2" between the fans and the bottom of the battery box where this will be mounted. Hopefully that provides enough airflow using a pair of 75-100cfm fans.
Looks very nice! Thanks for the build photos. Edit: any reason one couldn't rotate that top panel 180 degree and mount it with the 7 1/8" dimension vertical (fins up)?

Last edited by tomofreno; 07-02-2012 at 09:05 AM.
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  #655  
Old 07-02-2012, 09:53 AM
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Default Re: 10kW / 60A DIY charger open source design

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Originally Posted by tomofreno View Post
Looks very nice! Thanks for the build photos. Edit: any reason one couldn't rotate that top panel 180 degree and mount it with the 7 1/8" dimension vertical (fins up)?
None at all, as long as some care was taken to make sure the display/switches don't interfere with the driver board, it's pretty tight in that area.

I will be bringing out the AC and battery wiring through the face that would become the bottom though, so it would probably be desirable to bring out the wiring through the display/switch side and engrave accordingly.

If doing that the 11" dimension would be reduced to 8 5/8 + fans.

This charger didn't exist when I designed my battery box and it was a late decision to go with it so my build is an adaptation to fit a very specific shape/size/airflow.

If I was designing an enclosure for a more mainstream flat mounting with heat sink up it would look quite different.
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  #656  
Old 07-02-2012, 04:11 PM
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Lightbulb Re: 10kW / 60A DIY charger open source design

From my simulations and experience, I can see that power factor correction, or PFC, is important, and perhaps even more so than I had originally considered. The problem is, essentially, that a single phase AC source has zero crossings during which time no usable power can be extracted. So, in order to maintain a constant output voltage (or current), energy must be stored.

Inductors store energy in the form of current and a magnetic field, so they are best used where a fairly constant current must be maintained. But their operation during times of near zero crossing of the power source involve inductive spikes and high voltages, and/or fast operating diodes and other semiconductors to handle this, or snubbers which can waste energy. Inductors tend to be expensive and heavy, especially for high currents and low frequency.

Capacitors are generally the preferred means of storing energy, and they are generally inexpensive and lightweight. They store energy in the form of voltage, so they are ideal where a fairly constant voltage is needed and where the load may draw surges of high current. But the storage of energy requires a high charging current during much of the higher voltage portions of an AC power supply, and without current limiting, the current can be extremely high and is limited mostly by the impedance of the power source and the capacity of the wiring and protective devices such as fuses and circuit breakers. These high current surges into capacitors cause current distortion and low power factor, which means that the current may be much higher than it would be for the same power resistive load.

There is an interesting article on PFC techniques I found at:
http://cktse.eie.polyu.edu.hk/Tse-IEEElecture2.pdf

I need to absorb some of that information and then maybe make some proposals on possible design improvements using PFC. I may need to rethink some of the suggestions I have made for using a simple inductor, and/or a precharge resistor.
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  #657  
Old 07-02-2012, 06:06 PM
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Default Re: 10kW / 60A DIY charger open source design

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Originally Posted by PStechPaul View Post
From my simulations and experience, I can see that power factor correction, or PFC, is important, and perhaps even more so than I had originally considered. The problem is, essentially, that a single phase AC source has zero crossings during which time no usable power can be extracted. So, in order to maintain a constant output voltage (or current), energy must be stored.

Inductors store energy in the form of current and a magnetic field, so they are best used where a fairly constant current must be maintained. But their operation during times of near zero crossing of the power source involve inductive spikes and high voltages, and/or fast operating diodes and other semiconductors to handle this, or snubbers which can waste energy. Inductors tend to be expensive and heavy, especially for high currents and low frequency.

Capacitors are generally the preferred means of storing energy, and they are generally inexpensive and lightweight. They store energy in the form of voltage, so they are ideal where a fairly constant voltage is needed and where the load may draw surges of high current. But the storage of energy requires a high charging current during much of the higher voltage portions of an AC power supply, and without current limiting, the current can be extremely high and is limited mostly by the impedance of the power source and the capacity of the wiring and protective devices such as fuses and circuit breakers. These high current surges into capacitors cause current distortion and low power factor, which means that the current may be much higher than it would be for the same power resistive load.

There is an interesting article on PFC techniques I found at:
http://cktse.eie.polyu.edu.hk/Tse-IEEElecture2.pdf

I need to absorb some of that information and then maybe make some proposals on possible design improvements using PFC. I may need to rethink some of the suggestions I have made for using a simple inductor, and/or a precharge resistor.
There is already a PFC version of the charger available, have a look at what Valery has already done with the design and perhaps there's some improvements you can recommend.
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  #658  
Old 07-06-2012, 06:46 AM
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Default Re: 10kW / 60A DIY charger open source design

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Originally Posted by mckemie View Post
I've been getting a bad feeling about my charger order. Here is the situation:
1) I placed an order and paid via PayPal April 18
2) I exchanged emails with Valery April 19
3) On April 20, I posed a few questions, including shipping date, but got no response.
4) On May 3, I queried again and did get a response which estimated shipping "next week".
5) On May 18, I sent another query asking for a delivery. And got no response.
6) Today, May 23, I called (650)-400-3591 and got a recorded message telling me "the mailbox is full".

I'll wait a couple of days more and see if PayPal can offer a remedy.
I did finally receive the charger a few weeks ago; mid-June, I guess. Charger seems to work, but I haven't thoroughly exercised it. I struggled to get the external wiring done. One of the problems is that the outside screw terminal strip is too small for the needed wire and lugs. Finally used 8ga for the battery side and 10ga for the ac side and filed down some lugs. When attached to the screw terminal strip, the wires are uncomfortably close to one another.

I wonder if the charger can be used as a DC-DC? I am experimenting using a surplus UPS to provide backup 240vac from my car battery. Typical battery voltage is 160v (48 cells) while the UPS apparently wants at least 167v. So, I wonder if the charger could be used to stepup 150-160vdc to 170-200vdc?
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  #659  
Old 07-08-2012, 04:52 AM
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Default Re: 10kW / 60A DIY charger open source design

the design is a Buck converter, which means the input has to be higher than the output.
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  #660  
Old 07-08-2012, 12:21 PM
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Default Re: 10kW / 60A DIY charger open source design

Quote:
Originally Posted by mckemie View Post
I wonder if the charger can be used as a DC-DC? I am experimenting using a surplus UPS to provide backup 240vac from my car battery. Typical battery voltage is 160v (48 cells) while the UPS apparently wants at least 167v. So, I wonder if the charger could be used to stepup 150-160vdc to 170-200vdc?
the PFC version can be rewired to do that since it has a booster stage inside, non-PFC version can't.

A couple of solutions I see:

1. Add a few cells to your car. Probably hard to do

2. Add an off-car 12V battery in series to your car's battery whenever you want to power your house with your car. Since the UPS is stationary, you can permanently mount the battery there and hook it up to a separate 12V charger that will keep the battery in charged state. If you size that 12V battery so that it has a higher capacity than your car pack, you will never completely run it down when it's in series with the pack. Note that your pack voltage won't be 160V under load - both due to the current draw and due to sag from dropping SoC. This will be especially important if your ambient temps drop below 10C. I would probably design for 2.9-3.0V cell voltage, which means you would have a shortage of 167-139V = 28V. Perhaps you could get away with 2 12V batteries.

3. Build a booster (similar design to the PFC stage of our charger). Most flexible but probably most expensive solution.

Thanks,
Valery.
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