# Dcdc fuse keeps blowing



## rwaudio (May 22, 2008)

I believe that Jack R's solution on EVTV with the same problem was a diode, simply keep the current from feeding back from the dc/dc to the pack under acceleration.

Make sure you find one of suitable voltage/current.

Something like this might do the trick
http://www.ebay.co.uk/itm/DC-Power-Supply-Stud-Rectifier-Diode-1000V-20A-w-Wire-/190683664601?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2c65a1d0d9#ht_1693wt_1396

If using a diode that was intended to be a rectifier the current must be derated for DC use, since as a rectifier it would only conduct 50% of the time.


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## PStechPaul (May 1, 2012)

The stud mount diode is rather hard to deal with. You can use a 35A 1kV bridge rectifier, and you can parallel two of the internal diodes for a total of 70 amp capacity (although best not to count on more than 50A because of uneven current sharing). Here is one for less than $4:
http://www.newark.com/fairchild-semiconductor/gbpc3510/bridge-rectifier-1ph-35a-1kv-qc/dp/18C6691
And the specs:
http://www.fairchildsemi.com/ds/GB/GBPC1506.pdf

You should run separate leads from each AC leg to the battery, to help equalize the current. It needs to be bolted to a good heat sink, as the forward drop may be as high as 1.4V at 30 amps which is almost 45 watts.


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## EVfun (Mar 14, 2010)

You need to put in inductor in series with the input to the DC to DC converter to keep the converters input capacitance from trying to smooth ripple on the DC pack. Tesseract explains it to me starting about here.


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## skooler (Mar 26, 2011)

Hi all,

I thought a diode would be the answer, surely it would only need to be 30 amps though? .

What really annoys me is that is is advertised for use in EVs yet isn't actually fit for purpose! Grrrrr!

Anyway. U just popped another fuse in. The main pack is currently charging for the first time so I thought I'd get some juice into the accessory battery.

The dcdc has been running for about 45 mins and is too hot to touch. It is mounted on an aluminium sheet, the bonnet (hood) is open and it has plenty of air to circulate.

Its hot enough to make some insulation tape on a nearby cable feel takky.

Is this anything to worry about?

- must admit that I'm not impressed by it so far. Hopefully evnetics can build me a nice one for under $500 ;-)


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## dtbaker (Jan 5, 2008)

skooler said:


> Hi all,
> 
> The fuse on my 400w Chennic Dcdc converter is blowing every time I accelerate.
> 
> ...


doesnt sound normal at all.... either there is a big load on it, or it is not handling the voltage drop on the input side when you sag under load. I found the chennic sensitive to the nominal voltage matching design nominal, so if you have a mismatch and/or massive voltage sag under load, the chennic will not be happy.

is the dc-dc 'always on' ?
have you identified ay 'significant' loads when EV is off, on but just sitting?
what kind of sag are you seeing in pack voltage under load?
do you have any aux-battery in parallel w/ dc-dc? if so are you SURE the aux battery is in decent condition and not drawing huge load to re-charge, or shorted, or....?


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## skooler (Mar 26, 2011)

dtbaker said:


> doesnt sound normal at all.... either there is a big load on it, or it is not handling the voltage drop on the input side when you sag under load. I found the chennic sensitive to the nominal voltage matching design nominal, so if you have a mismatch and/or massive voltage sag under load, the chennic will not be happy.
> 
> is the dc-dc 'always on' ?
> have you identified ay 'significant' loads when EV is off, on but just sitting?
> ...


Hi Dan,

The DCDC is wired into a contactor. The plan is to have it so that it comes on during charging and while driving. 

I have had it running while 'testing' (playing) and I turned it on while the car was charging earlier to top up the acc battery.

There are no significant loads with the car off.

I am using 4 Sinopoly 60AH (B) cells as my accessory battery. It is brand new but...

I had an issue with a parasitic load when I first installed the battery and it went completely flat. all cells were below 1v, one wouldnt register a voltage on my meter. I managed to get all of them back to life and holding a charge so I dont think that its an issue

Sag is about 110V at 600A. from 150ish (not bad with LA!)

I tried running without the acc battery. The only thing the dcdc was powering was the soliton and it cut out with a 12v too low error every time I stamped on the pedal.

Im starting to think the issue is just the fact that its not a very good piece of kit.

It definately shouldnt be getting too hot to touch!


