Driving four motors(3-6V), two L298N motor drivers, and with an Uno rev 3, what would be the recommend battery setup for this?
I'm planning on using two 18650 Lipo batteries, what's the minimum voltage I could get away with? There are cheaper options like 1.2V batteries, but I think 2 of those would be way to little voltage.
Would a couple 3.7V batteries be the minimum I could use?
How long do you want the car to run for? What is the current draw of the project?
If we were to guess as to which battery pack to get, I own one of these batteries 48V 100Ah 5kWh LiFePO4, and would be as good of a guess as any for which battery for you to get
I've another one on the way. Lots of current to drive your RC car.
On the other hand, measure the current that the project consumes would take the guess work out.
A 2s Lipo from the r/c hobby world would serve you well.
As @Idahowalker points out the size and weight and capacity to deliver current are all variables.
The more you tell us about the device, the better we can say about the battery matter.
Also, do yourself a huge favor and lose the L298N - that's last century technology and will waste energy that would otherwise make your car go. Further or faster or both.
This kinda thing I random googled:
The 25C in the ad-talk means you could draw 2.2 x 25 = 55 Amps continuously and the battery would not break a sweat. Of course it would soon be discharged to the point of you need to stop…
The r/c world has a variety of batteries and devices to take care of them. Your mechanical concept my prefer the 18650. In either case you will need to consider charging, balancing and storage issues.
The 18650 looks to be able to provide 20 Amps continuously. I've seen an 18650 and I don't think I would test that…
@Idahowalker on that beautiful battery, what is the output spec for steady current draw and peak current?
a7
I think that would be perfect for me!
All jokes aside, I need these batteries in quite a small form factor, I think a double AA(or 18650?) case would be best.
The project would do well to last for about an hour or two, nothing crazy.
Also I'm not able to lose these motor drivers 
so will have to make do, and I'm not able to test any of the components atm to see any measurements:(
Thinking of using a couple of these atm
48V 100Ah 5kWh steady. Max charge current 50A, max nominal discharge 70A. 12.8kW peak.
Without knowing what the current draw is it will be another guess as to the Ah requirement to run for an hour or 2.
My DIY drone with the 1800mAh 120C LiPo lasts about 9 minutes.
This one with 15C would work better.
If the battery does not have a C rating "assume" 1C but could be less.
I see, the cheapest option is preferable right now (tight tight budget), but it seems spending that bit more on the battery packs designed for RC cars is going to be much better right?
Right.
Consider using a different H-Bridge, your L298 is costing you dearly in performance. You need to subtrract about 3 volts from the battery before any appreicable power can get to the motor. The 3V is based on the voltage drop in the L298 (~3V). Multiply that times the current and that is the amount of battery energy you are burning as heat. With MOSFETs you are losing only maybe 0.2 volts maybe less.
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