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Old 16-12-2018, 06:16   #1
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Getting from 110/20A to 48V DC @ 65A

I have a load (specialized DCDC charger) that can handle a very wide range of DC voltage input; I want to have 2400W of power available, but 65A is the max current it will accept.

So in 12V increments, it seems like 48V is needed, although 36V comes pretty close.

I want max flexibility from upstream shore power or onboard generator input.

So I'm thinking two separate power supplies / chargers, ganging the DC outputs, since

sometimes would only have 2x completely independent USA 110AC circuits available, not always 30A or 50A outlets.

I also want to be able to accept 220/240V "world power", either 50/60Hz.

True ground/earth will not always be available, usage off-grid in land vehicles as well as on boats, maybe fresh, more commonly seawater.

Well regulated steady input power is critical, as with sensitive electronics devices.

If I were made of money, it seems a pair of Mean Well RSP-1500-48 might do the trick.

Assuming it's OK to parallel on the output side.

Or would putting output from a pair of RSP-1500-24 in series be better?

A very highly recommended and **much** more economical solution is the ES120 PSU from HP/Compaq, for their data center blade servers, ( Part# 226519 or 253232 )

Built like a tank, super well regulated output, designed to produce 3kW (51.4V at up to 57A), continuously, 24/7 for years at a time.

Often go through eBay for under $60 delivered.

Problem is not flexible enough on inputs. Yes worldwide in frequency, 50/60Hz, but requires one big plug at 220/240V, no 120V for low-end US circuits.

Would really rather not have to add a transformer to the gadget chain.

All suggestions and discussions welcome, I'm an electrickery virgin on the AC stuff.
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Old 16-12-2018, 17:56   #2
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Re: Getting from 110/20A to 48V DC @ 65A

You might be able to find a powertec super switcher on ebay for fairly cheap. I used to use them to drive RF excited CO2 lasers.

For example here is one that takes 110 or 220 and outputs 48V at 36A

https://www.ebay.com/i/401648695793?chn=ps


Edit: Those 1500 watt Mean Wells are pretty inexpensive though. Like $300 each...barely even registers on the boating expenditure scale
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Old 16-12-2018, 18:33   #3
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Re: Getting from 110/20A to 48V DC @ 65A

Thanks, but I've been making some progress in the electrickery-specific forums.

The top-tier server PSUs I'm looking at are much better protected and stable regulated output than any Mean Well, and literally go for peanuts.

Many put the PSU output in series to get voltage up, maybe DC-DC boost in the mix, I need to get to 36V at least, 48 would be better.

Safety wrt the grounding is a sticky point, everyone's more used to shore grid power inputs, rather than mobile generator setups where there may be no ground at all.
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Old 17-12-2018, 05:21   #4
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Re: Getting from 110/20A to 48V DC @ 65A

I'm really not following what you are trying to do.


You have a device that you want to power that accepts a wide range DC input. I got that much.


It's a 2400W load, and can accept a max of 65A, so to get the desired 2400W load you need a minimum of 40VDC input voltage. I think I got that part.


Now you want to power that from worldwide mains power? So converting from mains AC to 40VDC or higher, and powering a 2400W load?


What's the max DC input voltage for your "wide input range device"? Can it accept 400VDC?


So you want to convert mains power to DC, to power a DC to DC converter, to charge something or other?
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Old 17-12-2018, 05:49   #5
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Re: Getting from 110/20A to 48V DC @ 65A

You've got it. And the DC charger / discharger will take care of just about any maintenance protocol for just about any type of cell, equalizing, load testing, balancing.

The max input is nominal 48V, actually spec'd at 50V

That ES120 PSU puts out 51.4V, but I've found a few howto's on lowering it a bit.

Problem is it only works on 200-240VAC, I'm looking for the greater flexibility as spec'd in the OP.
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Old 17-12-2018, 17:13   #6
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Re: Getting from 110/20A to 48V DC @ 65A

Maybe I'm underthinking it, but why not use 4 twelve volt batteries connected in series and use conventional battery chargers powered by whatever AC power you have available?


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Old 17-12-2018, 19:32   #7
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Re: Getting from 110/20A to 48V DC @ 65A

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Originally Posted by JOHNMARDALL View Post
Maybe I'm underthinking it, but why not use 4 twelve volt batteries connected in series and use conventional battery chargers powered by whatever AC power you have available?


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Yup, and you coudl use a Victron 48V charger, a number of which will accept a very wide range of AC (and DC) inputs.
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Old 18-12-2018, 01:21   #8
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Re: Getting from 110/20A to 48V DC @ 65A

You can't. Even with a perfect conversion with zero loss, which is impossible, 110v at 20a is 2.2kva, and 48v x 65a = 3.12kw. With a perfectly efficient conversion, you would get at best 45.8a at 48v. Pulling more current than that will overload your 20a 110v breaker.

However, the cheap and dirty way to convert 110vac to 48vdc would be with a Variac and a rectifier from an old stick welding machine, or a new rectifier with a suitable rating. The variac steps down the voltage, the rectifier makes a somewhat ripply DC out of the AC, and you fine tune the output voltage with the variac knob. You could knock down the ripple with a big LC filter if you are worried about it, but all it is, is a 60hz hum. No spikes or anything super nasty to your electronics. I use this variac/rectifier setup for manually charging my 48v bank on my electric boat, when using the ryobi lunchbox generator as a range extender, or when equalizing the batteries. You must watch it like a hawk, and be careful, especially with the primary connections, or touching the case if the ground connection is iffy. This is diametrically opposite from being idiot proof. This is an idiot electrocutioner. Wouldn't hurt to throw a couple of 100a fuses in there, too, BTW.

