400volt charger from server PSU's

Electric cars, trucks, ATVs, NEVs - things bigger than a motorcycle.
Post Reply
whereswally606   100 kW

100 kW
Posts: 1106
Joined: Jun 19 2011 2:11pm
Location: Cheshire, UK

400volt charger from server PSU's

Post by whereswally606 » Apr 26 2018 5:49am

Don't know if this is the best part of the forum for this but...

Copied and pasted from my rant post of Speakev.com

I retrospect I've been looking at ways to not be reliant on the rapid chargers. The was a chap from Metric mind in the US who put 3 Brusa chargers boosting his 3.3kw output of his 2011 leaf to 13kw needing not direct interface to the can network. He did a really nice job but not cheap. About £3-4k. Brusa now make a 22kw charger too, so that's also another expensive option.

Now, I wont do the following for several reasons. But... it is possible to buy very cheaply 12v server power supplies or ever 51.4v ones. which could be put in series to get higher voltages (if they have the DC grounds severed on all but one). (a lot of diy ebikers use such a setup to charge big packs) I have worked out you could use 5 or 6 server power supplies, link each to an 80v capable DCDC boost and the series the outputs to get near the voltage required by a Nissan LEAF. Then you might be able to use these instead of the purpose built Brusas. This however is forgetting all the safety concerns with High voltage and using things for which they were not initially designed, plus putting a lot of faith in cheaply built electronics

Has anyone done anything like this. Is there a reason that this might not be possible. Or advices to increase the safety of doing such a thing.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

kiwifiat   100 W

100 W
Posts: 109
Joined: Mar 16 2013 5:49pm
Location: Vancouver, Canada

Re: 400volt charger from server PSU's

Post by kiwifiat » Apr 26 2018 5:32pm

If I was doing this I would daisy chain four HP ESP120 2950W power supplies together after isolating three of them, hook the output up to a boost converter brick out of a gen2 prius inverter that can be had for as little as $100USD. A micro with a couple of simple control loops would yield a cheap ~12kW constant current/constant voltage lithium charger.

The problem is do you have four 230V mains lines that can supply 3kW each? I know in the UK a stove supply line will do 3kW but I expect the average three pin outlet wouldn't.
The only source of knowledge is experience.
Albert Einstein

whereswally606   100 kW

100 kW
Posts: 1106
Joined: Jun 19 2011 2:11pm
Location: Cheshire, UK

Re: 400volt charger from server PSU's

Post by whereswally606 » Apr 27 2018 4:29am

Yep got one esp120, interesting about the prius booster that's a good plan.

I figured all I would need to find is a 32amp capable 230v ac outlet, run all four chargers off of that via a 4 four way to some IEC kettle lead type plugs. The aim here is to be able plug into either a 32amp commando socket or a L2 charge point which could do 22kw.

I also thought in my original design idea all my boost convertors have current limiting so I could externalise the pots on all of them and trim them down on the fly to keep under the limit of what I'm hooked up to.

This is all hypothetical btw but I just want to keep my mind open to this for the future.

Thanks for the contribution KIWIFiat
one thing I'm a little skeptical is whether a prius inverter can boost to the 400v a Leaf battery needs. The Prius battery is really half the voltage of the Leaf one.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

kiwifiat   100 W

100 W
Posts: 109
Joined: Mar 16 2013 5:49pm
Location: Vancouver, Canada

Re: 400volt charger from server PSU's

Post by kiwifiat » Apr 27 2018 1:49pm

You can't get more than 7360W out of a 230V 32A socket so you would need multiple lines to achieve over 10kW. You are wise to be skeptical about everything you read on the missinformation superhighway. The Oak Ridge National Laboratory report on the 2004 Prius provides the following data on the Prius boost converter:
Prius_Boost_converter.PNG
500V at over 96% efficiency with an input voltage of 233Vdc and power out ~20kW, should do the trick.
The only source of knowledge is experience.
Albert Einstein

Punx0r   10 GW

10 GW
Posts: 4867
Joined: May 03 2012 8:16am
Location: England

Re: 400volt charger from server PSU's

Post by Punx0r » Apr 28 2018 8:25am

Domestic supply in the UK is usually single phase 240V @ 100A (24kW) so you shouldn't have trouble running a ~12kW charger. A typical cooker/stove circuit is 32A (7.7kW), same as the wall sockets ringmain, but it's quite normal to run a 50A feed for a ~10kW electric shower.

I can't shake the feeling that there might be something sketchy chaining together PSU or individual dc-dc converters to get ~400V. Cutting the safety ground seems risky even how it's normally done, but this is at a higher voltage. Also, can the output stage components rated for the voltage? Is isolation sufficient? Unless I'm mistaken last PSU in the chain is going to have a potential between its output and ground several times it would normally have when run on its own?

