Modding a PSU to use 12v Input - Is it feasible?

Beren · 13 Jun 2017 at 01:07

We are soon going to be living on a house boat which is creating a number of opportunities for both epic win, but also has some challenges.

We generate power from 4 sources - Solar, Wind, Generator and while in the Marina shore power.

The Solar, Wind and Alternator all put out 12v power to house batteries which are also charged while in the Marina as well as providing a separate 240v Circuit.

I can of course fit an invertor to switch the 12v DC back up to 240v A/C but that is both expensive and horribly inefficient.

The PC is just using a 12v and 5 volt rail anyway which makes me think I should be able to mod a power supply to give me a much more efficient solution.

That said the input D/C voltage is going to be a bit variable - 12v D/C on a boat tends to fluctuate from 12-13.5v.

There are a few mods on Youtube I will study but wondered if anyone here has any experience with this side of things?

Rroff · 13 Jun 2017 at 02:49

I'd assume you'd really need above 12v input - for stable supply the voltage will be regulated which usually results in some degree of voltage drop (usually around 1.5v or so in this kind of context but might be different). Not sure if it makes any odds for how inefficient a voltage inverter setup would be but most PCs and monitors these days can accept around ~90-100v upwards (some might need switching to 110v mode most should do it automatically).

Beren · 13 Jun 2017 at 03:19

The voltage I should be getting from the 12v supply on the boat won't drop below 12v unless the Battery bank went lower than 40% charge - at which point I would be turning the engine on anyway! I will have a think though, thanks for that.

Rroff · 13 Jun 2017 at 03:30

Do you need a full PC BTW? no idea on your circumstances and budget but most people I know who've lived for awhile out of vans or boats, etc. have tended to end up using desktop replacement laptops but obviously this can be expensive and limiting on upgrade potential, etc.

Beren · 13 Jun 2017 at 05:10

I don't strictly Need a full PC - but there are a number of reasons why something close would be good. The boat is a 50' ketch with 3 cabins for My wife, me and our 5 and 14 year old kids. I am going to be in marinas with very variable WiFi signal - I think the on board WiFi card on a new motherboard will enable me to pop an aerial outside the boat and one inside the boat to both pick up a weak signal and create a secure hot spot inside the boat - this is a discount off the PC cost from doing it with a very expensive marine solution. As I am going to have a variable connection I am also going to want to cache a reasonable amount of video on the machine and use it as the media hub for everyone else on the boat - I can't rely on Kodi and Netflix with no fiber connection. I can also potentially put together a value PC right now with a very good upgrade path and have a gaming pc on the boat at some point in the future. We need an Xbox in the main Saloon, a PS4 in the 14 year old's Cabin, Cartoons and Movies for the 5 year old, Crime and Food TV for my Wife and just more YouTube and Instagram access than you ever thought possible for the 14 year old...

EsaT · 13 Jun 2017 at 10:00

While modern PSUs actually make 3,3V and 5V from main transformer 12V output those can't be modded to work at 12V.
For example 5V standby needed for booting PC is generated from mains...

PicoPSU's maker has DC-DC ATX power supplies which would fit to that use like this:
http://www.mini-box.com/M4-ATX
Googling ATX PSU 12V also gives some other PSUs for car etc use.

SupraWez · 13 Jun 2017 at 11:17

As above, look for DC/DC PSU for use in cars etc.

Or depending how electronically minded you are you could look at a regular PSU and bypass the bridge rectifier and feed it DC directly, I have not done this myself but see no reason why it wouldn't be possible, basically bypass the AC input and conversion to DC, the question would be how clean the input needs to be and at what voltage, as mentioned above to get clean 12v, 5v and 3.3v you would require a higher input voltage to filter, clean and regulate.

Beren · 13 Jun 2017 at 23:06

EsaT said:
While modern PSUs actually make 3,3V and 5V from main transformer 12V output those can't be modded to work at 12V.
For example 5V standby needed for booting PC is generated from mains...

PicoPSU's maker has DC-DC ATX power supplies which would fit to that use like this:
http://www.mini-box.com/M4-ATX
Googling ATX PSU 12V also gives some other PSUs for car etc use.

Oh that is really useful - I am going to have to be a bit careful with the 250W limit - but otherwise that is perfect. Cheers - i had come across a few 12v PSU's but they were hideously expensive.