AirX Marine Windgen and LiFePO4

[Evenstar]

I've recently completed most of the upgrades to LFP technology on the boat. Specific details are complex, but it's a 24V, 720Ah system with a dual power bus and a CAN Enabled Emus BMS. All we need to know about the BMS really is that it can't control non-CAN chargers, so I have to connect non-CAN sources like my windgen to the load bus. There is no easy way to close the charge contactor without the CAN chargers on...stupid design but I have to live with it for now. The wind generator's Voltage Regulation Setpoint will be lowered to a little below fully charged voltage, so it won't try to raise the voltage high enough to damage things, but will add current to supply house loads when the batteries aren't completely charged. That's not what I'm trying to sort - this 400W generator is not enough normally to actually *charge* anything, just defray consumption.

What I am trying to sort out here is protecting the wind generator from a protection event where the load contactor shuts off. The AirX marine on an open circuit will freewheel itself to death if it's not put in brake mode. So if there is a protection event when I am off the boat and the batteries turn off, the wind generator will freewheel until someone shuts it off manually.

The Windgen has a + and - leads. You short them together in order to brake the system or turn it off.

What I would like to do is use a simple SPDT relay to automatically short out the windgen power leads and brake it in the even of a power off condition.

Below is the diagram - at the top is the recommended installation method with a break-then-make switch.

At the bottom is my proposed solution - a SPDT relay that runs a wire between the windgen's + and - thread on the Normally Closed circuit. It is powered from the house power, which means that when the load contactor is closed (all is normal) the relay is activated and the circuit is open.

If the Load Contactor opens, the wind generator will be put into Open Circuit mode and start freewheeling. But the relay will lose power, which then closes the wire that crosses the + and - wires on the wind generator, braking the wind generator until power is restored.



Does this seem like a stupid or dangerous solution to the problem? Does anyone have any other brilliant ideas how to protect the wind generator?

[Timd_chapman]

This is exactly what I’m investigating at the moment and came to the same solution as you. My big concern is that the relay would be energised most of the time. I would really like a solution where the relay is open when the wind generator is charging and closed, (energised), when the BMS says the battery is full.

[travellerw]

Originally Posted by Timd_chapman

This is exactly what I’m investigating at the moment and came to the same solution as you. My big concern is that the relay would be energised most of the time. I would really like a solution where the relay is open when the wind generator is charging and closed, (energised), when the BMS says the battery is full.

Thats a dangerous design. If the relay fails, %95 of the time they fail in their off state (unless the contacts get welded). If you design it like that, then a failed relay will disable the charging cutoff. This could possibly lead to damaged batteries, or at least a HVD event.

Even high quality relays fail more than I would be comfortable with.

[pcmm]

There is a problem with the design. in order for the wind gen to charge, the manual switch needs to be in the "on" position instead of the shorted position. By inserting the relay the way you indicate, when the relay closes, you not only short the wind generator, but you also short the BATTERY as well.......

[seandepagnier]

If you already invest in expensive batteries and management systems, why do you want to use the cheapest wind generator available?

There are other wind generators that are a lot better in basically every way including the ability to integrate with your batteries.

[travellerw]

Originally Posted by boat_alexandra

If you already invest in expensive batteries and management systems, why do you want to use the cheapest wind generator available?

There are other wind generators that are a lot better in basically every way including the ability to integrate with your batteries.

Please enlighten us as to which wind generators will integrate with LiFePo4 batteries. I'm genuinly curious as I don't know of any.

[Jim Cate]

Perhaps I'm missing something here, but our AirX's internal regulator shuts the system down (via an internal short) when the voltage reaches the set point. This will happen quickly when it sees an open circuit. In practice, when it reaches the set voltage it begins to PWM the output to limit the voltage and if it continues to rise (as when seeing an open circuit) shuts it down completely. It then periodically restarts, the voltage rapidly rises and it again shuts down.

If my understanding of the system is correct, don't see how it will harm your batteries or system.

Jim

[travellerw]

Originally Posted by Jim Cate

Perhaps I'm missing something here, but our AirX's internal regulator shuts the system down (via an internal short) when the voltage reaches the set point. This will happen quickly when it sees an open circuit. In practice, when it reaches the set voltage it begins to PWM the output to limit the voltage and if it continues to rise (as when seeing an open circuit) shuts it down completely. It then periodically restarts, the voltage rapidly rises and it again shuts down.

If my understanding of the system is correct, don't see how it will harm your batteries or system.

Jim

What voltage does that happen at?

Of course there are lots of schools of thoughts on LiFePo4... but for me, I don't want my system over 13.8V. I also don't want my system held at over %90 charged for a long period of time.

In a strong wind situation (not uncommon here in the Caribbean), the wind generator could push past the 14V mark (maybe even as high as 14.4V) before cutting out.

[seandepagnier]

Originally Posted by travellerw

Please enlighten us as to which wind generators will integrate with LiFePo4 batteries. I'm genuinly curious as I don't know of any.

Something with an external regulator. I wouldn't really trust the air-x regulator with lithium batteries, but I suppose in theory it would work.

You can probably modify the air-x by removing the internal regulator and using rectifiers, or maybe just turn the knob all the way to maximum voltage and you could run it into another regulator preferably with a dump load to prevent overcharging.

The air-x regulator tends to stop the blades quickly and takes a while to start again.. a better regulator could instead slow the blades while continuing to produce some power.

The air-x is probably the worst of the commonly used wind generators, I think because it's the cheapest.

[Jim Cate]

Originally Posted by travellerw

What voltage does that happen at?

Of course there are lots of schools of thoughts on LiFePo4... but for me, I don't want my system over 13.8V. I also don't want my system held at over %90 charged for a long period of time.

In a strong wind situation (not uncommon here in the Caribbean), the wind generator could push past the 14V mark (maybe even as high as 14.4V) before cutting out.

The Airx regulator is user adjustable via a pot on the outside of the housing, so readily accessible. You can set it for whatever voltage you wish.

Dunno how you would deal with the 90% charge issue, but that's true with solar as well, isn't it?

Jim

[travellerw]

Originally Posted by Jim Cate

The Airx regulator is user adjustable via a pot on the outside of the housing, so readily accessible. You can set it for whatever voltage you wish.

Dunno how you would deal with the 90% charge issue, but that's true with solar as well, isn't it?

Jim

Ahh I didn't realize the Air-X had an adjustable voltage cutoff.

As to the %90 issue. For solar it really depends on the controllers you have. If you have a fully programable controller its not an issue. You simply set a voltage to charge to, then stop (no float).

Frankly I think the OP is going to find this a "non-issue". If his solar bank is sized appropriately, then I'm guessing his wind generator will be manually switched off %90 of the time. The extra power is just not required with LiFePo4 batteries. Sure, the extra power is nice on rainy/cloudy days to help carry the load. On sunny days, the solar should easily fill everything back up since there is no long absorbtion phase.

[Tim francis]

I’m dealing with this too.

I have 400 ah lifepo4 and bought a new air x because it was 500 dollars off the regular price. It was brand new in the box but never used.

I’m still not 100 percent understanding everything.

I have an electrodacus bms. 490 solar.

I understand that the internal regulator in the wind x will read the voltage on the electrodacus and not the battery bank. I’still going to take me a while to figure all this out because this isn’t my thing.

Frustrating