Randall wrote:
>>Once again, most battery chargers are NOT voltage regulated.
>
>
> It occurs to me that this may be a bit obscure to some. Simple battery
> chargers (like most inexpensive units) are nothing more than a transformer
> to convert AC line voltage to a suitable value, and a full wave rectifier to
> convert it to DC. Among other things, this means that their output voltage
> depends on their input voltage, which can vary substantially, as much as 30%
> or more. (Yeah, I know, the specifications are tighter than that, but
> consumer appliances have to deal with reality, not specifications.)
>
> To deal with the varying input, inexpensive chargers typically have a
> relatively high open-circuit voltage and then limit current output by having
> a relatively high internal resistance.
>
> The other way of solving the problem is to have some sort of electronic
> circuit that senses the input (or output) voltage and makes appropriate
> adjustments ... this is known as voltage regulation. Since it adds
> significant cost to the unit, voltage regulation is not found in most
> inexpensive battery chargers. A fully regulated 10 amp 12v power supply may
> cost several hundred dollars, while I recently saw a 10 amp 12v battery
> charger on sale for $30.
>
> Randall
>
Sounds like we agree that if the voltage stays at 14.6 or so, no damage will be
done to the battery.
If the battery's are being damaged, then the voltage must be rising to above
14.6 V for some reason.
Dan writes on page 21...
The only components in the charger are a transformer with a multi-tap primary,
a rectifier, a
switch, an ammeter and a timer. The switch has 3 positions - slow charge, fast
charge, and boost.
The only difference in the three positions is the tap on the primary of the
transformer, which
changes the output voltage of the secondary. There is no regulation whatever.
... On the slow
setting, the output voltage is 13.4 V. On the fast setting it is 14.8 V, and on
the boost setting it
is 17.6 V. These measurements were made with no load. ... but I'm certain the
voltage goes down from
the heavy loading. The label on the unit states the voltage drops to 7 volts at
the full 240 amp
output.
In Dan's scenario, and assuming the charger is set to slow, what causes the
voltage on the battery
charger to rise above 14.6 V and force additional amperage into the battery? Is
it only the
variability of the AC voltage source?
Don Malling
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