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Discussion Starter · #1 ·
Hi all,
When driving home Monday night my 12 volt accessory battery died. The 20
amp, 1000v DC fuse for the IOTA 55amp DC-DC converter blew, and it wasn't
charging the battery. The high voltage (HV) positive for the converter is
wired directly to the HV traction pack. The HV negative for the converter is
wired to contactor that is only on when "key on" is applied. So, the
converter only comes on when "key on" is on. Previously, I had it wired
directly to the negative of the HV traction pack, so it was always on. The
12 v output was (and still is) wired to a 50 amp automative relay to only
power the battery when "key on" is on.

So, the question is, why did my 20 amp HV fuse blow?

I'm going to replace it with a 25 amp fuse, as I'm wondering if I was simply
drawing 20 amps for too long a period, and it caused it to blow. However, I
may have something else mis-wired. Anyone have any advice?

Thanks!
--corbin
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Discussion Starter · #2 ·
corbin dunn wrote:

> When driving home Monday night my 12 volt accessory battery
> died. The 20 amp, 1000v DC fuse for the IOTA 55amp DC-DC
> converter blew, and it wasn't charging the battery. The high
> voltage (HV) positive for the converter is wired directly to
> the HV traction pack. The HV negative for the converter is
> wired to contactor that is only on when "key on" is applied.
> So, the converter only comes on when "key on" is on.
> Previously, I had it wired directly to the negative of the HV
> traction pack, so it was always on. The
> 12 v output was (and still is) wired to a 50 amp automative
> relay to only power the battery when "key on" is on.
>
> So, the question is, why did my 20 amp HV fuse blow?
>
> I'm going to replace it with a 25 amp fuse, as I'm wondering
> if I was simply drawing 20 amps for too long a period, and it
> caused it to blow. However, I may have something else
> mis-wired. Anyone have any advice?

Do you have any provision for precharging the DC/DC's capacitors or otherwise managing the huge inrush current that will result each time you connect HV to the DC/DC input?

Unless you address this inrush current, you will likely keep blowing the fuse.

Some people have recommended NTC inrush limiter devices as a solution. If you search the archives, you should find a comprehensive post by Lee Hart describing modifications required to make the Iota (and similar) *power supplies* survive in the role of DC/DC in a conversion.

Cheers,

Roger.

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Discussion Starter · #3 ·
corbin dunn wrote:
> When driving home Monday night my 12 volt accessory battery died. The
> 20 amp, 1000v DC fuse for the IOTA 55amp DC-DC converter blew, and it
> wasn't charging the battery. The high voltage (HV) positive for the
> converter is wired directly to the HV traction pack. The HV negative
> for the converter is wired to contactor that is only on when "key on"
> is applied. So, the converter only comes on when "key on" is on.

Iotas have no inrush limiting. When the input is first connected, they
draw a *huge* current surge in an attempt to instantly charge their
input capacitors. This is what blew the fuse.

> Anyone have any advice?

A bigger fuse is the wrong answer. Even 20a is too big; it won't blow it
even if the DC/DC is overloaded.

Instead, add an inrush limiter in series with the HV input. They only
cost about $1 from Mouser, Digikey, etc. These parts have a high
resistance when cold (to limit the initial current), but then fall to a
much lower resistance when hot (about 20 times lower). Size it by
finding out the real maximum input current, and pick an inrush limiter
that can carry this current continuously. If your pack is around 144v,
this will be about 6 amps.

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

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Discussion Starter · #4 ·
Lee's excellent write up on the Iota,
http://www.evdl.org/pages/iotamods.html


----- Original Message ----
From: Lee Hart <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Wed, February 2, 2011 12:29:07 PM
Subject: Re: [EVDL] Blown HV fuse for DC-DC converter, why?

corbin dunn wrote:
> When driving home Monday night my 12 volt accessory battery died. The
> 20 amp, 1000v DC fuse for the IOTA 55amp DC-DC converter blew, and it
> wasn't charging the battery. The high voltage (HV) positive for the
> converter is wired directly to the HV traction pack. The HV negative
> for the converter is wired to contactor that is only on when "key on"
> is applied. So, the converter only comes on when "key on" is on.

Iotas have no inrush limiting. When the input is first connected, they
draw a *huge* current surge in an attempt to instantly charge their
input capacitors. This is what blew the fuse.

> Anyone have any advice?

A bigger fuse is the wrong answer. Even 20a is too big; it won't blow it
even if the DC/DC is overloaded.

Instead, add an inrush limiter in series with the HV input. They only
cost about $1 from Mouser, Digikey, etc. These parts have a high
resistance when cold (to limit the initial current), but then fall to a
much lower resistance when hot (about 20 times lower). Size it by
finding out the real maximum input current, and pick an inrush limiter
that can carry this current continuously. If your pack is around 144v,
this will be about 6 amps.

