<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">On 2/20/2019 2:23 PM, Greg D wrote:<br>
</div>
<blockquote type="cite"
cite="mid:27aaa95b-5d3c-c30e-9a23-2dfd415e99a1@gmail.com">
<pre class="moz-quote-pre" wrap="">
Just putting a ham radio in my EV was a challenge, since one can't pull
much power from the "accessory" outlet. Mine is only rated to 8 amps,
and most mobile rigs can pull up to 13 amps. In some cars, going direct
to the relatively small 12v battery isn't much better unless the car is
on or actively charging. </pre>
</blockquote>
<p> </p>
<p>This was the issue I had with my 2006 Prius, where the 12 VDC
battery is about the size of a motorcycle battery. The tiny
battery was primarily to boot the electronics that control the
hybrid power system. I discovered that the 240 VDC-to-12 VDC
switching down-converter, used to recharge the small 12 VDC
battery and power the 12 VDC lighting & accessories was
capable of several hundred watts at 12 VDC when running. <br>
</p>
<p>I connected a 55 AH Optima Yellowtop AGM deep-cycle battery
through a Hellroaring isolator across the small Prius 12 VDC
battery. This battery was just narrow enough to lie on it's side
in the hidden lower trunk of the Prius. When the hybrid power
system comes on and starts producing 12VDC, the FET switch would
close and charge the added battery. The Hellroaring device is
not the run-of-the-mill diode RV battery isolator. It uses a
power-FET switch that has less than .05 VDC drop at 75-150 amps
when on. This was critical in the Prius -- the DC-DC converter
only produces about 12.8 VDC, instead of the typical 13.8 V or
more, when on. (Apparently, Toyota was trying to maximize the
life of the small 12 VDC battery by not charging it as highly as
car batteries usually are.) The Optima would never have recharged
fully with the usual .4-.7 VDC drop through a typical diode
isolator. <br>
</p>
<hr width="100%" size="2">
<p>Another trick I have done with the Optima is to power
high-current loads off the lighter jack (a.k.a. "DC power outlet.
Connect a short heavy (12-14 GA) red-black zipcord DC cable
between the battery and a PowerPole DC distributer panel. Then
connect about 20 feet of 18-20 GA red-black zip cord between the
battery and a lighter plug connector. <br>
</p>
<p>Normally, engine-on a moderate current will flow from the car's
power system through the lighter socket to the added battery.
When you key up a full-power HF rig with a 25 A TX draw, most of
the current comes from the added battery; not the lighter
connection. When the terminal voltage of the added battery drops
a few tenths of a volt below the car's charging system voltage, a
larger charging current will try to flow through the lighter
socket to the second battery. But as the current tries to
increase, the voltage drop across the 18-GA zip cord increases,
limiting the inrush current to something the lighter socket can
handle (8-10 A). As the second battery reaches full charge, the
voltage drop across the zip cord decreases, allowing the second
battery to ultimately reach the same voltage (+/- millivolts) as
the car's battery and charging system. It's basically an
el-cheapo semi-constant-current charging system.<br>
</p>
<p>This works like a charm to throw high-power HF rigs, 300-watt
inverters, 100-watt-out VHF/UHF Micors, etc into a vehicle with
just a lighter jack, on short notice. <br>
</p>
<hr width="100%" size="2">Stephen H. Smith wa8lmf (at) aol.com <br>
Skype: WA8LMF<br>
EchoLink: Node # 14400 [Think bottom of the 2-meter band]<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
Live Off-The-Air APRS Activity Maps<br>
<a class="moz-txt-link-rfc2396E" href="http://wa8lmf.net/map"><http://wa8lmf.net/map></a><br>
<br>
Long-Range APRS on 30 Meters HF <br>
<a class="moz-txt-link-rfc2396E" href="http://wa8lmf.net/aprs/HF_APRS_Notes.htm"><http://wa8lmf.net/aprs/HF_APRS_Notes.htm></a><br>
<br>
<p><br>
</p>
<p><br>
</p>
<p><br>
</p>
<p><br>
</p>
</body>
</html>