# [EVDL] Heating Core Relay Tackled



## EVDL List (Jul 27, 2007)

I think the problem is that you're trying to cut high voltage DC while
drawing maybe 10-20 amps. Without that protection, you may have an arc that
continues across the contacts when you're trying to open the circuit. If
you take the AC system and try to run it on DC without the protection, you
are risking an extended arc when you disconnect. That can trash your
contacts and damage other components in the area. AC is easy to break
because of the 60 Hz zero crossings. DC takes other techniques to squelch
the arc.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Bill Dennis
> Sent: Tuesday, December 27, 2011 10:19 PM
> To: 'Electric Vehicle Discussion List'
> Subject: [EVDL] Heating Core Relay Tackled
> 
> I got the relay for my ceramic heating core installed this past weekend so
that
> I can start driving the car on pre-dawn winter mornings without chattering
> my teeth faster than the Curtis PWM switching frequency. The relay is a
> bulky DPDT monster that arrived in pieces, with instructions for assembly.
A
> hefty diode connects across the relay's load side. Two RC snubbers (one
on
> each pole) span the + and - contacts. And an arc-squelching magnet juts up
> between the + and - connectors on the battery side (it had actually broken
> off in shipping, requiring a JB-welded reattachment). In addition, the
12V
> connections also came with their own diode. When the heat is turned off
> and the relay opens, a little green spark jumps out into the magnet and
> quickly fizzles.
> 
> I guess I'm wondering why so much protection is needed on the relay's
high-
> voltage paths (diode, snubbers, and magnet to boot). And what would you
> have to do if you simply wanted to take one of those little floor heaters
you
> buy in WalMart or Home Depot, prop it up in the car and convert it to run
on
> DC. Would you need a second one of those rotund relays, or is there a
> simpler way?
> 
> Thanks.
> 
> Bill
> 
> 
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

My ceramic project is a "work in progress", but (after talking to some elec=
tronics geeks) quickly learned that a relay won't work with DC (A contactor=
will). So my next idea was a semiconductor relay, and my geeks say that=
the relays want to have AC to break the signal.

I am currently breadboarding a controller made of an opto-isolator, and a M=
OSFET.
I got the MOSFET from China via ebay. My ceramic is 4 separate elements,=
each 200 watts.
I will make up 4) PWM channels, so the load on each MOSFET will never rise =
above 2 Amps.

The biggest challenge I see is digging the heater core out of the dashboard=
. I dread that, and I have resigned myself to waiting for a 70 degree da=
y. It has been a cold December, and the little truck can't go to work wi=
th me if the temp is under 32. I'm thinking that it will be May before I=
tackle the installation. Until then, I am working on the control.



________________________________
From: Mike Nickerson <[email protected]>
To: 'Electric Vehicle Discussion List' <[email protected]> =

Sent: Tuesday, December 27, 2011 11:16 PM
Subject: Re: [EVDL] Heating Core Relay Tackled
=

I think the problem is that you're trying to cut high voltage DC while
drawing maybe 10-20 amps. Without that protection, you may have an arc t=
hat
continues across the contacts when you're trying to open the circuit. =
If
you take the AC system and try to run it on DC without the protection, you
are risking an extended arc when you disconnect. That can trash your
contacts and damage other components in the area. AC is easy to break
because of the 60 Hz zero crossings. DC takes other techniques to squelch
the arc.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Bill Dennis
> Sent: Tuesday, December 27, 2011 10:19 PM
> To: 'Electric Vehicle Discussion List'
> Subject: [EVDL] Heating Core Relay Tackled
> =

> I got the relay for my ceramic heating core installed this past weekend so
that
> I can start driving the car on pre-dawn winter mornings without chattering
> my teeth faster than the Curtis PWM switching frequency. The relay is a
> bulky DPDT monster that arrived in pieces, with instructions for assembly.
A
> hefty diode connects across the relay's load side. Two RC snubbers (one
on
> each pole) span the + and - contacts. And an arc-squelching magnet juts up
> between the + and - connectors on the battery side (it had actually broken
> off in shipping, requiring a JB-welded reattachment). In addition, the
12V
> connections also came with their own diode. When the heat is turned off
> and the relay opens, a little green spark jumps out into the magnet and
> quickly fizzles.
> =

