Hi Rufus, I appreciate all the inputs my friend. Don't worry about offending me, I learned to accept many people just the way they are, even the bullies are not a big problem for me anymore, I keep thinking about the injustices they must have faced during their childhood and cut them lots of slack. Pirates are a different story though, I would kill them at first chance with any means available to me and with no regard to their childhood. Kill or be killed is an extremely simple decision. Anyway getting back to nicer thoughts like maintaining our 900A/H bad boy batteries : 1. The efficiency for a low power device may be misleading. What matters is the amount of wasted power. At 85% efficiency and 138W output we are dissipating only 24Watts. About the same power as one tail light. Some folks said their daily energy usage was about 100AH. Although Ampere Hours is not a unit of energy, lets say it is 100A X Average Battery Voltage X 1Hour of energy. If we restore 80% of this energy running the engine with a 110Amp alternator for about one hour we have 20 X Average Battery Voltage X 1Hour of more energy to restore. At 10A this will take only 2 Hours because the lead acid battery as you know will recharge close to 100% efficiency at low current charging. 24W dissipation for two hours averaged over 24 hours is like 2W. Considering a night light is about 15W the power wasted by our equalizer is not going to be anything significant. Run the Diesel for an extra hour at tapering current and you will waste several orders of magnitude more energy I would think. Not to mention the possible wet stacking damage, wasted runtime between engine maintenance, the noise annoyance etc, we are golden with the DC/DC. 2. The voltage reference for the float and equalize levels comes from the 5V "band gap" reference from the Linear Technology LT1247 integrated circuit we are using. The data sheet claims the reference is 0.2% accurate from 0C to 50C temperature. This is good enough thermal stability for me. I don't need to know what a band-gap reference is. 3. Temperature compensation is manual. Also, the equalizer does not have the power to overheat a 450A/H battery even if the battery has a shorted cell. Your 120Ampere alternator will overheat a defective battery during the bulk charge. 4. Although I will have doomsday fuses inside the box these fuses will not protect the three 16AWG wires connecting the terminals of the battery switch to the equalizer. I think we should add three wires with large ring lugs and 15A in line fuses to be wired to the battery switch terminals and include it as an installation kit. Thanks, for the excellent point. Give my respects to Mr. Murphy too, and let's keep him out of our box. By the way, I forgot to add the color options to the spec. Hey how about we use Mr. Henry Fords idea. "You can have it in any color you like as long as it is black". Cheers Buddy By the way Rufus, do you want to be the beta test boat for the "breadboard" in couple of Months? Notice I downgraded the prototype to a breadboard status because I don't want to incur an extra $500 PCB spin cost. The homemade wiring board will be quite reliable though. It has to pass the DVT.
> Date: Tue, 31 May 2011 21:17:54 +0000 > From: rlagg...@mail.com > To: liveaboard@liveaboardonline.com > Subject: Re: [Liveaboard] Battery Equalizer-Status > > I've read many of the posts but not sure I got to all. A couple Q's. > > 1) 85% efficiency (worst case, right?) Seems fairly low depending much/often > it hits the worst case. So what's the HIGH effiency and what do you project > an average usage might rack up? Would it be around 85% or higher? Would any > particular installation/usage materially improve the efficiency? > > 2) What's the accuracy of the charging control circuit? (Which I _think_ is > what you're redesigning due to change in sensing circuit due to increase > design current). I'm not and EE or really familiar with circuitry (been 40 > years since I messed with ham stuff) but - IIRC (I'm a lead acid guy) the > newer sealed batteries are very vulnerable to excess charging rates _and_ > excess total charge. So accuracy, depending on battery type, seems important. > > 3) Is there any value in tempeature sensing at the battery? Do'nt recall if > equalization heats up the battery... > > 4) This box permanently wired into the boat's battery circuits. What are the > fail modes? Eg. what happens of the main semi-conductor switch shorts? Or is > that possible - maybe they always fail open? Anyway, what happens to the > boats wiring when the box goes bananas? What happens to the box when it goes > bananas - how hot does it get? > > It sounds like you know what you're doing - I not trying to stick you. This > is just my normal approach to any technology - I always bow to Murphy. > > Cheers, Rufus > > > > ----- Original Message ----- > > From: