Just had another thought on braking: Using a comparator to sense when the voltage exceeds a given point you could use that to trigger an SCR. Once triggered it will stay latched until the windmill stops spinning. It would be self resetting in that sense. Again, I offer this as a nugget for thought. Others may take this and run with it or not. It may prove to be worth while, it may just be another one of those bad ideas I sometimes have.

 

Using a comparator to sense when the voltage exceeds a given point you could use that to trigger an SCR. Once triggered it will stay latched until the windmill stops spinning. It would be self resetting in that sense.

thanx, buddy. that sounds also interesting. going to review some videos to understand how scr works in detail. will be back soon

 

Once triggered it will stay latched until the windmill stops spinning. It would be self resetting in that sense.

ok, so far as i understand - pls confirm or deny...

lets set the voltage level where to turn on SCR on 28v

1 - wind starts, voltage starts to rise from zero to battery level 24V - nothing happens, as voltage is lower than battery voltage, so turbine just turns freely and raising rpms to useful level - great so far

2 - voltage gets over 24V, battery is being charged, voltage slowly raises as the SOC of the battery rises until

3 - voltage gets to trigger value 28v, SCR turns on the heater(kanthal wire) designed to have enough watts to stop turbine.

4 - kanthal temperature rises first, as turbine starts loosing rpm because of this heavy load, kanthal temperature goes down until voltage gets down to zero, as turbine is stopped by heater power draw

5 - as no voltage is present on SCR, it disconnects the heater and goto point 1

 

Sort of. But after reading your scenario I realize that the battery will hold the SCR latched until its voltage drops to around 0.6V. There would have to be a little more than just the SCR and window comparator. But give me some time to ponder this. I'll see if I can bang out a drawing a little later.

Mostly, I offer the idea of an SCR for the sake of the crowd. Perhaps someone else with more knowledge will run with it.

 

they are all built to charge leadacid batteries. i didnt find any LIFEPO4 charging controller. if you have some link, pls paste. the only link i found from you was to the google search, so nothing specific.

That whole Google link was nothing but Lifepo4 charge controllers, I'm not going to choose the one you need that's up to YOU. You spend the time reading and researching what fits your needs, not me. Just because they are mainly used with solar panels doesn't mean they can't be adapted to wind, electric after its generated doesn't know where it's coming from or care for that matter.

You keep insisting that Lifepo4 doesn't need a charge controller, but people selling them say it does -
"Do you need a charge controller with a LiFePO4 battery?
Thus, there are advantages for the lifespan of the batteries to be charged through an LiFePO4 charge profile, and if you want to get the full capacity our of the battery, you will need a charge controller with an LiFePO4 profile." From - https://www.amptron.com.au/qa-blog/charging-lithium-lifepo4-batteries-from-solar-panels


You have seemed to devolved into 2 different things since the start of the thread, charge control and over speed control. They aren't the same thing.

My mentioning SSR's was in refference to cutting out the charge when a certain charge level is reached in the battery using the voltage comparator to do it.

 

You keep insisting that Lifepo4 doesn't need a charge controller, but people selling them say it does -
"Do you need a charge controller with a LiFePO4 battery?
Thus, there are advantages for the lifespan of the batteries to be charged through an LiFePO4 charge profile, and if you want to get the full capacity our of the battery, you will need a charge controller with an LiFePO4 profile." From - https://www.amptron.com.au/qa-blog/charging-lithium-lifepo4-batteries-from-solar-panels

shortbus, sorry, but you either dont understand topic charging of lifepo batteries, or you are just a victim of marketing BS.

your expert mentioned a specialized lifepo4 charger. what he told is marketing BS of this type: charge controller with an LiFePO4 profile.

what lifepo profile???? there is nothing like lifepo profile! profiles are there to charge lead acid batteries, some bulk, boost, float and so on... this is specific for lead acid only. they need to be fully charged, topped to 100%SOC during every cycle in order to avoid sulfation and aging of a battery EVERYTIME before they can be put in discharge.

