Monkworks MZ-30L Voltage Regulation Question

[kirkbauer]

We just replaced our backup alternator with a MZ-30L generator and I have an operational question. We have removed the pin that causes the MZ-30L to operate at a lower voltage level (14.2V). The goal was to allow both the primary and backup alternators to be enabled at the same time without causing issues.

However, we found that after startup, when the battery is low, the primary alternator is not able to keep the voltage high enough to prevent the MZ-30L from also generating charge (based on the output on the "Enabled" wire). So, after startup, if both are enabled, we have both alternators generating power. Is this going to be bad for either device? Or is it only an issue to have both enabled when the battery doesn't need that much current?

In the future we may switch our primary alternator to a higher-voltage (it is internally-regulated), but until then I need to know if our SOP needs to be to keep the MZ-30L disabled when not needed so that we can guarantee it doesn't generate electricity simultaneously with the primary alternator.

 

[Carl Froehlich]

However, we found that after startup, when the battery is low, the primary alternator is not able to keep the voltage high enough to prevent the MZ-30L from also generating charge (based on the output on the "Enabled" wire). So, after startup, if both are enabled, we have both alternators generating power. Is this going to be bad for either device? Or is it only an issue to have both enabled when the battery doesn't need that much current?

The short answer is no assuming no negative underlaying conditions. DC generators/alternators provide power based on buss voltage. If one has a higher output voltage than the other it will pick up more load than the other. I refer you back to the “house diagram” of generating machines running in parallel.

Setting up the MonkWorkz as a standby generator normally keeps it turned off if the primary alternator is putting out the standard ~14.2vdc. If you have a low battery on start up you will see the MonkWorkz come on line if buss voltage drops to ~13.7VDC.

If you wire the MonkWorkz to your EMS you can get an indication when the MonkWorkz is on. You can also put a light on the panel as discussed in the install manual. Keep in mind that the MonkWorkz does such a nice job you may miss your primary alternator failing unless you have such indication.

Note - if in standby mode the Monkwokz comes on at 13.7VDC but then regulates to ~14.2VDC. This translates to the MonkWorkz not automatically turning off and going back to the standby mode if the primary alternator is functioning properly. Here is where you need an external switch to turn it off, then back on. I found this out during testing when I turned off the primary alternator to make sure the MonkWorkz picked up the load.

Carl

 

[kirkbauer]

The short answer is no assuming no negative underlaying conditions. DC generators/alternators provide power based on buss voltage. If one has a higher output voltage than the other it will pick up more load than the other. I refer you back to the “house diagram” of generating machines running in parallel.

Setting up the MonkWorkz as a standby generator normally keeps it turned off if the primary alternator is putting out the standard ~14.2vdc. If you have a low battery on start up you will see the MonkWorkz come on line if buss voltage drops to ~13.7VDC.

If you wire the MonkWorkz to your EMS you can get an indication when the MonkWorkz is on. You can also put a light on the panel as discussed in the install manual. Keep in mind that the MonkWorkz does such a nice job you may miss your primary alternator failing unless you have such indication.

Note - if in standby mode the Monkwokz comes on at 13.7VDC but then regulates to ~14.2VDC. This translates to the MonkWorkz not automatically turning off and going back to the standby mode if the primary alternator is functioning properly. Here is where you need an external switch to turn it off, then back on. I found this out during testing when I turned off the primary alternator to make sure the MonkWorkz picked up the load.

Carl

Thank you, Carl. We do have the "enabled" connected to the PFD so we can see when the MonkWorkz is generating power.

So what do you recommend for standard operating procedure? Leave both alternators on all the time (based on your note it sounds like this might lead to an active/active situation in some cases)? Or is it best to just keep the MonkWorkz disabled until there is an issue with the primary?

 

[Carl Froehlich]

Thank you, Carl. We do have the "enabled" connected to the PFD so we can see when the MonkWorkz is generating power.

So what do you recommend for standard operating procedure? Leave both alternators on all the time (based on your note it sounds like this might lead to an active/active situation in some cases)? Or is it best to just keep the MonkWorkz disabled until there is an issue with the primary?

I have both on all the time. No real reason not to, and one less pilot action if the primary alternator goes south.

I do recommend testing this standby feature a couple of times a year to verify the MonkWorkz is functioning properly.

Carl

 

[Traash]

We just replaced our backup alternator with a MZ-30L generator and I have an operational question. We have removed the pin that causes the MZ-30L to operate at a lower voltage level (14.2V). The goal was to allow both the primary and backup alternators to be enabled at the same time without causing issues.

However, we found that after startup, when the battery is low, the primary alternator is not able to keep the voltage high enough to prevent the MZ-30L from also generating charge (based on the output on the "Enabled" wire). So, after startup, if both are enabled, we have both alternators generating power. Is this going to be bad for either device? Or is it only an issue to have both enabled when the battery doesn't need that much current?

