# [EVDL] EV Charger Isolation



## EVDL List (Jul 27, 2007)

I have no idea whether most commercial chargers are isolated or not,
but there are ways to do it that are probably cheaper than a huge
isolation transformer. They can use a high-frequency (20kHz-200kHz)
transformer; because of the higher frequency, it doesn't need to store
as much energy at once, so it can be smaller and lighter transformer.
However, it needs better/more expensive materials so that it doesn't
have lots of loss at higher frequency.

First, you convert to DC, non-isolated. Then, you use a DC-DC
switched-mode power supply like a flyback converter, forward
converter, push-pull converter, or one of many others. These convert
DC to high-frequency AC (often square wave), put that through the
high-frequency transformer (which often has 3 or more windings for
things like sensing and removing DC bias), and convert to isolated DC
on the other side.

I'm not what most commercial chargers use for their isolation, if they
use anything.

-Morgan LaMoore

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## EVDL List (Jul 27, 2007)

Hello Dave,

My charger which is a PFC-50 is not isolated, so I made the EV electrical 
system isolated to the EV frame.

Install the battery charger in a glass non conductive compartment and fan 
pressurize it. Only the battery charger chassis is grounded.

Install the batteries in a glass non conductive enclosure and applied a fan 
exhaust of about 100 to 150 cfm heavy duty exhaust duct work.

Install all chassis plates, contactors, relays, terminal strips, circuit 
breakers and fuse in a glass non conductive enclosure, which also has a 
positive fan pressure.

Install the controller and related equipment in a glass or plastic water 
tight enclosure which also has a positive fan pressure.

All fans and blowers have a air filter attach to the inlet.

Install two safety contactors between the batteries and the main contactor 
and controller, so the battery charger voltage is not in connection to the 
main contactor, controller and motor while the batteries are charge.

If you need to charge other than the normal place you charge, than there 
should be a onboard GFCI circuit breaker between the input plug and the 
battery charger and any other tap off circuits.

The input AC plug and connector should be a isolated type, meaning the 
ground bar in the connector and plug should not be self grounding to a metal 
shell. It is prefer to use a nylon connector and plug.

I do not use a metal male receptacle connected to the EV. It is a water 
tight in line plug connector, that is design to fit into a deep aluminum 
water tight housing made by Power Anderson, normally use for a 200 amp 4 
wire power connectors.

If you only do charging at one central charging station which is normally at 
home. Then use a GFCI circuit breaker in your panel and lay down one of 
those vinyl garage floors for the EV to sit on.

Test the voltage leakage of the battery post to the battery enclosure 
surfaces and to the EV frame while charging. If you read any voltage that 
is greater than that one battery, then its time to clean the battery pack, 
no matter how clean they look.

If your EV is none of the above, you could go to a savage company to try to 
find a dry type transformer that has duel primary windings and duel 
secondary windings. The primary will normally be two pair of 240 volt 
windings and the secondary will be two pair of 120 volt windings. The 
transformer should be at least a 15 KVA rating.

To make this a isolated one to one ratio transformer, connected the primary 
240 volt leads in parallel and the secondary 120 volt leads in series which 
will be a 240 output. If you need 120 volt output, then connected the 
secondary 120 leads in parallel.

Only connect the input circuit ground wire to the housing, but do not 
connected any secondary ground wire to the chassis. To develop a grounding 
circuit, connected the ground wire to any one of 120 volt lines if you are 
using a 120 volt secondary.

If you are using a 240 volt secondary, which the two 120 volt leads are 
connected together in series, then tap the ground wire at the junction that 
ties the two 120 windings in series. This is how a ground circuit is 
develop at a transformer for a building service entrance.

A new shield floor mounted single phase transformer that is rated at 240x480 
primary and 120/240 secondary 60 hz 15 kva or about 15000 watts/240 volts = 
about 62.5 amps which could be use on a 50 amp circuit drawing about 40 amps 
continuous normally cost $1500.00 whole cost.

Roland




----- Original Message ----- 
From: "Dave Delman" <[email protected]>
To: <[email protected]>
Sent: Tuesday, November 13, 2007 8:19 PM
Subject: [EVDL] EV Charger Isolation


> Are all/most commercial EV Battery Chargers isolated? If so do the usw a 
> big isolation transformer or is there another method?
>
> Thank you,
>
> Dave Delman
> Sent via my Treo700p
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

Hi Dave,

The commercial (OEM) EVs all had an isolation in the
form of an inductive charger (a coil sending high
frequent energy via a paddle into a recepticle on the car) 
but all practicle systems you can buy today are conductive,
meaning that they use wires and a connector to hook up the
charger to the car.
Most all are not isolated, because the battery pack itself
is isolated from the car already, so there is nothing to
be gained by isolating the charger, except the corner cases
where someone opens the battery box while charging and those
cases, plus the cases of damaged charger wiring and connector
can safely be dealt with using a GFCI (Ground Fault Current
Interrupter, a device that acts as a breaker and opens when it
sees that a small amount of current is "lost" in the circuit
it protects, which means that there is a leak to ground.)
You will find GFCI on outlets in wet areas in and around the
house, though there are EV'ers who prefer to plug into a
non-GFCI outlet because they have experienced "nuisance trips"
where due to dirty batteries the current to the vehicle ground
(chassis) and to the earth became large enough to trip the GFCI
without being a danger, resulting in an uncharged vehicle.