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

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Discussion Starter · #5 ·
On 2 Feb 2011 at 9:26, Roger Stockton wrote:

> If you search the archives, you should find a comprehensive post by Lee
> Hart describing modifications required to make the Iota (and similar)
> *power supplies* survive in the role of DC/DC in a conversion.

This is in the EVDL library.

http://www.evdl.org/pages/iotamods.html

David Roden - Akron, Ohio, USA
EVDL Administrator

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Discussion Starter · #6 ·
Roger Stockton wrote:
>> If you search the archives, you should find a comprehensive post by Lee
>> Hart describing modifications required to make the Iota (and similar)
>> *power supplies* survive in the role of DC/DC in a conversion.

EVDL Administrator wrote:
> This is in the EVDL library.
> http://www.evdl.org/pages/iotamods.html

Thanks guys!

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

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Discussion Starter · #7 ·
Hi Lee,

Lee Hart <[email protected]> wrote:

> corbin dunn wrote:
> > When driving home Monday night my 12 volt accessory battery died. The
> > 20 amp, 1000v DC fuse for the IOTA 55amp DC-DC converter blew, and it
> > wasn't charging the battery. The high voltage (HV) positive for the
> > converter is wired directly to the HV traction pack. The HV negative
> > for the converter is wired to contactor that is only on when "key on"
> > is applied. So, the converter only comes on when "key on" is on.
>
> Iotas have no inrush limiting. When the input is first connected, they
> draw a *huge* current surge in an attempt to instantly charge their
> input capacitors. This is what blew the fuse.
>
> > Anyone have any advice?
>
> A bigger fuse is the wrong answer. Even 20a is too big; it won't blow it
> even if the DC/DC is overloaded.
>
> Instead, add an inrush limiter in series with the HV input. They only
> cost about $1 from Mouser, Digikey, etc. These parts have a high
> resistance when cold (to limit the initial current), but then fall to a
> much lower resistance when hot (about 20 times lower). Size it by
> finding out the real maximum input current, and pick an inrush limiter
> that can carry this current continuously. If your pack is around 144v,
> this will be about 6 amps.
>
>
Thanks! I had previously read your page at:
http://www.evdl.org/pages/iotamods.html

Unfortunately, I'm too much of an electronics newbie to really know what to
do. For this part:

>The bridge rectifier was held by the screw immediately above the yellow
boxed-in toroid. In mine, it was poorly soldered. I removed the bridge, and
replaced it with two GE Sensors >CL-30 inrush limiters, mounted in the 4
holes where the bridge used to be. This makes the input *DC ONLY* but adds
inrush protection.

I'm unsure what the bridge rectifier is. I will purchase two GE Sensor CL-30
limiters and try to figure out where to install them. I'm guessing you
soldered them to the bridge? (Sorry if this is an ignorant question). I will
also try to take pictures as I go along so others can repeat what I do as a
tutorial.

Also, is there a specific kind of epoxy you use to epoxy the components in?
I would also like to do that.

Thanks!

-corbin

Other notes, for anyone else interested:
The CL-30 on digikey:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KC003L-ND
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Discussion Starter · #8 ·
corbin dunn wrote:
> Thanks! I had previously read your page at:
> http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
> of an electronics newbie to really know what to do... I'm unsure what
> the bridge rectifier is. I will purchase two GE Sensor CL-30 limiters
> and try to figure out where to install them. I'm guessing you
> soldered them to the bridge?

The bridge is a flat black rectangle about the size of a matchbook with
four leads. On mine, it was poorly soldered, and the bridge isn't needed
for a DC input anyway. So it was expedient to take it out, and use the
empty 4 holes to mount the CL-30's. They go side by side. If you
numbered the holes 1-2-3-4, then one CL-30 goes in holes 1-2, and the
other in holes 3-4.

I used the CL-30 because I already had some. The CL-40 would also work,
perhaps a little better as it has twice the cold resistance (cuts the
inrush more).

Without the bridge rectifier, the input is DC ONLY! Cut off the AC plug,
clearly mark your wires + and -, and be sure to use an input fuse. The +
and - are labelled on the PC board where the bridge rectifier is.

You could also add the inrush limiter externally. But be careful how you
mount it: Inrush limiters work by getting HOT! You will burn yourself if
you touch it in operation. They will melt any plastics they come in
contact with. I'd get a bakelite screw terminal block, and mount the
inrush limiter to that (it won't melt or burn).

> Also, is there a specific kind of epoxy you use to epoxy the
> components in? I would also like to do that.

I just used hardware store general purpose epoxy. Be careful to clean
the parts well first. There were weak attempts to conformally coat
things in the one I modified. The coating material is very thin, clear,
and comes off very easily (like bad paint). Attempting to epoxy things
to this coating will immediately fail. You'll have to scratch it off first.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Discussion Starter · #9 ·
Thanks Lee!

