Peter, You do NOT need a voltage booster with the K3. If you allow a 12V lead-acid battery to drop to 10.5 you have just over-discharged it and have already caused it at least minor damage. Using a voltage booster to squeeze out a few more amp-hours will yield only a few more minutes of operation, and a disappointment next time you use the battery and find out its capacity is much reduced (permanently).
The boosters are sold for other rigs that require around 13.8V (standard for a vehicle battery while engine is running). The K3 has a wonderfully wide voltage acceptance so it doesn't need that gadget (which also wastes a portion of the power that it converts). In the solar and portable power field, battery system controllers are routinely set to shut loads off at 10.5 (or as high as 11.5) volts to prevent battery damage. Electraft built that in for us! K3 ideal for battery operation with NO accessories. Just make sure your power cables are of sufficient size to minimize voltage drop. Incidentally -- Best longevity of a lead-acid battery is achieved if you normally discharge it no more than half-way. Voltage can only give you a clue to the state-of-charge, but not going below 11.75 volts is a reasonable guideline. This applies to deep-cycle batteries. Automotive engine battery should not be discharged that much because it will damage the battery, and you may not be able to restart the vehicle. Smile! Windy > Many thanks for information Hector > I have looked on two of the major suppliers of amateur radio > equipment in the > U.K.. and they don't appear to stock the MFJ unit but I will keep > looking as it > appears to get over the voltage drop problem. > Peter > G3UCA. > ----- Original Message ----- > From: Hector Padron > To: Peter Sinclair > Sent: Sunday, February 21, 2010 10:36 AM > Subject: Re: [Elecraft] Elecraft K3 > > > Good morning Peter,I did that test for you,I put my K3 to > send a string > of dots at 50wpm with 13.8V and 100W out,then started to drop the PS > voltage > until I saw PO drop to 50W and that happened at 10.5V,below that > voltage the > whole radio turned off. > I am using that MFJ product on my SUV to keep the battery > power always > at 14V when I use my IC-7000 on HF mobile,it works great,I can even > have the > engine off without alternator charging and the output of that box > remains at > 13.8v. > > Hector > AD4C > > > > "For a refined ham it is compulsory to own a k3" > > --- On Sat, 2/20/10, Peter Sinclair <g3...@blueyonder.co.uk> > wrote: > > > From: Peter Sinclair <g3...@blueyonder.co.uk> > Subject: [Elecraft] Elecraft K3 > To: Elecraft@mailman.qth.net > Date: Saturday, February 20, 2010, 10:36 PM > > > Has anyone done any tests of voltage input against power > out on the > K3 ? > What I want to know is when running on a battery fully > charged to > about 13 volts at what level of voltage does the power drop off to > say 50 Watts > ? > I see MFJ has a unit (4416B) to get over this problem.Has > anyone any > experience with this unit. > Peter G3UCA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
