blown a DCDC converter

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nonlineartom   1 kW

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blown a DCDC converter

Post by nonlineartom » Sep 19 2012 4:54pm

Had a 15W dcdc converter from Lyen, worked fine for a few minutes then trying it with a multimeter it all of a sudden started outputting the source voltage on the output terminals, I've heard about this happening to this type of DCDC converter and blowing lights / grear that's connected, didn't expect it to fail so soon.

I really urgently need a solution for going from 50V to 12V can anyone recommend anything? everything available in the UK is either fixed 12/24V or 32V maximum. Is it fairly simple to roll your own converter?
Commuter bike: 10T MAC Schwinn Panther Beach Cruiser on 12S LiPo, super stealth hill eater
Forest trail eater: Crystalyte 5306 KMX Viper with 24" wheel. 100A controller 18S LiPo
Pocket rocket: 8T MAC e-BMX 18s LiPo. Missile for testing to destruction
Summer ride: 8T MAC Kona Joe MTB / chopper / beach cruiser hybrid bike. 24" wheels and a lot lot of style.
--------------------------------------------------------------------------------
Respect and fear the ancient god LiPo and pray he is merciful.

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marty   10 MW

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Re: blown a DCDC converter

Post by marty » Sep 19 2012 5:26pm

Look here:
Cheap DC-DC converters for over 60v input.
http://endless-sphere.com/forums/viewto ... =16&t=2264

38,841 DC/DC Converters for sale here:
http://www.mouser.com/Search/Refine.aspx?N=254455
MARTY
Volt Electric Vehicles
http://www.voltev.com

velias   100 W

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Re: blown a DCDC converter

Post by velias » Sep 21 2012 2:56pm

Same thing happend to me with same lyen DC/DC converter
It worked fine for a few months then I plugged it in while my pack 16S life was fresh off the charger
and pow, blew my 100 dollar headlights.

I think it was just at or above the input voltage limit with the batterys freshly charged up to 58 volts or so.
I should have waited a few minutes or discharged the pack for a second before hooking it up.

It would have been good to have used a dc/dc converter that is isolated so if anything ever goes wrong,
the voltage from the input doesnt appear at the output.

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nonlineartom   1 kW

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Re: blown a DCDC converter

Post by nonlineartom » Sep 21 2012 3:57pm

difficult to do. I've heard several cases of these lyen dc-dc's failing and killing the gear. Trying the mehtod of using a 2A switched power supply from a powertool charger to see if that works, feeding the 240V AC input with 50V DC and see if it will still happily pump out 12V DC. Results to follow.

How could you isolate the dcdc to protect against a full voltage throughput, a fuse won't work will it? on my trike I have a proper PCB that has the DCDC on it to go to the various 12V devices then a further 5V dcdc.
Commuter bike: 10T MAC Schwinn Panther Beach Cruiser on 12S LiPo, super stealth hill eater
Forest trail eater: Crystalyte 5306 KMX Viper with 24" wheel. 100A controller 18S LiPo
Pocket rocket: 8T MAC e-BMX 18s LiPo. Missile for testing to destruction
Summer ride: 8T MAC Kona Joe MTB / chopper / beach cruiser hybrid bike. 24" wheels and a lot lot of style.
--------------------------------------------------------------------------------
Respect and fear the ancient god LiPo and pray he is merciful.

velias   100 W

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Re: blown a DCDC converter

Post by velias » Sep 21 2012 4:17pm

any dc-dc with a primary-secondary transformer would be isolated.

I carved open the Lynn dc-dc converter I dont remember seeing any transormer in it.
I think the dc-dc chip was a national semiconductor (now TI) chip and if I remember it was rated at its high limit for input voltage in.
who knows maybe it was counterfeit or something.

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GITech   100 W

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Re: blown a DCDC converter

Post by GITech » Sep 22 2012 2:16pm

I am using a "laptop PC" power supply on 16s (59.9v nominal) rated for 12v 5A output. It is isolated.

I've run the batt down to cutoff (~52v) and the power supply still ran fine.

I had to try 4 different ones before I found one that worked. Good thing I had them laying around. :)

It has held up to a good deal of abuse, I don't think I will ever go back to the "DC/DC converters".

I also fused the input and output this time, but haven't blown one yet anyway. Better safe than sorry.

Later,
Jay
Ebike: Wallmart Genesis frame, unique Lovejoy 2-speed simplified/redundant drive mounted on custom aluminum swingarm conceptualized by me, machined by Thud. Brushless 80-100~100kv w/halls, 16s6p - 59.9v, 30Ah, 1.7+KWh, Fully Loaded Lyen 12 FET 3077 controller w/ Cycle-Analyst, full custom lighting.

Thanks to Justin at ebikes.ca for saving ES!

Ideas and projects by GITech are protected by: http://creativecommons.org/licenses/by-nc-nd/3.0/

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