I'll post photos to my website once I get it done so we can have other
people replicate the instructions.

--corbin


Lee Hart <[email protected]> wrote:

> corbin dunn wrote:
> > Thanks! I had previously read your page at:
> > http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
> > of an electronics newbie to really know what to do... I'm unsure what
> > the bridge rectifier is. I will purchase two GE Sensor CL-30 limiters
> > and try to figure out where to install them. I'm guessing you
> > soldered them to the bridge?
>
> The bridge is a flat black rectangle about the size of a matchbook with
> four leads. On mine, it was poorly soldered, and the bridge isn't needed
> for a DC input anyway. So it was expedient to take it out, and use the
> empty 4 holes to mount the CL-30's. They go side by side. If you
> numbered the holes 1-2-3-4, then one CL-30 goes in holes 1-2, and the
> other in holes 3-4.
>
> I used the CL-30 because I already had some. The CL-40 would also work,
> perhaps a little better as it has twice the cold resistance (cuts the
> inrush more).
>
> Without the bridge rectifier, the input is DC ONLY! Cut off the AC plug,
> clearly mark your wires + and -, and be sure to use an input fuse. The +
> and - are labelled on the PC board where the bridge rectifier is.
>
> You could also add the inrush limiter externally. But be careful how you
> mount it: Inrush limiters work by getting HOT! You will burn yourself if
> you touch it in operation. They will melt any plastics they come in
> contact with. I'd get a bakelite screw terminal block, and mount the
> inrush limiter to that (it won't melt or burn).
>
>
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Discussion Starter · #10 ·
Lee Hart wrote:

> corbin dunn wrote:
>> Thanks! I had previously read your page at:
>> http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
>> of an electronics newbie to really know what to do... I'm unsure what
>> the bridge rectifier is. I will purchase two GE Sensor CL-30 limiters
>> and try to figure out where to install them. I'm guessing you
>> soldered them to the bridge?
>
> The bridge is a flat black rectangle about the size of a matchbook with
> four leads. On mine, it was poorly soldered, and the bridge isn't needed
> for a DC input anyway. So it was expedient to take it out, and use the
> empty 4 holes to mount the CL-30's. They go side by side. If you
> numbered the holes 1-2-3-4, then one CL-30 goes in holes 1-2, and the
> other in holes 3-4.
>

Lee - Thanks again for the help on this! I got some CL-40s last friday night and fixed it up Saturday. 80 miles later things seem to be going okay.

I took some pictures in case anyone else wants to see how it is done:

http://www.corbinstreehouse.com/blog/2011/02/plug-bug-iota-dc-dc-converter-fix/

Whoever owns http://www.evdl.org/pages/iotamods.html is welcome to steal my pictures (and/or text) and add it to the library.

--corbin


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Discussion Starter · #11 ·
Hi Corbin,

That is a lovely looking car and a nice neat looking conversion.

Thanks for taking the trouble to post your pics of the Iota fix -
others will find them helpful, I'm sure.

On your comment about replacing the Iota's caps... If I understand
your blog correctly you have 48 x TS LFP160 cells wired in series.
Although the 'nominal' voltage of the pack is only 48 * 3.2 = 153.6V,
the charger could raise that to well over 180V (48 x 3.8V) easy. I
understand that for reliability you shouldn't take caps to more than
half their rated voltage. So you may want to reconsider changing them
out for higher spec'ed ones if the opportunity arrises. They are not
esp expensive and, as you know, breaking down is a PITA!

Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk

corbin dunn wrote:

>
> On Feb 2, 2011, at 11:21 AM, Lee Hart wrote:
>
>> corbin dunn wrote:
>>> Thanks! I had previously read your page at:
>>> http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
>>> of an electronics newbie to really know what to do... I'm unsure
>>> what
>>> the bridge rectifier is. I will purchase two GE Sensor CL-30
>>> limiters
>>> and try to figure out where to install them. I'm guessing you
>>> soldered them to the bridge?
>>
>> The bridge is a flat black rectangle about the size of a matchbook
>> with
>> four leads. On mine, it was poorly soldered, and the bridge isn't
>> needed
>> for a DC input anyway. So it was expedient to take it out, and use
>> the
>> empty 4 holes to mount the CL-30's. They go side by side. If you
>> numbered the holes 1-2-3-4, then one CL-30 goes in holes 1-2, and the
>> other in holes 3-4.
>>
>
> Lee - Thanks again for the help on this! I got some CL-40s last
> friday night and fixed it up Saturday. 80 miles later things seem to
> be going okay.
>
> I took some pictures in case anyone else wants to see how it is done:
>
> http://www.corbinstreehouse.com/blog/2011/02/plug-bug-iota-dc-dc-converter-fix/
>
> Whoever owns http://www.evdl.org/pages/iotamods.html is welcome to
> steal my pictures (and/or text) and add it to the library.
>
> --corbin
>
>

