15 Vdc power adapter

Thread Starter

1-3-2-4

Joined Dec 26, 2008
199
Besides radio shack does anyone know of a place that would have a 15v dc power adapter with a 1A output?

The one that RS sells is almost $30 which seems a tad way over priced.
 

Thread Starter

1-3-2-4

Joined Dec 26, 2008
199
Maybe you can help me figure this out.. So I have a linksys 12V 1A power adapter.. it's unregulated and with no load I get 17.6 VDC when I put about a 1A load it goes to around 12.6 or so..

If I was going to put it on a load that was only 650 mA it's output voltage would be around 14.2-15?

first place I looked at was Amazon but was looking for some offered on prime.
 

bountyhunter

Joined Sep 7, 2009
2,512
Maybe you can help me figure this out.. So I have a linksys 12V 1A power adapter.. it's unregulated and with no load I get 17.6 VDC when I put about a 1A load it goes to around 12.6 or so..

If I was going to put it on a load that was only 650 mA it's output voltage would be around 14.2-15?

first place I looked at was Amazon but was looking for some offered on prime.
You are better off just getting one that is regulated so the voltage doesn't vary so much.
 

SPQR

Joined Nov 4, 2011
379
This is a fantastic question that I've always been confused about, and so reading a little, I've found the "KVL loop" explanation HERE.

Let's see if I do this right:

Vload = Vo - (Iload * Ro)

So let's assume your data on the unloaded wart:

12.6 = 17.6 - (1 * X)
so X = 5

Vload = 17.6 - (.65 * 5)
Vload = 14.35

Now let's wait to see if experts agree that (1) I've used the right formula and (2) I've used the right assumptions regarding Ro.

This is important enough for me that I might do another thread depending on their responses.
I wonder if this formula applies to switching power supplies.

Another great question!
 

Thread Starter

1-3-2-4

Joined Dec 26, 2008
199
You are better off just getting one that is regulated so the voltage doesn't vary so much.
Well it will be regulated by the way of a LM317 any extra will be heat.. not sure how hot, but I'm building a SLA battery charger output voltage should be around 13.4 vdc @ 650 mA
 

Thread Starter

1-3-2-4

Joined Dec 26, 2008
199
I have a question.. So I switched to a regulated supply that's 18.6V for the output anyways on the project I'm doing.. maybe it's because I ran the battery down to 11.5 V last night but it's been on charge for about 3 hours now and the LED is still lit, I assume it's charging rate is 650 mA but my battery voltage on the 12V 18 Ah battery is showing 13.05 volts.

How long does it normally take to fully charge it?
 
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