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I bought a 50W*2 stereo amplifier from eBay (i believe the values are overrated, though) and i wanted to use it on my motorcycle. It works just fine, but then i wondered about the power consumption: I tested the power consumption with my trustworthy digital multimeter (UNI-T) at 1/4 of the volume.

I set it on 10 Amps thinking that it may be much, but the meter broke. I figured i made a mistake, so i used an analog 15A ampere meter (the panel type) which went all the way up to 15A and stop there, because of the plastic limitations (it hit the plastic really hard as soon as i hook up the amplifier).

It would rarely reach 12A, and every time the led of the bluetooth module of the amplifier blinked it would go back to 15A, which is weird...no bluetooth module should use 3 amps of power.) Then i sensed something was wrong...again.

I had some car fuses laying around and i decided to test it with those. I first started with a 15A fuse. The amp worked properly... Then i tried a 10A fuse. Again, no problem, then i used a 8A fuse, which didn't blow.

Then i noticed i had a 2.5 A fuse among the rest of those. I hooked the amp up as usual. The fuse was fine. I let it play music for a minute at 1/2 of the volume and the fuse did not blow...

Now i am wondering what is the actual current that the amplifier draws from the battery...15A can't be right. It barely gets 4-5 degrees hotter after intense use ( i used it for 2 hours with a computer PSU). This is the amp I used two 4 Ohm speakers (rated for 60W), with the engine off, and the battery was at 12.4 volts.

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  • \$\begingroup\$ Describe how you connected the meters. \$\endgroup\$ – replete Apr 25 '17 at 14:52
  • \$\begingroup\$ Since these are ammeters i connected them in series: The plus of the meter at the + terminal of the battery and the - at the + terminal of the amplifier. \$\endgroup\$ – Andrei Grigore Apr 25 '17 at 14:53
  • \$\begingroup\$ User-error. You either connected the meter wrong, or had it on the wrong setting or, had the test leads in the wrong sockets, or ... something else. \$\endgroup\$ – brhans Apr 25 '17 at 15:01
  • \$\begingroup\$ This is literally how i connected it: mstworkbooks.co.za/natural-sciences/gr8/images/… Just that instead of the bulb is the amplifier. \$\endgroup\$ – Andrei Grigore Apr 25 '17 at 15:03
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    \$\begingroup\$ If the analog ammeter instantly goes to 15A but a 2.5A fuse in its place lasts a minute, the setup of the ammeter is a question. Is it known to be good? (Proven with other measurements.) Do you have any power resistors lying around that you can measure voltage across as an alternative current measuring method? \$\endgroup\$ – replete Apr 25 '17 at 15:15

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