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Discussion Starter #1
Re: [EVDL] Preventing Iota current draw (John O'Connor)

Hi John,

I have a similar setup to what Philip describes below, except using a key switch relay instead of a contactor. I added a small thermistor ($1.38 from Mouser) in the positive wire to the Iota take up some of the initial current draw. Without this thermistor, the relay was welding itself shut when I turned the key. My car has a 288V pack - you might not need the thermistor with a smaller pack, but for $1.38 it's not a big deal.

Good luck,
Richard

> My IOTA wiring went through several drafts before I finally decided on
> something (I think) I like. To prevent it from unnecessarily drawing
> current from the traction pack, the negative side of the IOTA input is
> wired to the switched-side of my negative-side contactor. This way it
> can only be powered from the traction pack when the key is in the
> "run" position. (The positive side is wired directly to the positive
> side of the traction pack.)
>
> Knowing that I also wanted to keep the accessory battery charged from
> external power, I have the IOTA's input switchable between AC (i.e.
> external power) or DC (traction pack). This relay defaults to the "AC
> input" position; it switches to the "DC" position only when the key is
> in the "run" position and AC power is not present. (There are also
> interlocks, of course, to prevent the Curtis's KSI relay and the
> negative-side contactor from switching on when AC power is present.)
>
> To doubly-ensure that the IOTA is isolated when the vehicle is just
> "sitting" (i.e. no AC power present and key not in "run"), I have an
> SW-60 contactor on the positive side of the IOTA's output, which only
> switches on with the key in "run" or with AC power present. (As Lee
> mentioned, there really shouldn't be any noticeable draw from the
> accessory battery back into the IOTA, but at least this way I can be
> really sure. :)

Richard Hamje
Portland, OR
[email protected]
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Discussion Starter #2
Re: [EVDL] Preventing Iota current draw (John O'Connor)

Richard and others,

I am looking for suggestions on wiring the thermistor into my system so that
it can dissipate the heat. Lee mentioned that they get hot under operation.
I would like to heatsink it to the bottom of my electrical box (and the
aluminum plate underneath it), but with just two bare legs and the body of
the thermistor, I haven't come up with anything I like yet.

Suggestions?

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Richard Hamje
Sent: Tuesday, September 28, 2010 9:06 AM
To: [email protected]
Subject: Re: [EVDL] Preventing Iota current draw (John O'Connor)

Hi John,

I have a similar setup to what Philip describes below, except using a key
switch relay instead of a contactor. I added a small thermistor ($1.38 from
Mouser) in the positive wire to the Iota take up some of the initial current
draw. Without this thermistor, the relay was welding itself shut when I
turned the key. My car has a 288V pack - you might not need the thermistor
with a smaller pack, but for $1.38 it's not a big deal.

Good luck,
Richard




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Registered
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70 Posts
Discussion Starter #3
Re: [EVDL] Preventing Iota current draw (John O'Connor)

Mike,
A thermistor is a negative temperature coefficient device. As the temperature
goes up, the resistance decreases.
They are not intended to be placed on a heatsink. Lee's warning is to prevent
you from placing it too close to

other components or materials that would be affected by the elevated temperature
of the NTC.
Typically they are placed vertical and away from other heat sensitive materials
like plastic.
You also don't want them to be suspended upside down, in the past I've seen
devices get hot enough
to desolder themselves and fall out of the circuit board (this was obviously a
bad design that operated the NTC
beyond it's rating, but it illustrates my point. Other NTC's on this same
design that were not upside down
continued to work even at the high temperatures).



----- Original Message ----
From: Mike Nickerson <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Tue, September 28, 2010 8:21:55 PM
Subject: Re: [EVDL] Preventing Iota current draw (John O'Connor)

Richard and others,

I am looking for suggestions on wiring the thermistor into my system so that
it can dissipate the heat. Lee mentioned that they get hot under operation.
I would like to heatsink it to the bottom of my electrical box (and the
aluminum plate underneath it), but with just two bare legs and the body of
the thermistor, I haven't come up with anything I like yet.

Suggestions?

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Richard Hamje
Sent: Tuesday, September 28, 2010 9:06 AM
To: [email protected]
Subject: Re: [EVDL] Preventing Iota current draw (John O'Connor)

Hi John,

I have a similar setup to what Philip describes below, except using a key
switch relay instead of a contactor. I added a small thermistor ($1.38 from
Mouser) in the positive wire to the Iota take up some of the initial current
draw. Without this thermistor, the relay was welding itself shut when I
turned the key. My car has a 288V pack - you might not need the thermistor
with a smaller pack, but for $1.38 it's not a big deal.

Good luck,
Richard




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| Multiple-address or CCed messages may be rejected.
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