DIY Electric Car Forums banner

dc-dc converter

28K views 141 replies 33 participants last post by  favguy 
#1 ·
I just found some dc-dc converters on ebay, I'm looking at a Vicor V1-251-09 200v to 12v model and am wondering if anyone is familiar with this one. I sent a request to the seller for the datasheet but while I'm waiting I figured I would post it here .
 
#2 ·
That would be VI, not V1... and did you not even try Vicor's website?

http://www.vicr.com/cms/home/technical_resources/Data_Sheets

The -09 (-O9?) suffix doesn't seem to be current, but VI-251 means it has a 150VDC nominal input and a 12VDC output. Note that part number VI-25P has a 13.8VDC output and therefore would be much better suited for use in an EV. All the VI converters have a provision for trimming the output voltage over a narrow range (+/- 10%) so you could get up to 13.2V on your 12V model but that still isn't enough to keep the 12V battery charged. I personally think relying on just a DC-DC converter for the 12V system in a vehicle is way too risky - at least use a small garden tractor battery so if/when the dc-dc finally blows up from the abuse you aren't stranded.
 
#3 ·
#9 ·
I bought this vicor and am very unhappy. I ended up needing two so that the vacuum, lights, contactor, and potentially blower or windshield wipers could all be powered.

Since it only gives out 12 volts it does a fail job of charging the accessory battery. I need the accessory battery to turn on the contactor. I often use an extra charger to charge the accessory battery just because I don't trust the vicors will give me the required power.

I recommend against buying this, buy something that outputs 13.8 volts.

Jim
 
#11 ·
I bought this vicor and am very unhappy. I ended up needing two so that the vacuum, lights, contactor, and potentially blower or windshield wipers could all be powered.

Since it only gives out 12 volts it does a fail job of charging the accessory battery. I need the accessory battery to turn on the contactor. I often use an extra charger to charge the accessory battery just because I don't trust the vicors will give me the required power.

I recommend against buying this, buy something that outputs 13.8 volts.

Jim
its only ~250W, of course you'd need two for a car.... at 12V, thats 20A, I'd use at least that on my motorcycle. I think a MINIMUM for a car/truck is 3-400W.

Did you trim it up with resistors to get 13.2V?
 
#10 ·
my old curtis is only 300 watts, but is enough for everything including fan...

In prep for my pack upgrade from 96v to 120v I did step up to 500 watt chennic, so should be more than enough. I got the 13.5v output in case I ever charge a 12v battery, but for now I just go direct with no aux battery. I ordered one voltage step down from my 'nominal' to avoid low end brownout when batteries are at full load/sag...
 
#12 ·
I have these exact Vicor DC-DC units, and I got them on ebay from Troy Gaud at Azure Dynamics. He does not have a data sheet for them; he will send you the generic VI 200-Series Vicor data sheet, which does not in fact have this part number listed anywhere on it.

The -09 suffix signifies that these converters were a from a custom run by Vicor for Solectria/Azure made around 2007. They vary a little in spec from a standard VI-251-xx converter, as they are listed at 200V nominal input voltage, and the part# call-out would normally be 150V. Vicor will not discuss the specs of these units with anyone not from Azure, (ask me how I know...) but Troy told me that according to the Azure engineers, they are good down to about 130V, and up to a little over 250V input. They are also in fact "IU" suffix-class, which means -40 to 85 degrees C operating range, and 200W max output. I also have the -09 series matching Booster units, which allow you to run several booster bricks off of one 200 Series control unit. I haven't installed them yet, but I'll be using 4 or 5 boosters and a control unit, for either 75 or 90 amps of max current at 13.2V. Just what a late-model car needs.

These DC-DC converters can be trimmed up to 13.2V output by installing a trim resistor. If you only have 200-Series units, and no boosters, you can match them in trim and still use them together, as Jack Rickard has documented. His implementation, complete with a schematic and some thoughtful instruction, is here:

http://jackrickard.blogspot.com/2009/10/this-week-on-mini-cooper.html

Don't use Jack's resistor values on the VI-251-09! The correct one is 422K, from Section 5 of the Vicor Manual. You could also put in a pot and trim the output manually. In any case, it is instructive to just RTFM:

http://cdn.vicorpower.com/documents/applications_manual/DesignGuideAppsManual_200J00.pdf

I actually think this unit and the matching booster are superb quality equipment, particularly for the price, and the ones I got from Troy were brand new. They are in fact the very units you will find if you open up the Azure Dynamics DC-DC converter, and at $50 versus the hundreds they cost new, you really can't go very wrong. My understanding is Azure has "hundreds" of them to sell...

TomA

Not a shill for Vicor or Azure Dynamics, though both have been nice to me on the telephone...
 
#15 ·
These DC-DC converters can be trimmed up to 13.2V output by installing a trim resistor. If you only have 200-Series units, and no boosters, you can match them in trim and still use them together, as Jack Rickard has documented. His implementation, complete with a schematic and some thoughtful instruction, is here:

http://jackrickard.blogspot.com/2009/10/this-week-on-mini-cooper.html

Don't use Jack's resistor values on the VI-251-09! The correct one is 422K, from Section 5 of the Vicor Manual. You could also put in a pot and trim the output manually. In any case, it is instructive to just RTFM:

http://cdn.vicorpower.com/documents/applications_manual/DesignGuideAppsManual_200J00.pdf
Wow, thanks! I never knew that. I will be trying this first thing when I get home from school for the summer.
 