ahmet erkan > > Sent: 05/28/11 03:18 PM > > To: liveaboard@liveaboardonline.com > > Subject: [Liveaboard] Battery Equalizer-Status > > > > Hi Guys, > > Things went South with the paper design for a while but we are back on > > track with our product. > > Originally the output current rating was 5A at 13.8V. I thought this may be > > a bit low for a 400AH 1/2 bank > > so I doubled it to 10A. It was easy to re-design the transformer and pick a > > lower resistance FET and a > > higher current rated Schottky diode but the current sense resistor > > dissipation increasing from 5W to 10W > > screwed up the power dissipation budget for the board as well as the box. > > Currently the plan is to use a > > ferrite core current transformer with a 20:1 ratio to reduce the power > > dissipation at the sense resistor > > to a low 0.5W and give us higher efficiency. > > > > Preliminary Specifications : > > Input voltage range : 8.4Vdc to 15Vdc. > > Output current rating : 10Adc (Vin=12V, Vout=13.8V) TBD based on operating > > temperature range. > > Minimum efficiency : 85% (Vin=12V, Vout=13.8V, Iout=10Adc) > > Operating temperature range : TBD > > ON/OFF toggle switch. (Left side of the box. Up is ON) > > EQUALIZE/FLOAT SWITCH (Right side of the box. Up is EQUALIZE) > > Three green LED's to show charge rate. (Approx 25%, 50%, 100%) > > Wiring through 4 X 16AWG wires to a 4 gang terminal block at the bottom > > surface. > > Internal Fuses > > Internally adjustable float level (Pre calibrated to 13.8V adjustable to > > 12.5Vmax fully CCW to 14Vmin fully CW) > > Internally adjustable equilize level (Pre calibrated to 14.8V adjustable to > > 13.5Vmax fully CCW to 15Vmin fully CW) > > Bulkhead mount box (Mounting hole pattern (4" X 6") Hardware TBD > > Height : 5.5" max > > Width : 8" max > > Depth : 2.5" max > > Waterproof to 10ft depth TBD > > Price target $300 > > > > Functional Description (copied and pasted from a previous e-mail) > > > > 1. Start the engine, and begin charging. (with the battery switch in "BOTH" > > position) > > Continue charging until the battery voltage reaches the maximum and the > > regulator > > begins to taper down the charge current. > > 2. Shutdown the engine > > Shutdown when the current drops to 80% (recommended) or 30% or 99%. > > Just know that when the charge current begins to taper down, the efficiency > > of the charging process also begins to go down. > > 3. Flip the battery switch to "BANK 1" on odd days and to "BANK 2" on even > > days. > > The Equalizer LED's will first indicate "CHARGING" and then "FLOATING" and > > then "CHARGED". > > The cycle timing will depend on the Ampere Hour rating and condition of > > your batteries. > > 4. Flip the battery switch back to "BOTH" position. > > > > I am building the prototype, to make sure it meets the latest specs. > > I would like to send this prototype (free of charge) to a volunteer to > > validate my (DVT) design > > verification testing. The DVT validation volunteer can keep the prototype > > and also get > > a 50% discount on a deliverable unit if he/she wants it as a spare. > > > > The DVT volunteer should tell me the A/H rating of his dual house banks, > > and the diameter of the > > terminal studs behind his battery switch, and how long wires he needs from > > where he wants to > > install the equalizer to the back side of the battery switch. > > > > Again, please let me know if you disagree with any of these specifications. > > Now is the time to evaluate and implement the suggested changes. > > > > Now I have to talk my wife into spending $3,000 for a new scope and a > > current probe to do the lab testing. > > You guys are killing me :-) > > Wait, I remember Ben Okopnik said he would buy the DC/DC. I wish he would > > give me a part number ! > > > > Happy sailing > > Ahmet Erkan > > _______________________________________________ > Liveaboard mailing list > Liveaboard@liveaboardonline.com > To adjust your membership settings over the web > http://liveaboardonline.com/mailman/listinfo/liveaboard > To subscribe send an email to liveaboard-j...@liveaboardonline.com > > To unsubscribe send an email to liveaboard-le...@liveaboardonline.com > The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ > > To search the archives > http://www.mail-archive.com/liveaboard@liveaboardnow.org > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html
_______________________________________________ Liveaboard mailing list Liveaboard@liveaboardonline.com To adjust your membership settings over the web http://liveaboardonline.com/mailman/listinfo/liveaboard To subscribe send an email to liveaboard-j...@liveaboardonline.com To unsubscribe send an email to liveaboard-le...@liveaboardonline.com The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/liveaboard@liveaboardnow.org The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
