That's an interstuing approch, thanks. I was not aware of the fact that a 12 V (or 14.4 Volt) alternator would supply 16 or even 18 VDC when connect to a 16 or 18 V battery stack.
In mmy case battery capacity is no issue, there is plenty of space to even fit 8 two volt cells. The point is the absolute lack of space for a second or larger frame alternator.
On second thought is might be an option to use an 18 V battery stack (with the stock alternator connected to the +18 VDC of the stack) and use a 18 => 12 V DC DC 30 amp converter to supply the needed charging current to the starter battery and the car electrical system.
Cheers, Dick
PA3DUV
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----- Original Message -----
From: "1800 Toll Free" <TollFree1800@...>
To: <ham_amplifiers@...>
Sent: Thursday, January 11, 2007 1:05 AM
Subject: [ham_amplifiers] Mobile power supplies revisited
Here's another thought, more geared towards the gentleman in .eu who was
looking at running a bunch of 2 volt batteries in series, and home
charging it.
I have done this in the past, and although it isn't the best method, since
your going to use 2 volt batteries, you can still accomplish this and stay
within the realm of 16 volts.
Take 2 of those 2 volt batteries and run them in series, creating 1X 4
volt cell.
Connect that in series, neg from the new bank to + on the car battery, and
run your amp from the + side of the new battery bank. From vehicle ground
to amplifier B+, you will see app 16 volts.
Now, the trick is here...
Take ONLY the B+ out from the ALTERNATOR (I always disconnect the vehicle
CHARGE lead at the alternator, then run a dedicated lead from the alt to
the battery stack), and connect it as well to the top of the battery stack
(to the 16 volt side).
Since the cars electronics will all still see 12 volts, and the alternator
will have to produce 18 volts to charge the 16 volt system, everything
charges nicely.
I also think it is best to take and run a relay / solenoid setup to
disconnect the extra 4 volt stack when not being used, to prevent
overcharging. Usually 10 to 45 minutes of charging while driving around
is sufficient. Just use a solenoid to disconnect the B+ from the alt to
the top of the 16 volt stack to the + / - junction of the 12 and 4 volt
batteries.
This works well in systems where you can't install a second alternator.
Your car works fine, the amp works fine, everything charges nicely, BUT,
you don't get something for nothing. Your alternator is usually running >
manuf ratings, and you won't see rated Aout at 18 volts.... Expect about
20 percent less... Or even less efficiency. Still, makes it easy to run
increased collector voltage cheaply.
--Toll_Free
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