Cheers

Mike


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## Yukon_Shane (Jul 15, 2010)

skooler said:


> Hi Dan,
> 
> The DCDC is wired into a contactor. The plan is to have it so that it comes on during charging and while driving.
> 
> ...


 
Unfortunately I can't offer you any advice with regards to how to fix your current DC/DC but I thought it might be appropriate to point out that Evnetics is currently working on a DC/DC converter that is designed for DIY Electric Vehicles. Just in case you were thinking of replacing yours (which it looks like you might have to).


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## PStechPaul (May 1, 2012)

I'm not very familiar with the DC-DC converters used in EVs in this application, but as I understand it, it uses the full battery pack voltage (in this case 144V nominal, 110-150V swing), and provides 12 VDC (or 13.8 VDC for charging), at 400 watts, or about 33 amps.

Definitely the unit should not be getting so hot. At 90% efficiency it should only use 40 watts. But that was listed as maximum efficiency, so that is not a very useful specification:
http://www.chennic.com/show-products.asp?id=33&JCDI41

The wording is obviously written by someone who is not really fluent in English, so I also wonder about the technical qualifications of the designer and the quality of the components. 

If you can get by with just 300 watts, and a 12V output rather than 13.8 for charging, you could use the following, which is just $97:
http://www.mpja.com/12V-25A-Hengfu-Power-Supply/productinfo/16488+PS/

It may not be well-known, but AC-DC switching supplies first rectify the line voltage, so for this supply, rated at 85-132 VAC, it will work on your battery pack from 120 VDC to 186 VDC. I don't know what the Chennic costs, but I think it may be a lot more. Of course this supply is open frame, so you'd need to enclose it and seal the connections for automotive use, and maybe supply fan cooling.

I really think it's better to have a separate battery for accessories, and use the vehicle mechanical power for charging, maybe with an alternator connected to the motor shaft. This would also eliminate the problem of the DC-DC converter being starved during acceleration. If it does not have an undervoltage lockout, many switching supplies will draw more and more current as the input voltage drops, until it can be enough to blow a fuse as you are seeing. But even at 100V input, a 400W supply should not draw any more than 5 amps. If you are melting 15 and 20 amp fuses in the primary circuit, there is definitely something seriously wrong. And the overheating is another telltale sign.


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## EVfun (Mar 14, 2010)

skooler said:


> Hi all,
> 
> I thought a diode would be the answer, surely it would only need to be 30 amps though? .
> 
> ...


The DC to DC really shouldn't get HOT while charging and with minimal 12 volt loads. When charging the ripple is limited to 120 Hz. That doesn't move a lot of amp hours in and out of the caps. I suppose it could warm the caps some.

The issue of the controller blowing the DC to DC fuse can happen because current can flow in and out of the caps 15,000 times a second as the controller draws power in pulses. This problem is somewhat new, and old, to the home conversion EVers. Controllers used to be largely unfiltered, just the capacitance needed to protect them self, back in the day of SCR controller running at around 1500 Hz. Then the Curtis PMC controllers came out and they have enough input capacitance that they didn't create a large 15kHz ripple. Later offering from DCPower Systems and Cafe Electric followed this trend. We got used to not having to deal with this high frequency ripple that can move a lot of amps back and forth (fuses measure the current both ways and add it up.) The Soliton and NetGain controller don't control this ripple on the DC bus. That means either the other items connected to the pack need to be built to deal with it, or the user needs to add that protection for them. It is actually easy if you follow the thread link I have earlier and listen to the posts from Tesseract.


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## dtbaker (Jan 5, 2008)

skooler said:


> I tried running without the acc battery. The only thing the dcdc was powering was the soliton and it cut out with a 12v too low error every time I stamped on the pedal.



this is the big clue that the chennic unit nominal may be set higher than you think, and not handling the sag under load.... the chennics are not 'bullet proof' and do NOT like input voltage less than-10% of design nominal. review your chennic manual or plate on the side, what nominal input is your unit expecting?

second issue is if your dc-dc is not always on, and your aux battery is handling prarasitic loads until you turn the car on.... the dc-dc will be working VERY hard to top off the ux battery as soon as you turn on the car. I would suggest that you leave the dc-dc always on in this case so that the aux battery is basically always full and just handling the pull when the dc-dc struggles with mometary sag or spikes from sudden loads when turning on headlights, heaters, or vacuum pump.


ps. I am not impressed w/ the Chennic, and will try an ACME next I think. My first Curtis was faultless, but expensive. I tried the Chennic which was cheap, but the first one only lasted a year and then input side shorted out. I had a spare which I installed, but am not trusting it.... EvolveElectrics has a pretty good price on the ACMEs, and Justin is telling me that people have had good luck with them.


