Learn me about car batteries + electronics!

[Logistics]

So I was thinking about getting an Optima battery (so I don't have to worry about gasses or fluid leakage) to power my project electronics, especially headphone amplifiers. However, the last time I remember bringing this up on a message board, the consensus was that such a battery would cause a gigantic in-rush of current at initial power-up that it would either ruin the amp or blow it's fuses, every time.

So let's say I want to power a little 2W audio amplifier IC with an Optima battery; how do I keep it from ruining my amp? (I seem to remember someone mentioning using a trickle-switch!)

[Gianni]

Re: Learn me about car batteries + electronics!

AFAIK the buttery can't create a big inrush current.
The inrush current is caused by the load, usually CAP: when they are discharged and you connect a power source, they charge very quickly and the peak current can be very high.
The peak current depends on the circuit impedance: connector, wires, tracks, fuse ...
So I can't see why a battery can cause an high inrush current.
The difference between battery and a power supply is that the battery can give you high current,it is limited only by its impedance, while PSU are usually current limited.
Anyhow if you want to limit the inrush current you can use a NTC thermistor connected between PSU and amplifier.
They are often used inside PSU; the only problem with them is that they limit the current only when they are cold, the best way to limit inrush current is to use a fixed power resistor that is shorted after few seconds from power on using a relay. In this way even if you shut down and turn on quickly your electronic appliances, the resistor always limit the current until the relay shorts it, while a NTC thermistor can't since if it is hot, its value is low.

Just my 2 cents
Gianni

[kc8adu]

Re: Learn me about car batteries + electronics!

for your use dont worry about it.
unless you are using one of those 2 farad caps like the boom boom amp guys use.
i have a yellow top d31 on my bench here.no problems at all with it.
just make sure you fuse any wiring you use.

[Logistics]

Re: Learn me about car batteries + electronics!

Sweet! Thanks guys.