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Discussion Starter · #12 ·
It is not common to *double* the working voltage of electrolytes,
but giving it a 20% margin is a good idea.
So, if you know the charger takes the voltage up to 180V or higher
and your DC/DC will see this voltage, then it may help to
increase the 200V caps to 225V versions, but it is not required.
I know of an EV'er who had a 192V AGM pack and even he used
an Iota.
It only failed when he forgot to unplug his DC/DC while
charging his 192V pack, it was doing OK if he only plugged it
in some time after the charger was done, even though you can
easily see that a 192V pack will sit at around 16 x 13V = 208V,
but when charging AGMs the voltage can go to 16x15V = 240V!

Apparently the Iota has more margin than just the 200V minimum.

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Martin WINLOW
Sent: Tuesday, February 08, 2011 3:33 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Blown HV fuse for DC-DC converter, why?

Hi Corbin,

That is a lovely looking car and a nice neat looking conversion.

Thanks for taking the trouble to post your pics of the Iota fix - others
will find them helpful, I'm sure.

On your comment about replacing the Iota's caps... If I understand
your blog correctly you have 48 x TS LFP160 cells wired in series.
Although the 'nominal' voltage of the pack is only 48 * 3.2 = 153.6V,
the charger could raise that to well over 180V (48 x 3.8V) easy. I
understand that for reliability you shouldn't take caps to more than
half their rated voltage. So you may want to reconsider changing them
out for higher spec'ed ones if the opportunity arrises. They are not
esp expensive and, as you know, breaking down is a PITA!

Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk

corbin dunn wrote:

>
> On Feb 2, 2011, at 11:21 AM, Lee Hart wrote:
>
>> corbin dunn wrote:
>>> Thanks! I had previously read your page at:
>>> http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
>>> of an electronics newbie to really know what to do... I'm unsure
>>> what the bridge rectifier is. I will purchase two GE Sensor CL-30
>>> limiters and try to figure out where to install them. I'm guessing
>>> you soldered them to the bridge?
>>
>> The bridge is a flat black rectangle about the size of a matchbook
>> with four leads. On mine, it was poorly soldered, and the bridge
>> isn't needed for a DC input anyway. So it was expedient to take it
>> out, and use the empty 4 holes to mount the CL-30's. They go side by
>> side. If you numbered the holes 1-2-3-4, then one CL-30 goes in holes

>> 1-2, and the other in holes 3-4.
>>
>
> Lee - Thanks again for the help on this! I got some CL-40s last friday

> night and fixed it up Saturday. 80 miles later things seem to be going

> okay.
>
> I took some pictures in case anyone else wants to see how it is done:
>
> http://www.corbinstreehouse.com/blog/2011/02/plug-bug-iota-dc-dc-conve
> rter-fix/
>
> Whoever owns http://www.evdl.org/pages/iotamods.html is welcome to
> steal my pictures (and/or text) and add it to the library.
>
> --corbin
>
>

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Discussion Starter · #13 ·
Hi Martin -- thanks for the advice; you are right, I am using 48 of TS LFP200 cells, and if I did charge them to 4.0v each that would be 192 volts, which might be cutting it close! The DC-DC charger is not connected to the pack when charging; only when I turn on the key, closing my negative side contactor. I will look into replacing them sometime in the near future.

--corbin

Martin WINLOW wrote:

> Hi Corbin,
>
> That is a lovely looking car and a nice neat looking conversion.
>
> Thanks for taking the trouble to post your pics of the Iota fix -
> others will find them helpful, I'm sure.
>
> On your comment about replacing the Iota's caps... If I understand
> your blog correctly you have 48 x TS LFP160 cells wired in series.
> Although the 'nominal' voltage of the pack is only 48 * 3.2 = 153.6V,
> the charger could raise that to well over 180V (48 x 3.8V) easy. I
> understand that for reliability you shouldn't take caps to more than
> half their rated voltage. So you may want to reconsider changing them
> out for higher spec'ed ones if the opportunity arrises. They are not
> esp expensive and, as you know, breaking down is a PITA!
>
> Regards, Martin Winlow
> Herts, UK
> http://www.evalbum.com/2092
> www.winlow.co.uk
>
> On 8 Feb 2011, at 05:31, corbin dunn wrote:
>
>>
>> On Feb 2, 2011, at 11:21 AM, Lee Hart wrote:
>>
>>> corbin dunn wrote:
>>>> Thanks! I had previously read your page at:
>>>> http://www.evdl.org/pages/iotamods.html Unfortunately, I'm too much
>>>> of an electronics newbie to really know what to do... I'm unsure
>>>> what
>>>> the bridge rectifier is. I will purchase two GE Sensor CL-30
>>>> limiters
>>>> and try to figure out where to install them. I'm guessing you
>>>> soldered them to the bridge?
>>>
>>> The bridge is a flat black rectangle about the size of a matchbook
>>> with
>>> four leads. On mine, it was poorly soldered, and the bridge isn't
>>> needed
>>> for a DC input anyway. So it was expedient to take it out, and use
>>> the
>>> empty 4 holes to mount the CL-30's. They go side by side. If you
>>> numbered the holes 1-2-3-4, then one CL-30 goes in holes 1-2, and the
>>> other in holes 3-4.
>>>
>>
>> Lee - Thanks again for the help on this! I got some CL-40s last
>> friday night and fixed it up Saturday. 80 miles later things seem to
>> be going okay.
>>
>> I took some pictures in case anyone else wants to see how it is done:
>>
>> http://www.corbinstreehouse.com/blog/2011/02/plug-bug-iota-dc-dc-converter-fix/
>>
>> Whoever owns http://www.evdl.org/pages/iotamods.html is welcome to
>> steal my pictures (and/or text) and add it to the library.
>>
>> --corbin
>>