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## skooler (Mar 26, 2011)

Thanks for all the help!

I'm going to follow the advice in this thread.

My todo lis is...


Install a Diode on the input side - to stop the input caps from being drained
Install a heatsink - to help with heat disipation (maybe an ali block underneath? its currently on a 2mm sheet)
Fully charge the acc battery and see if the DCDC remains hot while running
rewire so that it is 'always on'
I will update once I have done these on how things have gone.

I will put up with the chenic for now and upgrade as soon as evnetics release one... I'm sure that it would be bulletproof!

Cheers,

Mike


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## skooler (Mar 26, 2011)

Just had a look at the chennic site...

Im not onvinced that mine is the same model, look at the heatsink, I also have no plate whatsoever on mine...










http://www.chennic.com/up_files/file201001020504521412.pdf

This is where I purchased it:

http://www.ebay.co.uk/itm/Isolated-...957?pt=LH_DefaultDomain_0&hash=item19cacd4e4d

Cheers

Mike


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## skooler (Mar 26, 2011)

yeah sorry,

its the 144v version.

same seller though


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## electricmini (Oct 21, 2008)

Hi Mike

I've got quite a few universal-input 7.5V @ 30A output PSUs here (Meanwell 200W units), which should work fine with your pack voltage. A pair can be adjusted & wired with their outputs in series to make 14.4V 

I've also got several other PSUs, including a Vicor battmod & large booster module (would be great with a liquid-cooled plate & waterproof box)
Send me a p.m. if you still have no luck with the Chennic unit.

P.S. any news on that Sinopoly cell?

Richard


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## Overlander23 (Jun 15, 2009)

I would (and do) use an inductor on the input as Tesseract recommends, otherwise the ripple from the controller will kill the converter's input caps. The diode won't protect from the ripple. 

I had the same fuse-blowing problem, solved it temporarily with a rectifier but ultimately ditched it, and I now use an inductor instead (http://parts.digikey.com/1/parts/659021-inductor-tord-hi-amp-100uh-horz-2312-h-rc.html).

I have no problems with my Chennic... On my 205v nominal system it only really pulls a couple of amps. And I use an Odyssey 12v AGM as a buffer and failsafe.


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## PStechPaul (May 1, 2012)

I looked at the price and specs on the eBay site. $123 is not a bad price for a 400W DC-DC converter. But you can get a 300W switching supply for under $100, and a 500W unit for $200.
http://www.newark.com/xp-power/lcl500ps12/switching-power-supply/dp/52R2914
It provides a highly regulated 12VDC over a range of 127 to 370 VDC and its dimensions are 250x127x50 mm. It is 88% efficient at full output, so it will only dissipate about 48 watts with 400 watts output. 

The Chennic needs to be specified for input voltage, and the output voltage seems to be 13.8V at 0 amps, and 12V at full output. There is no line or load regulation spec, so I think it may be essentially unregulated. Also I could not find the dimensions for the Chennic, but it looks like it is mostly a big heat sink. You don't need that for 48 watts at full output.

Mean-Well has a line of intelligent battery chargers and PSUs that might be better than the Chennic:
http://www.meanwelldirect.co.uk/product/12V-60A-Intelligent-Battery-Charger/PB-1000-12/default.htm


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## dillond666 (Dec 27, 2010)

Hi Skooler,

You might want to check out my youtube video showing the fault on my brand new Chennic DC-DC. 
http://youtu.be/8sEOQfKpfUk
I use a zilla and had blown a couple of fuses which were glass fast blow like the original I got with the Chennic.
I replaced it with a slow blow HRC style fuse and it's been fine ever since. I do believe the inductor is the right way to go, I've had one on the bench for months and never quite got round to fitting it 

I trust you have the + and - connected permanently and are switching on and off with the other wire? If you are not doing this, you will have a huge inrush each time you switch on (built in protection is crap)and that will fatigue the fuse.