> I guess I'm wondering why so much protection is needed on the relay's
high-
> voltage paths (diode, snubbers, and magnet to boot). And what would you
> have to do if you simply wanted to take one of those little floor heaters
you
> buy in WalMart or Home Depot, prop it up in the car and convert it to run
on
> DC. Would you need a second one of those rotund relays, or is there a
> simpler way?
> =

> Thanks.
> =

> Bill
> =

> =

> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111228/cbe4b574=
/attachment.html =

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

With a civic, it's an 8 hr. day-- dash out; wiring disconnected, steering w=
heel lowered, then accessing the heater element. Fortunately, it's DO-ab=
le!


Thinking about converting a gen. 5 ('92-95) Honda Civic? See http://home.bu=
dget.net/~bbath/CivicWithACord.html for DVD and tons more info!
____ =

__/__|__\__ =

=3DD-------/ - - \ =

'O'-----'O'-'
Would you still drive your car if the tailpipe came out of the steering whe=
el?
OR Lic. "LCTRNS"


----- Original Message -----
From: Will Schmit <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Cc: =

Sent: Wednesday, December 28, 2011 3:53 AM
Subject: Re: [EVDL] Heating Core Relay Tackled

My ceramic project is a "work in progress", but (after talking to some elec=
tronics geeks) quickly learned that a relay won't work with DC (A contactor=
will). So my next idea was a semiconductor relay, and my geeks say that=
the relays want to have AC to break the signal.

I am currently breadboarding a controller made of an opto-isolator, and a M=
OSFET.
I got the MOSFET from China via ebay. My ceramic is 4 separate elements,=
each 200 watts.
I will make up 4) PWM channels, so the load on each MOSFET will never rise =
above 2 Amps.

The biggest challenge I see is digging the heater core out of the dashboard=
. I dread that, and I have resigned myself to waiting for a 70 degree da=
y. It has been a cold December, and the little truck can't go to work wi=
th me if the temp is under 32. I'm thinking that it will be May before I=
tackle the installation. Until then, I am working on the control.



________________________________
From: Mike Nickerson <[email protected]>
To: 'Electric Vehicle Discussion List' <[email protected]> =

Sent: Tuesday, December 27, 2011 11:16 PM
Subject: Re: [EVDL] Heating Core Relay Tackled

I think the problem is that you're trying to cut high voltage DC while
drawing maybe 10-20 amps. Without that protection, you may have an arc t=
hat
continues across the contacts when you're trying to open the circuit. =
If
you take the AC system and try to run it on DC without the protection, you
are risking an extended arc when you disconnect. That can trash your
contacts and damage other components in the area. AC is easy to break
because of the 60 Hz zero crossings. DC takes other techniques to squelch
the arc.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Bill Dennis
> Sent: Tuesday, December 27, 2011 10:19 PM
> To: 'Electric Vehicle Discussion List'
> Subject: [EVDL] Heating Core Relay Tackled
> =

> I got the relay for my ceramic heating core installed this past weekend so
that
> I can start driving the car on pre-dawn winter mornings without chattering
> my teeth faster than the Curtis PWM switching frequency. The relay is a
> bulky DPDT monster that arrived in pieces, with instructions for assembly.
A
> hefty diode connects across the relay's load side. Two RC snubbers (one
on
> each pole) span the + and - contacts. And an arc-squelching magnet juts up
> between the + and - connectors on the battery side (it had actually broken
> off in shipping, requiring a JB-welded reattachment). In addition, the
12V
> connections also came with their own diode. When the heat is turned off
> and the relay opens, a little green spark jumps out into the magnet and
> quickly fizzles.
> =

