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Power supplies , parallel and/or series?
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maddox



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Power supplies , parallel and/or series?

Just something that came up. I do have a big Powersupply, 24V 100A.
But that's a heavy, non commercial monster.
Searching for something simular indicates a bank and/or backbreaking monster.

But I was thinking. There is a slew of Chinese , easy to use LED powersupplies in voltages our chargers like.

Can those be seen as a "battery" and able to be put in series or parallel as needs demand?

Post Fri Jan 27, 2017 10:20 am 
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Valen
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you can series power supplies provided they don't have an earth reference.
I wouldn't parallel them without knowing a whole bunch about how they work internally though.

24V 100A is 2.4Kw, what the hell are you charging lol?

At that power level I'd be looking at surplus supplies from like blade centres and the like
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Post Fri Jan 27, 2017 12:42 pm 
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Nick
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I'm with Jake; running switching PSUs in parallel is not likely to work unless they are specifically designed for it.

My favourite brand of switching supplies is Meanwell, never had one fail yet. They will be more than a cheapo LED supply but they won't blow up in your face either! Have a look at this series: http://www.meanwell.com/productPdf.aspx?i=366

These supplies WILL run in parallel and can supply 7 Kw Shocked if you have a 30A mains circuit.
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Post Fri Jan 27, 2017 5:31 pm 
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maddox



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We're using a Turnigy quadkore 4*20A 6S charger.

Just to be sure we can charge the 8000mAh 5S packs for Bullfrog in a suitable time.

An idea I have. What is the problem with paralleling those PSU's?

If it's ripple or feedback, why not adding diodes to eliminate those issues? If diodes can take that kind of power. (should be, as there are rectifier bridges for forklift pack chargers...)

If you want to go the full hog, why not adding capacitators and coils to make the output as stable as possible?

Post Sat Jan 28, 2017 5:23 am 
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Nick
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How many small PSUs are you thinking of hooking up in parallel? I couldn't find a cheap PSU on eBay rated over 30A, so it would take seven of them to give you 200A, in Aussie dollars they cost $434, while the Meanwell PSU is $507. After you add in the diode and resistor balancing network with a heatsink, the cost is almost the same and the single Meanwell PSU is smaller and more reliable.

Its not voltage ripple like you get on the output of a single PSU, the problem is having the regulator circuits in each PSU fight each other in a feedback loop. If you look through the data sheet of that supply I linked to, one PSU is the master and controls the other PSUs so that doesn't happen,

Here is an interesting discussion on the topic: https://www.eeweb.com/electronics-forum/power-supplies-in-parallel-problem It casts doubt on the idea of using diodes and still requires supplies with sense inputs that the cheapo LED supplies don't have. Even these guys who are all presumably more qualified than us are not sure what will really happen.
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Post Sat Jan 28, 2017 6:06 am 
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Glen
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Parallel charge your packs then you only need a modest power supply and single charger.
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Post Sat Jan 28, 2017 8:10 am 
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Nick
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That's not going to work for Mario; he needs to charge four 8AH packs at once and do it at the maximum rate they can take. However its done he really needs a gigantic PSU.

I just noticed a fundamental flaw in the whole idea: the Turnigy quadkore charger has quite modest input leads, they look like 10 gauge wire in the photos. that won't take 100A for the length of time it takes to charge a large lipo, at the very least the input wiring is going to get very toasty.
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Post Sat Jan 28, 2017 8:46 am 
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marto
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I think you mean series glen?
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Post Sat Jan 28, 2017 9:07 am 
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Glen
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No, parallel. that is how nearly every EV motorbike is done. Read up on places like endless sphere and the like, its called "bulk charging"

You use a para board like this - http://www.buddyrc.com/power-system/paraboard-parallel-charge-board.html

Making all your packs effectively one giant pack and then you charge it at the collective maximum rate.

For eg my EV mini bike has 4x 5ah 6s packs. That makes it a 6s 20Ah pack to the charger and this is charged at 6s of voltage and 20A (5a per battery) on a single icharger taking exactly 1 hour if they are all flat, keeping them balanced as you go.

This saves an ungodly amount of fucking around dealing with 4x chargers and the like. Lots of chargers now can handle it, icharger 3010b, 4010 duo, turnigy reaktor etc etc can do 8s at 30 amps.

The done thing is to balance the packs individually every X amount of cycles.
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Post Sat Jan 28, 2017 9:20 am 
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Nick
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Completely OT, I didn't know you were running the EV at such a low voltage, any plans to bump it up to 48V for the trike?
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Post Sat Jan 28, 2017 9:34 am 
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Glen
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It is already Smile 12s at 10ah in the bike, 6s at 20ah for bulk charging.
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Post Sat Jan 28, 2017 9:34 am 
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Nick
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That's more like it!
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Post Sat Jan 28, 2017 9:40 am 
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marto
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In that case I am not sure how this solves anything. I thought you were meaning bigger voltage for less current. With the quad reactor would be better not to parallel as you would get more balance resistors which takes the time.

Just still need a big ass PSU. You did series PSUs with ground tricks didn't you glen?

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Post Sat Jan 28, 2017 10:06 am 
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maddox



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Back to base then with the idea.

But that doesn't solve the problem for us.
As written at the start, its a bank and/or backbreaking PSU.

The Mean Well is 550+ and 3.3kg...

But what is, that is. We'll find a solution.

Post Sat Jan 28, 2017 12:06 pm 
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Nick
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I found that PSU for $360 USD (336 euros at the moment), is it possible to import it without too much cost? I'm just thinking that its going to be less weight than a bank of smaller supplies and maybe not that much more expensive in the long run. There are probably other brands out there doing cheaper 2400W supplies.
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Post Sat Jan 28, 2017 12:25 pm 
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