Awesome DC/DC converter 36-72v in 12v 20a out $20

[magudaman]

I just got two of these because I need some higher currents and these are small and light weight so they are 36v-72v in and put out 12v at 20 amps. They have trim too. Pretty fancy for $20 heres the link:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=130179644505&ssPageName=STRK:MEWA:IT&ih=003

 

[TylerDurden]

Sweet!

 

[Ypedal]

nice.. i inquired about shipping to canada !!!.. these could come in handy !

 

[magudaman]

I got mine. I ordered two and they got here in no time. The link above is dead but he made a new auction here: http://cgi.ebay.com/MicroVerter-DC-DC-Converter-48VDC-7A-12VDC-20A_W0QQitemZ130181032192QQihZ003QQcategoryZ58286QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

So I just wanted to do a little mini review. The units are brand spanking new! It got here only 2 days after I made payment and was well packed in anti-static bags and everything. After some initial mounting difficulties and quickly finding S+ and S- need to be connected for regulation, I did some testing. All testing done with 66v input. At lower wattage output (75 watts) I was seeing something 78% efficiency but I didn’t buy this unit for low wattage. So I pumped up the load to 18.5 amps and saw efficiencies of around 84%. Even though this is pretty good efficiency it had to dissipate 40 watts at the heat sink, so I was forced to add a heat sink to my design. The voltage regulation is very impressive, never getting more .1v off 12v, plus if you do remote sense then it will compensate for loss in the wires no mater how long they are.

Below are pictures of my finished case:

 

[flip_normal]

Double shhweeet,

looks like DC/DC converters are the way to go. Can't wait to get the two dozen 5W 30A ones I've got ordered. Should be able to test them using the 48V supply off the moped and the two Dewalt packs I've already got.

Christmas is coming early for some and efficient, cost effective power converters should make easy to build, fast charging battery packs a possibility for all in the new year.

 

[fechter]

Can't beat that for $20!

What do you need 20 amps for? You could run an aircraft landing light off that.

 

[diver]

could i ask what you need these for. If you have 72 volts why drop down to 12. is it to power an accessory?
thanks butch

 

[ngocthach1130]

Yeah we have accessory like HID lights and headlight that run on 12v. Some of us also cool our motors with 12v blower fan so just tapping into one battery from our pack will result in the drain on the battery to be unbalance so we step down voltage from 72 to 12v to run the stuff.

Magudaman, would you be able to come up with a schematic for the wiring you have there? I bought 2. Did you use connector for those erected pin?

 

[magudaman]

First off the unit I am using in the pictures there is for my RC truck charger that runs on 12v. Instead of carrying a heavy lead acid battery to the track or favorite bash spot I can take 5 lbs of lithium and this DC-DC converter. It lets me charge in the field at full rate of 180w to my rc truck. The charger of course only runs on 12v so it sucks around 18 to 19 amps because of inefficiencies. I have an additional unit that I want to put on my ebike for any sort of 12v accessories ie lights, cell charger, cigarette lighter ect.

ngocthach1130 -

Dang I really wish I would have taken a picture of what I did before I boxed it all up. On the heavy pins I used a drilled out spade connector like the one on the right:

I crimped my wire to the one side and soldered it to the post after I slipped out the drilled end. For the input side I soldered wire directly to the four input pins, two positive and two negative. You need to be sure to connect the sense pins to the output.

 

[ngocthach1130]

Yeah i had problem finding out what the s+ and s- were. The datasheet from the ebay site didn't explain a lot. It doesn't list much about the trim and the OG pin either.

 

[magudaman]

Check out these pages for info on

Trim: http://www.roassoc.com/apps/ap05b.pdf

required remote sensing: http://www.roassoc.com/apps/ap06.pdf

THe rest of the interesting stuff that seems to be missing from that other data sheet is in here too:

http://www.roassoc.com/apps/apps.htm

 

[diver]

thanks for the info. I just bought one because i want to add air horns to my bike and was not sure how to tap into the supply voltage. your picture is better then a thousand words for a guy like me
again thanks for the info
Butch

 

[Rassy]

Thanks magudaman. I have one on order also. I have been using an old 5AH SLA for running my brake relays, turn signals, horn, and some other lights. I hope this is just an easy swap. Those spec sheets scare me since I don't understand most of it. What should I have to do to it to handle these variable small loads?

 

[ngocthach1130]

well if you add them all up in parallel and they still don't add up to the 20a peak then you should be good. With so much stuff to plug in you should look into more of a power distribution hub instead of a huge chunk of wires and connector.

 

[magudaman]

Unless I missed something I don't think low transient loads are any kind of problem for these converters. As long as you have those sense lines connected to your output as shown in the diagram you should have perfect regulation that is set at 12v, the unit does all the regulation stuff for you.

 

[Rassy]

Thanks magudaman. I think the fuse on my aux. battery is 20 amps and it has never blown. It will be nice to get away from the nuisance of charging the extra battery, etc.

ngo... said:

With so much stuff to plug in you should look into more of a power distribution hub instead of a huge chunk of wires and connector.

Yes, as fun stuff gets added, a few extra wires are required. But a hub wouldn't clean up much, since items are distibuted between the trike and trailer. I have only three connectors at the trailer hitch: A four flat for the throttle wires; a two flat for the + 12v and -12 V; and a five flat for the power/brake relays and the turn signals.

Now if fechter and Ted keep going on regen ideas, I may have to learn what a FET is all about, etc. and really load up the trailer with stuff.

Oh, yes, I forgot the solar panels!

 

[Rassy]

Ordered the converter on Sunday, came in the mail on Thursday. Being solder challenged, will just use common connectors. Don't know where the small spade females came from, but they fit on the pins snuggly. If the connectors give trouble, my retired EE buddy will help me solder everything up. He almost went to work for RO Associates in the early 80's, but didn't want to stay in the Bay Area and relocated in Oregon instead.

Won't have any time for this project for the next week, and will report how it works after installation.

Edit: Hey, look, the date on my camera corrected itself today. Strange, because it has been used and uploaded several times since I noticed it was off by almost a week.

 

[ngocthach1130]

awww crap. I was cleaning out the parts box few days ago and threw out some of those big round connector. Didn't even reallize they would fit. Guess i'm off to radio shack to be ripped off again.

 

[Rassy]

ngo... said:

Guess i'm off to radio shack to be ripped off again.

The connectors don't really fit "properly". They require a little squeeze with the pliers to create a snug fit, which is why plan B includes solder.

 

[Rassy]

Finally got the DC/DC converter installed, but too late for a ride. I installed a switch between the batteries and the converter, because it has a small draw all the time. It seems to work perfectly. With the 48V battery pack fully charged, it checked out between 11.97 and 11.99 volts on my DVM, depending on what was turned on. Will check it out again after the batteries are partially discharged.

 

[magudaman]

I was running mine on around 32v yesterday and it still was not browning out on the output side. Still holds around 11.99v. I think I was exceeding the input current...I'm not sure if that is a problem or not. Does anyone know if you can exceed 7amps input with out damage?

 

[Timbo]

That looks really neat - what does it weigh??

 

[ngocthach1130]

Hmmm i'm guessing about a pound or less. This is hand estimating.

 

[magudaman]

It weighs 7oz or around 200 grams, according to the spec sheets.

 

[fechter]

I think it's supposed to have overcurrent protection, so if you try to exceed the maximum current, it will start to brown out. The only other thing to watch out for is temperature. Make sure it doesn't get too hot.