In the future we may switch our primary alternator to a higher-voltage (it is internally-regulated), but until then I need to know if our SOP needs to be to keep the MZ-30L disabled when not needed so that we can guarantee it doesn't generate electricity simultaneously with the primary alternator.

My system operates as yours does. I use an Earthex battery which has quite a draw after start (I've seen 30 amps). This drops bus voltage below the MZ-30L trigger point. After the battery had charged, I've noticed that the MZ doesn't reset unless the switch is cycled. I have chosen to run the MZ in the off position until needed. Monthly check of capabilities keeps the warm fuzzy alive.

 

[N787KV]

I have both on all the time. No real reason not to, and one less pilot action if the primary alternator goes south.

I do recommend testing this standby feature a couple of times a year to verify the MonkWorkz is functioning properly.

Carl

I agree with Carl. The less switches you need to flip when something goes south and at the worst time the better. One possible procedure could be to switch the MZ to standby mode as part of your per-departure checklist or flow. Link it to turning on your fuel pump maybe. This allows time for your main alt to charge the battery enough to bring up the Buss voltage.

 

[Jetmart]

I installed mine today. Great unit. I went the other route. Guess I am a bit old school. I have it set up to be off at all times. I will switch it on when I get a low voltage alarm from the main generator. I have the alarm set to 14.0 volts. I want it manual incase I want to shed some load prior to the MonkWorkz coming on. With a good battery a main alternator failure should not be an urgent issue. Having it manual allows MonkWorkz voltage to be left at received at 14.4 Volts. I think having 14.4 volts on the back up is better for battery charging and would be no concern using the MonkWorkz for a longer term if required.

 

[planenutz]

Note - if in standby mode the Monkwokz comes on at 13.7VDC but then regulates to ~14.2VDC. This translates to the MonkWorkz not automatically turning off and going back to the standby mode if the primary alternator is functioning properly. Here is where you need an external switch to turn it off, then back on. I found this out during testing when I turned off the primary alternator to make sure the MonkWorkz picked up the load.

Thanks for this note Carl.

I'd not noticed this point when I did the testing in flight and instead assumed that once the alternator was back online it would have pushed the buss voltage over the MWz threshold again, relagating the MWz back onto standby. Handy to know, cheers.

 

[kirkbauer]

I just did a test flight today and left both alternators on for the ~30min flight (also EarthX battery). I noticed that the MWz was active a lot early on (obviously for charging) but kept turning on throughout the flight. I will try to toggle it off and back on again next time to see if that stops that behavior.

 

[Carl Froehlich]

I just did a test flight today and left both alternators on for the ~30min flight (also EarthX battery). I noticed that the MWz was active a lot early on (obviously for charging) but kept turning on throughout the flight. I will try to toggle it off and back on again next time to see if that stops that behavior.

I discussed the programming for the MonkWorkz with Bill Judge a few years ago. I suggested that he program it to come on at 13.5vdc and hold at 13.8VDC or so. Then if buss voltage went above 13.8VDC (as in the primary alternator was pushing voltage higher) then it would turn off and return to standby mode. He told me his EarthX customers wanted the higher 14.2 VDC output to better feed the EarthX.

At any rate I never had the MonkWorkz turn on by buss voltage being low (other than during testing). I run two PC-625 batteries in parallel (normal operation) so do not see much of a buss voltage drop - as in I never have a panel brownout when starting. I guess you Earthx guys will just need to add a POH section to manually cover this issue.

Carl

 

[monkworkz]

As always I'm slow on the uptake here... but yes, even the 14.2 V setting can be "sticky" in that the generator can turn on and stay on.

Collectively, myself and testers have run hundreds of hours with the generator sharing the load with an alternator and there are no issues.

The only real issue is that you probably want to know if you've had a failure, and that's what the status pin 2 is there for, to let you know that the generator is active. And if its active all the time then the status isn't much help.

Cycling the enable will kick it back in standby if your main is doing its job.

Generally, if your main alternator is doing it's job well it will be at 14.4 V, and the MZ won't come on line but at startup when the RPM is low and the Lithium battery is HUNGRY, the MZ may come on line. Once the battery charging is done and the main can carry the load at 14.4 V then the MZ notices that it's not putting out any current and it enters standby mode, and the status will update.

Some alternators run at less than 14.4 V, and in this case the alternator and generator may share the load, and again, this isn't an issue but cycling the enable will kick it into standby provided the main is doing it's job.

Now, why did I choose 14.2 V, and disregard Carl's fine suggestion to lower the operating voltage to 13.8V...

Well, I wanted to be able to get home, and 13.8 V won't charge my backup battery on the other side of a Schottky diode because of the 0.4-0.6 volt drop.

And, you know, I'm not selfish, I also wanted you to be able to get home too! So that's the how I set up the regulator.

And I also get asked why the voltage isn't user adjustable...

Two reasons:
1. Potentiometers are terrible. The typical way you make things adjustable is using a "pot" and they fail over time. One of my customers was getting random OV events, only when his main was on. I gave him my old adjustable alternator regulator that I wasn't using any more and the OV events stopped. The pot started to fail and the voltage would randomly, briefly, spike(and dip but this wasn't noticeable). So, I use fixed resistors that offer much better reliability.

