# input current to buck/boost regulator?

#### Poor old sod

Joined Jul 25, 2017
193
have 360w 30A out 24vdc - 12vdc regulator, what input current should i expect at full load, pls?

#### Papabravo

Joined Feb 24, 2006
20,992
have 360w 30A out 24vdc - 12vdc regulator, what input current should i expect at full load, pls?
As a matter of practice, when actual information is lacking, my default efficiency for all DC-DC conversion processes is 80%. So if the output power is 360 Watts, then I would proceed as follows:

$$\cfrac{360 \text{ Watts}}{0.80}\;=\;450 \text{ Watts - Input Power}$$

$$\text{Then,}$$

$$\cfrac{450 \text{ Watts}}{24 \text{ Volts}}\;=\;18.75\text{ Amperes}$$

Was that the calculation you were looking for? You can of course use a different efficiency if you have the data to support such an assumption, so your mileage may vary.

#### Poor old sod

Joined Jul 25, 2017
193
thx. is that current enough to blow a 15A auto blade fuse ove 10sec?

#### Papabravo

Joined Feb 24, 2006
20,992
thx. is that current enough to blow a 15A auto blade fuse ove 10sec?
You'll have to check the datasheets on the fuses you are using. That is something you'd expect them to mention.

#### Poor old sod

Joined Jul 25, 2017
193
afair auto fuses will pass rated current, but blow instantly on 2x rated current.
thats all i remember. my cct is battery to load hard wired, nothin delicate, it has 15A fuse, i could make it 20A, BUT....

#### LowQCab

Joined Nov 6, 2012
3,935
It's hard to find an Automotive-Fuse-Holder ( ATO/ATC ) that is
completely reliable at a continuous ~20-Amps,
this depends heavily on the environment it is being used in.
If You need dependability,
go with a "Maxi-Fuse" style Fuse-Holder, and keep it totally dry and cool.
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