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Discussion Starter · #14 ·
Hi Lee, So they are still needed with DC only AND at a good 300V
rating (for 120V nominal system) but only 1/10th the capacitance?
That would make the replacements a LOT cheaper than replacing with the
same cap but 300V rating, yes? MW

Lee Hart wrote:

> On 2/8/2011 4:02 AM, Martin WINLOW wrote:
>> Corbin... On your comment about replacing the Iota's caps... If I
>> understand
>> your blog correctly you have 48 x TS LFP160 cells wired in series.
>> Although the 'nominal' voltage of the pack is only 48 * 3.2 = 153.6V,
>> the charger could raise that to well over 180V (48 x 3.8V) easy.
>
> And 200v is only 48 x 4.166v; not that inconceivable.
>
>> I understand that for reliability you shouldn't take caps to more
>> than half their rated voltage.
>
> A better way to say it is that the higher the voltage, the shorter the
> life. It's not linear; if a part lasts (say) 10,000 hours at 50% of
> rated voltage, it will last about 3000 hours at 80%, 1000 hours at
> 100%,
> and 100 hours at 110% of rated voltage. Much about 110% it essentially
> goes *bang* quite soon.
>
>> So you may want to reconsider changing them out for higher
>> spec'ed ones if the opportunity arrises. They are not
>> esp expensive and, as you know, breaking down is a PITA!
>
> These capacitors aren't even needed for DC operation. They are there
> to
> filter out the ripple when operated on AC. On DC, you can easily get
> by
> with 1/10th the capacitance (to filter the high frequency switching
> noise).
>
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
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Discussion Starter · #15 ·
Lee Hart wrote:

> On 2/7/2011 11:31 PM, corbin dunn wrote:
>> Lee - Thanks again for the help on this! I got some CL-40s last
>> friday night and fixed it up Saturday. 80 miles later things seem to
>> be going okay. I took some pictures in case anyone else wants to see
>> how it is done:
>
> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's will
> eliminate your fuse blowning problem.

Well, bad news! I got about 100 miles total before I had more trouble. This time the DC-DC converter stopped working. I took it out and one of the CL-40s I installed had got so hot that it melted the solder and was floating loose in the box! It was also brittle; I moved it around in my hand and it fell apart. It also looked like it was getting so hot that it started to burn the epoxy I put on the component next to it.

I know you said they run hot..but that seems excessive! Maybe I did something wrong?

Anyways, do you (or anyone else) have a recommendation for an inline inrush limiter? The IOTAs sold by EVSource has some sort of inline limiter (see http://www.evsource.com/tls_dcdc.php )

--corbin


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Discussion Starter · #16 ·
>
>
Lee Hart wrote:
>
>> On 2/7/2011 11:31 PM, corbin dunn wrote:
>>> Lee - Thanks again for the help on this! I got some CL-40s last
>>> friday night and fixed it up Saturday. 80 miles later things seem to
>>> be going okay. I took some pictures in case anyone else wants to see
>>> how it is done:
>>
>> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's will
>> eliminate your fuse blowning problem.
>
> Well, bad news! I got about 100 miles total before I had more trouble. This time the DC-DC converter stopped working. I took it out and one of the CL-40s I installed had got so hot that it melted the solder and was floating loose in the box! It was also brittle; I moved it around in my hand and it fell apart. It also looked like it was getting so hot that it started to burn the epoxy I put on the component next to it.
>
> I know you said they run hot..but that seems excessive! Maybe I did something wrong?
>
> Anyways, do you (or anyone else) have a recommendation for an inline inrush limiter? The IOTAs sold by EVSource has some sort of inline limiter (see http://www.evsource.com/tls_dcdc.php )
>

Actually, I may still go with another inrush limiter. Maybe my problem was using the CL-40. I never measured my input amperage (I don't have a way of measuring past 10 amps). Now, the CL-40 I was using is rated for 6 amps continuous. The CL-30 is 8 amps. The IOTA DLS-30 draws 7 amps AC, while the DLS-55 draws 13 amps. Lee -- did you happen to convert DLS-30s?

