I would have a few questions about using batteries.
I am building a slider with a Nema 23 and two Nema 17 motors (for sliding with heavy load and two angle of rotations) and I am thinking about the power supply with batteries. As the TB 6600 driver for Nema 23 requires 9 volts minimum, I would like to use two NP-F batteries combined together in serial connection. (14.8 V)
My questions are the followings:
Are the cheap NP-F batteries on Aliexpress, etc.. reliable or would they explode?
Is it true that 1C discharge (max current) is safe to use? The 3 motors together have around 5-6 ampers load, so would a 6000mAh battery could serve it?
If I combine two batteries (3.7V NP-F) with around 3000mAh capacity, it will be 6000 mAh in summary, so would that be enough to use for my 3 motors?
For how long do you want the stepper motors to operate? Stepper motors are very inefficient - they draw the full current even when stationary - and are really not suitable for battery power for any extended period of time.
You will have to provide a link to the datasheet for the batteries if you want advice about them.
If you connect two 3.7v batteries in parallel you get 3.7v with double the capacity. If you connect them in series you get double the voltage (7.4v) but with only the same capacity as a single battery.
You need to be very careful if you are connecting LiPo batteries in parallel. If they are not both fully charged at the time of connection you could get a huge current flowing from one battery to the other - enough to cause a fire. It will also be necessary when charging the parallel pair to charge them equally - read about balanced charging.
Unfortunately I can't find any information about the maximum load for these batteries, mainly for the chinese ones. Thats why I thought, an 1C consumption would be safe. Combining, I meant serial connection, so from 7.4V it would make 14.8V.
As this will be a camera slider, the portability is important, so batteries are necessary. The maximum operating time of 1 hour would be enough.
As you mentioned, connecting two Li-ion batteries in serial is not safe because of the charging difference, what kind of power supply would you suggest instead?
Unfortunately V-Slot batteries are really expensive but they provide 14.8V
You can safely connect battories in serial. When charging them, charge each battory alone.
You can exstend battory life by depowering the steppers assuming that no force is present. Depowered steppers have no holding torqe but repowering them they might make a small jump when power is applied.
Thank you. This sounds good. So if I connect two NP-F in serial to get 14.8V, it won't cause any problem.
I will have separate charger device and would like to charge the batteries separately, just combining them for the useage.
You've got it. As long as the drivers handle those 14.8 volts it's all okey. Check the stepper drivers for setting the current used. Max stepper current might not be needed for working. Using a bit lower stepper current the step responce will get slightly slower but it's probably not important for Your application.
The drivers can handle that voltage. I try to set the current correctly, a bit lower then necessary to prevent unwanted high temperature and damage.
I will also think about depowering the motors when not used.
Many thanks to all of you! I appreciate your help. Today I learned a lot.