Electronics > Beginners

12V DC routing

(1/7) > >>

paulca:
Hi,

I know I asked this last year, but I didn't get a viable solution then and have decided with an alternative.

In short I have 12VDC solar power available in the garage.  I would like to use that 12VDC in the office, 10 meters away in the upper floor.  Originally I thought as the system is rated for 10amps, I would need to route 10Amps, or 120W and needed to use a boost converter to save on expensive thick cable by transmitting the DC at 50V or higher.

Now I have a plan B, which should be cheaper and easier.  Ballast.  A can put a lead acid in the office, run the 12V up over 1.5mm cable and put a CC/CV buck converter on the end, connected to the lead acid.  The CC/CV PSU will simply limit the charge current on the 10 meter wire run to 2 Amps.  So it will effiectively charge the office battery 24/7 at no more than 2Amps.  Even if I pull 20 Amps from it to run a DC/DC power supply at 20Amps.

Anyone see any problems with this approach?  It's basically running a remote CC/CV charger as a load on the existing solar system.  If it goes low battery, it will shut the load off.

tszaboo:
10m 2.5mm cable is 21 EUR in the local home improvement store  :-//

fourtytwo42:
The problem I see is hours of sunlight. Assuming your charging source is PV then for example on a short winter day you will only be able to transfer 10AH to the battery.

paulca:

--- Quote from: tszaboo on January 18, 2022, 04:13:01 pm ---10m 2.5mm cable is 21 EUR in the local home improvement store  :-//

--- End quote ---

Yes, but if I start pulling more than a few amps the voltage drop will start to bring me well under 12V and may cause other issues.

I think 2.5mm at 10A still results in something like a 1.4V drop.

Mostly the 12V will be used to run other battery chargers, headphone amps and electronics bench supplies.  Basically a lot of low wattage stuff.  However the DC/DC bench supplies I have can buck 20Amps and boost 5Amps (input limited).  So there is a use case for temporary, periodic, short term high current draws that would not be possible with 12VDC over any civilised thickness of cable without a >1V drop.


--- Quote from: fourtytwo42 on January 18, 2022, 04:19:07 pm ---The problem I see is hours of sunlight. Assuming your charging source is PV then for example on a short winter day you will only be able to transfer 10AH to the battery.

--- End quote ---

It's backed by a 100Ah battery.  So as long as I keep an eye on the main solar battery levels over winter and don't drain it.  It should be fine.

DenzilPenberthy:
Your 12v battery will not like being kept at 12v. It will need something like 14.4v absorbtion charge and then storage at a float voltage of something like 13.8v.

This seems like a very complicated and expensive solution to a problem that's not really much of a problem.

You can work out volt-drops for yourself based on a 10m circuit and how much load you forsee drawing, but even 16sqmm wire is only £1.67/m and that will be good for <5% volt drop at 20A

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

You can buy by the metre from here (or tonnes of other places)
https://www.tlc-direct.co.uk/Main_Index/Cable_Index/Singles_1/index.html

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version