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  #11  
Old 06-19-2012, 07:55 PM
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Default Re: [EVDL] ac box

Willie,

As Roger said, 1V drop at 50A is 50W, which will cause quite a bit of heating.

I use this 8AWG wire for various projects in my lab; it's very
flexible and easy to work with:

http://www.powerwerx.com/wire-cable/power-wire-automotive.html

-Morgan LaMoore

[quote] Willie McKemie <xxx@xxx.xxx> wrote:
> ...
> They don't say anything about wire heating; I wonder if that is an
> issue.
>
> I think wire gauges larger than 10 will be too difficult to manage for
> my purposes.
> ...

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  #12  
Old 06-19-2012, 11:55 PM
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Default Re: [EVDL] ac box

You have to de-rated any conductor to 80% of the ampere rating of the
conductor of the actual ampere load.

For example: A single stranded copper No. 12 AWG wire on a 20 amp circuit
breaker is rated for 16 amps with acceptable voltage drop.

A single stranded copper No. 10 AWG wire on a 30 amp circuit breaker shall
have no more than 24 ampere load on it.

A single stranded copper No. 8 AWG wire on a 40 amp circuit breaker shall
have no more than 32 ampere load on it.

And a single stranded copper No. 6 AWG wire on a 50 amp circuit breaker
shall have no more than 42 ampere load on it which is to protect a thermo
circuit breaker from overheating.

A single stranded copper No. 6 AWG wire rated at 90 C. has a 55 ampere
rating on a 60 ampere circuit breaker will be require for a 50 amp in and
out as you stated.

Now if you bundle these single stranded copper wires in three or more wires
in a cable, you have to de-rated the rated current carrying another 20%.

Example: the No 6 stranded copper wires that are rated at 55 amps on a 60
amp circuit or 55 x .80 = 44 amps for a conductor length of 50 feet. If
your length is about 25 feet of conductor, than your maximum ampere is about
49.5 amps or as close to 50 amps as you want with a voltage drop range
between 1 and 3 percent.

Your breaker size shall be 1.25% over the actual current rating of the
conductor and the conductor shall also be 1.25% over the rating of the
conductor.

There should be at least 2 inches of space around the size of a 2-pole AC
contactor that will have a actual 50 amp load should be rated for 60 amperes
which will be a definite purpose AC contactor. The size of these contactors
are about 2.5 inches wide by 3.5 inches high by 3.75 inches deep.

The enclose for this type of contactor should have at least 1.5 inches on
each sides of the contactors, making the enclosure size 5.5 inches wide by
7.5 inches high. You could get by with a 6 inch wide by 8 inch high by 4
inches inside depth.

Roland





----- Original Message -----
From: "Willie McKemie" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Tuesday, June 19, 2012 8:57 AM
Subject: [EVDL] ac box


> I'm about ready to re-configure my ac wiring and relay for my new 10kw
> charger and I need to find a box, probably suitable plastic, to house
> the relay, power supply for the relay, and related stuff. Up to 50 amp
> 240vac going in and up to 50 amp ac going out. Also, low power up
> 240/120vac relay signal going in and out. Something like 8"x6"x4", I
> think. Maybe bigger. Will someone suggest a source for such boxes?
>
> I'll look for 10ga wire for the 50 amp path but may have to settle for
> 12ga.
>
> --
> Willie, ONWARD! Through the fog!
> http://counter.li.org Linux registered user #228836 since 1995
> Debian3.1/GNU/Linux system uptime 91 days 4 hours 52 minutes
>
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  #13  
Old 06-20-2012, 12:15 AM
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Default Re: [EVDL] ac box

[quote]On 19 Jun 2012 at 23:50, Roland Wiench wrote:

> You have to de-rated any conductor to 80% of the ampere rating of the
> conductor of the actual ampere load.

I may be wrong, but my understanding of the NEC is that the 20% derating
applies only with sustained loads.

This might indeed be the case with a charger. However (again my
understanding), normally this load factor is only applied to dedicated
circuits in home or industrial wiring, not to general purpose circuits.

