Powerboost 500c or 1000c

[Retserrof]

Hi there, I need either the powerboost 500c or 1000c to convert a 3.7v 3400Mah battery to 5v to power an arduino micro.
What I need to know is, which one do I need? My arduino wiring runs at about 1000mAh, so it is taking 1000mAh from the battery. HOWEVER, I am not going to use the powerboost to simultaneously charge and use my arduino micro. I will be using my arduino micro at 1000mAh, but will be charging the battery when I turn the arduino off via a toggle switch.
So basically, it's kind of how a phone works where you plug it in to charge, but take it off the charger when you want to go somewhere.

Thank you for any suggestion!

[adafruit_support_bill]

My arduino wiring runs at about 1000mAh, so it is taking 1000mAh from the battery.

mAh is a measure of battery capacity - not current. Do you mean that your circuitry is drawing 1000mA (1A) in operation? If that is the case, you should use the PowerBoost 1000c.

[Retserrof]

Yes, typo.

Which one is preferable if the circuitry is drawing about .8A or .9A?
Thanks

[adafruit_support_bill]

Either one can put out that level of current - as long as your battery can supply enough current on the input side. Since you are boosting the voltage, you will need around 1.5A input at 3.7v to get 1A output at 5v.

The 500C will have to work quite a bit harder to put out current at that level. If you will be running for extended periods at that level, I would recommend the 1000C.