So, the charger usually is not isolated and does not need to be
to be safe, as long as your batteries are not easily accessible
while the vehicle is charging.
A safe installation connects the car chassis to the earth ground
and a second safety is to use a GFCI in the power wires (either
120V or 240V) so it will detect any irregularity and disconnect.

Hope this clarifies,

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Dave Delman
Sent: Tuesday, November 13, 2007 7:19 PM
To: [email protected]
Subject: [EVDL] EV Charger Isolation

Are all/most commercial EV Battery Chargers isolated? If so do the usw a big isolation transformer or is there another method?

Thank you,

Dave Delman
Sent via my Treo700p

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## EVDL List (Jul 27, 2007)

HF transformers are actually far cheaper than an equivalent transformer 
at 60Hz. Laminations and copper wire are expensive!

HF transformers do require more design time and more knowledgeable 
engineers, and in general the device needs to be designed around the 
specific application as opposed to a using general purpose off-the-shelf 
part.

Danny



> Morgan LaMoore wrote:
> 
> >I have no idea whether most commercial chargers are isolated or not,
> >but there are ways to do it that are probably cheaper than a huge
> ...


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## EVDL List (Jul 27, 2007)

AFAIK, all of the EV chargers which have regulatory approval (UL, CSA, etc.) 
and are sold to OEMs are fully isolated from the power line. Some of them 
are boat-anchor types such as the venerable Lesters. More modern ones such 
as Brusa, Zivan, and Delta-Q are lightweight high-frequency switcher types.

I think this is probably a liability issue as isolation improves the overall 
safety profile of the charger. Fitting your EV product with a charger that 
has the logos one expects on a commercial device removes one more potential 
point of liability. 

I'd hate to be the engineer who designed a forklift or burden carrier, 
sitting on the witness stand as the plaintiff's attorney asks me whether I 
chose a UL approved charger for the product, and if not, why not.

However, the EV chargers which are popular with EV hobbyists (which 
describes most members of the EVDL) tend to be non-isolated because it's 
appreciably cheaper to manufacture such a charger. They give you more bang 
for the buck (oops, pun not intended ;-). AFAIK, none of them is currently 
UL or CSA approved. One popular brand doesn't even come with a built-in 
GFI; you must add one externally (I wonder how many users really do). 

These are pretty much an at-your-own-risk proposition. The size of that 
risk is the subject of some controversy here, but I don't think anyone would 
argue that unisolated chargers are safer than isolated chargers.

David Roden
EVDL Administrator
http://www.evdl.org/


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## EVDL List (Jul 27, 2007)

Hey Dave, I plug mine into a GFCI outlet since most outdoor outlets are
such. The ones in my garage are also. So count one for me 

But I won't argue with you. Your point is valid.

Mike Willmon

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of David Roden (Akron OH USA)
Sent: Tuesday, November 13, 2007 9:29 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] EV Charger Isolation

AFAIK, all of the EV chargers which have regulatory approval (UL, CSA, etc.)

and are sold to OEMs are fully isolated from the power line. Some of them 
are boat-anchor types such as the venerable Lesters. More modern ones such 
as Brusa, Zivan, and Delta-Q are lightweight high-frequency switcher types.

I think this is probably a liability issue as isolation improves the overall

safety profile of the charger. Fitting your EV product with a charger that 
has the logos one expects on a commercial device removes one more potential 
point of liability. 

I'd hate to be the engineer who designed a forklift or burden carrier, 
sitting on the witness stand as the plaintiff's attorney asks me whether I 
chose a UL approved charger for the product, and if not, why not.

However, the EV chargers which are popular with EV hobbyists (which 
describes most members of the EVDL) tend to be non-isolated because it's 
appreciably cheaper to manufacture such a charger. They give you more bang 
for the buck (oops, pun not intended ;-). AFAIK, none of them is currently 
UL or CSA approved. One popular brand doesn't even come with a built-in 
GFI; you must add one externally (I wonder how many users really do). 

These are pretty much an at-your-own-risk proposition. The size of that 
risk is the subject of some controversy here, but I don't think anyone would

argue that unisolated chargers are safer than isolated chargers.

David Roden
EVDL Administrator
http://www.evdl.org/


_______________________________________________
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## EVDL List (Jul 27, 2007)

> Dave Delman wrote:
> > Are all/most commercial EV Battery Chargers isolated? If so do the
> > use a big isolation transformer or is there another method?
> 
> ...


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## EVDL List (Jul 27, 2007)

The 96 Volt Delta-Q charger in my VW is isolated, very small and sealed. It 
is totally quiet too, unlike the Lester in the Citicar. I do nothing but 
plug in the car and leave it until I remember to unplug it sometime the next 
day. It is quite self-sufficient, turns itself off when it is done.

Gail
----- Original Message ----- 
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, November 16, 2007 7:27 AM
Subject: Re: [EVDL] EV Charger Isolation




> > Dave Delman wrote:
> >> Are all/most commercial EV Battery Chargers isolated? If so do the
> >> use a big isolation transformer or is there another method?
> >
> ...


----------



## EVDL List (Jul 27, 2007)

Where did you get a 96V Delta-Q charger???? I only see up to 72V on
their website.

De



> Gail Lucas <[email protected]> wrote:
> > The 96 Volt Delta-Q charger in my VW is isolated, very small and sealed. It
> > is totally quiet too, unlike the Lester in the Citicar. I do nothing but
> > plug in the car and leave it until I remember to unplug it sometime the next
> ...


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