diy solar

diy solar

LiFePO4 and PMA Wind Generator

TGPB

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Aug 16, 2020
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Working through the logistics of converting my L16 Flooded Battery system to LiFePO4 batteries. Just discovered that my Flexguard NC25A-12 Wind charge controller will not work with LiFePO4 batteries. I have it connected to 4 huge dump load resistors.

Need recommendations on a charge controller that can work with the LiFePO4 batteries Solar System, Generator Powered Charger and send unneeded wind energy to the dump load.
 
Lots of charge controllers out there for wind. I found the controller, and it looks adjustable. Why won't it work?
 
Lots of charge controllers out there for wind. I found the controller, and it looks adjustable. Why won't it work?
Are you referring to the Flexguard Controller?
It has worked great for the last 10+ years with the L16 batteries. Their web site says in bold letters not to use with LiFePO4.
 
Can the chargers absorb voltage be adjusted? If so, I don't see why it can't be LFP compatible. LFP packs are pretty easy to charge. Terminate the CV stage after a certain number of minutes. Easy.
 
I don't have anything to do with wind generation personally but the questions that have been asked on the forum that have prompted me to look at specifics, most of the wind controllers I've seen are lead acid specific and can not be reconfigured to be suitable for lithium. I'm sure there are types that can be of course.
 
I have found the "Lithium ready" label on many products to be worthless, as they are talking about lithium drop-ins. Just like many lead acid ready products prematurely float, and have much too low absorb voltages. In the end, its incumbent upon the installer to understand the packs needs, and directly compare to the specs of the charger.
 
Can the BMS trigger the dump load? The thing with the Permanent Magnet Alternator is that if the wind is blowing it doesn't stop producing power, hence the dump load.
 
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Can you the BMS trigger the dump load? The thing with the Permanent Magnet Alternator is that if the wind is blowing it doesn't stop producing power, hence the dump load.

Okay, this is the issue. A BMS by default opens the battery circuit. This would disable the dump load as the battery has to be in-circuit.

I reported the post to have it moved to the wind turbine forum:

 
Anybody here have sucess connecting a PMA to LiFePO4 batteries???
 
Anybody here have sucess connecting a PMA to LiFePO4 batteries?
I think snoobler identified the issue below.

Okay, this is the issue. A BMS by default opens the battery circuit. This would disable the dump load as the battery has to be in-circuit.
Can you duplicate the circuit that took the battery out of the wind turbine and substituted the dump load? I would guess it was a double throw relay triggered by voltage. It may have been make before break but hopefully someone with more turbine knowledge can clarify.
 
The PMA is never removed from the battery. The controller simply activates the dump load contactor at a set voltage to draw power off the batteries.
 
The PMA is never removed from the battery. The controller simply activates the dump load contactor at a set voltage to draw power off the batteries.
Then if you can connect the PMA in the same functional way that it was operating before it should not make a difference that the Lithium batteries go offline when they are fully charged. The only wrinkle is if the dump load was designed to operate with the batteries connected and create a trickle charge then totally disconnecting the batteries may require an increase in the dump load. I am not sure what you mean by, "to draw power off the batteries."
What kind of load does the PMA need to see?
 
The WT needs to see a load equivalent to its output at all times. That load is either the battery or the dump load. The dump load is essentially a relay to close the (+) leg of the dump load with the battery as the (-) is common with the battery.

The WT charge controller uses battery voltage to engage the dump load. If it suddenly doesn't see battery voltage due to the BMS disconnecting, it doesn't engage the dump. The WT is unloaded. If the wind is sufficient, it overspeeds and grenades.

The work around would be to have two NO relays energized by battery. If voltage is lost, relays close in a way to complete the circuit with the dump load.

I believe the existing charge controller would work with the above change.
 
Thanks for the detailed work around. I only knew the concept but not enough about the details to help with a solution. So the coil voltage of the relays needs to be matched to the voltage of the battery and at least one of the relays needs to be rated for the Amperage of the dump load.
Still working it out in my head what that relay circuit would look like but will let the OP ask the detailed questions.
 
Yes, or through a converter to 12V.

And they would need to be NC relays as I clearly stated they would close when voltage is lost... sheesh.

Note that my idea is plucked from the intergluteal cleft, and it may not survive scrutiny. Once sketched out, something horrifying may leap from the page.
 
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Adding a few relays isn't going to protect LiFePO4 batteries from the higher voltage created by a PMA. The Flooded batteries can handle the variable power of the PMA but the LiFePO4 needs a constant voltage input for charging.

They offered me another equipment option of using a
1. Missouri Wind Voltage Reducing Device $411.99
+
2. MidNite Classic 150 MPPT Charge Controller $639.35

In their
video on this setup it says the reason for the Voltage Reducing Device is to protect the MidNite Classic 150 MPPT from excessive voltage. I'm waiting for them to get back to me as to why I would need the VRD since my PMA produces 120v @ 4000 RPM and the MidNite Classic 150 MPPT has an operational voltage of 150v. Not sure how the dump load would work with the 2nd option of equipment. To get the PMA to 4000 rpm I would need to be in a hurricane, not too likely here In Idaho.
 
Adding a few relays isn't going to protect LiFePO4 batteries from the higher voltage created by a PMA. The Flooded batteries can handle the variable power of the PMA but the LiFePO4 needs a constant voltage input for charging.

The above is not a true statement. BOTH types of batteries use essentially identical charge profiles, and BOTH have a "constant voltage" requirement for 2nd phase charging.

The LFP battery will protect itself. That's the problem. The LFP BMS will go open circuit if the voltage goes too high thus disabling the dump load circuit.

You need a wind charge controller that can cope with this situation. You need to ask, "what happens when the battery BMS goes open circuit and the battery voltage goes to zero?"
 
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