DC to DC converters

Technical discussion on converting internal combustion to electric
ckas
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DC to DC converters

Post by ckas » Tue, 06 Nov 2007, 06:37

Hey all - Ive had a quick look for DC to DC converters, im needing one to convert 72 volts into 12 (or 13.8 really) volts. Anyone know of any good, preferably local, suppliers?

Chris

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Post by jpcw » Tue, 06 Nov 2007, 15:52

I contacted the DC shop (www.dcshop.com.au), they have a second company (sorry can't remember the name) that supplied me with one. Basically it was just a switch mode power supply which has a 110 - 240V input range and a 12v output at 6A which they tweaked up to ~13.5V. Apparently a lot of switch mode power supplies don’t care if they are running on DC or AC. If you are going to use it for charging a 12V battery you can get away with a low current one provided it is a constant current unit otherwise it will overload and trip out when you switch it on and the battery wants more than its max. If you are going to run everything directly from the converter then you need to work out what the max draw is with all your lights on etc. There is a photo of it in my album, I’ll try to update that with one showing the actual model details later tonight

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ckas
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Post by ckas » Wed, 21 Nov 2007, 02:48

I got one from the Amtek company.
Nice people to deal with.
The 9262 Mascot cost me about 270aud including shipping

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Post by jpcw » Fri, 23 Nov 2007, 05:30

What were the specs on that, about the same cost as mine, 6.5A @ 13.5v
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Post by Andrew » Fri, 23 Nov 2007, 19:05

check out e_crazyman on Ebay (search for switch mode power supplies). This guy is in China. We have bought 15 55volt 100watt DC supplies for our EV, these accept 90 to 260 volt AC or up to 360 volts DC. We ordered these items specially and worked out to be AU$29 landed. The guy will make up supplies to any spec. Maybe worth checking out yo. Image

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Post by ckas » Sun, 25 Nov 2007, 01:49

The 9262 mascot is 13.6v 6 amps

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acmotor
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Post by acmotor » Wed, 28 Nov 2007, 08:17

e_crazyman (in Hong Kong) also does 13.7V 10A switchmode supplies designed for lead acid charging. I have bought 6 of these so far and the are quite bullet proof. These worked out to AUD$39 landed. Image
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Post by zeva » Sat, 15 Dec 2007, 05:24

Are you guys using these DC-DCs to power your vehicle's 12V auxilliary
systems? I wouldn't have thought 6-10 amps was nearly enough to run the
headlights (etc). Most of the EVDL guys recommend 300W minimum rating
for your 12V DC-DC converter (i.e ~25 amps)..

(I'm using an IOTA DLS-45 in the MX5, though their input range is more like
120-180V.. no good for 72V systems)

I spoke with Peter Mitso at Amtex (.com.au) a while back about DC-DCs,
they do some nice units around the 300W mark for all sorts of input
voltages. Another good one is V-Infinity (.com), though they're a little more
expensive.
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Post by Simon » Fri, 19 Dec 2008, 23:46

I brought this 100w switchmode power supply to use as a DC-DC converter.
Image
Its a Soanar MP-3175 from Jaycar.
I need some help with wiring it up.
Do I wire 96v+ into "L" and 96v- into "N"? or doesnt it matter which way round they go?
And not connect anything to ground? Image

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Post by Johny » Fri, 19 Dec 2008, 23:53

Hi Simon. No it doesn't matter at all. It was intended for AC so your DC will get put right either way. Are you wiring this via fuses and some kind of relay?

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Post by Simon » Sat, 20 Dec 2008, 00:01

Hi Johny
Thanks!
Yeah I'm wiring with fuses on + and - and switched on by a relay when the key is turned to on.

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Post by acmotor » Sat, 20 Dec 2008, 00:06

Correct, just wire it straight in, either + or - to L or N

It just connects to a bridge rectifier (and some filter components) via a 5AG 3A fuse internally, but don't rely on this to protect wiring to the SMPS.
Any wiring from the battery pack should be fused at the battery pack ( both + and - wires ) a 3AG (1 1/4") inline 2A fuse would be fine.
Any competent inspector would look for this and it may save you trouble.

I use the same supply x 2 in red suzi running off 300VDC each with the outputs in parallel and set roughly to the same voltage 13.8V.

Note. the supply should be switched to 110V not 220V on the switch on the inside PCB in your case.
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Post by Johny » Sat, 20 Dec 2008, 00:08

Sounds good. You may have trouble at turn on as the inrush current that switch mode power supplies draw is often up above 20 Amps briefly. Just don't worry that you have done something terrible if the fuse(s) blow. Slow blow fuses may be required.