I'm thinking that I may simply need a CL-101, which can handle 16A continuous.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KC024L-ND

I would expect the input amperage to be lower given that that is 16A continuous at 120 VAC...but I'm not sure how the AC rating would apply to a DC system.

-corbin

References:
http://www.evsource.com/datasheets/iota/DLS-110-55%20Manual.pdf

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Discussion Starter · #17 ·
On 2/10/2011 9:56 PM, corbin dunn wrote:
>
>
Lee Hart wrote:
>
>> On 2/7/2011 11:31 PM, corbin dunn wrote:
>>> Lee - Thanks again for the help on this! I got some CL-40s last
>>> friday night and fixed it up Saturday. 80 miles later things seem to
>>> be going okay. I took some pictures in case anyone else wants to see
>>> how it is done:
>>
>> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's will
>> eliminate your fuse blowning problem.
>
> Well, bad news! I got about 100 miles total before I had more trouble. This time the DC-DC converter stopped working. I took it out and one of the CL-40s I installed had got so hot that it melted the solder and was floating loose in the box! It was also brittle; I moved it around in my hand and it fell apart. It also looked like it was getting so hot that it started to burn the epoxy I put on the component next to it.
>
> I know you said they run hot..but that seems excessive! Maybe I did something wrong?
>
> Anyways, do you (or anyone else) have a recommendation for an inline inrush limiter? The IOTAs sold by EVSource has some sort of inline limiter (see http://www.evsource.com/tls_dcdc.php )

Hmm, let's see...

I modified an Iota DLS-40, which is a little bit lower current. Maybe
your DLS-55 draws more current, and so needs a little higher current
inrush limiter.

What is your pack voltage? I modified it for a 156v pack (thirteen 12v
batteries). The lower the pack voltage, the higher the current. If your
pack voltage is less, that could do it. Note: The Iota is designed to
run on 120vac, which is 170vdc. It really won't work well at low DC
voltages like 120vdc.

Did you measure the current that it acutally draws? That will provide
the information needed to size the current rating of the inrush limiter.
If you bought spares, use two of them in parallel for each limiter.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Discussion Starter · #18 ·
Lee Hart wrote:

> On 2/10/2011 9:56 PM, corbin dunn wrote:
>>
>> On Feb 7, 2011, at 10:43 PM, Lee Hart wrote:
>>
>>> On 2/7/2011 11:31 PM, corbin dunn wrote:
>>>> Lee - Thanks again for the help on this! I got some CL-40s last
>>>> friday night and fixed it up Saturday. 80 miles later things seem to
>>>> be going okay. I took some pictures in case anyone else wants to see
>>>> how it is done:
>>>
>>> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's will
>>> eliminate your fuse blowning problem.
>>
>> Well, bad news! I got about 100 miles total before I had more trouble. This time the DC-DC converter stopped working. I took it out and one of the CL-40s I installed had got so hot that it melted the solder and was floating loose in the box! It was also brittle; I moved it around in my hand and it fell apart. It also looked like it was getting so hot that it started to burn the epoxy I put on the component next to it.
>>
>> I know you said they run hot..but that seems excessive! Maybe I did something wrong?
>>
>> Anyways, do you (or anyone else) have a recommendation for an inline inrush limiter? The IOTAs sold by EVSource has some sort of inline limiter (see http://www.evsource.com/tls_dcdc.php )
>
> Hmm, let's see...
>
> I modified an Iota DLS-40, which is a little bit lower current. Maybe
> your DLS-55 draws more current, and so needs a little higher current
> inrush limiter.
>
> What is your pack voltage? I modified it for a 156v pack (thirteen 12v
> batteries). The lower the pack voltage, the higher the current. If your
> pack voltage is less, that could do it. Note: The Iota is designed to
> run on 120vac, which is 170vdc. It really won't work well at low DC
> voltages like 120vdc.
>
> Did you measure the current that it acutally draws? That will provide
> the information needed to size the current rating of the inrush limiter.
> If you bought spares, use two of them in parallel for each limiter.

My pack voltage is 154v nominal (48 3.2v thundersky cells). The inrush limiter probably blew on my last drive home where I took the pack lower than nominal -- that probably caused the converter to pull more current and made it blow the limiter. (as a guess!). I shouldn't ever be lower than 134v based on my cell cutoff voltage.