> I guess I'm wondering why so much protection is needed on the relay's
high-
> voltage paths (diode, snubbers, and magnet to boot). And what would you
> have to do if you simply wanted to take one of those little floor heaters
you
> buy in WalMart or Home Depot, prop it up in the car and convert it to run
on
> DC. Would you need a second one of those rotund relays, or is there a
> simpler way?
> =

> Thanks.
> =

> Bill
> =

> =

> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111228/cbe4b574=
/attachment.html =

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Will,
the problem with ceramic heaters is not the constant current draw.
There are actually 2 problems:
1. Turn ON: the ceramic heater element has serious PTC
(Positive Temp Coefficient) behavior, so at the moment
you turn the heater on, it may draw 5 or 10 times the
current because the temp of the element is low.
With the element warming up the resistance increases
and the current drops, so after an initial 1 or 2kW
peak, the element may settle into drawing 200W.
If you do not dimension your controller to deal with
the 10x peak, you may lose control, in the sense that
your MOSFET may turn ON for the last time in its life
and you will have to figure out how to turn your heater
OFF again.

2. Turn OFF: if you want to stop the heater (or the temp
has risen enough) you want to turn the heating element OFF.
This will always cause a spike in voltage, due to the
inductance of the wiring and the high voltage.
This spike can kill semiconductors and cause arcs that
do not self-extinguish, so it is good to think about what
to do if your normal on/off control fails.
Especially since most silicon (transistors, FETs) have a
tendency to fail shorted (ON). In case your element starts
overheating (usually protected with a small bimetal that
should break the AC current, but has no chance of stopping
a serious DC current)

Both these reasons are why there has been quite a bit of
discussion about heater control in the past and you can
find it, including a relatively simple and very safe design
with a crowbar-relay to stop the heater in case of an
overheating event - the protection circuit does not try to
open the DC current but instead shorts the heater so that
the overload will blow the fuse. Of course the fuse must be
a properly rated high voltage DC fuse or you will get a
fireball event instead.

Note that there is no functional or operational difference
between a relay and a contactor, just that a contactor is
a heavy duty relay:
http://en.wikipedia.org/wiki/Contactor

Hope this helps,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] 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: [email protected] [mailto:[email protected]] On Behal=
f Of Will Schmit
Sent: Wednesday, December 28, 2011 3:54 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Heating Core Relay Tackled

My ceramic project is a "work in progress", but (after talking to some elec=
tronics geeks) quickly learned that a relay won't work with DC (A contactor=
will). So my next idea was a semiconductor relay, and my geeks say that=
the relays want to have AC to break the signal.

I am currently breadboarding a controller made of an opto-isolator, and a M=
OSFET.
I got the MOSFET from China via ebay. My ceramic is 4 separate elements,=
each 200 watts.
I will make up 4) PWM channels, so the load on each MOSFET will never rise =
above 2 Amps.

The biggest challenge I see is digging the heater core out of the dashboard=
. I dread that, and I have resigned myself to waiting for a 70 degree da=
y. It has been a cold December, and the little truck can't go to work wi=
th me if the temp is under 32. I'm thinking that it will be May before I=
tackle the installation. Until then, I am working on the control.



________________________________
From: Mike Nickerson <[email protected]>
To: 'Electric Vehicle Discussion List' <[email protected]>
Sent: Tuesday, December 27, 2011 11:16 PM
Subject: Re: [EVDL] Heating Core Relay Tackled
=

I think the problem is that you're trying to cut high voltage DC while draw=
ing maybe 10-20 amps. Without that protection, you may have an arc that =
continues across the contacts when you're trying to open the circuit. =
If you take the AC system and try to run it on DC without the protectio=
n, you are risking an extended arc when you disconnect. That can trash y=
our contacts and damage other components in the area. AC is easy to brea=
k because of the 60 Hz zero crossings. DC takes other techniques to sque=
lch the arc.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On =

> Behalf Of Bill Dennis
> Sent: Tuesday, December 27, 2011 10:19 PM
> To: 'Electric Vehicle Discussion List'
> Subject: [EVDL] Heating Core Relay Tackled
> =

