Limiting voltage to weather radio

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Shadowcatcher
Shadowcatcher Solar Expert Posts: 228 ✭✭✭
in Solar Beginners Corner #1
I have a Recom weather radio that stays home except when we are camping. We were on the edge of a tornado warning area one year and far enough from any town that would have had a waring siren to not be able to hear one. The Radio has 4 AA batteries but the wall wart for AC is 12V. It will not work using rechargeable batteries so minimum voltage is 6V.
I would like the be able to use this on the 12V system in the trailer but the voltage at times is 14.4V during charging from the converter or solar panels. Is there a way to regulate a 12V feed?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: Limiting voltage to weather radio

    You can get small 12 volt cigarette lighter to 12/9/6/etc. down converters for cars (switchable output voltage, different DC adapter tips).

    Seem to work OK. You probably will need to measure the "idle" current to see how much they draw when your radio is on standby.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • calbiker
    calbiker Banned Posts: 50 ✭✭✭✭
    #3
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    Re: Limiting voltage to weather radio

    I operate all my 12V wall wart electronics directly off the battery in my RV. My solar increases battery voltage up to 14.8V. No problems at that voltage. Electronics include Vizio LED TV & WD TV Live (including hard drive). I avoid using inverters or dc/dc converters to maintain efficiency.

    Cal
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
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    Re: Limiting voltage to weather radio

    Interesting thing I found years ago - - wall wart voltages are almost always way above stated.
    Example, not at all uncommon to see 9 volts from a "6 volt" adapter. I've seen as high as 17 volts from a so-called 12 volt unit. So I often used a 9 volt AC adapter to power 12 volt devices, thus actually supplying it with roughly 12 volts. I often wondered why the devices didn't go up in smoke when powered with the AC adapters they came with. :(
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Limiting voltage to weather radio
    waynefromnscanada wrote: »
    Interesting thing I found years ago - - wall wart voltages are almost always way above stated.
    Example, not at all uncommon to see 9 volts from a "6 volt" adapter. I've seen as high as 17 volts from a so-called 12 volt unit. So I often used a 9 volt AC adapter to power 12 volt devices, thus actually supplying it with roughly 12 volts. I often wondered why the devices didn't go up in smoke when powered with the AC adapters they came with. :(

    Because they have ### mA current potential, and whatever they are connected to pulls the Voltage down in accordance with its current draw. Or should, at least. If you use a wall wart that's over-rated for the current need of whatever you're trying to power the Voltage will be high. But let's face it; many of these things are meant to run on batteries, which have a range not a fixed Voltage.

    And some of these little black boxes have manufacturers' ratings that are science fiction. :roll:
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #6
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    Re: Limiting voltage to weather radio
    Cariboocoot wrote: »
    Because they have ### mA current potential, and whatever they are connected to pulls the Voltage down in accordance with its current draw. Or should, at least.

    "Or should at least" There, you said it. Should, but in my experience, almost never did. The newer transformerless, electronic adapters are, thankfully, a whole different story, as least so far in my experience. If they say 12 volts, that's what I find them to be, max rated load, or no load.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Limiting voltage to weather radio

    Yes; much better regulated than the old wind-a-transformer-to-the-approximate-Voltage-and-stick-in-one-rectifier-and-a-small-capacitor type. :p

    In theory a 500 mA 9 Volt wall wart should be at 9 Volts when 500 mA is drawn. In practice ... it more or less depends on who made it and how much they cared. Good Voltage regulation costs money, you know. That eats into profits! :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: Limiting voltage to weather radio

    you guys are going too far with this as i don't believe an ac adapter to be warranted by the op unless he happens to be using an inverter anyway and even then the modsine types aren't always friendly to ac adapters. he would just like to go from 12vdc to 6vdc. what bill has recommended will probably be good as long as they didn't also depend on the load amps pulling the voltage down as some of those adapters do. the no load voltage on the adapter is the giveaway for you don't want to see 9, 10, or even 12v on the output with nothing attached. these higher voltages may damage the electronics in some items such as your weather radio. many times items that work off of 6v will work off of 5v too so don't rule out trying a usb adapter.

    if you are good with electronics you can use a 3 terminal ic regulator chip with a few other appropriate compenents and a good heat sink.
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  • westyd1982
    westyd1982 Solar Expert Posts: 85 ✭✭
    #9
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    Re: Limiting voltage to weather radio

    I suggest measuring the voltage of the wall wart. I also find that the older ones usually were much higher than 12v (16-18v). I run a number of 12v labelled devices from my batteries with no trouble. The ones I have taken apart all have their own built in power supply. I haven't wrecked anything yet, but you never know. I run small computers and routers.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
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    Re: Limiting voltage to weather radio

    Like Niel said, the OP isn't actually talking about wall warts. Wayne and I got off track because we Canadians are easily distract ... SQUIRREL! :p
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #11
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    Re: Limiting voltage to weather radio
    if you are good with electronics you can use a 3 terminal ic regulator chip with a few other appropriate compenents and a good heat sink.
    You can wire up a IC 7806 three terminal 1 amp regulator (1 dollar on Ebay) to a 3 position barrier terminal block, about 3 dollars on Ebay. With as little draw as a weather radio, I don't even think a heat sink would be required. Might need a small capacitor on the output though.
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  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
    #12
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    Re: Limiting voltage to weather radio

    Take a look on ebay. Do a search for 12v "DC to DC".

    I bought two different ones. One for regulated 5v and one for 12v. Those two volatages will take care of 90% of the wall wart transformers.
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  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    #13
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    Re: Limiting voltage to weather radio

    I decided to go with an adjustable buck converter from ebay. We will see how well it works. Thanks very much for all the help.
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