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Limit DC current from LiPo battery? Answered

Dear Colleagues, 

could you please advise if there is a way to limit DC current from LiPo battery? 
I need to push the high current (80A) through very low resistance circuit, but do not want to fry LiPo. So need to limit the current at 80A

I am not an electronic professional, and all solutions coming to my mind are based on increasing resistance of circuit (by adding resistance manually, or constructing something like FET-regulated limiter). The problem here is that I will generate lots of heat, and need too much space for its dissipation.




2 years ago

If you need to limit the amps to a low resistance load, then you just need to use a lower voltage, or like you say, add resistance into the circuit. If you use a linear voltage or current regulator, that is the equivalent of inserting a "smart resistor" one that can change value depending on the current drawn or the different between the input and output voltage. In reality, this is generally regarded as the "pass" transistor, as how hard it is turned on is governed by a smart circuit, through feedback.

However, a linear regulator will dissipate (Vin-Vout)*I amount of power, so that may not be practical, especially for high power applications, so generally you would use a buck or boost converter. Switching converters work on the same principle, relying on constantly measuring the output and responding in a particular way as to reduce the difference between measured and the target value (called a reference.) Things like buck converters do this by effectively turning on and off a transistor completely, very VERY fast, (think hundreds of thousands of cycles per second!!!) and using a LC filter to filter out the choppy power and make it smooth. Boost converters work by the "springy" nature of inductors to create large voltage spikes that can be captured by a a diode and a capacitor forming a high power peak detector circuit.


2 years ago

The people that make and use LiPo often include a fuse that protects the battery from damaging current.

Your job is to make your motor load controller smart enough to always limit your current draw irregardless of pilot commands to go to warp 9 !!!

Tesla the electric car manufacturer has a huge battery plant 30 min drive from my home and besides liquid cooling uses one semiconductor per cell to charge and protect in discharge the thousand batteries plus used in series and parallel, block construction to quickly exchange a self fused pack.


2 years ago

You can't in the sense your trying to.

An electrical system draw what current it needs from the supply. Trying to restrict the current flow will change the wattage (power used)

You can limit the current by changing the resistance, Ohms law.

Technically you could put a current regulator circuit in there but depending on what your trying to do may result in things not working as you expect.


Watts= Amps x Volts

Amps = Volts / Resistance

If you want to change the current you need to change the voltage AND/OR the resistance.

Your low resistance is going to generate a LOT of heat anyway.

Tell us more about what your doing maybe there is a better way.