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regulating power from solar bank

simonp80

May 5, 2018
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I've scoured the net and being a beginner can't make sense of the information and am looking for some coaching.

I have a live aboard vehicle with a solar array and want to run a games console without using an inverter as that's inefficient. The console runs at 12v internally but I assume connecting directly to the battery bank would be a no no as the voltage can reach 14.4 at bulk charging, but will also drop close to the required output voltage as the bank depletes. I'm assuming I need some kind of regulator or stabiliser - not sure of the correct lingo as what I've read seems confusing.

The console itself runs at 250w maximum

I've looked at a variety of 12v boost and buck converters, some atx psu's - but I'm not sure what these are, or what is suitable for the job - ideas?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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It may use 12V internally, or it may use 12V as a source of multiple lower voltage rails internally.

Is it powered by an external power supply, or does it plug directly into the mains? If the former, can you show us details of what is written on the power supply.
 

simonp80

May 5, 2018
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As a further update - it looks at though the xbox runs at about 120 watts during heaviest use. However do I need to account for a power spike as the machine starts up? If so, is it worth factoring in a percentage as a buffer?
 

simonp80

May 5, 2018
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The power supply is external. The plug running to the xbox has two pins - one at 5v and one at 12. I was thinking I shouldn't have to open the machine - which is welcome.

The power supply does have specs which seem ridiculous at 17.9a @ 12v and 1a @5V.

I'm assuming the insane amperage is for external devices since the machine alone running at full pelt draws around 120watts
 

(*steve*)

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OK, very useful to know that it is a x-box.

The consensus seems to be that you're best off running it from an inverter. However you can get PC power supplies that have a 12V input. These provide the rails you require, and at the sort of currents you require. See here.
 

dave9

Mar 5, 2017
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I'd do some testing to determine what the real minimum voltage is for your xbox (One?). You shouldn't want to deplete your battery much past 12.0V for longevity's sake (unless deep cycle? You're being far too lazy to not supply ALL data about your setup).

There are buck regulators that aren't very expensive with (supposedly) a mere 1V dropout, meaning if you had 12V in, they could produce 11V out within the respective specs. 5V is more of an afterthought, you could add a 2nd switching regulator for it but I'd measure that too since the 1A PSU spec may mean it's some small fraction of that, even a linear regulator tacked on to the 12V output might suffice.

SO, if you have a way to provide a variable voltage at the necessary amps then you can figure out how low it's stable. If you can't and are aiming for utmost efficiency then there's the question of investment and research to do so.

For example, in a state where the solar cells are charging the battery at 14.4V, it would be more efficient to have a voltage threshold where a relay or ORing diodes are used such that the output from the solar cells, is fed directly into a 12V switching supply or a bit over that to be the primary current supply, so you get the power with one less middleman from the solar array rather than after it's bucked down to the battery 14.4V charge level.

Anyway there's not much point in further speculation without all specs of all components, but I did notice on ebay that some 15A buck regulator boards are available for about $10 delivered, then add a ~couple bucks to derive 5V from that with few more components.

https://www.ebay.com/itm/15A-DC-DC-...-Power-Supply-Module-Hot-Voltage/162983444001
 

simonp80

May 5, 2018
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Apologies if I've been lazy- I didn't know you wanted more info beyond the power. I've tagged a picture of the ps data below.

The solar to pc power supplies are expensive. Is there no other way to provide the power?

Yes, Xbox one

My battery bank currently stands at 220Ah though I have a 520w solar array which have usually charged the bank by noon and so I think I could comfortably double its size- I was thinking of doing that anyway.

Also there is the float charging point during the battery bank charging cycle after the bulk charge at 14.4 which then drops the voltage to13.8v - whether that makes things more complex?

So- the buck converters must have an input voltage above the output? Is that the problem with them?

I definitely don't want to use an inverter since there's little point moving from 12 to 240 and back to 12 again. That's just musical electric chairs.

Apologies if I have missed anything - I am a novice in electronics and not always sure what info is relevant- thanks for your patience and help.
 

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simonp80

May 5, 2018
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Just so I understand - do most DC to DC methods require a voltage differential between input and output?

I could always wire the bank and pannels in series providing 24v - thus providing me with a distinct differential, though I would have to buy a new inverter as my current one is only 12v.

I was hoping to find a way of doing this without dropping £100's on components with one function. I don't mind upgrading the bank as that's used throughout the system
 

kellys_eye

Jun 25, 2010
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Buck - output is lower than the input
Boost - output is higher than the input
Buck-boost - best of both worlds, does both!

By far the easiest solution is to use an inverter - which can be dual-purposed to some other task when not using the XBox
 

simonp80

May 5, 2018
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It's the easiest as it's literaly plug and play and iido own one that is capable but the idea of going from 12 - 240 - 12 seems wasteful when I have a ltd amount of energy. I'm proposing to use this completely off grid so trying to get rid of inefficienties.
So maybe a buck boost converter? I've seen them available on eBay at good prices.

Do I need to account for a spike of current draw at start up? Looking at online testing the Xbox draws about 120w during heaviest use- that comes out at 10A. Should I then aim for a 15A converter?
 

kellys_eye

Jun 25, 2010
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In order to keep any power supply operating 'safely' (thermally and 'stressly') you should always aim for a 50% lee way in capacity so if you 'need' 200W then purchase 300W.

Efficiency works in many ways though - how 'inefficient' is it to purchase a converter that has only one specific use as opposed to one that could be used in multiple applications?
 
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