> I got the relay for my ceramic heating core installed this past =

> weekend so
that
> I can start driving the car on pre-dawn winter mornings without =

> chattering my teeth faster than the Curtis PWM switching frequency. =

> The relay is a bulky DPDT monster that arrived in pieces, with instructio=
ns for assembly.
A
> hefty diode connects across the relay's load side. Two RC snubbers =

> (one
on
> each pole) span the + and - contacts. And an arc-squelching magnet =

> juts up between the + and - connectors on the battery side (it had =

> actually broken off in shipping, requiring a JB-welded reattachment). =

> In addition, the
12V
> connections also came with their own diode. When the heat is turned =

> off and the relay opens, a little green spark jumps out into the =

> magnet and quickly fizzles.
> =

> I guess I'm wondering why so much protection is needed on the relay's
high-
> voltage paths (diode, snubbers, and magnet to boot). And what would =

> you have to do if you simply wanted to take one of those little floor =

> heaters
you
> buy in WalMart or Home Depot, prop it up in the car and convert it to =

> run
on
> DC. Would you need a second one of those rotund relays, or is there a =

> simpler way?
> =

> Thanks.
> =

> Bill
> =

> =

> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111228/cbe4b574=
/attachment.html
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

BTW,
A so-called "solid state relay" has the same problem as
all other semiconductors: they tend to fail shorted.
In other words, if you want to be able to guarantee that
you can turn your heater off, then you need to find
another way than the electronics to break the path of
the DC current. That means either a mechanical switch, =

a properly rated breaker (if necessary with a manual
disconnect pull cord) or a fuse + crowbar circuit.
At least one of those in addition to your control
or you might lose all control when your heater control
decides to fail full on...

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] 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: Cor van de Water =

Sent: Wednesday, December 28, 2011 6:19 AM
To: 'Electric Vehicle Discussion List'
Subject: RE: [EVDL] Heating Core Relay Tackled

Will,
the problem with ceramic heaters is not the constant current draw.
There are actually 2 problems:
1. Turn ON: the ceramic heater element has serious PTC
(Positive Temp Coefficient) behavior, so at the moment
you turn the heater on, it may draw 5 or 10 times the
current because the temp of the element is low.
With the element warming up the resistance increases
and the current drops, so after an initial 1 or 2kW
peak, the element may settle into drawing 200W.
If you do not dimension your controller to deal with
the 10x peak, you may lose control, in the sense that
your MOSFET may turn ON for the last time in its life
and you will have to figure out how to turn your heater
OFF again.

2. Turn OFF: if you want to stop the heater (or the temp
has risen enough) you want to turn the heating element OFF.
This will always cause a spike in voltage, due to the
inductance of the wiring and the high voltage.
This spike can kill semiconductors and cause arcs that
do not self-extinguish, so it is good to think about what
to do if your normal on/off control fails.
Especially since most silicon (transistors, FETs) have a
tendency to fail shorted (ON). In case your element starts
overheating (usually protected with a small bimetal that
should break the AC current, but has no chance of stopping
a serious DC current)

Both these reasons are why there has been quite a bit of discussion about h=
eater control in the past and you can find it, including a relatively simpl=
e and very safe design with a crowbar-relay to stop the heater in case of a=
n overheating event - the protection circuit does not try to open the DC cu=
rrent but instead shorts the heater so that the overload will blow the fuse=
. Of course the fuse must be a properly rated high voltage DC fuse or you w=
ill get a fireball event instead.

Note that there is no functional or operational difference between a relay =
and a contactor, just that a contactor is a heavy duty relay:
http://en.wikipedia.org/wiki/Contactor

Hope this helps,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] 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: [email protected] [mailto:[email protected]] On Behal=
f Of Will Schmit
Sent: Wednesday, December 28, 2011 3:54 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Heating Core Relay Tackled

My ceramic project is a "work in progress", but (after talking to some elec=
tronics geeks) quickly learned that a relay won't work with DC (A contactor=
will). So my next idea was a semiconductor relay, and my geeks say that=
the relays want to have AC to break the signal.