Ianhill   100 kW

100 kW
Posts: 1412
Joined: Sep 25 2015 5:55pm

Re: 400volt charger from server PSU's

Post by Ianhill » Apr 28 2018 7:38pm

Sockets in the UK come in 2 flavours a radial circuit fused at 16amp, then a ring circuit fused at 32amp this allows around 7400watt to flow on the circuit depending on the frequency and voltage on the grid for the day. But never more than 16amp from a single outlet so a dual socket can supply the full 32amp on its own of its in a ring circuit.

Showers and cookers use larger radial circuits typically 10mm cable with 4mm earth on a 45amp breaker giving upto 10.8kw max on a single circuit.

It looks to me like 2 radial circuits would be minimuim of what is needed on separate 45amp breakers with 2 10mm cables to form two separate radials.

Typically the tail's coming into the house are 16mm and top out around 80-100amp on the fused connection to the grid this depends in if your supply is TT (earth rod) tns tncs (neutral separate or combined separate on the sheithing of the armour cable).

But in truth this is unrealistic if you can not get three phase your going to be looking at massive voltage drop at the distribution board when that is turned on you will be able to watch any incandecent lights go dimmer it's like having your shower and cooker full pelt all at once it can cause a spike again not good.

I'd imagine the output across the last supply will only be that of its own output like a battery only sees it own voltage but the insulation to the first would need to be considered there's 400volts at play so no leakage path though yourself to ground or its big time game over dc is a nasty way to go holds you in it my foreman had a egg in the palm of hand from a dc circuit loads of skin grafts and massive lump of cooked inners left.
Last edited by Ianhill on Apr 30 2018 10:48am, edited 2 times in total.

User avatar
JoeG   10 mW

10 mW
Posts: 32
Joined: Feb 04 2009 10:53am

Re: 400volt charger from server PSU's

Post by JoeG » Apr 30 2018 9:47am

I charge my 91 Geo Metro EV (14kw lithium pack) with Meanwell PSU's and one thing I found out was that in America at least, device & circuit ratings are not for continues use. You can only pull 80 percent of a devices rate current continuously, and when doing so, wires & connectors get warm. I have charged my car on a 30A circuit for 4 years now pulling 22A at 240V (5kw) with no issues, but like I mentioned earlier, things get pretty warm. I use an infrared temperature gun to verify everything is working safely. Each component has a temperature rating, & you need to stay below it for it to survive.

whereswally606   100 kW

100 kW
Posts: 1106
Joined: Jun 19 2011 2:11pm
Location: Cheshire, UK

Re: 400volt charger from server PSU's

Post by whereswally606 » May 02 2018 2:42am

I've experienced the same thing trying to charge the leaf of the 2kw brick and a long extension. When I came to unplug the socket was noticeably warmer.

I was more thinking that I would use the 7kw Level 2 capable sockets usually there are two side by side. That should give me 14kw.(I don't think id ever leave my car when doing this type of a charge.) But realistically this is a project I will probably never get to do. Tesla outlets can give out 22kw and 11kw but I don't know that I could find the handshake protocol for that connection, and suspect the monitor their outlets pretty closely for any non tesla owners trying to connect.

Anyway thanks everyone for the input, enlightening
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

Ianhill   100 kW

100 kW
Posts: 1412
Joined: Sep 25 2015 5:55pm

Re: 400volt charger from server PSU's

Post by Ianhill » May 02 2018 1:11pm

There's a guy named Damien maguire from Ireland he has hacked the gen2 and gen3 tesla inverters it maybe worth getting in touch with him for a spot of advice, he has some great videos on YouTube showing how to enable them he uses an external logic board to grab basic data from them it would be nice to see the stock logic board hacked to communicate it's can data.

I'd love to build an EV, he is doing a budget build to show that the cost don't have to be mental he is doing a cheap brushed build, diy controller and salvaged lithuim pack, not sure on the specs but he is aiming for a cruise of 70mph with 40miles range for €1000 total cost even if he breaks it buy a few quid it's still impressive, I'd have to go the induction route for some good rpm or try and make a light Robin reliant 3 wheeler with an ipm motor from a zero Sr something whacky.

whereswally606   100 kW

100 kW
Posts: 1106
Joined: Jun 19 2011 2:11pm
Location: Cheshire, UK

Re: 400volt charger from server PSU's

Post by whereswally606 » May 03 2018 3:43pm

I'm subbed to him already, yeah he seems a decent chap with his heart definitely in the right place. Getting parts second hand cheap ain't always that easy. Evmotorwerks got back to me on a kit for 12kw at about $1450 or half of the assembled cost. That's still lots more than 4 esp120s and a 2gen Prius inverter. But a hell of a lot smaller.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

kiwifiat   100 W

100 W
Posts: 109
Joined: Mar 16 2013 5:49pm
Location: Vancouver, Canada

Re: 400volt charger from server PSU's

Post by kiwifiat » May 03 2018 9:13pm

The prius boost converter is surprisingly small, the linked picture gives an idea of scale if you are familiar with a scope probe.

Image

The image is from N Kirkby's blog: http://www.nkirkby.net/how-to-turn-on-t ... er-module/
The only source of knowledge is experience.
Albert Einstein

Post Reply