High Eff DC Charging: Server PSU's Topic is solved

Development and discussion of fast charging systems eg Chademo , CCS etc
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AdvancedEnergySys
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High Eff DC Charging: Server PSU's

Post by AdvancedEnergySys »

Guys I would like your opinions on a couple different methods of charging using high output server power supplies.

1. https://www.ebay.com/p/1641499866
Involves a 12v c7000hp 2.4kw power supply that features power factor correction, 120-240VAC input, and are easy to separate the dc ground planes to wire in series for any multiple of 12V and 200+ amps. Is there any reason not to take advantage of a few of these in series and a Prius gen 2 boost/buck circuit OR utilizing the power factor corrected and smoothed 400VDC rectified mains in the same?

2. https://www.ebay.com/itm/1PC-Huawei-R48 ... .l4275.c10
This one is the interesting one however, it's a 52V 50A 3kw communications psu that feature canBUS control over the output voltage AND current! I imagine separating the ground planes for series operation should be straight forward and a simple canBus Arduino with some CC/CV code should be enough to charge at substantial rates.

I apologize if I'm committing any EV sins and I know legality in other countries may not make these methods practical but I am curious just for the sake of reasoning through the logic.
Thanks!
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Re: High Eff DC Charging: Server PSU's

Post by johu »

I'm using the second method with two 50V server supplies in series for charging a test pack. BMS controls charge current via CAN to stay below 3.6V per cell. For a typical 400V EV conversion I wouldn't deem it feasible as you'd need 8 modules.
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Re: High Eff DC Charging: Server PSU's

Post by bexander »

I have used the second method with 3pc of Eltek FlatPack 2 HE in series controled over CAN. Served me very well when I was using a 134V nominal battery pack.
Now I'm upgrading to a 360V battery pack and I will start by using a Prius Gen 3 inverter to charge.

A friend will soon test with 7pc of FlatPack 2 HE in series for a 360V pack..
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Re: High Eff DC Charging: Server PSU's

Post by Mouse »

bexander wrote: Mon Dec 21, 2020 3:01 pm I have used the second method with 3pc of Eltek FlatPack 2 HE in series controled over CAN.
I've got two Eltek Flatpak2 chargers I'm going to be using in an electric motorbike project. Would you be able to share any details of how you controlled them over CAN?
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Re: High Eff DC Charging: Server PSU's

Post by rstevens81 »

bexander wrote: Mon Dec 21, 2020 3:01 pm I have used the second method with 3pc of Eltek FlatPack 2 HE in series controled over CAN. Served me very well when I was using a 134V nominal battery pack.
Now I'm upgrading to a 360V battery pack and I will start by using a Prius Gen 3 inverter to charge.

A friend will soon test with 7pc of FlatPack 2 HE in series for a 360V pack..
Remember you could always connect the elteck chargers to the low side of the Prius DC DC and boost to 360v, which would probably be slot safer than non insolated boosting mains to battery voltage.

Note I really like the idea of using the Prius inverter as a charger, but it also really scares me that someone might have a terrible accident. The worst case scenario being someone electrocutes the postman as he brushes past your car to deliver that paper spam through the mailbox.
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Re: High Eff DC Charging: Server PSU's

Post by johu »

rstevens81 wrote: Fri Jan 15, 2021 10:03 am Note I really like the idea of using the Prius inverter as a charger, but it also really scares me that someone might have a terrible accident. The worst case scenario being someone electrocutes the postman as he brushes past your car to deliver that paper spam through the mailbox.
Yes it is very important in these setups (and also present in the schematics) that you have a GFCI in the car first thing. And also solidly ground the chassis to PE while charging. That way if there is an isolation fault to chassis the GFCI will trip and leave the postman alive.

I think Renault run a very similar charging arrangement supported by isolation management.
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Re: High Eff DC Charging: Server PSU's

Post by rstevens81 »

I am a huge fan of multiple points of failure.
You have probably worked out my deep fear is someone misses something critical from not understand and not reading properly.
I just don't want the actions of one person to force legislation that would prohibit what we are doing
I know it is a very fine line between inhibiting inovation and being cautious.
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Re: High Eff DC Charging: Server PSU's

Post by johu »

Of course. Maybe lets not dive too deep into that discussion again. Like everything here, inverter charging is just a piece of the puzzle, a possibility. You as a converter have to make sure to implement a legal system and follow good engineering practise. After all your work must be approved by the authorities anyway. For my Polo conversion I had to spell out every possible failure mode with non-isolated charging and the GFCI method was approved.
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Re: High Eff DC Charging: Server PSU's

Post by bexander »

Mouse wrote: Fri Jan 15, 2021 9:52 am
bexander wrote: Mon Dec 21, 2020 3:01 pm I have used the second method with 3pc of Eltek FlatPack 2 HE in series controled over CAN.
I've got two Eltek Flatpak2 chargers I'm going to be using in an electric motorbike project. Would you be able to share any details of how you controlled them over CAN?
Absolutely, see this thread:
viewtopic.php?f=17&t=1351
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Re: High Eff DC Charging: Server PSU's

Post by bexander »

rstevens81 wrote: Fri Jan 15, 2021 10:03 am
bexander wrote: Mon Dec 21, 2020 3:01 pm I have used the second method with 3pc of Eltek FlatPack 2 HE in series controled over CAN. Served me very well when I was using a 134V nominal battery pack.
Now I'm upgrading to a 360V battery pack and I will start by using a Prius Gen 3 inverter to charge.

A friend will soon test with 7pc of FlatPack 2 HE in series for a 360V pack..
Remember you could always connect the elteck chargers to the low side of the Prius DC DC and boost to 360v, which would probably be slot safer than non insolated boosting mains to battery voltage.

Note I really like the idea of using the Prius inverter as a charger, but it also really scares me that someone might have a terrible accident. The worst case scenario being someone electrocutes the postman as he brushes past your car to deliver that paper spam through the mailbox.
If you are using a isolated charger the AC input connector and cable from connector to charger will still be un-isolated so a short to car body will result in the same situation as with an unisolated charger. By using a isolated charger the chance of critical fault is somewhat reduced. However, the HV DC battery is more than capable of causing dangerous situations as well and the isolation in a charger is only between AC-side and HV DC battery. ALL chargers are isolated from AC to case (car body).
No matter what charger you are using, care must be taken as described by johu.
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Re: High Eff DC Charging: Server PSU's

Post by rstevens81 »

My point got somewhat confused (my fault)

If you already have the chargers, you can fix the pwm of the Prius inverter and boost it to 360v and you would benefit because the elteck chargers and the outputs would be galvanically isolated from the mains, with no actual cost, which just adds an extra layer of safety. There are quite a few of ways things can go wrong regardless of what charger is used, which always need to be considered. But I'm quite sure you know what you are doing.

I'm 99.9% sure I'm going to use a Prius charger in my set up, but would always hesitate to recommend it for the reasons stated above (which to be fair is a bad reason, but you can understand the reasoning)
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Re: High Eff DC Charging: Server PSU's

Post by bexander »

rstevens81 wrote: Fri Jan 15, 2021 7:18 pm But I'm quite sure you know what you are doing.
Well, people, including me, think they know what they are doing up to the point when something goes wrong and the opposite is proven... :)
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