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: [email protected] > 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 [email protected] To adjust your membership settings over the web http://liveaboardonline.com/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.liveaboardonline.com/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