Derek


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## skooler (Mar 26, 2011)

Hi all,

Having a play with the dcdc at the moment.

It's also making a hissing sound after about 20 mins use.

At first I thought that it was the sinopoly cells venting but the sound is definitely the dcdc.

Does anybody else have this or have I got yet another problem with this unit!

I will try my luck with it over the next few weeks and decide whether or not to replace it!

I will have a read up properly later. On my helpers iPad ATM.

Richard,

The cell has been packaged up on the back seat of my car for the last couple of weeks! Apologies, I WILL post it on Monday!

P.s. my helper has suggested it could be damp / condensation boiling inside the unit? It's changed from an electrical hissing to a boiling sound while if written this post.

Cheers,

Mike


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## PStechPaul (May 1, 2012)

The hissing sound could very likely be one of the electrolytic capacitors overheating and venting, and it may eventually fail violently. If you watch the youtube video posted by dillond666, he discovered that an unusually long screw for the cover plate had shorted to one of the capacitors. 

If you apply rated voltage to the converter, it should draw no more than about 10-20 watts, or 100 mA from a 144V supply, and the case should get only barely warm. I'd also be interested to know the open circuit output voltages at a normal range of applied voltages, and also under nominal load. The manufacturer specs leave much to the imagination, and I think there are much better and less expensive options available.


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## electricmini (Oct 21, 2008)

skooler said:


> Hi all,
> 
> Having a play with the dcdc at the moment.
> 
> ...


Sometimes switching PSUs will make noises, it's the magnetic forces inside the transformer. (often a high-pitched whining noise)

If it's more of an electrical arcing noise (like a welding set), then that's bad!

I did once have a switching PSU which made a noise - and a stink!
Turns out a caterpillar had crawled inside and got itself right across the terminals of the mains rectifier - so it fried with 300+ Vdc across it!

PSU still worked after I cleaned it....



skooler said:


> P.s. my helper has suggested it could be damp / condensation boiling inside the unit? It's changed from an electrical hissing to a boiling sound while if written this post.
> 
> Cheers,
> 
> Mike


I think I'd disconnect it before it blows up. It doesn't sound healthy...

Richard


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## skooler (Mar 26, 2011)

Hi all,

Quick update.

I cautiously left the dcdc on while working on other areas of the car. Fire extinguisher on hand!

I monitored the acc battery voltage every so often. Once it reached ~14.3v the noise gradually faded and it cooled down.

I am fairly confident that it's because the battery is near fully charged so not working as hard.

As for the fuse... I blew another! Has anybody got any suggestions for an inductor?

Cheers,

Mike


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## Tesseract (Sep 27, 2008)

skooler said:


> H...
> As for the fuse... I blew another! Has anybody got any suggestions for an inductor?...


Had you read the thread that EVfun linked to on the first page of this thread you wouldn't be asking this now...


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## PStechPaul (May 1, 2012)

What is the load on the converter while doing your testing? Can you monitor the input and output current? What is the input and output voltage with no load? Does it still get hot? 

You say it may work much harder at 12V than 14V, and I assume that is the voltage on a separate battery on the output. So you are using it as a battery charger? Is it really made for that purpose? It should have some current limiting and a voltage limit so it charges the battery at a safe current and then keeps it topped off with a "float" voltage. If it's a 400W unit and it's charging a 12V battery it may put out over 30 amps, but not much more. Are you blowing a 30 amp fuse on the output? In that case it is not current regulated and you may be charging with 100 amps or more, which will pop a 30A slow-blow fuse in about 30 seconds. If you are blowing a 30 amp input fuse on a 144V supply, I suggest wearing full body armor, as that is around 10kW and a serious explosion, with shrapnel and toxic fumes, may ensue!


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## PStechPaul (May 1, 2012)

Tesseract said:


> Had you read the thread that EVfun linked to on the first page of this thread you wouldn't be asking this now...


I just read part of that thread, and although I can see where the inductor should help reduce high current pulses and excess heat in capacitors not designed with low ESR, it does not make sense that it should be needed when the motor and controller are not running. If this happened while the OP was working on other parts of the car, there should be no ripple on the batteries. And I also question why there should be so much ripple on the battery pack while running. The controller should have its own inductor and low ESR capacitor on the input, and probably also a rectifier (unless it has regen back to the pack). 

