# My DC current problem

#### gingerfox

Joined Oct 7, 2011
3
i have dc power surce of 45V DC and 40 Milliamps current. my output current is in mili's and i need atleast 3.5 Amp at output..how I can arrive to the 3.5 Amp ? any Electronic circuit can do that?

#### crutschow

Joined Mar 14, 2008
25,991
You need to obtain a power source that can deliver at least 3.5A. There's no way to increase the power output of a power supply with extensive modifications.

#### kubeek

Joined Sep 20, 2005
5,736
i have dc power surce of 45V DC and 40 Milliamps current. my output current is in mili's and i need atleast 3.5 Amp at output..how I can arrive to the 3.5 Amp ? any Electronic circuit can do that?
If you could do with 0.5V then 3.5A will be theoretically possible. Anyway, you will never get more power out than the initial 1.8W.

#### mcgyvr

Joined Oct 15, 2009
5,394
And always get a power supply that can provide more than what you need. Its never a good idea to run them at 100% capacity.

#### SgtWookie

Joined Jul 17, 2007
22,220
You could get 3.5A out of it if you were willing to settle for only ~437mV out.
40mA @ 45v is 1.8W, so 1.8W/3.5A = 514.3mV; figure ~85% efficiency in the power conversion and you get ~437mV.

Another thing you could do is to charge a capacitor for a period of time, until it got to nearly 45v, then apply the load. You can wind up with a good bit more than 3.5A that way, but it's only for a short period of time; the instant that the connection closes.

Joined Dec 26, 2010
2,148
45V DC, but only a few tens of mA: does that ring any bells with anyone?

This sounds rather like someone trying to nick some power from a phone line. I would be delighted to hear some other explanation.

#### SgtWookie

Joined Jul 17, 2007
22,220
Yep, caught me half asleep this time.

#### gingerfox

Joined Oct 7, 2011
3
Thank you SgtWookie

I can leave it down to 12V as my intantion is to be able to charge a car battery and I need to stay with 12v to 13v with 2 or more amps I like your Idea with the capacitor is there a drawing or more information on how to do it? and how after I charge the capacitore I can amplifier the current? please help.
Thank you

#### SgtWookie

Joined Jul 17, 2007
22,220
With only 1.8 Watts available, you will only get a maximum of 132mA at 13.6v; the float voltage for a 12v lead-acid battery. That is if a converter were 100% efficient; and you will not get 100% efficiency out of a converter.

You cannot use the telephone line as a power source, or the telephone company will turn off your telephone service and charge you extra for the power that you have tried to steal from them.

#### gingerfox

Joined Oct 7, 2011
3
With only 1.8 Watts available, you will only get a maximum of 132mA at 13.6v; the float voltage for a 12v lead-acid battery. That is if a converter were 100% efficient; and you will not get 100% efficiency out of a converter.

You cannot use the telephone line as a power source, or the telephone company will turn off your telephone service and charge you extra for the power that you have tried to steal from them.

I am not using the phone line.....lol I have a solar panel that I am getting indor 45 volt and no Current at all only 40 milliamps I am trying to increase the current in any possible way. any one please help?