I have a 9Vdc/350mA battery charger, would that be sufficient to charge a 7.4Vdc/500mAH battery? Could someone explain the voltage and amperage of the charger and what it should be in relation to the voltage and amperage hour of the battery? How do these measurements affect the charging time of the battery?
Normally charger voltage is 30% higher than that of the battery.In your case the time required to charge the battery is 500/350 hours.
A bit of guesswork here - It's current that charges a battery, and to get the current the charger voltage must exceed the battery voltage. So yes, it will work. The question is, is it safe to leave it connected and forget about it. Old dumb chargers just used a small amount of current that was safe. New smart chargers charge at a much higher current and stop every so often and measure the battery voltage to decide if the battery is full. On that basis, the 9V charger may not be safe to leave connected for an extended period because it will never stop charging. I yield to any real battery experts out there :-) Got me interested found a thesis on design of an FPGA charger which talks about charging characteristics of NiMh and Li-Ion. Also, some battery packs have a built-in thermistor to measure battery temperature, but I presume in e.g. a cellphone that the circuit to run that is built into the phone, not the charger (all my chargers are 2-pin). I have successfully charged a 6V NiMh battery pack from a 12V source using a dropping resistor, but as I say, not left it connected for long.
Its is not as simple on amperage. You must match voltage, to within a tenth of a volt, or you risk destroying the battery, charger, or both. Chargers are usually current limited, so if they don't smoke, they will charge the battery at their maximum rate. This is usually not fast enough to overheat the battery and let the magic smoke come out. This is not to say that if one were to series enough batteries together to match a Prius' battery, that Prius charger will not try and nuke them. As to charging time, this is a delicate balance between what the battery was designed to take, and what the charger is able to give. NiCd batteries have to trickle charge, while Lithium batteries can take a full charge in tens of minutes. The case temperature while charging tells all.
That you are designing for a 7.4V battery suggests to me that you're making a lithium-ion or lithium-polymer charger, and these are not simple to make. Charging them improperly can cause destruction of the battery, sometimes in a spectacular fashion (an explosion, for instance). Apple had to shell out quite a bit of money when their improperly-designed PowerBook 5300 caused a number of school and residence fires. This isn't the charger that comes with an E-Flite RC helicopter by chance is it? If this is in fact a LiPo battery, don't use that charger, or any charged designed for fixed-voltage or fixed-current use.
seems the swap contained in the charger is defective, probably some corrosion. swap it back forth various cases then take your studying. commonly used is 12v (13.8v) in both modes. Low may be about a million amp extreme could no longer exceed 4 amps as bike batteries besides as Jel-cells could no longer be charged with more effective than 4 amps. search for a MC pulse charger, they are about one hundred money yet can fix secure you battery, unlike a common charger which will finally wreck a battery. A pulse charger will save plates maintained and sparkling of equipped up sulfides which short out between plates. a real reliable Pulse-charger is made with suggestions from Tesla yet expenditures about $1500.00 yet you may under no circumstances favor yet another battery back. Wishing you nicely,
