DC-DC converter sizing

[Wahki]

I need some advice on sizing a DC-DC Stepdown converter, actually I need to know whether what I can get will work and what I need to make it work...

I'm trying to build this 24v system but cannot source the recommended step down converter (40amp 24v-12v DC-DC), the largest I'm able to get is a 15amp unit. Now this is less than half the amp size recommended, and therein lies my problem. I will only be running lights on the 12v side.

So, do I simply increase the fuse size before the converter, or do I have to play around with wire sizes to limit the amps (? like I know what I'm talking about, I'm a complete noob here!).

 

[John Frum]

The size of the dc2dc converter you need depends on the maximum 12 volt dc load capacity you require.
What is your maximum 12 volt dc load capacity in watts?

 

[Zwy]

Amazon.com

That's 120a, I use a 60a. I figure a 50% derate should easily cover any overload situation. Just remember the bigger you go, the larger the cables running in and out. Don't skimp on the size of cable, I think many burn out a converter with low voltage.

 

[Wahki]

The size of the dc2dc converter you need depends on the maximum 12 volt dc load capacity you require.
What is your maximum 12 volt dc load capacity in watts?

I'll only be running lights off 12v and I've calculated it will be using 150watts (I've added some extra at the top, should it be required).

 

[John Frum]

I'll only be running lights off 12v and I've calculated it will be using 150watts (I've added some extra at the top, should it be required).

150 watts / 12.8 volts = 11.71875 amps.
If you are going with one of the cheap generic ones I would de-rate by .5.
That means get the 20-25 amp model.

 

[Wahki]

Thank you very much for all the replies, highly appreciated!
In the process I also discovered that Amazon Global now ships directly to South Africa, which it didn't do before so now I can buy items that are quoted by the international community without having to search for alternatives from elsewhere...

 

[stok]

Thank you very much for all the replies, highly appreciated!
In the process I also discovered that Amazon Global now ships directly to South Africa, which it didn't do before so now I can buy items that are quoted by the international community without having to search for alternatives from elsewhere...

good day my fellow South African, that is indeed good news for us on the southern tip. FYI I saw a lot of vacancies for amazon staff in the local press, I think that amazon might be planning to fully expand in South Africa, currently you can buy 272Ah lithtech prismatic cells from takealot for R3499 (+- $233) which is very expensive, you can get 100ah cells from lithiumbatteriessa for R950 ($64) not sure how the dollar price compares with the prices in the USA

 

[Drooling Piston]

If all u can find are 15amp units and u need more, a lot of these will work together with a second or third charger. The chargers don’t cancel each other out but rather work together. Two 15 amp units will give u the potential for 30 amps of charging capacity.

 

[Lt.Dan]

I just bought one from Daygreen, Google them, they seem like a pretty well put together place, and have converters up to 150a! I just ordered a 48v to 12v 100a DC Converter. We'll see if its any good.