Would it hurt to use a larger limiter? Here's a 12A, 5.0 Ohm (@25 deg C):
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=570-1053-ND

Or a 14A 4 Ohm one. I'm guessing what I really need is something that has 2.5-5 Ohms of resistance when cold, and very little when hot that also has an appropriate amp rating. If I just size the amp rating larger.... I don't see how that could be bad. Then again...I'm on page 50 of a basic EE book I'm borrowing from a friend. :)

corbin



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Discussion Starter · #19 ·
Hi Corbin,

Good for you!
Brush up on that EE and soon you will be able to
give the *answers* to these questions!

Let's see if we can guesstimate some advice from
the data that you gave - please go ahead and try
to find the actual data ( =measurement ) but for now:

You have a 55Amp power supply, so it will be able to
deliver up to 55A x 14V = 770W
Since it will likely be around 80% efficient, it will
likely consume not more than 770/0.8 = 960W
At your pack voltage, this is max 7A so you should be
able to measure it to verify!
(You said you were driving at night, so switch on your
lights and everything else that you were running to
see the same consumption.)

Now what can have caused your NTC to fail?
- was it specified to have some airflow and the
place where you mounted it was enclosed, so it
got too hot?
- the hot-resistance was too high, so at up to 7A
continuous the dissipation was too high at the NTC
and the NTC got damaged?
- the inrush current caused a temperature spike above
the device rating, so it broke down?
- other failure (mechanical, wrong part?)

Let's see with the 5 Ohm device you suggested:
If you use 1 to protect the Iota then it will cause
a current spike of 150V / 5 Ohm = 30A and although
this will be a staggering 30A x 150V = 4.5kW at the
moment of closing the contact, it will likely charge
the Iota input cap within 5 ms according to the
formula: I x t = V x C
(Current times Time equals Voltage(change) times Capacitance)
assuming the Iota input cap no more than 1000uF this leads
to a time of (150 x 0.001)/30 = 5 millisec.
This reduces the energy of the 4.5kW spike to 4500 x 0.005 = 23J
and because the device is specified for 100J you should be fine.
You see in the spec that at 120V it is recommended to use no
more than 6000uF while at 240V this device should charge up
no more than 1500uF capacitance - that is the limit of the
max Joule spec...
Note that the above calculatoin is for a single device
in line with your Iota, so having two devices in series
(one in each power lead) will cause the current to be half
but also the time to double...

So since the Energy is fine, let's see what else:
Continuous current?
The datasheet even has a nice table for the different
current and steady state dissipation. You see that at
7A it will eventually reach 5.7 Watts of dissipation.
At lower current the dissipation will go down.

What is the difference between your failing Iota and the
decription on the EVDL?
What I see in the Iotamods description is the suggestion to
use CL30 which has 0.06 Ohm resistance at 100% load (8A)
http://www.ge-mcs.com/download/temperature/920_325a.pdf
You used CL40 which has 0.11 Ohm resistance at 100% load
(6A) so if I understand it right, you used a part with
double the resistance in series with a load that has a
larger power draw (heavier Iota).
So the result is that the NTCs will run hotter (double
the resistance is double the voltage drop so double the
power dissipated. The higher temp will somewhat counter-act
the higher resistance, but I guess that the basic problem
was that you used a part that is spec'ed for 6A at an
ambient of 25 deg (77F) at a current up to 7A, where I
do not know the ambient temp...
The fact that it de-soldered itself is enough indication
that it got too hot, apparently you need to use the CL30
or an Ametherm or other part that has about the 2.5 Ohm
cold and (more importantly) 0.06 Ohm or lower hot rating
to get the same result as Lee and others have.

Success!

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of corbin dunn
Sent: Friday, February 11, 2011 11:29 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Blown HV fuse for DC-DC converter, why?


Lee Hart wrote:

> On 2/10/2011 9:56 PM, corbin dunn wrote:
>>
>> On Feb 7, 2011, at 10:43 PM, Lee Hart wrote:
>>
>>> On 2/7/2011 11:31 PM, corbin dunn wrote:
>>>> Lee - Thanks again for the help on this! I got some CL-40s last
>>>> friday night and fixed it up Saturday. 80 miles later things seem
>>>> to be going okay. I took some pictures in case anyone else wants to

>>>> see how it is done:
>>>
>>> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's
>>> will eliminate your fuse blowning problem.
>>
>> Well, bad news! I got about 100 miles total before I had more
trouble. This time the DC-DC converter stopped working. I took it out
and one of the CL-40s I installed had got so hot that it melted the
solder and was floating loose in the box! It was also brittle; I moved
it around in my hand and it fell apart. It also looked like it was
getting so hot that it started to burn the epoxy I put on the component
next to it.
>>
>> I know you said they run hot..but that seems excessive! Maybe I did
something wrong?
>>
>> Anyways, do you (or anyone else) have a recommendation for an inline
>> inrush limiter? The IOTAs sold by EVSource has some sort of inline
>> limiter (see http://www.evsource.com/tls_dcdc.php )
>
> Hmm, let's see...
>
> I modified an Iota DLS-40, which is a little bit lower current. Maybe
> your DLS-55 draws more current, and so needs a little higher current
> inrush limiter.
>
> What is your pack voltage? I modified it for a 156v pack (thirteen 12v