And also I do not understand why a DC-DC converter of this size would use a buck topology. It is rather risky because if the switching transistor or drive should fail, it would either short the primary to ground, or allow the inductor to saturate and dump the primary voltage directly into the battery on the output. Why not use a more standard push-pull topology which is inherently safer for the output?


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## Tesseract (Sep 27, 2008)

PStechPaul said:


> I just read part of that thread, and although I can see where the inductor should help reduce high current pulses and excess heat in capacitors not designed with low ESR, it does not make sense that it should be needed when the motor and controller are not running.


Skooler did not say whether the controller/motor was running or not.




PStechPaul said:


> And I also question why there should be so much ripple on the battery pack while running. The controller should have its own inductor and low ESR capacitor on the input, and probably also a rectifier (unless it has regen back to the pack).


The controller should have it's own inductor, huh? Do you have *any* idea what an inductor rated for 1000A and with enough inductance to matter would cost? Or how big it would be? Just to get the ripple current to +/-20% of the rated current would require 10 sets of 00K130LE Kool-Mu cores glued together, and those cost $70/pair. Oh, and there are already 3 film capacitors inside his controller that cost $68 each. 

It makes no sense to add a $700 inductor (not including winding or assembly) or increase the capacitance in the controller in $68 increments just to protect a $200 dc/dc converter from the controller's ripple; especially when you can use a $5 inductor on the input to the converter to do the same.



PStechPaul said:


> And also I do not understand why a DC-DC converter of this size would use a buck topology.


The Chennic DC/DC converter doesn't use a buck topology. Where did you get the idea that it did?


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## PStechPaul (May 1, 2012)

Tesseract said:


> Skooler did not say whether the controller/motor was running or not.


 He said he was working on other parts of the car. So it seemed unlikely that it was running. It's an important part of the puzzle, anyway. 



> The controller should have it's own inductor, huh? Do you have *any* idea what an inductor rated for 1000A and with enough inductance to matter would cost? Or how big it would be? Just to get the ripple current to +/-20% of the rated current would require 10 sets of 00K130LE Kool-Mu cores glued together, and those cost $70/pair. Oh, and there are already 3 film capacitors inside his controller that cost $68 each.
> 
> It makes no sense to add a $700 inductor (not including winding or assembly) or increase the capacitance in the controller in $68 increments just to protect a $200 dc/dc converter from the controller's ripple; especially when you can use a $5 inductor on the input to the converter to do the same.


I'm thinking about AC VF drives, which usually have link inductors or at least a provision for them. But this is generally to smooth the link and to reduce reflected ripple back to the AC supply, although this is generally more current ripple than voltage ripple because of the input rectifiers. DC PWM drives for BDC motors may be a totally different animal, and I'm not experienced in their design or use.



> The Chennic DC/DC converter doesn't use a buck topology. Where did you get the idea that it did?


I'm probably thinking about the Open Revolt controller in another thread, or the video of the BMW conversion project where a buck converter is described. Is there any detailed info on the Chennic? I could not find very much at all, and it was confusing that it could be used both as a battery charger and a 12V DC-DC accessory supply. No specs on line or load regulation. 

Sorry if I have made any "stupid" assumptions. But there are some things about EV conversions that do not seem quite "right", and I'm trying to understand the reasons for certain problems and component choices.


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## skooler (Mar 26, 2011)

Tesseract said:


> Had you read the thread that EVfun linked to on the first page of this thread you wouldn't be asking this now...


Hi Jeffrey,

I have read it, I'll be perfectly honest - I understand why a Inductor is needed but I dont understand how to calculate its size? Or are you saying that a 100uH inductor will be suitable for most EV DCDC applications due to the minimal voltage sag? (overkill is always necessary and all that!)

To answer some other questions and clarify some points,

PStechPaul,
No load on the DCDC while testing - Except for the battery its charging. other than that its just the normal parasitic loads on the car. Im guessing it cooled down once the battery was fully charged and that load went away!

Unfortunately I have no way of measuring the current. Any recomendations on a cheap meter?

There is no fuse on the output. Just a 15/20Amp fuse on the input.

While testing nothing else on the car was 'on', the fuse only blows when the car is being driven.

Finally, it makes perfect sense to me why the controller would not protect the other components by using its own inductor. the other components should fend for themselves!