Nor is it (to my knowledge) applied to an electrical device to be connected
to the mains (in this case an EV).

Again, I may be mistaken, but I think that in this case it's probably safe
for the builder to take the following maximum loads as reasonable and
acceptable :

AWG 14 - 15a
AWG 12 - 20a
AWG 10 - 30a
AWG 8 - 40a
AQG 6 - 50a

AWG 12 or AWG 10 wire is definitely too small for a 50a load.

David Roden - Akron, Ohio, USA
EVDL Administrator

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  #14  
Old 06-20-2012, 12:35 AM
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Default Re: [EVDL] ac box

Indeed.
Look at (certified - not cheap crap) extension cords.
NEMA 5-15 cords typically have 14 ga but long cords can
be had with 12 ga to reduce voltage drop (which may easily be
as bad as losing 15V in a 100 ft cord)
The 10 gauge is typically used for 30A "generator" cords
but also to connect 30A clothes driers.
6 gauge is used for stoves drawing 50A.
I once had a 3-wire 6 gauge extension cord to bring 240V 50A
to my driveway. I used it once and gave it away with my truck
when I sold it, because it would typically only be used for
EV (or RV) connection.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of EVDL Administrator
Sent: Tuesday, June 19, 2012 11:13 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] ac box

[quote]On 19 Jun 2012 at 23:50, Roland Wiench wrote:

> You have to de-rated any conductor to 80% of the ampere rating of the
> conductor of the actual ampere load.

I may be wrong, but my understanding of the NEC is that the 20% derating
applies only with sustained loads.

This might indeed be the case with a charger. However (again my
understanding), normally this load factor is only applied to dedicated
circuits in home or industrial wiring, not to general purpose circuits.

Nor is it (to my knowledge) applied to an electrical device to be
connected to the mains (in this case an EV).

Again, I may be mistaken, but I think that in this case it's probably
safe for the builder to take the following maximum loads as reasonable
and acceptable :

AWG 14 - 15a
AWG 12 - 20a
AWG 10 - 30a
AWG 8 - 40a
AQG 6 - 50a

AWG 12 or AWG 10 wire is definitely too small for a 50a load.

David Roden - Akron, Ohio, USA
EVDL Administrator

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To send a private message, please obtain my email address from the
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  #15  
Old 06-20-2012, 04:45 AM
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Default Re: [EVDL] ac box

Willie McKemie-2 wrote
> ...
> I think wire gauges larger than 10 will be too difficult to manage for
> my purposes.
> ...
>

I can't believe no one has suggested the obvious solution here: use two #12
wires in parallel.

--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/ac-box-tp4655805p4655846.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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  #16  
Old 06-20-2012, 04:25 PM
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Default Re: [EVDL] ac box

[quote]Jeffrey Jenkins wrote:
> I can't believe no one has suggested the obvious solution here: use two #12
> wires in parallel.

That can be a viable solution. I used 4-conductor #10 for 50amp
quick-charger on a fleet of Zap Xebras for a Pizza delivery business. It
was an expedient solution because I couldn't get ultra-flexible
2-conductor #6 cable in the time frame allowed.

The risk is that if one wire breaks, the other one is left carrying all
the current. It can overheat, and start a fire without the fuse blowing.
This can be handled by putting a separate fuse in each wire, properly
sized for the wire's current rating.
--
If we knew what we were doing, it wouldn't be called research, would it?
-- Albert Einstein
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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  #17  
Old 07-05-2012, 01:15 PM
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Default Re: [EVDL] ac box

[quote] Willie McKemie wrote:

> I think wire gauges larger than 10 will be too difficult to manage for
> my purposes.

I've been making some progress on this project. I didn't find any
flexible "appliance" cord greater than 10ga so I ended up using 10ga
for the 240vac path. I did get stiff single conductor 8ga wire for the
~165vdc path.

