On Wed, 27 Jul 2011 22:02:14 -0400, Tony V wrote:

An advertisement in QST magazine caught my eye and I wonder if some one
has used something similar to this in gliders(we don't need 25 Amps at
12 Volts):
http://www.mfjenterprises.com/Produc...ctid=MFJ-4416B The idea
is to keep the voltage supplied to your electrics constant even if the
battery voltage drops to as low as 9 Volts (in the above example).

Assuming you're using it to maintain 12v off a nominally 12v battery, the
only problem I'd see is that once the battery drops below about 11.5v
there's not a lot left in it. Maintaining 12v out of the black box is
probably going to suck the last juice out of the battery pretty fast. Add
on the 90% efficiency of the thing and merely by fitting it you've just
increased your power drain by 11%. Bottom line: I wouldn't use one this
way because I don't think it would help much.

However, if you want to run a higher voltage device off a 12v battery,
its a good idea.

I carry a 28v R C Allen turn & slip in my Libelle, which uses a solid
state 12v = 28v converter in its power cable. This works perfectly. The
device is tiny - a single PCB inside heat-shrink tube and about 40mm x
15mm, so I haven't seen what on the board. However, I'd lay long odds
that it contains a Maxim step-up voltage switching regulator, say a MAX
1771, a power MOSFET and 6 passive components.

http://www.maxim-ic.com/datasheet/index.mvp/id/1030

The MAX1771 can handle up to 2 amps and costs $US 3.55 - that is a Buy It
Now price on eBay, so I'd guess you could have a working voltage
converter for $8 or less - say 12 bucks if you sprung for input and
output connectors rather than simply soldering the wires on.

At that price I'd also try using one to power a 14v radio off a 12v
battery rather than adding an extra 2v cell.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |