# anyone else had trouble w chennic dc-dc?



## Ziggythewiz (May 16, 2010)

Have you already added the diode and inductor as discussed by Jack R and others?


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## EVfun (Mar 14, 2010)

Is the Chennic sold under brand names? I've had good luck with the Kelley Controller HWZ Series DC/DC Converter. 
http://kellycontroller.com/hwz-series-dcdc-converter-108v-to-135v-25a-p-681.html
Sometimes 1 product is sold under a number of names. I'm not using any inductor or diode but I am using a Zilla controller.

With most of these cheaper DC/DC converters I would recommend trying to stay from the low end of the acceptable input voltage range. I'm running a 108 volt converter (84v to 146v input range) with a 120 volt (38 cell) LiFePO4 pack. Be careful not to exceed the max input voltage. I have a range from about 100 volts to 133 volts. I will likely increase my pack by 1 more cell.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> Have you already added the diode and inductor as discussed by Jack R and others?



no. these failures have been in a vehicle w/ Curtis 1221c controller. shouldn't need diode/inductor.


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## Ziggythewiz (May 16, 2010)

Doesn't the curtis just produce lower ripple, which i think is what the inductor is for, but you would still get sag and have the DC-DC caps trying to drive the car without the diode, right? I may have misheard things.


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## skooler (Mar 26, 2011)

Just add the diode and inductor for a couple of $$$.

Takes less than an hour to install.

I see no reason why you wouldn't, even as a precaution?


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## dtbaker (Jan 5, 2008)

skooler said:


> Just add the diode and inductor for a couple of $$$.
> 
> Takes less than an hour to install.
> 
> I see no reason why you wouldn't, even as a precaution?



just bugs me since it *shouldn't* be needed. Seems like if the unit is that sensitive, it ought to have that stuff inside to protect itself. The Soliton is the only controller I am aware of that kicks back enough ripple to suggest the need for adding external diode+inductor to protect the dc-dc and charger.

but.... maybe its better to add these items to the default de facto standard schematic.

do you have specific models and sources for purchase of appropriate diode/inductors? perhaps a simple schematic or physical picture of a sample install for non-EE types? 

I did order some inductors and diodes for a future build using a Soliton controller, but haven't really gotten down to planning the layout of everything, or see a 'clean' way to mount these little inductors without making a little peg board or something.


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## Tesseract (Sep 27, 2008)

dtbaker said:


> ... The Soliton is the only controller I am aware of that kicks back enough ripple to suggest the need for adding external diode+inductor to protect the dc-dc and charger.


Nope, the NetGain Controls controllers also use film capacitors - with less total capacitance than us, even - and so they reflect quite a bit of ripple back onto the battery pack, too.

If your Chennic dc/dc is blowing up with a Curtis 1231C then perhaps it is just a crappy dc/dc? More specifically, the wild swings in pack voltage that are typical in an EV might be causing instability/oscillation in the dc/dc. Or it could just be that when the pack voltage is on the low end of its operating range the amount of current required could exceed what the power stage components are actually capable of handling.


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## dtbaker (Jan 5, 2008)

Tesseract said:


> Nope, the NetGain Controls controllers also use film capacitors - with less total capacitance than us, even - and so they reflect quite a bit of ripple back onto the battery pack, too.


...good to know! Really only the Zilla and Soliton's are on my radar.  The Miata I'm working on right now came with a Zilla, and I have a Soliton on the shelf for the next build... This Chennic was in my daily driver Swift with Curtis 1221c controller and 120v nominal Li pack.



Tesseract said:


> If your Chennic dc/dc is blowing up with a Curtis 1231C then perhaps it is just a crappy dc/dc?


this is the basic conclusion I am coming to, which is why I started the thread.  yes, $99 for 500watt dc-dc is attractive, but not if they die in less than 12 mo. The Chennic MUST be overly sensitive to either the high at end of charge, which only lasts a few minutes, or the low under full load sagging at low end SOC, which I usually avoid. I was pretty sure I ordered the correct model for my nominal pack voltage and expected voltage swing from low sag to high end of charge. I've emailed Chennic to see if they will replace/refund/warranty, but have not heard back yet.

The Miata came with a Belktronix, which seems super-beefy sealed unit. I had an ACME on the shelf for next build, which I have stuck into the Swift to get it back on the road. The ACME looked to be a good value at $220 for 650watts and specs look good, but its an open-chassis design with fan and might turn out to be sensitive to dust/dirt/mist even installed in a fairly protected place under hood.


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## skooler (Mar 26, 2011)

Don't forget that sag is probably just as much (if not more) of an issue as ripple.

As soon as the volts go down the amps will go up to compensate (on the input side). My 400w chennic seems to pull ~450watts no matter what the voltage is.

The below thread has all of the details, especially the last couple of posts.

http://www.diyelectriccar.com/forums/showthread.php?t=75037

Cheers,

Mike


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## mk4gti (May 6, 2011)

Also read this thread I opened recently (also a chennic)

http://www.diyelectriccar.com/forum...another-dcdc-fuse-blowing-thread-79202p3.html

I have a few 100uH inductor coils left over, I can mail you a couple.


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## dtbaker (Jan 5, 2008)

skooler said:


> Don't forget that sag is probably just as much (if not more) of an issue as ripple.
> 
> As soon as the volts go down the amps will go up to compensate (on the input side). My 400w chennic seems to pull ~450watts no matter what the voltage is.
> 
> ...


I didn't have any problem with fuses... My dc-dc is 'always on', so the aux battery never needs a big recharge. The aux just covers the momentary sags when big things like headlights or vac pump clicks on. 

I'm curious to hear if people have had Chennics die prematurely, or running ok for more than a couple years.


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## dtbaker (Jan 5, 2008)

mk4gti said:


> Also read this thread I opened recently (also a chennic)
> 
> http://www.diyelectriccar.com/forum...another-dcdc-fuse-blowing-thread-79202p3.html
> 
> I have a few 100uH inductor coils left over, I can mail you a couple.


thanks for the offer.... I just got a couple for a future build w/ Soliton. I just dont think this is the problem with the vehicle the chennic was in though; the Curtis 1221c shouldn't need any inductors... I think its just that the Chennics are just plain not very good.


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## dtbaker (Jan 5, 2008)

dtbaker said:


> I think its just that the Chennics are just plain not very good.



Been days now.... zero response from Chennic regarding repair/replacement of the two units I had fail after less than 1 year service each..... so, they're off my 'good value' list.

I've installed an ACME in the Swift, which is a nice looking open-frame design with fan, etc. and the Miata (should be rolling soon) had a Belktronix which looks like a super solid sealed design. We'll see how those hold up!


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