current to charge battery

[prkaye]

How much current is drawn from an alternator to charge the battery? I ran my engine today, and with only the Dynon EFIS/EMS and the fuel pump operating, my ammeter (which is positioned at the alternator output) was reading 13 amps. This seems quite high to me. My battery was a bit low because I had been configuring stuff in the EFIS, so I'm wondering how much current should be expected for charging the battery?
When I turned on my radios, pitot heat and all the lights, the ammeter was showing up to 50 amps... this seems really high for a vfr airplane!!

[AltonD]

The alternator field itself draws 5-6 amps. Strobes draw quite a lot of juice.

I have an IFR stack and with everything turned on, I am drawing 54 amps. I think you are ballpark.

I also know that with the B/U B&C alternator, I can get within the 20 amp limit by turning off strobes and one landing light (primary alt field off).

[Mel]

Current drawn from the alternator is dependent on quite a few things. If the battery is low, it will draw considerable current until fully charged. Incandescent bulbs draw quite a bit. Pitot heat will draw a lot.

[Andy Hill]

How much current is drawn from an alternator to charge the battery?

As a wild guess, up to whatever the Alternator will produce

Having drained the battery as you did, and just got the engine going, I saw 50A+ (with no other signifcant loads) for a short while with a 60A PP Altn.

Also a good point to make to those who use, say, a 20A fuse on a 40A Alternator, stating their max load is <20A. But the battery...

Andy

[elippse]

Originally Posted by prkaye

How much current is drawn from an alternator to charge the battery? I ran my engine today, and with only the Dynon EFIS/EMS and the fuel pump operating, my ammeter (which is positioned at the alternator output) was reading 13 amps. This seems quite high to me. My battery was a bit low because I had been configuring stuff in the EFIS, so I'm wondering how much current should be expected for charging the battery?
When I turned on my radios, pitot heat and all the lights, the ammeter was showing up to 50 amps... this seems really high for a vfr airplane!!

You are showing the total load on the alternator, not the battery charging current. A much better location for your ammeter is in the line from the battery to the buss, with the alternator connected to the buss. That way you will read charge current, from the alternator to the battery from the buss, or discharge current from the battery to the load on the buss when the alternator is off or not supplying all of the load. The slower your engine is running, the higher will be the field current to the alternator. Keep in mind the total load is the field, the master relay coil, and any load on this buss which is on.