there is nothing like this in lithium battery. you can charge and discharge lithium whenever and however. its not over-aging if cycled anything between 20-80%SOC. the only problem is that their cells are about to be disbalanced in time, changing their internal resistance so much, that one cell of the pack will be overcharged/overdischarged. as this happen, the complete chain of cells is loosing practical capacity to the lowest cell capacity, that wrong cell...(serial)

to avoid this, lifepo specialized charger must have not only plus and minus connectors, but also each cell connector. something like this:


that charger must have a special program, microprocessor and balancer to be able to charge lifepo4 batteries.

so far so good. if there is ANY charger like the one from the site you mentioned as expert site, which has only 2 connectors - positive and negative - IT IS A LEAD ACID CHARGER, which is being sold as a very special charger supporting lifepo4 with special lifepo4 profile. BS BS BS. such a charger has no clue whats happening with cells, he only sees cumulative overall voltage lets say 14.4V, which seems to him as everything is allright, because 14.4/4=3.6v per cell, so perfect! in fact 14.4v summary can be 3x3.3v cells and 1x4.5v cell. this cell is dead and was killed by this special profile charger recommended by your expert. as this...

https://www.amptron.com.au/20a-12v24v-mppt-solar-charge-controller.html

typical BS for 150 dollars and you get one nice marketing phrase for free with this product as a gift. supports lifepo4 profile... real HW value = 20 dollars, another 130 dollars value of that phrase.

Note: Crude language replaced by moderator.

 

@racmaster If your so knowledgeable, why are you asking questions here?

 

So I am asking again for you to stop throwing stones.

Why is it that you think disagreeing with you is "throwing stones"?

 

I was giving the wrong term in some of my post on this. Instead of saying "voltage comparator" what I was talking about is called a "window comparator". Sorry for any confusion.

 

As promised, here's what I'm thinking: In the diagram below is the whole system. I've included a battery charging system, you can do whatever you feel is right. The "Over Voltage" box contains circuitry to monitor when the generator is outputting too much voltage, an indication of an overspeed condition. When sensed, it fires an SCR, which remains on until power is removed or the generator stops spinning. There is no circuitry to shut the SCR off, it shuts off when its voltage drops (essentially) to zero. So it will activate the brakes in that case. Once the generator stops spinning it shuts off. Finding an SCR that can handle the current will be the trick. That's partly why I suggested a relay in an earlier post.


This is a blowup of the circuitry. As for the exact circuitry for the Over Voltage circuit, it should consist of a reference voltage and a comparator with some hysteresis. The SCR has its own hysteresis in that once it's on it doesn't shut off until the voltage reaches or crosses zero volts. Likely there are better circuits or ideas, but this is what came to my mind.

Beyond any of this - I can't be of any further service. I wish you well in your endeavor.

Good luck.

 

@racmaster If your so knowledgeable, why are you asking questions here?

im not asking for help with lifepo4 charging... thats something im fully aware.

im asking for help to arrange circuit switching power from generator between battery and load fulfiling 2 conditions.

durable and simple.

 

im asking for help to arrange circuit switching power from generator between battery and load fulfiling 2 conditions.

Wait - WHAT?

I thought at first you were wanting the diode to charge the battery. Then somehow it morphed into overspeed protection. Now you're asking about switching between the generator and the battery for your load?

I'm thoroughly confused. I guess you can ignore everything I've said so far because I'm not sure I was addressing your needs.

 

As promised, here's what I'm thinking:

thanks for your effort, Tony. thats very similar approach, i was thinking about. could be one working option.

reading the logic, i want to ask one question. SCR is a part, which is normally open and when it gets triggered, it switches to closed... is there similar device, which acts opposite? normally closed and when triggered, opens?

 

Now you're asking about switching between the generator and the battery for your load?

by load i mean the resistive braking of the turbine, of course... so what is the target now is exactly what you supposed, switching power between battery and resistive load/brake...