> batteries). The lower the pack voltage, the higher the current. If
> your pack voltage is less, that could do it. Note: The Iota is
> designed to run on 120vac, which is 170vdc. It really won't work well
> at low DC voltages like 120vdc.
>
> Did you measure the current that it acutally draws? That will provide
> the information needed to size the current rating of the inrush
limiter.
> If you bought spares, use two of them in parallel for each limiter.

My pack voltage is 154v nominal (48 3.2v thundersky cells). The inrush
limiter probably blew on my last drive home where I took the pack lower
than nominal -- that probably caused the converter to pull more current
and made it blow the limiter. (as a guess!). I shouldn't ever be lower
than 134v based on my cell cutoff voltage.

Would it hurt to use a larger limiter? Here's a 12A, 5.0 Ohm (@25 deg
C):
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=570-105
3-ND

Or a 14A 4 Ohm one. I'm guessing what I really need is something that
has 2.5-5 Ohms of resistance when cold, and very little when hot that
also has an appropriate amp rating. If I just size the amp rating
larger.... I don't see how that could be bad. Then again...I'm on page
50 of a basic EE book I'm borrowing from a friend. :)

corbin



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Discussion Starter · #20 ·
Ametherm makes excellent parts,
http://www.ametherm.com/Data%20Sheets/MS32%205R020.pdf


----- Original Message ----
From: corbin dunn <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Fri, February 11, 2011 12:59:09 AM
Subject: Re: [EVDL] Blown HV fuse for DC-DC converter, why?


Lee Hart wrote:

> On 2/10/2011 9:56 PM, corbin dunn wrote:
>>
>> On Feb 7, 2011, at 10:43 PM, Lee Hart wrote:
>>
>>> On 2/7/2011 11:31 PM, corbin dunn wrote:
>>>> Lee - Thanks again for the help on this! I got some CL-40s last
>>>> friday night and fixed it up Saturday. 80 miles later things seem to
>>>> be going okay. I took some pictures in case anyone else wants to see
>>>> how it is done:
>>>
>>> Congratulations, Corbin. You fixed it! I'm quite sure the CL-40's will
>>> eliminate your fuse blowning problem.
>>
>> Well, bad news! I got about 100 miles total before I had more trouble. This
>>time the DC-DC converter stopped working. I took it out and one of the CL-40s I
>>installed had got so hot that it melted the solder and was floating loose in the
>>box! It was also brittle; I moved it around in my hand and it fell apart. It
>>also looked like it was getting so hot that it started to burn the epoxy I put
>>on the component next to it.
>>
>> I know you said they run hot..but that seems excessive! Maybe I did something
>>wrong?
>>
>> Anyways, do you (or anyone else) have a recommendation for an inline inrush
>>limiter? The IOTAs sold by EVSource has some sort of inline limiter (see
>>http://www.evsource.com/tls_dcdc.php )
>
> Hmm, let's see...
>
> I modified an Iota DLS-40, which is a little bit lower current. Maybe
> your DLS-55 draws more current, and so needs a little higher current
> inrush limiter.
>
> What is your pack voltage? I modified it for a 156v pack (thirteen 12v
> batteries). The lower the pack voltage, the higher the current. If your
> pack voltage is less, that could do it. Note: The Iota is designed to
> run on 120vac, which is 170vdc. It really won't work well at low DC
> voltages like 120vdc.
>
> Did you measure the current that it acutally draws? That will provide
> the information needed to size the current rating of the inrush limiter.
> If you bought spares, use two of them in parallel for each limiter.

My pack voltage is 154v nominal (48 3.2v thundersky cells). The inrush limiter
probably blew on my last drive home where I took the pack lower than nominal --
that probably caused the converter to pull more current and made it blow the
limiter. (as a guess!). I shouldn't ever be lower than 134v based on my cell
cutoff voltage.


Would it hurt to use a larger limiter? Here's a 12A, 5.0 Ohm (@25 deg C):
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=570-1053-ND

Or a 14A 4 Ohm one. I'm guessing what I really need is something that has 2.5-5
Ohms of resistance when cold, and very little when hot that also has an
appropriate amp rating. If I just size the amp rating larger.... I don't see how
that could be bad. Then again...I'm on page 50 of a basic EE book I'm borrowing
from a friend. :)

corbin



_______________________________________________
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