Selecting a battery that can handle my current draw

I'm working on a project that uses a small 12V DC Pump and needs to be battery operated. I do have a 12V battery but it is far to heavy for the vehicle to carry, I was hoping to get away with using 9V's because I noticed the motor did turn on at 9.

I hooked everything up using a MOSFET to control the pump but whenever my code turns the pump on the Arduino resets. Clearly I'm asking too much of the 9V batteries I was hoping to use. I hooked up my meter and it looks like the pump is drawing about 500 mA when operating at 12V. I can't seem to get a clear answer online but the general consensus is that 9V's cannot supply that much current due to chemical process limitations.

Anyway, I've been shopping around and noticed that maximum current output doesn't seem to be a standard spec for batteries which seems odd to me. Does anyone have any advice for selecting a battery that can keep up with a infrequent current draw of say 600mA? I'm not too concerned about capacity or anything like that, mostly that it is relatively lightweight and doesn't cause the Arduino to reset.

I found this one below which seems fine but again doesn't say anything about the current its able to provide. Thanks.

This battery is a 1300mAh rechargable battery (Lipo) that can supply 500mA for 2.6 hours. Research Lipo batteries before considering. FYI, if you short the leads together it will burst into flames instantly. Other than that , it can easily supply the current you need.

You need to distinguish the capacity of the battery (in mAh) from the instantaneous current capability. Most LiPo batteries have a "C" rating. For example that HobbyKing battery that @raschemmel links to is rated 25C continuous and 50C burst. That means it can deliver 25 times 1300mA (or 32.5 amps) continuously - though not for very long, of course.

I doubt very much if the battery can deliver 1300 mAh from successive charges. Most battery manufacturers are "generous" with their capacity specifications. Base your project design on being able to use 50% of the sticker capacity.

...R

Anyway, I've been shopping around and noticed that maximum current output doesn't seem to be a standard spec for batteries which seems odd to me.

I think you are mistaken about this. Any battery capable of providing current to drive a motor or other power-consuming device will specific it's current capability. Perhaps not in an obvious form. All those C ratings for Lipo and LiFepo batteries are a current rating. 20C which is typical, means that the battery can supply all of its available current in three minutes.

The other solution, which is not very good, is that if you get your pump to run from a 9V battery, well then do it. And use a separate 9V battery to run the arduino.

Thanks for all the responses guys! I was unaware of the C rating and what that actually meant. I think I'm going to go with the LiPo battery, I can't believe I hadn't seen any of those in previous searches, the size is perfect. Until then I have had luck using a second 9V for the pump. Performance leaves much to be desired, but hey proof of concept.

Other than LiPo your options are NiMH (perhaps 8--10 AAA's) or LiFePO4
(4 cells in series would give 12V, but these cells are often odd shapes like
CR123). LiFePO4 is a safer lithium chemistry than LiPo and will survive
many more recharge cycles (LiPo are frankly poor at this).