Re: Military Radio Question

Hi Chuck

Yeah, the wall warts are marked with output voltages that are only
approximate. The real test of the wall wart would require that it be
hooked up to charge a capacitor. That will indicate the maximum voltage to
which the battery will charge.
The average Lead-Acid, Calcium, 12 volt battery will require about 14.8
volts to begin boiling out its electrolyte.
Charging batteries might not be "rocket science", but it can get
complicated. There is so much good info available on the Internet that it
would be wrong of me to pretend that I'm an expert only because I understand
a little about the subject.
A wall wart, marked as about 9 or 10 volts DC with a 12 volt bulb in
series with it, can be used as a decent float charger. I'll assume that
anyone reading this group will see the technology behind this low cost,
readily available system.

Jerry



"chuck" <nospam@xxxxxxxxxx> wrote in message
news:J1u0f.7942$vw6.5655@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Jerry,
>
> The 10 volt DC wall wart is unfiltered and the designated voltage is 10
> vdc rms? So it would be supplying 14.1 volts peak?
>
> Trying to understand how the 10 volt supply will charge a 12 volt battery.
>
> Thanks.
>
> Chuck
>
> Jerry Martes wrote:
>> "Rod Maupin" <gridman@xxxxxxxxx> wrote in message
>> news:11k3j0s7dujl92a@xxxxxxxxxxxxxxxxxxxxx
>>
>>>I posted this on another group, but you all seem really smart here.
>>>
>>>I have a military radio (PRC-1099) and a battery. I want to buy a power
>>>supply that will power the radio but which can also be used to charge the
>>>battery. The radio needs a 12V power supply to run. The battery is a
>>>lead-calcium type, and is supposed to be charged at 1A for 5 to 6 hours.
>>>
>>>Buying a 12V power supply is easy, but do supplies normally have a
>>>variable current output? I am not an authority on power supplies or
>>>charging batteries, so I need some help here.
>>>
>>>Thanks,
>>>
>>>Rod KI7CQ
>>
>>
>> Rod
>>
>> For what reason is it needed to require the battery to be charged
>> within 6 hours? If it is practical to charge the battery "overnight",
>> the requirements could be much less expensive.
>> There is alot-alot of information on the Internet about charging
>> lead-acid batteries. The lead-Calcium is the type cell commonly used in
>> most automotive autos today.
>> If this was my radio, I'd use a wall wart with a 12 volt lamp in series
>> between the wall wart and the battery. . A 10 volt DC, 1 amp wall wart
>> would probably be close to proper for this radio. The series lamp will
>> limit the charge rate.
>>
>> If the battery terminal voltage is restricted to being no higher than
>> 14.8 volts,the battery will not boil off its electrolyte.
>>
>> Jerry
>>

.

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