I appreciate your sincerity Jim. Yes you are right. One cannot even "begin to explain" wiring without a thorough understanding of Ohm's law. A quick check of Ben's circuit reveals 50ft of 18AWG wire will limit the worse case peak charging current to less than 10A. (One lead-acid battery fully discharged, and the other continually kept charged.) A 10A fuse in series will insure the wire will never be overloaded. 25Ft of 18AWG common extension cord will do the job safely without the necessity for high temp insulation. Shorter wire with high temp insulation will also do the job but why pay more. While in boost mode the 18AWG wire will be out of Ben's circuit. So according to Mr. Georg Ohm, you were wrong on all accounts. You were also wrong according to the safety agency rules on cable ampacity. BTW, from your choice of phraseology I have a feeling you are not going to take me seriously, so ask our electrical expert Norm and he will tell you how Andina, who is another electrical expert in another boating list uses wires to limit current in "combiners" which are perfectly safe products and the safety and reliability of the method is proven in the boating market. Sorry if I was too hard on you Jim, I mean well.
Cheers Ahmet SV8827 Date: Mon, 29 Jun 2009 08:12:51 -0700 From: [email protected] To: [email protected] Subject: Re: [Liveaboard] 12 to 24 volts On Sun, Jun 28, 2009 at 7:54 PM, ahmet erkan wrote: There may be some issues connecting a discharged battery in parallel with a charged one. Small gauge wire at the proper length with high temperature insulation might limit the current to an acceptable level. S/V 8827 Ahmet I don't know how to begin explaining how bad an idea that is. Using wire, as a current limiter is unadvised. The temp rating of the insulation is irrelevant. The wire will heat up, and likely melt. > From: [email protected] > Date: Sun, 28 Jun 2009 14:14:52 -0500 > To: [email protected] > Subject: Re: [Liveaboard] 12 to 24 volts > > On Sun, Jun 28, 2009 at 08:35:44AM -0400, [email protected] wrote: >> >> Once upon a time there was available at J C Whitney a relay just for that. >> The Volkswagen of some vintage had two six-volt batteries under the back >> seat wired in parallel. The relay would put them momentarily in series >> (while disconnecting the six-volt feed) sending twelve volts to the starter >> for cold-weather starting. > > That was a cute idea on their part. Again, wiring it up wouldn't take > much - here, I'll sketch it: > > http://okopnik.com/images/flip.pdf > > When the relay/switch is in the off/unpowered position, the two > batteries are tied in parallel, and the watermaker is disconnected from > the circuit. In the other position, the two batteries are connected in > series, powering the watermaker. > > Do note that if you're charging while running the watermaker, only one > of the batteries will get charged - which means that your total series > voltage will start dropping after a while. Solving *that*, however, is > quite a bit more complex (but does provide one possible answer to "why > are there 12v-to-12v inverters?" :) > >> They may still have this relay available somewhere. > > If not, just look for a DPDT relay that can carry at least twice the > current required by your watermaker. > > > -- > * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET * > _______________________________________________ > Liveaboard mailing list > [email protected] > To adjust your membership settings over the web > http://www.liveaboardnow.org/mailman/listinfo/liveaboard > To subscribe send an email to [email protected] > > To unsubscribe send an email to [email protected] > The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ > > To search the archives > http://www.mail-archive.com/[email protected] > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html Hotmail® has ever-growing storage! Don’t worry about storage limits. Check it out. _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html -- http://neon-buddha.net _________________________________________________________________ Windows Live™ SkyDrive™: Get 25 GB of free online storage. http://windowslive.com/online/skydrive?ocid=TXT_TAGLM_WL_SD_25GB_062009 _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