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Post by acmotor » Sat, 20 Dec 2008, 00:19

Hoops is right about power.
red suzi draws 25A with everything on at 12V = 300W
The 100W SMPS actually cuts back at 12.5A after drooping a bit in voltage so with 2 it is only just there.
But then it is not very often I am going backwards with the headlights on and my foot on the brake with the fan on full in the rain while the horn is going. Image
...and the SMPS are charging the 12V aux 20Ah SLA so there is a bit of a time buffer.

300W would be a minimum for all up continuous as there are other loads that I don't have. e.g. 2000W sound system.

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Post by Simon » Sat, 20 Dec 2008, 00:22

Yeah it says "Cold start inrush current 40A"!

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Post by acmotor » Sat, 20 Dec 2008, 00:45

I checked the inrush and it is well within the i^2t spec of fast acting 3AG wire fuses and not as bad as it sounds. (only ms in time)

I made up this PCB with ceramic 5 ohm inrush resistors on red suzi but in the end found it worked fine without it. The input filter inductor in the SMPS does most of the work.

I can have up to 375VDC going to the supplies so Simon's 96VDC will be no issue, even with the SMPS caps in parallel.
Always try to use fast acting fuses with any semiconductor equipment. It means that the bang is not as loud.

Image

One supply runs off +300VDC, the other off -300VDC to centre of battery pack.
The fuses are after the resistors and these are fed from the DC input terminals on the Danfoss.
The whole lot is inside the vast Danfoss cabinet !

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Post by Simon » Mon, 22 Dec 2008, 20:53

I wired it up yesterday and it doesn't seem to work. It's set to 110v on the internal switch and the output is only 8.1v-8.2v and adjusting the pot only increases it from 8.1v upto 8.2v.
So I tested it on 240vAC with it switched to the 240v setting and it gives 13-15v.

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Post by Johny » Mon, 22 Dec 2008, 21:07

Hmmm. I wonder if they have a built in brown-out sensing system...
I don't have one of these but acmotor has a couple. Let's see if he is able to help when he sees your post - shouldn't be long.

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Post by acmotor » Tue, 23 Dec 2008, 07:30

96V is a bit on the low side when it is expecting 110 x 1.4 = 154VDC although most SMPS seem to work down to less than half voltage.
Mine are of course working on the 220V mode with voltages of 250VDC to 375VDC when expecting 308VDC.

One test, just to check voltage switch is actually wired up...
If you switch to 220V does it still give the same output voltage ?

Was the 8V with or without a load ? if so, how much load ?
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Post by Simon » Tue, 23 Dec 2008, 18:33

The voltage switch must be wired up because the output voltage drops to 3.2v when its in 220v mode.
The 8V (110V mode) was without any load. Looks like not all SMPS are created equal, oh well.

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Post by jpcw » Tue, 30 Dec 2008, 22:16

One thing I noticed. There are a couple of conversions using plain PC power supplies such as the 750W Thermaltake PSU’s running at between 120 – 144V input. You can get ones up to 1600W for around the $400 mark.
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Post by zeva » Tue, 30 Dec 2008, 22:26

Here's an interesting possibility I came across recently:

http://www.computronics.com.au/meanwell/sd-500/

They're based in Perth (handy for us). ~$170 inc GST for a 500W DC-DC converter, not bad! 12V output but tunable 11-15V so should work in conjunction with a "12V" lead acid if set to 13.8V output.
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Post by bga » Thu, 01 Jan 2009, 00:57

A quick snoop of the computronics web side reveals some more options:

The 500 watt supply Ian mentions is available in two input voltage ranges: 19~72VDC and 72~144VDC

For 144V and up, the conventional DC/AC supplies can be used:

MeanWell PSP-600-13.5 124-370VDC, 600W, 44A/13.5V $181+GST in Stock
MeanWell PSP-1000-13.5 127-370VDC, 1000W, 67A/13.5V $415+GST in Stock

No mention of load sharing, but the PSP600 has lots of I/O, so maybe.

I've used Meanwell power supplies in projects for some time and have had a good experience with them.

Also, they have a good range of soldering accessories such as bar solder, soldering stations, solder pots, the sort of stuff that none of the usual retailers carry.

Cheers
BGA
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Post by Simon » Thu, 01 Jan 2009, 21:11

Thanks Ian for that link. Looks good and the price is right too! I will get one of those soon.

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Post by Peter C in Canberra » Fri, 02 Jan 2009, 02:35

I got the big brother of the Iota 45 that ZEVA was selling, the Iota 90 (IE 90Amp output) via the Aldridge Electrical Industries (02-95409966). It cost me $594 inc freight but that was around the time the exchange rates were moving. Most likely a bit more now. I have not tested it yet but assume it works the same as the Iota 45. Both are intended for USA AC power in.
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