# Cheap DC/DC converter



## peggus (Feb 18, 2008)

You can look for Vicor power supplies on eBay. It is hard to find 144V input capable ones but you can use several 48V units in series. 

For example: if you have a 144V pack you'd get 3 48V in to 12~15V out Vicor units like this one: 140094905713 (though not from this seller). Connect each Vicor across 4 batteries in your pack so that Vicor 1 is powered by battery 1-4, number 2 is powered by 5-8, and unit 3 by 9-12. Connect the outputs in parallel and presto you have a 144V to 12V 300W DCDC converter. Need more power? add more Vicors! Just don't load your pack unevenly. 
You'll also need some protection and support circuits, see Vicor application notes for further details on that.

Another option is to look for a Vicor PFC Megapack with 12V~15V output modules. They will generally run from 100 to 300Vdc input. I use something similar on my EV, a 600W, 12V Aztec PFC power supply.


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## frodus (Apr 12, 2008)

and if you read the Vicor application notes, you are NOT supposed to parallel the driver modules. There's nothing in the manual about stacking several Driver boards together, only drivers and boosters.. If you have a driver and several boosters, its fine, but if they're all drivers, its not something that they say you should do, and I've verified with their engineers. The problem is, each one has closed loop control circuitry inside. boosters don't, and use the driver's control circuitry.

If you need more power, get a high power from the get go, otherwise it may lead into issues with not being able to regulate the output on several modules. you could get a driver module, and several boosters though, that works just fine (verified). 

And if you say it works, thats great, but just try loading it... SOMETIMES the output goes into some weird modes. I worked at GE for 5 years as a lab rat on their Turbine control systems and their Wind Energy. We used some of their modules and put them through HELL testing their limits. We tested them in parallel and circuitry was added to parallel them, but it was more expensive (R&D, parts cost, board layout etc) than getting a driver and several boosters. Plus, boosters are cheaper and don't have the control circuitry on them, and they're guaranteed to work together.


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## Cornelius (Sep 15, 2007)

Another brand of power supply that works well as a DC to DC converter is Iota. The Iotas are used in many EV conversions. I have a 75A model in my S-10. Since it also feeds an AC inverter, I bought a higher current model than most EVs would need.

Here's the manufacturer's website with their various models:

http://www.iotaengineering.com/12vdc.htm


I bought mine from Northern Arizona Wind & Sun. They have several models with various current ranges to choose from. Simply add up your 12v current needs and select the appropriate model. Here's a typical one for EV use:

http://store.solar-electric.com/dls-45.html


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## elevatorguy (Jul 26, 2007)

Twilly said:


> Anyone have some ideas on making / reconfiguring a DC/DC converter? I have heard that some people are using 120Vac in/12 Vdc out battery chargers and feeding them with 120-144 Vdc... Any brand names or model numbers that are confirmed to work?
> 
> Thanks
> Twilly


I am looking for a less expensive dc/dc also, wanting to do on the cheap. 
You can't just feed any 120 ac charger dc as they are transformer input, some switching supplies will accept dc and ac, I have yet to find one that will work for me.
Jerry


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## evric (Oct 26, 2008)

Mean Well SP-500-13.5 - has DC input specs of 124 - 370Volts DC. When tested they work down to less than 120V. Output is adjustable as well around the nominal 13.5V. Eric


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## sailfish11 (Sep 15, 2007)

evric said:


> Mean Well SP-500-13.5 - has DC input specs of 124 - 370Volts DC. When tested they work down to less than 120V. Output is adjustable as well around the nominal 13.5V. Eric


I like the specs (and price!) of the Mean Well unit -- but I'm worried about the 'if it's too good to be true...' axiom. I did a quick search on the EV Album and found a few that are using that brand.

Do you know of anyone using it? Is it tough enough for EV use?


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## sailfish11 (Sep 15, 2007)

peggus said:


> You can look for Vicor power supplies on eBay. It is hard to find 144V input capable ones but you can use several 48V units in series.
> Another option is to look for a Vicor PFC Megapack with 12V~15V output modules. They will generally run from 100 to 300Vdc input. I use something similar on my EV, a 600W, 12V Aztec PFC power supply.


Wow, this may be the answer I've been looking for. I have a 320V system; so can I just line up a bunch of 48V (or whatever) in series? 

I've looked for the Vicor Megapack and can't find anyone selling one -- anyone have link?


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## KiwiEV (Jul 26, 2007)

Twilly said:


> Anyone have some ideas on making / reconfiguring a DC/DC converter? I have heard that some people are using 120Vac in/12 Vdc out battery chargers and feeding them with 120-144 Vdc... Any brand names or model numbers that are confirmed to work?
> 
> Thanks
> Twilly


This might help. Scroll down the page to "September" here and see how I did mine. There are links galore too. Hope it helps.


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