I spoke with technical guy in this company. The patent covers controlling each of these DC-DC from central unit. Their philosophy is not to equalize which is wasteful and impossible anyway he said. Each battery should take as much as it needs (if I remember, your words Lee!), so they're not trying to equalize them. So many parameters affect the voltage that it's loosing battle. They prevent overcharging by sensing dV/dt across each battery (by central unit with so many inputs) and then the units shunts each battery accordingly, at the rate programmed into it' The shunting ramp's shape is also patented, but there is no magic there.
That's why the string length is limited - by amount of inputs detecting dV/dt. I suppose it's expandable for different models they offer. Seems like modification to mk2 or mk3 you're talking about are done here with the exception that main brains are brought outside each unit to a central one. I asked about advantages over Powercheqs. They say powercheqs see only adjacent batteries while their device can see all batteries in the string at once and decide which ones to shunt to deliver only to weakest one right away rather than wait for the chain of powercheqs to move enough charge through the chain. Makes sense, and, accordingly complicates things. Always trade offs... Their device is OK for chemistries with pronounced dV/dt gradient (like PbA) only. Victor Lee Hart wrote: > > Victor Tikhonov wrote: > > Browsing for something else, I found this site: > > > > http://www.skiebus.com/bms.htm > > > > They make something similar to powercheqs but instrad of > > DC-DC or flying capacitor they use flying inductor which > > stores the energy being shuffled around. > > > > On their site it's shown as symmetrical bi-directional device, > > which is not the case for trivial DC-DC. > > The circuit they show is the standard buck-boost converter found in any > textbook. The diode-plus-switch they show is just a MOSFET. I don't see > how they got it patented unless the examiner was hung over, or they > claimed some trivial enhancement. > > Jon "Sheer" Pullen wrote: > >> Me & Lee discussed a small mod to the mk3s that would let them > >> perform this operation across a entire string; similar technique. > > For those that want to play, here it is. Assume two Rudman MK1 or MK2 > regulators on two batteries. You also need a 60 Hz impedance-limited > "class 2" transformer with two 24v windings (or two identical > transformers; I used a pair of 120vac-to-24vac 10va doorbell > transformers with their primaries connected together). Wire like this > (view with fixed width font): > ________________ _________________ > +12v___|________________|____0 ____|_________________|______+12v > | Rudman | _| || |_ | Rudman | > | Regulator #1 | _| || |_ | Regulator #2 | > Battery| _____|____| || |____|______ | Battery > #1 | |_| _|_ | 0 | _|_ |_| | #2 > | MOSFET |_ /_\ | 24v/24vac | /_\ _| MOSFET | > | | | | | 60Hz Class2 | | | | | > -12v___|__________|__| | transformer | |___|__________|______-12v > |________________| |_________________| > > Disconnect the Rudman Regulator's on-board resistor. Connect the 24vac > transformer secondary as your external "load" resistor. A class 2 > transformer winding has several ohms of DC resistance; it will get hot, > but won't burn up if the Regulator ever latches fully on. > > Note the phasing dots "0"; the two transformer secondaries are connected > OPPOSITE from each other -- this is important. > > How it works: Suppose battery #1 reaches "full" first. Regulator #1 > turns its MOSFET on. Current flows thru the left transformer winding > (phasing dots positive) and current ramps up. This loads battery #1, > pulling its voltage down, so the regulator turns off. The inductive > energy stored in the left winding makes the voltage across each winding > reverse (phasing dots negative). There is no path on the left side, but > on the right side, this makes the MOSFET's body diode conduct. The > inductive energy is therefore dumped into battery #2, charging it. > > The reverse is true if battery #2 is higher in voltage. Instead of > burning up the energy in resistors, this circuit dumps it into the other > battery! > > You need the impedance-limited transformers because nothing prevents > Rudman Regulators from latching full "on". A high quality efficient > transformer would saturate, and place nearly a dead short across the > battery, and the MOSFET would fry. The class 2 transformer is an easy > way around this without any modifications to the regulators. > > If you DO happen to use two 120vac-to-24vac transformers, what happens > if you plug these primaries into the AC line? You have individual > battery chargers for equalization! The transformer secondary and MOSFET > body diode form a simple transformer-rectifier charger. Battery voltage > is limited by the regulator as usual, and charging current is limited by > the class-2 transformer's impedance. > > One tip if you use this scheme for charging; put an AC-rated capacitor > in series with the transformer primaries before connecting them to the > AC line. If a regulator latches fully on while you are charging, the > transformer will overheat because it is delivering its full current into > what it sees as a shorted load *and* the battery is supplying additional > current into the secondary. A series capacitor in the primary limits the > primary current, and thus keeps the transformer from overheating. > > This is a real dumb-and-dirty circuit. It works, but BIG improvements > can be made if one is willing to modify or redesign the MK1 or MK2 > regulators. > -- > Lee A. Hart Ring the bells that still can ring > 814 8th Ave. N. Forget your perfect offering > Sartell, MN 56377 USA There is a crack in everything > leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