I am currently breadboarding a controller made of an opto-isolator, and a M=
OSFET.
I got the MOSFET from China via ebay. My ceramic is 4 separate elements,=
each 200 watts.
I will make up 4) PWM channels, so the load on each MOSFET will never rise =
above 2 Amps.

The biggest challenge I see is digging the heater core out of the dashboard=
. I dread that, and I have resigned myself to waiting for a 70 degree da=
y. It has been a cold December, and the little truck can't go to work wi=
th me if the temp is under 32. I'm thinking that it will be May before I=
tackle the installation. Until then, I am working on the control.



________________________________
From: Mike Nickerson <[email protected]>
To: 'Electric Vehicle Discussion List' <[email protected]>
Sent: Tuesday, December 27, 2011 11:16 PM
Subject: Re: [EVDL] Heating Core Relay Tackled
=

I think the problem is that you're trying to cut high voltage DC while draw=
ing maybe 10-20 amps. Without that protection, you may have an arc that =
continues across the contacts when you're trying to open the circuit. =
If you take the AC system and try to run it on DC without the protectio=
n, you are risking an extended arc when you disconnect. That can trash y=
our contacts and damage other components in the area. AC is easy to brea=
k because of the 60 Hz zero crossings. DC takes other techniques to sque=
lch the arc.

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On =

> Behalf Of Bill Dennis
> Sent: Tuesday, December 27, 2011 10:19 PM
> To: 'Electric Vehicle Discussion List'
> Subject: [EVDL] Heating Core Relay Tackled
> =

> I got the relay for my ceramic heating core installed this past =

> weekend so
that
> I can start driving the car on pre-dawn winter mornings without =

> chattering my teeth faster than the Curtis PWM switching frequency.
> The relay is a bulky DPDT monster that arrived in pieces, with instructio=
ns for assembly.
A
> hefty diode connects across the relay's load side. Two RC snubbers =

> (one
on
> each pole) span the + and - contacts. And an arc-squelching magnet =

> juts up between the + and - connectors on the battery side (it had =

> actually broken off in shipping, requiring a JB-welded reattachment).
> In addition, the
12V
> connections also came with their own diode. When the heat is turned =

> off and the relay opens, a little green spark jumps out into the =

> magnet and quickly fizzles.
> =

> I guess I'm wondering why so much protection is needed on the relay's
high-
> voltage paths (diode, snubbers, and magnet to boot). And what would =

> you have to do if you simply wanted to take one of those little floor =

> heaters
you
> buy in WalMart or Home Depot, prop it up in the car and convert it to =

> run
on
> DC. Would you need a second one of those rotund relays, or is there a =

> simpler way?
> =

> Thanks.
> =

> Bill
> =

> =

> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111228/cbe4b574=
/attachment.html
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Bob Bath wrote:
> > With a civic, it's an 8 hr. day-- dash out; wiring disconnected,
> > steering wheel lowered, then accessing the heater element.
> > Fortunately, it's DO-able!
> ...


----------



## EVDL List (Jul 27, 2007)

I kept the existing heater core and use a 240 vac 2000 watt water heater 
design for a large diesel engine. Purchase it at my independent auto parts 
store where I been going to since the 50's.

This heater is about 2.5 inches in diameter and 18 inches long. Comes with 
a plug in optional thermostat and pump. I opt to use a Honeywell immersion 
aqua stat temperature control that inserts into the water tank.

The water tank is made of 3 inch copper pipe 3 foot long with 3 inch caps 
solder on each end. A standard radiator fill neck and two 3/4 inch copper 
pipe nipples was solder to this tank. This tank is attach to the same 
existing mountings that the old coolant radiator was.

Double insulated the tank, lines and hoses with that A/C black form hose 
insulation.

Ran this heater unit as a duel voltage using 120 vac at 8 amps at 1000 watts 
from a on board 7000 watt alternator-inverter that has two outputs of 25 
amps at 120 vac.