#18 ·
Can I pose some questions here also?

I am going to get converters for both my compact tractor and my MR2.

For the MR2 I will wait until I know what voltage I am going to run at and then get an isolated 500W+ 13.8V converter. I figure that is the sort of thing I will need to run a car.

But for the tractor. I only have 48V. Can I use a golf buggy type non isolated 120W 12V converter?
I dont know if the 12V vs 13.8V and isolated vs non isolated will be an issue.
I am planning on running some lights and the reversing contactors.

Guidance will be much appreciated.
Thank you.
 
#22 ·
As an alternative to the Vicor: Densei-Lambda (TDK-Lambda?)
Theses DC-converters (I got four of them) have although a great input range and a adjustable output.


300W (25A) per unit will be more than enough, so I can perhaps leave one out of the car.
Nice feature: If I wire them parallel, they will (hopefully) share the load.
I hope that this will hold the temperature down.
Everything theoretical, not tested yet.

TDK-Lambda:
http://us.tdk-lambda.com/lp/products/ph-series-ff.htm

documents:
http://us.tdk-lambda.com/lp/ftp/Specs/ph-ff.pdf
http://www.ic-on-line.cn/IOL/datasheet/ph300f280-_278821.pdf
 
#30 ·
Francis I don't think you're supposed to parallel these things like you do with batteries, if they're Vicor models anyway. They make a master and a slave unit for added watts. Just an FYI.:)
Nice thing about putting them in parallel is doubling the ah and being able to increase voltage to about 14.5v which is what we should all be using. Is very simple, been doing it sice 2002 on Li-ion conversions as only 12v-15v source without any batteries for system source..
 
#29 ·
It will be a good test of these vicors. If no worky, then I will use one on my trike that SOMEDAY I will finish.
BTW. If you have an Iota 55 (1000watt unit) and using 100 watts, will it use more or less overall watts compared to a Vicor 100 watt unit putting out 100 watts?

Theory to me is that a car with a big V-8 motor will use more gas than a moped, both traveling at 30mph.

francis
 
#32 · (Edited)
I've been following this thread with interest as I've been thinking about DC/DC converter options lately. I'd like an opinion on the following as an option.

Laptop computer power supplies are readily available that use a universal input of 100V to 240V AC @ 50 to 60Hz. With an output of 15V @ 8A. These can be bought for as little as £6, (around $9) each. I know that they will also work with a DC input of 144V/156V nominal. Obviously 8A is inadequate for a DC/DC coverter, but would it be feasible to run 3 or 4 in parallel to give a suitable power output?, and if so would they need a diode on each units output to avoid upsetting one another? 15V should be within tolerence for the 12V system if used with no battery (as it would see 14.4V with an ICE alternator anyway). If used with a small lead acid battery, would the battery cope with the slightly higher charge/float voltage of 15V? or possibly the supplies output could be trimmed down to 13.8V/14.4V by finding and changing out the right resistor?

Has anyone tried this yet and had any joy?
 
#33 ·
With the way electronics are designed, connecting a device designed to work on AC input like the Iota and computer PS will likely not hold up at it's rated output amps because you're only using half of the rectifier diodes thus only 50% of the design power. Using only half will likely burn out in this application due to a doubling of it's design amps if you try and draw full capacity from it.
 
#36 ·
Thanks for the input so far guys,

But... Electricar, although I appreciate your input, your understanding of bridge rectifiers appears to be flawed, during an AC cycle, power is first chanelled through 2 diodes of the bridge, then during the second half of the cycle the other two diodes. When applying DC, dependent on which way the polarity is, one set of 2 diodes or the other is solely used, power input is not halved. Also, as the supply voltage can be anything from 100V to 240V on this type of unit the DC battery voltage (at least at 144V/156V) is well within the design range the unit can cope with and is expecting from rectified from AC, DC input voltage.

My concern isn't input, it's more about output and using these in parallel to achieve a suitable stable current supply, the point made about isolation is a good one. I will test my existing laptop supply for this, but as they can be used with up to 240V AC input, I'll be amazed if the output is not isolated.

As for saving a buck... I partly agree on this one, but controllers aside, a lot of "bespoke" EV components are often very overpriced due to the low volume demand, and are often only slightly rehashed from existing non EV equipment available for a fraction of the price due to economies of scale!
 
#37 ·
Thanks for the input so far guys,

But... Electricar, although I appreciate your input, your understanding of bridge rectifiers appears to be flawed, during an AC cycle, power is first chanelled through 2 diodes of the bridge, then during the second half of the cycle the other two diodes. When applying DC, dependent on which way the polarity is, one set of 2 diodes or the other is solely used, power input is not halved...
I just realized the error of my thoughts on that. ;) You're right each set does take the full current through them. Rectifying power through one set continuously however doubles the average amps through them and really boosts the heat build up which is likely a contributor to the early failures. What was I thinking initially. Electronics class was way back in the early Reagan days...:)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top