I plan on using batteries for my arduino and some 9v motors. mAh isn't particularly a concern, I just want the best value. I've looked at sparkfuns batteries and chargers and they seem to be low voltage and expensive when you get the charging circuit. I'm not totally against using nicad, should I just get some rechargeable AA batteries or is there a better way that has a similar cost? Would it be possible for me to make my own charging circuit for nicad AAs so I can keep them in my device and do I need any external hardware to monitor battery charge? Can I use 6 AAs to power the 9v motor unregulated or is that a bad idea?
Any tips on the issue are appreciated, this is a new subject to me. Thanks.
edit: maybe I'm thinking of NiMH, are those simple to chage like NiCad?
edit2: each motor looks like it could draw up to .8A each stalled and I will be using two. They are only rated up to .3A each though, i don't plan on exceeding that.
Note, rechargeable AA batteries are 1.2 volts instead of 1.5 volts. So you would need 8 AA batteries to get 9.6 volts total.
You can get rechargeable 9v batteries that are in the form factor of the 9v battery used in smoke alarms fairly cheaply, but the capacity of these isn't that high.
stoopkid:
That's pretty neat, I might give that a try. I'm just worried about the reliability of an nobrand chinese battery of such apparent complexity.
edit: it also appears to be pretty big. Again, I have no real requirements but I wonder if there are low capacity ones that are smaller.
I'm sure there are probably branded versions. For my potential app, I need 12+ hours of continuous runtime (preferably 2+ days), and using only one charger port was desirable, since I generally need to charge camera batteries as well, and hotels don't always have that many outlets.
Bear in mind that most batteries these days are made in China, though I imagine as the Chinese implement environmental and worker safety laws, that the location for manufacturing will change to the next lowest bidder.