XPost: sci.electronics.basics, sci.electronics.design
From: SaySooth@TheMonastery.org
On Mon, 25 Feb 2013 22:45:10 -0000, "Ian Field"
wrote:
>
>
>"Jamie" wrote in message
>news:72pWs.41135$Q91.3308@newsfe26.iad...
>> Mike Cook wrote:
>>> A friend has a battery powered Ryobi lawn trimmer ("weed whacker") which
>>> doesn't work. The 12vdc wall wart puts out only ~ 12.4v.
>>>
>>> I charged the lead-acid gel cell using a car charger. The charge rate
>>> (selectable) was 0.5A. Afterward the trimmer seemed to work as new. Can
>>> the car charger be used to charge this battery? He can install a timer to
>>> limit charge time if that's something required.
>>>
>>> Thanks.
>>>
>>
>>
>> THe OEM charger most likely is unfiltered. Put a cap on the output but do
>> not connect it to the battery and then do a voltage check.
>
>
>The old "iron-transformer" chargers were usually impedance limited, so the
>off load voltage will be significantly more than nominal (enough to get a
>mildly sulphated battery going). In addition a capacitor would charge to the
>AC peak so what you read would be even higher still.
Until you load it.
Unloaded, an old xformer/rectifier battery charger always had
significantly higher voltage without a battery on it.
BIG ripple!
But once a battery is charged and even peaked out, that higher voltage
peak can blow the damned things up, so all charging sessions had to be
monitored to keep them from exploding. Then better chargers came out.
Now, I wouldn't be surprised if there wasn't one you could operate or
observe with your iPad. There are Wi-Fi and/or bluetooth handheld meters
now. That would be enough to know when to go shut it off.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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