Converting a unit powered via AC cord to Batteries?

killsurfcity

i have a piece of electronic gadgetry that runs off an AC cord now, but it would be way more convenient to run it off of batteries. it is fairly small and i don't think it's drawing very much current at all. i'd be willing to bet i could run it off a single 9v battery and that would be way more convenient. is it possible to convert it to battery power? if so, where can i get info on doing the modification?

thanks.

Uncle Krunkus · Posted: Thu Jul 31, 2008 5:46 am Post subject:

It completely depends on what the device is, what voltage the AC input is transformed down to, and how much current the circuitry draws at that voltage. You'll need to get inside the unit and find out what it's doing with the AC power first.

killsurfcity · Posted: Thu Jul 31, 2008 9:16 pm Post subject:

i guess there's probably no simple way you can tell me to find all that out. if it helps, it's a sony babycall baby monitor. like i said, i'd be surprised if it wasn't running on 9v.

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

That's running off AC? Not a wallwart? And this is a baby monitor or...?
Sounds wild.
Well if there is a wallwart, you can of course see the back of the unit for required voltage, and perhaps see the current rating on the wallwart for clues...

C

killsurfcity · Posted: Fri Aug 01, 2008 11:52 am Post subject:

the baby monitor has 2 parts obviously. the transmitter has a hardwired AC cord. the receiver runs off of a 9v battery, or a wallwort.

i opened up the transmitter last night, and the board is actually really well marked up. it appears that one section of it is running off of 9v and the other part is running off 5.6v.

maybe i'll post a pic of the insides when i get home.

killsurfcity · Posted: Sun Aug 03, 2008 10:11 am Post subject:

ok, so i decided to just wing it and hook up a 9v battery to (what seems to me) the most logical spot on the board. my theory was, that based on the layout, the 9v is being stepped down at some point to the 5.6v, so that if i connected 9v, i'd automatically get 5.6v.

based on an initial test, IT WORKS!

here's a couple images of what i did:

the board from the component side

Posted Image, might have been reduced in size. Click Image to view fullscreen.

the board from the solder side

Posted Image, might have been reduced in size. Click Image to view fullscreen.

the board with the 9v battery connected and power light on

Posted Image, might have been reduced in size. Click Image to view fullscreen.

so my question is... based on what you see here, is there any reason you think this should not work fine for the foreseeable future?

would you recommend doing anything else?

thanks![/img]

fonik · Posted: Mon Aug 04, 2008 5:18 am Post subject:

i would measure the current drawn by the device. battery powered baby monitor would not make much sense if you would have to change the cell avery 15min Wink

killsurfcity · Posted: Mon Aug 04, 2008 11:03 am Post subject:

good call. what would i need to do that? i'm more of a circuit-bendy time, so i'm not sure to doing things the right way Smile

blue hell · Posted: Mon Aug 04, 2008 11:12 am Post subject:

Most practical way would be to just connect the battery and just see how long it lasts ... you could always connect a set of six D cells in series to have more power.

One thing though, with the solution you came up with you should disconnect the battery when you run the board from the mains voltage as the batteries would get charged otherwise and batteries do not like that (they'll run hot and in extreme cases might explode).

killsurfcity · Posted: Tue Aug 05, 2008 4:35 am Post subject:

thanks for the input. if i can get a workable battery solution, the AC cord is going bye bye, so no need to worry about that.

fonik · Posted: Tue Aug 05, 2008 4:40 am Post subject:

killsurfcity · Posted: Tue Aug 05, 2008 11:03 am Post subject:

very true. i try to make all my stuff as safe as possible for that very reason.

billy_the_kid43 · Joined: Aug 11, 2008 Posts: 1 Location: ID

I was hoping to find a simple answer to my question but i don't think there is. Anyway, In the pictures below you will notice a speaker with amp attached and an ac power cord. In case it doesn't show up the power cord is labelled "AC Adapter, Class 2 Transformer, Input: 120 VAC 60Hz, Output: 9VAC 200mA"

At first I was hoping that I could simply cut the cord at the green line, strip the wires and attach a 9V battery but upon further inspection of the label it has an AC output. So the dc converter must be part of the amp is my guess. I don't much if anything at all about this stuff.

I want to make this amp battery powered so that I can put the speaker, amp, battery and my ipod in a container. I am trying to put together an electronic caller for my hunting adventures.

In the picture with speaker the Green arrow is the power cord attachment, the red arrow is the input from headphone jack and the blue arrow is the wires to second speaker.

What would I need to do to make this compatible and if there isn't a way to do it with whats here is there a small battery powered amp that I could easily attach a speaker or two and allow me to use my Ipod for input through 3.5mm jack? Thanks for any help you can offer.

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