24v to 12v conversion...20a 12v draws 20a 24v or 10a 24v?

[tree707]

Ok now there's some info i can work with. Many thanks everyone. Buck it is! Otherwise bye bye batteries

[Sunking]

Well here is the Monkey Wrench. It depends on what kind of Regulator he uses. If it is a Series or Shunt Regulator Input Current = Output Current. If his 12 volt load requires 20 amps or 240 watts, the input to the Regulator is 24 volts at 20 amps or 480 watts for 50% efficiency. Unless you know what you are looking for is what most people buy.

Why do they make such a mistake? Real simple you see two 24/12 Volt - 20 Amp for sale. One unit is $100, and the other is $300. Like an idiot you buy the $100 model. The $300 model was a Buck Power Converter where it takes 24 volts @ 10 amps and converts to 12 volts @ 20 amps.

So the bottom line is:

Series or Shunt Regulator is 480 watts in : 240 watts out. 50% efficiency.
The more expensive Buck Converter is 240 watts in, 240 watts out.

What escaped you the $300 unit is much less expensive than the $100 model geniuses.

You get what you pay for. If you do not pay attention to details, you end up voting for NoBama.

[Logan5]

I use the sealed cheap Chinese type converter 2 of them both 24 to 12 @ 10 amps with my load split between them. 5 amps @ 24 volts, They get too hot if you go over 7 amps. I have a 20amp converter here but it is made for 48 volts and I am only running a 24 volt bank at this time. If you plan on running a large load, consider a fan cooled unit. or add heatsink and or fan to a sealed unit.

[tree707]

Yeah i suppose there is a slight latent loss at the converter and then the lower efficiency but i was told is less than 5%

[Logan5]

it's not loss, it's the same power at 12 volts as 24 volts, half the amps @ twice the voltage.

[tree707]

Ok great. That is what i thought but one person told me different. I knew there was a little power loss in conversion but half didn't sound right

[Logan5]

I have a 24 volt UPS for security, I use a step down for 12 volts @ 10 amps, is a draw of 5 amps on my 24 volt battery @ 24 volts

[ButchDeal]

The problem I see is that the OP is using a 24volt battery to run a 12 volt load. That might be a problem unless he uses some type of 24v to 12v power supply or voltage regulator.

yep, he never said how he was getting the 12V.
Also check the specs, a lot of equipment can run on 12V and 24V...
Something I found handy as I purchased this camping unit which has an 18V output ...
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


and I found that this USB car adapter actually has a range of 12-24V...
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

(now I have some other USB car adapters that definitly do not work at 18V but I only needed one

[SunEagle]

you don't seem to understand the equation.

Watts = Volts X Amps

so in your example if you are using 240w = 12V X 20a
watts are what you are drawing so 240W = 12V X 20a = 24V X 10a

As volts go up, amps go down.

The problem I see is that the OP is using a 24volt battery to run a 12 volt load. That might be a problem unless he uses some type of 24v to 12v power supply or voltage regulator.

[ButchDeal]

I understand that...the question is in draw off the batteries. I'm not an electrician, but I wonder if amps are constant...as in I'm using 20amps of power to make 240 watts once its converted to 12v. Will I therefore be using 20amps off the 24 volt batteries?

you don't seem to understand the equation.

Watts = Volts X Amps

so in your example if you are using 240w = 12V X 20a
watts are what you are drawing so 240W = 12V X 20a = 24V X 10a

As volts go up, amps go down.

[tree707]

I understand that...the question is in draw off the batteries. I'm not an electrician, but I wonder if amps are constant...as in I'm using 20amps of power to make 240 watts once its converted to 12v. Will I therefore be using 20amps off the 24 volt batteries?

[solarix]

Ohms Law 101: Power = Volts x Amps 240watts / 12volts = 20amps

[tree707]

I have a 24 volt battery bank that I need to run some 12 volt equipment off. My question is if I am converting to 12 volt and I need to run 240 watts, will I be drawing 20 amps off the battery bank or 10 amps

Thanks