[Yaesu] FT1500, your input appreciated

[David Willmore]

> 1) FT1500 2m mobile purchased April, 2001. Works fine. Its manual says the current draw for 50W is 8 amps, 2 amps at 5 watts
> .
> 
> 2) Coleman Jumpstarter ModelPMJ8960 10Amp/hr portable battery. Its manual says its 12v cigarette lighter ports can provide 1
> 2v DC at 10A maximum.
> 
> 3) I connect the two with a home-brewed cord: Radio Shack fused cigarette lighter plug (w/LED indicator) spliced into a fact
> ory-supplied Yaesu power cord--each lead has its own fuse. Three fuses in all protecting against accidents. This cord is abo
> ut 10 feet long.
> 
> When I key up at 50 watts, the DC INput display goes from 12.6 volts to 10+ volts. I'd expect that.  Is it normal for the ri
> g to deliver that kind of punch to the battery?
> 
> Secondly, with the rig plugged into the Coleman or installed in the car connected to the automotive battery, in the OFF posi
> tion, when I disconnect the power cord, the radio "blips" or pops (heard on its speaker) and the display blinks once.  Does 
> the radio draw current even when turned off?
> 
> Thirdly, are these jumpstarter battery packs poor choices for ham use?

First some ground work.  The A*h rating of a lead acid battery is
normally given in a 10h or 20h value.  So, a '10A*h' battery
may be rated for 1A for 10 hours or .5A for 20 hours--depending on
which notation was used--sometimes the manufacturer will mention
that on the cell or in their data sheets.  Like most batteries, if
you draw more current, the useable life of the battery goes down
*faster* than current*time==constant would imply.  So, a 10 hour
plan rated 10A*h battery man last only 4 hours at 2A draw.

There is often a maximum curent draw limit from batteries.  For
smaller batteries like those used in cell phones and HTs, it can
be larger than the capacity of the battery.  For example older
sintered metal construction NiCd cells could be discharged at 
up to 20 times their capacity--for brief pulses.  Most more modern
cells have traded peak rate for total capacity--which for cell phones
and HTs is generally a good tradeoff.  For larger cells--like all
lead acid cells smaller than those made for power backup use--the
limit is rarely above 2 times their capacity.  It can be much
lower than that, as well.

So, without knowing the specifics of the battery in your Coleman,
it is hard to say what to expect or what is safe.  Also, I would
expect--at those current draw levels--for the ohmic losses to be
signifigant.  The 'cigarette lighter' type of plug/socket is not
a good low resistance connector.  Think about it for a second.  
The original goal was to *heat up*, so ohmic loss would only help
in that task.  Also, I have not seen any of those portable power
solutions that were built to what I would call 'best practices'.
The internal wiring may well be too thin and the switches/connectors
may well be under rated, as well.

For battery powering of a high current draw rig, I would suggest:
1) make the power run as short as possible
2) ensure that connectors of low ohmic loss are used
3) ensure that such connectors are properly installed
4) don't include anything it he circuit that doesn't
   absolutely have to be there--current meter, switches, etc.
5) use as thick of wire as is practical for the situation

So, I like lead acid batteries with lead lug terminals which you
connect to with crimp on (or solder cup for the large ones) ring
lugs and 10-24 hardware--don't forget the washers and some anti-
oxidation paste.

You'll need a fuse on the battery side of the connector to protect
the battery and its wiring.  On the radio side of the power
connector, you'll need a fuse to protect the radio and its wiring
and as short of a wire run as will fit your needs.

For the power connector, the standard these days is the
Anderson PowerPole connector.  They're good for 30-45A and they
are reasonably easy to install even with simple tools.  One thing
to keep in mind with these connectors is that their biggest flaw--
of which I'm aware--is that they need to be unmated and remated
once or twice a year to keep contact resistance from growing.
If they're used an an environment where they will be unmated/
mated every now and then, this isn't an issue.  If they're used
in an environment with a good amount of vibration, this isn't
an issue.  But, if you're burrying the thing in the back of
a rack where it will sit snuggly for years, you might think to
unmate/mate it as part of your regular maintenance schedule.

But, for your use--I'm guessing portable and temporary--it 
shouldn't be an issue at all.  And the "polarized, but non-
gendered" nature of the connectors will be a real win.

Best of luck!

Cheers,
David n0ymv