I used a plastic electric box from Lowes to contain the ac stuff:
two "120 amp" relays and a 120/240vac wallwart 12vdc power supply.
One high current cord coming in, one going out. One low current cord
going to the BMS, one coming back in to the wallwart.

I did my first test charge with the 10kw charger this morning. The
charger was painful to get, but I did eventually receive it:
http://www.diyelectriccar.com/forums/showthread.php/10kw-60a-diy-charger-open-source-59210p59.html
http://is.gd/nk8puX
I had a foot or two of 12ga wire in my 240vac path which I was
monitoring closely; I will normally bypass that segment with 10ga wire.
Over a few minutes, the charger ramped up to about 50 battery amps and
the 12ga segment got a little warm. My battery was very near full so
it only charged maybe 5 minutes. I need to the the car out and use it
some; we've been driving the Leaf primarily.

I've put in two "120 amp" relays to break both ac power legs. My
thinking is that, with a not isolated charger, it might be safer.
Even though I don't know the risks of using a non-isolated charger. I
understand that they can't be used in series. Do they pose a risk
running in parallel with other chargers?

Anyway, the 10kw charger looks very promising at this point. If only
it is reliable! With that one charger, I should now be able to charge
at the rate of about 30 mph. One comment on the charger: the provided
terminal strip is too small to accommodate the size wire and terminals
indicated by the currents expected.

BTW, using a 12vdc universal wallwart power supply seems to be a very
good way to control 12vdc coil relays. My BMS controller contains a
"20 amp" relay which I use to turn my wallwart on/off. The
wallwart performed well controlling a "40 amp" relay for several months
and now it is controlling the two "120 amp" relays. I first off-loaded
the BMS relay when my charging currents approached 20 amps.

--
Willie, ONWARD! Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime 107 days 3 hours 35 minutes

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  #18  
Old 07-06-2012, 03:17 AM
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Default Re: [EVDL] ac box

[quote] Willie McKemie wrote:

> On Tue, Jun 19, 2012 at 06:49:12PM -0500, Willie McKemie wrote:
>
>> I think wire gauges larger than 10 will be too difficult to manage for
>> my purposes.
>
> I've been making some progress on this project. I didn't find any
> flexible "appliance" cord greater than 10ga so I ended up using 10ga
> for the 240vac path. I did get stiff single conductor 8ga wire for the
> ~165vdc path.
>
> --
> Willie, ONWARD! Through the fog!

Hi Willie,

You could put singe core, heavy-gauge conductors in a piece of flexible conduit... MW

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  #19  
Old 07-14-2012, 01:17 AM
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Default Re: [EVDL] ac box

[quote] Lee Hart wrote:
> > I did my first test charge with the 10kw charger this morning. The
> > charger was painful to get, but I did eventually receive it:
> > http://www.diyelectriccar.com/forums/showthread.php/10kw-60a-diy-charger-open-source-59210p59.html
> > http://is.gd/nk8puX
>
> I'd be interested in continuing feedback on how this charger works out.
> It's very cheap, but from the photos I expect they have a lot to learn.

Well, I got good advice here on the wire size. I started with 8ga on
the dc side and 10ga on the ac. At 40+ battery amps, the ac wires got
pretty hot. The dc side seems ok. I just put 8ga on the ac side (4
segments, two big plugs) and things are better. At 45+ battery amps,
the ac wire gets warm. My goal is to put in ~50 amps from the new
charger plus ~8amps from my 1500w onboard charger. That would be about
34 mph. Right now, I'm fairly comfortable with ~40 amps from the new
charger plus the onboard charger. The BMS controlled relays appear
reliable; I'm about ready to try turning my back on them.

No trouble with the new charger; I've gotten about 200ah out of it, all
pretty closely monitored. The display uses four colors and two of
those have poor contrast. It needs a bigger screw terminal strip
(where ac goes in and dc comes out) that will take bigger wire with
bigger lugs.

Two things I'm looking for:
1) the afore mentioned screw terminal strip
2) 6ga multi strand flexible three conductor cable

--
Willie, ONWARD! Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime 115 days 15 hours 48 minutes

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