Charge 18650 battery pack with bldc water turbine

Thread Starter


Joined Nov 21, 2022
Hi everyone,

i want to charge a lithium ion 18650 battery pack with a water turbine in my yard.
The turbine has a bldc motor with 3 phases, my plan is to use a 3 phase rectifier and feed the output of that into a dc-dc boost converter which then goes to the BMS of the battery. I already have all of these (adequately sized) components lying around and I wanna make use of them, however three things concern me:

-) Voltage Ripple from the 3 phase rectifier, not knowing what is acceptable for the dc-dc boost converter and the following components
-) Do i need a seperate charge controller? The BMS should switch off if the battery is charged enough, the dc-dc boost converter would be set to the correct charging voltage for the pack of course.
-) The motor speed will vary, i plan on using the under voltage protection feature of the dc-dc boost converter to determine when the motor is at a useful speed for charging the batterys - good approach?

First time in an electronics forum, so if this topic is placed wrongly please move if for me.

Any help greatly appreciated.


Joined Jan 27, 2019
Welcome to AAC.

What is the output voltage (range) of the generator?
Do you plan to have any filtering between the rectifier and the converter?


Joined Jun 19, 2012
Have you done any testing to ensure that the generator output is in the ballpark for charging the battery?

Voltage and current output?

Thread Starter


Joined Nov 21, 2022
Thx for you quick replies.
So the generator says its 48 volt, however most of the time this thing never goes over 36 volts...
It has 30A max output
Battery pack voltage is 48
I am not sure if i need filtering, as the ripple from the 3 phase rectifier shouldnt be thaaat bad, but regarding filtering... i am not sure how to calculate the filtering caps needed.