ac current limiting

[AWG]

I have a 120V 2400W generator and use it to charge a 60V battery. The problem is depending on the state of charge and its voltage the generator will over-load or under-load.
Right now I am using a variac into a rectifier to adjust the voltage and limit the 120V max current to 22A with low battery. But as the battery voltage increases the generator current drops and I am not using it's full capacity.
So I rigged up a small motor and a current-sensor which drives the variac up or down to stay at 22A. On start up of the generator the variac starts at 0 until the current goes over 22A. Shutting down the variac returns to 0. This actually works well except I have about 200W to 300W transformer losses and it is a mechanical contraption.
They make electronic dimmers, I could use the motor drive on that but there must be a more elegant solution.
Any ideas?

 

[danadak]

"Normally" one thinks of a charge controller for a battery that terminates in
a floating charge, for a lead acid battery. That would take the variac and its
mechanical control out of the picture.

You looking for off the shelf solution or a design to build ?

 

[ahsrabrifat]

You can use a high-power buck converter with current control.

 

[AWG]

Thanks danadak and ahsrabrifat,
I have a circuit which will terminate any charging at a max voltage (60V). My battery is 17 series cells lifepo4 (51-62.5V).
The problem with a buck converter is the current limiting is absolute, ignoring voltage. I need a constant power (2200W) out of the generator, Amps x Voltage = Watt. Since the generator voltage (120V) is stable I need to keep an "eye" on the current, as the DC load voltage changes, from 51 - 60V and consequently also the current and total power.
So if I start with a discharged battery, set the AC current to 22A, as the DC voltage of the battery goes up, so the DC current goes down and I am using less of the available generator capacity. In reality I need to adjust the DC charging voltage, which my variac does. I have a electronic 10KW dimmer, (electronic variac) where a potentiometer changes voltage and so also current. I could use my motor drive in a bind, have not yet tried it.
A electronic potentiometer replacement circuit watching the AC generator current is what I need.
I have not yet found an "off the shelf" solution, there are 120V ac 3000W dc power-supplies available with settings for charge voltage and current limiting, but that will not keep my generator output stable. On those I would have to replace the current limiting pot (or voltage pot?) with a circuit watching the generator.

 

[AnalogKid]

I need a constant power (2200W) out of the generator,

No, you don't.

Charging lithium batteries is more complex, and *much* more dangerous, than charging other battery chemistries. Also, charging a string of them in series is not the best way to do things. Variations in aging of individual batteries causes uneven charging, where some batteries in the string are fully charged while others are not, leading to overcharging. Incorrect charging cost Sony millions of dollars.

https://electronics.stackexchange.com/questions/701904/power-schematic-questions

Researchers Have Finally Figured Out How to Stop Lithium Batteries from Spontaneously Combusting

Unexpected fires have kept experts cautious about the potential of lightweight batteries

www.smithsonianmag.com

The electric car industry has spawned a bunch of lithium battery charge controllers, including controllers for the switching required to charge them in parallel while discharging them in series. Linear Technology is big in this area.

 

[AWG]

thanks AnalogKid for your comment,
My battery is 1200AH, 50+KW, I have a balancer which keeps the cells within 0.003 to 0.002V, the charge current from a 2200W generator is very low for a 1200AH battery (+-40A) , my inverter is set at 70A max charge current, lifepo4 batteries don't burn.