A ITE 40 amp 120 vac solid state relay is use to control this heater unit 
either by the Honeywell temperature control in automatic control or can 
select direct manual control using a selector switch.

Using a transfer switch, I can quickly preheat this unit with 240 vac at 16 
amps using off board commercial power about 15 minutes before I leave 
heating up the cab to about 80F.

After preheating, I can drive about 5 miles, leave the EV park for a hour, 
and there is still enough heat to melt the snow off the windshield.

Could also use the main 180V battery pack of to power the heater through a 
contactor, but never tried that yet.

A master mechanic friend of my said, before you choose a vehicle, look at 
the hour rate manual to see how long it takes to replace something. My 
heater core is listed for 45 minutes and some vehicles are up to 8 hours!

Roland





----- Original Message ----- 
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Saturday, August 18, 2012 7:48 PM
Subject: Re: [EVDL] Heating Core Relay Tackled

If it's really hard to replace the heater core, you may as well keep it.
Add a small water tank with an immersion heater to make hot water, and 
circulate it through the stock heater core with a pump.


Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Initially, the Chevy S-10 heater core that the converter left in
(because it was too much trouble to take out and its weight really did
not matter on a 5000+lb conversion EV) was not used on my S-10 Blazer
EV. The lower powered Electric heater was fine for me, though it took a
while to defrost the windshield on the frostiest days.

But enough complaints from my girl friend (at the time, who would not
wear more clothes during the winter months), got me motivated to have a
Russco Electric water heater installed that worked like a charm: quick,
quiet, reliable, I never had any problems with as it was a solid as a
rock. But alas, Russco is out of the heater business, and a web research
did not show any used ones for sale. CanEV may have something similar as
they also sell to their Canadian climate customers.

But Roland may have the ultimate way to go. A web search using keywords
water heater diesel
gave several results with many items to choose from. It also showed that
ice racers like to preheat their coolant before a race so, a search with
keywords 
racing water heater
provided many more links to explore.


{brucedp.150m.com}


-


> Roland Wiench wrote:
> >
> > I kept the existing heater core and use a 240 vac 2000 watt water heater
> > design for a large diesel engine. Purchase it at my independent auto
> ...


----------



## EVDL List (Jul 27, 2007)

> On 18 Aug 2012 at 20:48, Lee Hart wrote:
> 
> > The ceramic (or sometimes nichrome) heating element can be used, but
> > everything else is AC only and will quickly fail on DC.
> ...


----------



## EVDL List (Jul 27, 2007)

> EVDL Administrator wrote:
> > I've converted home space heaters for EVs by replacing the AC fan motor with
> > a DC motor and adding a substantial contactor for the heating element.
> >
> ...


----------



## EVDL List (Jul 27, 2007)

> On 19 Aug 2012 at 14:22, Lee Hart wrote:
> 
> > Don't forget that you can't use the stock power switch, thermostat, or
> > safety overtemperature fuse. They will fail on high voltage DC!
> ...


----------



## EVDL List (Jul 27, 2007)

There exist two relatively simple solutions
that avoid having problems with breaking
high voltage DC:

1. the limit and overtemp (thermal fuse) are
wired into the DC that engages the contactor,
so when one opens then the contactor loses its
coil drive and opens.

2. the overtemp (thermal fuse) can be wired to a
"crowbar" which will short circuit the heater
so it blows the (DC rated!) HV fuse. This means
that the overtemp does not need to break DC, only
be able to withstand the DC as long as it is not
activated and carry the full current that blows
the DC fuse to protect the heater.


Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] 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: [email protected] [mailto:[email protected]] On
Behalf Of EVDL Administrator
Sent: Sunday, August 19, 2012 12:54 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Heating Core Relay Tackled



> On 19 Aug 2012 at 14:22, Lee Hart wrote:
> 
> > Don't forget that you can't use the stock power switch, thermostat, or
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> Cor van de Water wrote:
> > There exist two relatively simple solutions
> > that avoid having problems with breaking
> > high voltage DC:
> ...


----------