Back to my original question. What inductor is best to use?

http://www.ebay.co.uk/itm/Electroni...al_Components_Supplies_ET&hash=item2a1ebdccd4

http://www.ebay.co.uk/itm/BOURNS-PM...al_Components_Supplies_ET&hash=item3cc2a86ebf

?????

Will a diode have any use with the inductor or should I leave it out?

Thanks again!

Cheers,

Mike


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## dtbaker (Jan 5, 2008)

I think you are missing the forest for the trees with all the talk about controllers diodes and inductance.... the point is that the dc-dc is working too hard, and may already be damaged by getting so hot so many times.

The big question you should answer is WHAT is the load thats blowing the fuses? Is it your aux battery (that you said got drained to 0v, right)? something else???

get an inexpensive clamp ammeter/mutimeter (like a craftsman) and track the load down!


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## Tesseract (Sep 27, 2008)

skooler said:


> ...
> Back to my original question. What inductor is best to use?
> 
> http://www.ebay.co.uk/itm/Electroni...al_Components_Supplies_ET&hash=item2a1ebdccd4


This one is good. And since you are getting 5, you could put 2 of them in series for double the inductive goodness.

I wouldn't bother with the series diode.

I'm adding an entry to the FAQ on our website about this because this definitely qualifies as a frequently asked question.


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## skooler (Mar 26, 2011)

dtbaker said:


> I think you are missing the forest for the trees with all the talk about controllers diodes and inductance.... the point is that the dc-dc is working too hard, and may already be damaged by getting so hot so many times.
> 
> The big question you should answer is WHAT is the load thats blowing the fuses? Is it your aux battery (that you said got drained to 0v, right)? something else???
> 
> get an inexpensive clamp ammeter/mutimeter (like a craftsman) and track the load down!


Hi Dan,

to be clear there seems to be 2 seperate issues, the fuse (on the input side) and the heat.

The 'load' appears to be on the input side - when the controller pulls a lot of current, the voltage sags so the input caps on the DCDC get used to drive the car, more than 15/20A is pulled and the fuse blows.

The heat (and noise) issue has more or less gone away since the acc battery reached 14.3v. So the large load was the battery charging. The unit is still warm to touch but not worryingly.

I am confident the cells are ok.

Cheers,

Mike


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## dtbaker (Jan 5, 2008)

Tesseract said:


> I'm adding an entry to the FAQ on our website about this because this definitely qualifies as a frequently asked question.


so.... is the addition of some good externally added inductance recommended when using a Soliton controller? 

I am very curious now as I am planning on Soliton for next build, and didn't have to add inductor(s) for my first one when using archaic Curtis controller....


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## skooler (Mar 26, 2011)

Tesseract said:


> This one is good. And since you are getting 5, you could put 2 of them in series for double the inductive goodness.
> 
> I wouldn't bother with the series diode.
> 
> I'm adding an entry to the FAQ on our website about this because this definitely qualifies as a frequently asked question.


Thanks Jeffrey 

Just to be sure. they are only rated for 5A each. Will this be ok?

(My electrical knowledge ends far before inductors!)

Good idea with the FAQ section. Dont forget the frame leak stuff .

I will get back to you about that soon, I have a good video that I'm waiting for a friend to upload that you could probably use.

I seem to be the person that is asking every one of the FAQ's at the moment!

Cheers,

Mike


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## Tesseract (Sep 27, 2008)

dtbaker said:


> so.... is the addition of some good externally added inductance recommended when using a Soliton controller?
> 
> I am very curious now as I am planning on Soliton for next build, and didn't have to add inductor(s) for my first one when using archaic Curtis controller....


Generally speaking, it doesn't hurt to add the inductor and given that it only costs $5 or so it hardly seems like a crushing burden.




skooler said:


> Thanks Jeffrey
> 
> Just to be sure. they are only rated for 5A each. Will this be ok?
> 
> ...


Well I don't know for sure that those inductors will be okay Mike, since you didn't measure the input current to the DC/DC converter, but since 400W / 144V = 2.78A it seems like a safe bet, no?

And the frame leak question has already been added to the FAQ.


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## skooler (Mar 26, 2011)

Tesseract said:


> Well I don't know for sure that those inductors will be okay Mike, since you didn't measure the input current to the DC/DC converter, but since 400W / 144V = 2.78A it seems like a safe bet, no?




Yep that was my logic 

But why the 15A fuse on the input then?

Do you think that chennic are aware of the issue and simply upped the Fuse size to compensate?


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## Tesseract (Sep 27, 2008)

skooler said:


> ...But why the 15A fuse on the input then?
> 
> Do you think that chennic are aware of the issue and simply upped the Fuse size to compensate?


Fuses are mainly meant to protect wires and stuff from catching on fire, not to prevent already damaged equipment from being more damaged.

As for why Chennic does anything, you'll have to ask them!


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## EVfun (Mar 14, 2010)

skooler said:


> Yep that was my logic
> 
> But why the 15A fuse on the input then?
> 
> Do you think that chennic are aware of the issue and simply upped the Fuse size to compensate?


My guess is that since they left out the inductor, or other inrush limiting device, the large fuse is needed so it doesn't blow when the unit is first connected to power.


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## PStechPaul (May 1, 2012)

skooler said:


> PStechPaul,
> No load on the DCDC while testing - Except for the battery its charging. other than that its just the normal parasitic loads on the car. Im guessing it cooled down once the battery was fully charged and that load went away!


The battery is indeed a significant load, especially if it is deeply discharged and the DCDC is used as a charger. But the charging current should be limited according to the wattage of the converter, so 400 watts at 12V is about 33A.



> Unfortunately I have no way of measuring the current. Any recomendations on a cheap meter?


The $5 Harbor Freight meter is adequate for reading up to 10 ADC. You can just put the leads across the fuseholder with the fuse removed, but it's safer to keep the fuse in series. And be careful with the 144VDC battery bus voltage!

This 30A fuse tester may also be useful, but probably only for the 12V output side.

Even better might be an automotive type ammeter, such as this one which reads +/-30A, for $10: http://www.tractorsupply.com/universal-ammeter-0236601

DC clamp meters tend to be expensive. This is about the lowest price, at $110, but is a valuable tool for any serious EV modder: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_374070_-1



> There is no fuse on the output. Just a 15/20Amp fuse on the input.
> 
> While testing nothing else on the car was 'on', the fuse only blows when the car is being driven.


I suppose it is possible that the PWM ripple on the battery pack could be enough to cause problems, but I think it's more likely that the DCDC has no low voltage cutoff and tries to maintain output while the input voltage is too low. This is more a design flaw, as evidenced by the need to specify the exact pack voltage. 



> Finally, it makes perfect sense to me why the controller would not protect the other components by using its own inductor. the other components should fend for themselves!
> 
> Thanks again!
> 
> ...


If the Chinnic were properly designed, it would have an internal inductor and/or diode, or at least a recommended external component. But the only specifications available are poorly written and lack the most important basic information. It does not give a range of inputs, but only a nominal 144V value. It does not specify the line or load regulation and does not say what the charging current is. So it might be putting out much more than 30A which may damage the accessory battery. It is very important to read these values. If you don't have the necessary test equipment you may be able to borrow what you need, but having it on hand makes it a good investment. Good luck!


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## Overlander23 (Jun 15, 2009)

My 192v Chennic has a voltage input range of 150-255VDC, as told to me by Chennic when I was asking about their converters.

And we've done all of this before! Stick a diode/rectifier on the input and it stops the input fuse from blowing when a PWM controller is pulling current. Stick an inductor in there instead and same thing, except now the input caps have some protection.

It's not just theory... it's what actually works in practice! For real!


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## mora (Nov 11, 2009)

PStechPaul said:


> DC clamp meters tend to be expensive. This is about the lowest price, at $110, but is a valuable tool for any serious EV modder: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_374070_-1


If you are not afraid of ordering from China then see http://www.dealexcel.com/unit-ut204-ut204-dc-clamp-current-digital-multimeter_p465.html for example. There are other cheap clamp-style current measurement tools also. This isn't the cheapest one there. I got my Uni-T meters there and have been satisfied. These cost 3-4x more locally.

Get one (clamp-style meter) if you want to be safe about measuring any DC current. It is propably the most easiest way too.


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## skooler (Mar 26, 2011)

mora said:


> If you are not afraid of ordering from China then see http://www.dealexcel.com/unit-ut204-ut204-dc-clamp-current-digital-multimeter_p465.html for example. There are other cheap clamp-style current measurement tools also. This isn't the cheapest one there. I got my Uni-T meters there and have been satisfied. These cost 3-4x more locally.
> 
> Get one (clamp-style meter) if you want to be safe about measuring any DC current. It is propably the most easiest way too.


