# Looking for a specific transformer

Status
Not open for further replies.

#### Electric-T

Jun 4, 2017
212
you cannot put 10 - 0V at 10A through a potentiometer it will smoke instantly
you will need to use a DC-DC buck converter
Is the amperage too high?

#### BobK

Jan 5, 2010
7,682
Potentiometers are not power devices, they are not used to reduce voltage at anything beyond milliamps. At typical potentiometer is rated at 1/2 W.

You still haven't stated what battery chemistry you are trying to charge, so I will assume lead acid. These require roughly 14V for charging.

If you start with 30V and reduce it to 14V with anything other then a switch mode DC to DC converter (buck converter, as davenn called it), then, at 10A the potentiometer would have to drop 16V at 10A. That is 160W. Think how hot a 100W light bulb gets, now multiply that by 1.6. You will not find a 160W potentiometer. If you do, you will not be able to afford it.

But let's go back even further.

Can you tell us what you are trying to accomplish with a "variable voltage" battery charger? Have you wondered why you don't see "variable voltage" battery chargers commercially available? What is the problem you are trying to solve?

Bob

#### Electric-T

Jun 4, 2017
212
Potentiometers are not power devices, they are not used to reduce voltage at anything beyond milliamps. At typical potentiometer is rated at 1/2 W.

You still haven't stated what battery chemistry you are trying to charge, so I will assume lead acid. These require roughly 14V for charging.

If you start with 30V and reduce it to 14V with anything other then a switch mode DC to DC converter (buck converter, as davenn called it), then, at 10A the potentiometer would have to drop 16V at 10A. That is 160W. Think how hot a 100W light bulb gets, now multiply that by 1.6. You will not find a 160W potentiometer. If you do, you will not be able to afford it.

But let's go back even further.

Can you tell us what you are trying to accomplish with a "variable voltage" battery charger? Have you wondered why you don't see "variable voltage" battery chargers commercially available? What is the problem you are trying to solve?

Bob

#### kellys_eye

Jun 25, 2010
5,513
This thread is going to go on for dozens of pages if the OP doesn't start stating what he wants from his idea. One/two word answers don't cut it and we can't keep going by volunteering tiny bit after tiny bit based on 'nothing'.

Might I suggest you get yourself a list of requirements that you want from the charger - if you don't know what the requirements are (other than variable voltage which has already been explained as not being something chargers actually do) then you will never get a resolution to your problems.

We've offered loads of help so far but seem to be in the same place we were when we started!

#### Electric-T

Jun 4, 2017
212
This is purely an idea for a project. There is no immediate need for it. Im just exploring electronics. After studying theory for a while then experimenting on my breadboard, i figured it was time to try and design/build something. I
This thread is going to go on for dozens of pages if the OP doesn't start stating what he wants from his idea. One/two word answers don't cut it and we can't keep going by volunteering tiny bit after tiny bit based on 'nothing'.

Might I suggest you get yourself a list of requirements that you want from the charger - if you don't know what the requirements are (other than variable voltage which has already been explained as not being something chargers actually do) then you will never get a resolution to your problems.

We've offered loads of help so far but seem to be in the same place we were when we started!
I had an idea of a battery charger that charge 12v all the way down to those rechargeable 1.5v battery. Variable voltage is the only thing i want out of it. I understand amps have to be considered. I dont see why everybody seems to want more information i already got the answer i was looking for. I was asking if a certain transformer even exists. Turns out it does. Solved. This thread is going nowhere now haha. Thank you all for your input. Hopefully next time i post on here it doesnt turn into a mess like this has.

#### davenn

Moderator
Sep 5, 2009
14,150
Hopefully next time i post on here it doesnt turn into a mess like this has.

it wont if you are clear and precise in your information you give up front

OK then, we can close the thread

Status
Not open for further replies.

Replies
8
Views
560
Replies
5
Views
721
Replies
2
Views
669
Replies
7
Views
794
M
Replies
19
Views
3K
Mr. Land
M