Hi Randall,
You could look at it this way. The Red Top AGM Optima has survived use
in my later model car for five years so far with zero problems. It's
been fairly well discharged a couple of times. The 90 amp alternator
that is set at 14.4 volts has always charged it with absolutely no
operating problems. The alternator/regulator sometimes puts 80 plus
amps, sometimes 10 amps, into the battery. What ever is needed to
quickly charge the battery. Another Optima battery in my Ford truck
works the same way. AGM batteries are not nearly as sensitive to
charging conditions as the older gelled electrolyte cells were.
The only regulator is in the alternator which is set at a maximum of
14.4 volts. I don't know what regulator is in my Toyota alternator
except it has a maximum output of 14.4 volts & the charge rate tapers
off as the battery comes up to full 14.4 volt charge.
I built an adjustable, settable max. output voltage regulator into my
Sears bench charger 25 years ago. It's been used occasionally on the
Optimas & many other batteries. When the battery comes up to the set
voltage it switches off. If battery voltage drops a bit it switches back
on. With the charger left connected, it seems to switch on every few
days & charges a few milliamps for a short time. Charge rate is
proportional to how low the battery voltage is. As the battery voltage
rises, the charge rate tapers off. Same as with the alternator.
It isn't hard to build a simple adjustable output voltage
limiter/regulator into any simple charger. I found my circuit in an old
RCA transistor manual. Remember those. Seems like it used a couple of
TO3 transistors. I'll bet that there are chips now days that will do the
same thing. I'll bet you can buy many similar chargers off the shelf.
Maybe not "adjustable voltage limiting" but likely acceptable fixed
voltage limiting.
As you say, the charger has very high ripple, but when connected to the
battery capacitance the ripple is much lower.Your meter won't read the
120 Hertz ripple because the battery which acts like a large capacitor
when connected to the charger will filter the ripple out.
I also have a different AGM battery & Lucas alternator in my
Austin-Healey & everything works the same way.
Regards,
Dave Russell
Randall wrote:
>>But is it OK to charge an Optima using a regular charger as
>>long as I disconnect it after it as charge?
>>
>>
>
>As I read the info at
>http://tinyurl.com/339e3j
>I believe the answer is "probably not". Optima is very specific about using
>only a "regulated" charger, which is not what I would call a "regular"
>charger. (Or maybe a better way to put that is that my "regular" charger
>has no regulation.)
>
>You could probably put most of a charge in with a regular charger, but you'd
>need some way to accurately measure the peak voltage during charging. Since
>the charger output is not filtered, the voltage will vary between battery
>voltage and some peak value 120 times/second. My voltmeter won't read those
>peaks, but maybe yours will. An oscilloscope would be the only other way,
>IMO ... and even then, you'd have to (a) sit and watch it constantly, and
>(b) not put in a full charge.
>
>Randall
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