The right way to charge a bank of whatever voltage, where you don't have to babysit the batts as they charge, is to get a 110v input charger at the right output voltage for the bank. If you are dealing with a non standard voltage, a Variac makes a lot of sense.
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Old 18-12-2018, 14:14   #9
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Re: Getting from 110/20A to 48V DC @ 65A

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Originally Posted by JOHNMARDALL View Post
Maybe I'm underthinking it, but why not use 4 twelve volt batteries connected in series and use conventional battery chargers powered by whatever AC power you have available?
No, simple is good.

So a 12V*4 batts series'd to comprise one 48V bank.

4* 12V chargers pumping say up to 20A current into each batt's +/- posts

Load drawing 48V at 60A from the first + and last - bank posts

All concurrently, this would work just fine?

I see many controllers / PSUs / converters stating

"these units cannot be put in series" or "cannot be paralleled"

Does putting a buffer in the form of batteries in there upstream take care of whatever the problem there would be?
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Old 18-12-2018, 14:16   #10
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Re: Getting from 110/20A to 48V DC @ 65A

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Yup, and you coudl use a Victron 48V charger, a number of which will accept a very wide range of AC (and DC) inputs.
Sure at 10x the price.

Topic here is safe but effective and **cheap**.

Please
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Old 18-12-2018, 14:25   #11
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Re: Getting from 110/20A to 48V DC @ 65A

JOhn,

It may be helpful to describe what you are ultimately trying to accomplish, ie what are you using the power for?

Chris
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Old 18-12-2018, 14:26   #12
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Re: Getting from 110/20A to 48V DC @ 65A

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You can't.
I can't **what** ?

I'm not worried about some power losses from conversion in this case, ICE generated or mains power only.

> Pulling more current than that will overload your 20a 110v breaker.

Maybe you didn't read in the OP I already mentioned pulling current from separate gennies / circuits as needed. And taking advantage of 240V power when available, see below.


> Variac and a rectifier from an old stick welding machine, or a new rectifier with a suitable rating.

Sounds great, but highest priority here is well-regulated stable DC power output even when input AC is dirty.

Plus that approach sounds above my pay grade, would maybe need to hire a pro to walk me through step by step.

Would greatly prefer an approach I understand better.

But really, thanks very much (again) for reminding me of this "variac" concept, one day I hope to be qualified to start experimenting along those lines. Like when I dream about setting up a portable welder suitable for desert islands.
Quote:
Originally Posted by john61ct View Post
So I'm thinking two separate power supplies / chargers, ganging the DC outputs, since

sometimes would only have 2x completely independent USA 110AC circuits available, not always 30A or 50A outlets.

I also want to be able to accept 220/240V "world power", either 50/60Hz.
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Old 18-12-2018, 14:38   #13
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Re: Getting from 110/20A to 48V DC @ 65A

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JOhn,

It may be helpful to describe what you are ultimately trying to accomplish, ie what are you using the power for?

Chris
Immediate desire is getting full use of an iCharger 4010Duo, mostly for maintenance protocols (balancing, equalizing, load testing) on 2V cells up to 3-6V PB batts, at minimum 200AH, and also 60-180aH LFP cells at 3.2V.

Have a look at this "fallback so far" plan, not exactly elegant, but each source can be used **on its own** for normal day-to-day cycling duty charging of assembled LFP banks, say 400-1600aH.

Scenario A for 12V @4S, B for 24V @8S, C for 48V 16S after converter-boosted to 55.2V.

Thus saving wear and tear on the 4010Duo, only need to use it for the maintenance procedures.

________
A couple of "IBM 835W" PSUs series'd, plus also carrying an ESP120 as well 8-( , a kludge I'd really rather avoid.

3 configurations depending on upstream available:

A. One 835W PSU on its own, converter-boosted up to 13.8V output @60.5A, will run off 110AC pulling under 8A.

B. A pair in series @24V native, converter-boosted to 27.6V, same 60.5A, runs off a "normal" 15A 110AC circuit if you carefully limit current drawn.

If 2 series'd for 24V really is the limit,

C. To get up over 2200W, carry a separate HP ESP120, for use off 220/240 only.

All are world power compatible, 50/60Hz

_______
But, I'd really rather not carry multiple different sets of PSUs just to handle different current rates and both 110 and 240 supplies.
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Old 18-12-2018, 14:51   #14
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Re: Getting from 110/20A to 48V DC @ 65A

So after all that complexity, bringing it back to the simplest requirement:

Max 50V, bit lower is better

Minimum total power 2200W

Max amps is 65A, a bit lower is better

thus 35V is the **minimum** voltage if getting full usage power all from one power source, e.g. ES120.

If going to a pair, two 48V sources at 35A each would work

as would two 24V sources at 70A each, e.g. pairs of IBM 835W server PSUs

Total costs so far are under $120
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Old 18-12-2018, 15:23   #15
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Re: Getting from 110/20A to 48V DC @ 65A

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Originally Posted by john61ct View Post
No, simple is good.

So a 12V*4 batts series'd to comprise one 48V bank.

4* 12V chargers pumping say up to 20A current into each batt's +/- posts

Load drawing 48V at 60A from the first + and last - bank posts

All concurrently, this would work just fine?

No, that would give you 20A of charging @48V (four 12V, 20A chargers operating series)


Quote:
Originally Posted by john61ct View Post
I see many controllers / PSUs / converters stating

"these units cannot be put in series" or "cannot be paralleled"

Does putting a buffer in the form of batteries in there upstream take care of whatever the problem there would be?

No, it doesn't.


The issue with running some chargers in series is that the outputs aren't isolated. As an example, many have the negative output tied to the chargers ground, which connects to the ground on the power cord. If you put two such chargers in series, you get a dead short.
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