Graeme Cant wrote:
What about getting the best of both worlds? It seems agreed that only
the radio's performance improves with higher voltage. Why not keep a
12V system with its easy charging and standard sizes but add a DC-DC UP
converter into the radio circuit so that a constant 13-14V is supplied
to the radio even though the battery supply voltage drops?
I have no technical skill in electronics - meaning my ego isn't involved
if I'm told it's a stupid idea. Would it just be a further drain on the
battery or would it usefully improve the radio's range?
Older radios would generally benefit, but modern radios would see less
improvement.
Does such a
converter exist?
Yes; in fact, modern radios often have exactly this kind of power supply
built into them (my Becker transponder is an example of this). A
potential problem with an "add-on" external unit is the losses of the
conversion might overcome the value of the improved operation. I hope
someone will determine what's available out there and let's us know how
good they are.
More specifically on batteries, my glider has 4 x 6V 12ah cells arranged
in two series pairs connected in parallel (no, not my idea, the
manufacturer did it) which have reached the end of their life.
I've always wondered why DG thought that was a good idea.
The
original cells are clearly a carefully matched set (marked 6.47, 6.47,
6.45, 6.46).
How important is it that I match the replacements - and on which
characteristics? The Yuasa website seems to imply that the only
important things are that the cells be the same and the same age.
The DG owners here seem to just buy 4 batteries at the same time from
the same place and not worry about matching them. If you don't get a
good answer here, try the DG owners group listed on the
www.motorglider.org site.
Oh ...and the cells are almost impossible to remove from the glider so
they have to be charged in place in the series/parallel configuration.
Again, the DG owners group will offer a plethora of ideas, but this is
common for motorgliders anyway. The batteries are usually large enough
that they have to be mounted more firmly than the usual 7 AH unit,
making it hard to remove them. A solar panel on the trailer is a
favorite (or one placed next to the glider if it's tied down). I just
put charger on mine while it's at home in the trailer, then remove it
after it's charged. There's no need to keep it "topped up" if you are
flying at least once every month or so.
--
Change "netto" to "net" to email me directly
Eric Greenwell
Washington State
USA