Just purchased a Uni-T meter for £30. will do some digging once it arrives

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=360465140862&ssPageName=ADME:B:EOIBSA:GB:3160


I also purchased the Inductor and will post some pics of that and the install once it arrives.

Cheers,

Mike


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## dillond666 (Dec 27, 2010)

I too bought a UniTrend clamp meter last year (Ebay, from China). I bought the UT-204 because it is a true RMS meter although slightly more expensive. I have been happy with it. 
You need to use the REL button to zero the display before measuring DC.


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## PStechPaul (May 1, 2012)

I have a DC clamp probe that plugs into my multimeter. But I also found this one that is only $51 and free shipping from Hong Kong:

http://www.ebay.com/itm/UNI-T-UT204...374?pt=LH_DefaultDomain_0&hash=item3cc1162796

Yeah, it's the same one you guys found.


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## skooler (Mar 26, 2011)

Hi All,

Just adding a conclusion to this thread as it really winds me up when i read about a problem and the tried solution has not been confirmed as working!

I purchased the 100UH, 6.1A Inductor below.

http://www.ebay.co.uk/itm/260963856063?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

It was installed on the same input as the fuse. I chose the one above as it has a plastic bas that I have araldited to the top of the converter.

My clamp meter arrived, with a near flat 12v accssory battery I am seeing 3-3.5A on the input side and 30-35A on the output side. This Means that the DCDC is taking in much more power than its 400W rating.

My only worry now is heat. I purchased a laser thermometer, after about 30 minutes use the DCDC is around 80C the Inductor is about 70C (but mounted on top of the DCDC.

Heat soon drops once the accessory battery is fully charged.

I tested the solution by flooring the car (smoking tyres etc.), I pulled 600A for a couple of seconds several times. The fuse did not blow!

I also purchased a bridge rectifier to use as a diode but have not needed it.

Just to say a big thankyou to everyone that has helped me solve a very irritating problem that should never of existed!

Any thoughts on the heat issues?

Cheers,

Mike


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## PStechPaul (May 1, 2012)

If you are pulling 3.5 amps from the 144V battery pack and getting 35 amps at 12V output, it's 504 Watts in and 420 Watts out, or 83% efficiency. Not great, not bad. And if the input voltage is lower, and it's more like 3 amps, then it's only drawing 430 watts. Measurement accuracy is very critical when determining efficiency. But you can get a good idea just from how hot the converter gets. 80 watts sounds about right.


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## Ziggythewiz (May 16, 2010)

I don't think the heat's an issue. You shouldn't be typically driving with a dead ACC batt. As long as the DC-DC's just keeping things topped off, it shouldn't heat up much.


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## Tesseract (Sep 27, 2008)

skooler said:


> My only worry now is heat. I purchased a laser thermometer, after about 30 minutes use the DCDC is around 80C the Inductor is about 70C (but mounted on top of the DCDC.
> ...
> Any thoughts on the heat issues?


Your dc/dc does seem to be running quite hot, but the temperature rise of the inductor is normal and just indicates it is doing its job. 

Thanks for the feedback - whether the results are good or bad, every little bit adds to the sum of knowledge here.


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## skooler (Mar 26, 2011)

PStechPaul said:


> If you are pulling 3.5 amps from the 144V battery pack and getting 35 amps at 12V output, it's 504 Watts in and 420 Watts out, or 83% efficiency. Not great, not bad. And if the input voltage is lower, and it's more like 3 amps, then it's only drawing 430 watts. Measurement accuracy is very critical when determining efficiency. But you can get a good idea just from how hot the converter gets. 80 watts sounds about right.


Understand completely, its not very accurate but it is in the right ballpark and that makes me happy. what doesnt is the ammount of power the DCDC was pulling

Dont forget that a 144v LA pack is more like 160-170V fully charged, and the 12v output is actually 14.3v in my case.

So...
3.5A x 160v (was what my pack was at) is 560W in
35A x 14.3V = 500.5W Out

so~90% efficient - not bad.

Thats about 60w efficiency loss, or 60W of heat! no wonder its toasty!

Just as an FYI it is putting out less than 0.2A with a fully charged accessory battery and heat is not an issue.

Again, thanks for all the help! 

Cheers,

Mike


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