I am thinking to connect Lithium Battery & DC generator in parallel to drive the motor.
For e.g Lithium battery rating is 48v 20 ah with 1c discharge rating.
If my motor needs 10 ampere, I want 40% & 60% load sharing between Battery & Generator. 4 amps from Battery & 6 amps from Generator.
I know when Generator ramps up it will bypass the battery voltage which will cause difference & generator will try to charge the battery as well as drive the motor at the same time.

But since I don't want to charge the battery anytime what circuit I should use ?
Is this possible to avoid charging battery & split the load ??

What I understood up till now that in order to connect any two source in parallel we need voltage to be same irrespective of Ah, then both the source will be fully discharge at same time otherwise Current will from high voltage to low voltage which will try to equalize.

Please guide me if we need to match the voltage of battery then what should be done since battery voltage will change instantly under load & generator can't ramp up high in seconds to match the voltage.

 

The simple way is to add a Schottky diode in series with the battery.

How are you going to limit the battery current to 4A?

 

The simple way is to add a Schottky diode in series with the battery.

How are you going to limit the battery current to 4A?

To be Frank I don't know
I have very little knowledge in this field

 

If you can give us some more information about what you are trying to acheive, we may be able to offer some useful suggestions.

 

current sense resistor in each supply, voltage differential used to excite the generator. Battery is master and generator follows to your defined relationship

 

Are you intending to use the motor to drive the generator? This is beginning to look like an over-unity attempt .

 

I am thinking to connect Lithium Battery & DC generator in parallel to drive the motor.
For e.g Lithium battery rating is 48v 20 ah with 1c discharge rating.
If my motor needs 10 ampere, I want 40% & 60% load sharing between Battery & Generator. 4 amps from Battery & 6 amps from Generator.
I know when Generator ramps up it will bypass the battery voltage which will cause difference & generator will try to charge the battery as well as drive the motor at the same time.

But since I don't want to charge the battery anytime what circuit I should use ?
Is this possible to avoid charging battery & split the load ??

What I understood up till now that in order to connect any two source in parallel we need voltage to be same irrespective of Ah, then both the source will be fully discharge at same time otherwise Current will from high voltage to low voltage which will try to equalize.

Please guide me if we need to match the voltage of battery then what should be done since battery voltage will change instantly under load & generator can't ramp up high in seconds to match the voltage.

I am thinking of something similar, not for a "over unity" application but for a drone. My 3 phase bldc generator is connected to an engine which provides the bulk of the drone power. The battery acts like a giant capacitor, provides peak power, emergency power if motor fails, and smooths the generator current. I am thinking of putting a zener-mosfet circuit to limit generator output to a 12s voltage. I don't want to limit current from generator though, but don't want to blow up battery pack either. I think my strategy is to keep the battery pack in fully charged condition generator voltage the same, and hope current to battery isn't too high. I can't put a diode between battery and generator because battery powers the BLDC generator controller What am I missing?

 

There's no such thing as a "Brush-Less-D-C" "Generator",
if it's Brushless, then it's a Permanent-Magnet-Alternator.
Generators only produce DC Power, and must use Brushes to do it.
Alternators must use some sort of a Rectifier to produce a DC output.

You're missing 2 things .....
Efficiency, and Weight.

Every time You change the form of energy, there will be losses,
usually very substantial losses,
starting at around ~20 to ~30% for each form change, and usually much worse,
and,
Your Drone will be so heavy that it can't get off the ground.
.
.
.

 

There's no such thing as a "Brush-Less-D-C" "Generator",
if it's Brushless, then it's a Permanent-Magnet-Alternator.
Generators only produce DC Power, and must use Brushes to do it.
Alternators must use some sort of a Rectifier to produce a DC output.

You're missing 2 things .....
Efficiency, and Weight.

Every time You change the form of energy, there will be losses,
usually very substantial losses,
starting at around ~20 to ~30% for each form change, and usually much worse,
and,
Your Drone will be so heavy that it can't get off the ground.
.
.
.

1: Yes. I am using a BLDC motor to generate 3 phase power rectified by a VESC. Semantics aside, I am already doing this, the generator is controlled by a VESC in regenerative braking mode using FOC. This particular VESC can be 95% efficient for generating DC
2: My 2 stroke engine produces 8 hp and weighs 2 kg
3: My generator is rated at 5KW and weighs 2 KG
4: So, my total powerpack produces 5KW and weighs 4KG. Total drone weight will be 10KG, so I don't know where you get that it will be too heavy. 5KW for 10KG for an agricultural drone is well within what is possible

 

1: Yes. I am using a BLDC motor to generate 3 phase power rectified by a VESC. Semantics aside, I am already doing this, the generator is controlled by a VESC in regenerative braking mode using FOC. This particular VESC can be 95% efficient for generating DC
2: My 2 stroke engine produces 8 hp and weighs 2 kg
3: My generator is rated at 5KW and weighs 2 KG
4: So, my total powerpack produces 5KW and weighs 4KG. Total drone weight will be 10KG, so I don't know where you get that it will be too heavy. 5KW for 10KG for an agricultural drone is well within what is possible

thats going to be fantastic

 

What is possible is not the question,
what type of performance You expect is the real trick.
Balancing the Weight, Power, and Flight-Time, against Cost, is the very definition of compromise.

Is this a legitimate "Agricultural-Drone", that will be used on a Farm, or a Hobby / Toy ?
What is the budget for this project ?
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