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  #41  
Old 06-13-2012, 04:40 AM
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Default Re: Dcdc fuse keeps blowing

Quote:
Originally Posted by PStechPaul View Post
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/sto...0001_374070_-1
If you are not afraid of ordering from China then see http://www.dealexcel.com/unit-ut204-...eter_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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  #42  
Old 06-13-2012, 06:52 AM
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Default Re: Dcdc fuse keeps blowing

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Originally Posted by mora View Post
If you are not afraid of ordering from China then see http://www.dealexcel.com/unit-ut204-...eter_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.d...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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  #43  
Old 06-13-2012, 12:20 PM
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Default Re: Dcdc fuse keeps blowing

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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  #44  
Old 06-13-2012, 02:15 PM
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Smile Re: Dcdc fuse keeps blowing

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-...item3cc1162796

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

Last edited by PStechPaul; 06-13-2012 at 02:17 PM.
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  #45  
Old 07-01-2012, 06:04 AM
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Default Re: Dcdc fuse keeps blowing

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/2609638560...84.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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  #46  
Old 07-01-2012, 05:50 PM
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Thumbs up Re: Dcdc fuse keeps blowing

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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  #47  
Old 07-01-2012, 06:40 PM
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Default Re: Dcdc fuse keeps blowing

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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  #48  
Old 07-02-2012, 04:58 AM
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Default Re: Dcdc fuse keeps blowing

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Originally Posted by skooler View Post
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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  #49  
Old 07-02-2012, 06:46 AM
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Default Re: Dcdc fuse keeps blowing

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Originally Posted by PStechPaul View Post
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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