4/16/2023 0 Comments Battery isolator relay hummingFor any nickel-chemistry battery, use a maximum cell voltage of 1.42V as the 'float' voltage. The series resistor in the charger circuit (R2) acts as a current limiter in its own right as the cell voltage approaches the maximum. Technically, these battery types do not have a 'float' voltage as such, but what happens as the battery approaches full charge (nominally 1.42V/cell) is that the current falls from the normal C/10 rate to a lower value that's just sufficient to maintain a full charge. The method suggested here will not be found in any of the published data regarding charging, but it should work fine without causing battery damage. Nickel based batteries (NiCd and NiMh) are easily damaged by overcharging. It is entirely up to the reader to determine the suitability of the charger shown to the intended application. While I do not intend this simple project to become a full scale article about batteries, it is very important that you understand that unless looked after very well, any battery will have a much shorter life than normal, and will prove very costly to replace. Just what is float charge? It is simply a method for maintaining the charge in a cell or battery - float charging is used anywhere that batteries are used infrequently, but must be kept at full charge when not in use. Note: The voltages quoted above are for a single 12V battery - the project is designed for a +/-12V supply, so the float charge voltages must be doubled, as the two batteries are connected in series. It is worth noting that few of the commercially available chargers make these corrections, and fewer still are designed to provide a proper float charge. These voltages are critical, and if they are exceeded (or the room temperature is significantly above or below the 'standard' temperature), then the battery life will be significantly reduced. In contrast, a 12V SLA requires a float charge voltage of 13.8V (again at 25☌). The correct float charge voltage is 14.2V at 25☌. Although I have shown the system with an integral float charger, this is only really suitable for SLA (Sealed Lead-Acid) batteries - if you wanted to use NiCd batteries, then a proper charger designed for use with these cells should be used, although if set up as described, the charger should work quite well.įor Nickel-Cadmium (Ni-Cd) cells, you need 10 of them for a nominal 12V supply. It will be necessary to find a sensitive relay to minimise current drain, but these are quite readily available at low cost. Although it is possible to use a 'solid state' switch, these are not as good as a standard relay, which provides perfect isolation of the AC input. The sensor detects that you have switched on the preamp (or small power amp for that matter), and immediately switches off the charger, so while listening, there is no connection to the AC. The idea is that the charger is left permanently connected, but of course that would normally introduce some hum into the supply lines. The sensing circuit can be made so sensitive that a load of only 2.5mA is enough for the circuit to detect, and disconnect the charger. This project is one for the experimenter, but as shown will work extremely well. At last, remembering to turn the charger back on is no longer a problem! Http: hose who want the cleanest possible DC for sensitive preamps, battery power is ideal. Its not always about who gets to the finish line first, its who looks good when they get there. In this case im guessing the FPR, its either buzzing, or more likely the contacts are stuck closed leaving the FP powered on at all times.īoost is like Venereal Disease, one night of passion can result in weeks of pain (and work.) Sounds like it could be a relay, also you will see the simular symptoms with a fried alternator but the noise will go away when the key is turned off, and pulling the fuse will not stop battery drainage, as the alt shorts internaly. A faulty OPS will blow the fuel pump fuse if it shorts internaly, but not directly effect the FPR. This is in case the FPR fails, and can often be the explanation to hard starting, as the FP will not turn on until the OPS sees oil pressure. If the FPR fails, the oil pressure sensor(OPS) is a backup, when the OPS sees ~4PSI oil pressure it bypasses the FPR and sends power directly to the FP. The FPR sends power to the fuel pump(FP). The way the system works is when the key is turned on the ECM sends a signal to the Fuel Pump Relay(FPR) for 2 seconds unless it goes to crank, then turns it off. This way if you have no oil pressure, you're fuel pump shuts off before you blow up your motor The sender is saying you have oil pressure to it tells the relay to allow power to the fuel pump It's usually the oil pressure sender, not the relay itself
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