Homebrewed Electricity > Storage
Charging a 24v bank from a 48v bank...or vice versa...how to do it? Can it done?
makenzie71:
As it turns out...it doesn't work, unfortunately. If the 48v bank votlage is stable it fires up, but if the turbine is fluctuating voltage it goes flat. I think when the voltage is jumping around the MPPT function is screwing with it...I'm going to have to look for another solution.
Warpspeed:
--- Quote from: makenzie71 on March 07, 2021, 08:15:27 PM ---So i have a bunch of different turbines running at 24v and 48v. I want to simplify my load side...Is there a reasonable way to feed a 200 amp/hr 48v bank into or from a 100 amp/hr 24v bank?
--- End quote ---
Yes, a bi directional switching power supply would be pretty simple.
It only gets complicated if you require other than a direct fixed voltage relationship between the two batteries. If they are of similar battery chemistry, a fixed voltage relationship will work fine.
The batteries will act as if they were connected in parallel, and charge/discharge together with power flowing either way to keep the two voltages proportionally equal. A fixed 2:1 voltage relationship requires a fixed duty cycle of 50% on 50% off. That fixed duty cycle should be easy to generate with a digital counter.
A simple buck/boost topology with a series choke running constantly at a fixed duty cycle should be all that is required.
It should not require a "smart control system" as such, as the voltage relationship will always be fixed.
Warpspeed:
Ten days, and nobody has shown the slightest bit of curiosity in how to do this ?
So I will not bother going to all the considerable trouble to explain how a very simple bi directional switching power supply could effectively couple together two batteries (of the same battery chemistry) in parallel, but with the batteries having a different numbers of cells in each.
I am REALLY disappointed in you guys.
joestue:
a fixed 50% duty cycle buck converter can be made from the self oscillating half bridge driver irs2153.
Warpspeed:
Or a simple oscillator and a flip fop, assuming a 2:1 ratio of the number of cells and battery voltages of course.
That is all you need, no pwm, no voltage measurement, no control loop, no feedback.
If there are an odd numbers of cells in one or both batteries, it can still work with the appropriate fixed duty cycle, but 2:1 is dead easy and would probably cover most peoples needs.
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