2. Nobody calibrates their equipment. I'm not going to name any names but I got a note from a prominent individual in the RV community saying that the generator was running low, like 14.3 V when it should be 14.6 V. I said, huh, that's strange, I asked if he had a good voltmeter, like a Fluke, and that's when he found out that his EFIS was measuring low and for years he was flying around at 14.8V. So, by removing the infinitely adjustable voltage I'm doing my best to guarantee that you will be operating where you should be. So at your annual, before you adjust your alternator voltage based on the EFIS read out, probably hook up at quality voltmeter and make sure you know what the voltage actually is.

Secondary take away from #2: 14.8 V for thousands of hours won't hurt anything.(Probably?)

Have a great night.

Bill

 

[moosepileit]

Most EFIS have multiple power inputs, so there is a diode voltage drop if reading voltage there, good to check the raw bus close to the battery.

 

[Gearhead51]

Bill,

Any thoughts to have a voltage dip switch or jumper to select voltage? I'm looking to get one soon. I finally got rid of the PC680 and went to EarthX. O-360 with the XLT starter finally starts reliably with the EarthX, and I don't think I'll ever go back, but just in case...

 

[bjdecker]

Bill,

Any thoughts to have a voltage dip switch or jumper to select voltage? I'm looking to get one soon. I finally got rid of the PC680 and went to EarthX. O-360 with the XLT starter finally starts reliably with the EarthX, and I don't think I'll ever go back, but just in case...

Bill likes us to work at it with those pico-molex (or femto-) connectors

 

[monkworkz]

Bill likes us to work at it with those pico-molex (or femto-) connectors

The voltages should work well with AGM or LiFePO batteries(Oddessey and EarthX). I only switched over to an EarthX a few years ago, and before that I was running with oddessey 625s at 14.6 V, no issues.

 

[Dad's RV-10]

I've been chasing some issues with my Monkworkz, installed on my RV-10. I'm on my third regulator (the plane has 11 hours TT). Bill has been very supportive but I'm still trying to get this figured out.

For context, I have a 60 amp B&C primary alternator, the Monkworkz, a VP-X, a Vertical Power PPS and a single EarthX EXT1200 battery. Both the B&C and the Monkworkz are connected to the same lug on the PPS.

The first generator was throwing a thermistor code. Bill determined there was a broken pin on one of the aforementioned Pico receptacles on the board.

The second regulator would cycle on-and-off in one second intervals. Bill determined this was an issue with an older firmware version.

The most recent regulator will cycle on-and-off in 4 second intervals. I have tried everything I can think of with regard to when I "Arm" the Gen. I've started the engine with the Gen armed. I've recycled the switch after the engine is running (Off and then Arm). I've started the engine with the Gen "Off" and armed it after the engine is running. I started the engine with the Gen "Off," left it "Off" through takeoff and climbout, arming the Gen after reaching altitude giving the battery plenty of time to recharge to a normal state. I've recycled the Gen in flight (Off and then Arm).

All of the above results in the MZ cycling on-and-off in 4 second intervals.

The only thing that consistently results in the Monkworkz entering the "normal" standby mode is to switch-off the primary alternator in flight. The alternator amps drop to zero, the bus voltage quickly drops to the Monkworkz trigger voltage and the Monkworkz takes over the bus, all as intended.

Once I switch the primary alternator back On, then and only then will the Monkworkz enter its intended, normal standby mode (no more cycling on 4 second intervals).

Scratching my head. The regulators store data so I'll probably send this one back to Bill as well, so he can try to determine what's going on.

 

[Carl Froehlich]

How are you interfacing your Vertical Power box with both the primary alternator and Monkworkz generator?

 

[Dad's RV-10]

How are you interfacing your Vertical Power box with both the primary alternator and Monkworkz generator?

Sorry Carl, I don't really understand the question?

 

[Dad's RV-10]

Update:

At the suggestion of a friend, I tried an engine start configuration I had not previously thought of. With the MZ switch Armed, I started the engine with the Master switch set only to Battery (primary alternator not enabled). As previously mentioned, I have an EarthX battery which has a substantial amperage draw immediately after engine start.

After starting the engine but prior to enabling the primary alternator, the MZ cycled rapidly. The MZ can only output 15 amps at idle RPM, so there was no way it could give the EarthX what it was demanding. But the MZ regulator protects itself from any harm, despite the requested load.

After a few seconds, I turned On the primary alternator. The MZ immediately went into STBY mode and remained in STBY until I switched Off the primary alternator about 30 minutes into the flight. The MZ then performed as intended and returned to STBY after switching the primary alternator back On.

To summarize; starting the engine with the primary alternator OFF, the MZ Armed and enabling the primary alternator after engine start is resulting in normal MZ behavior.

I've already spoken with Bill about this. I'm going to fly a few more legs and then send this regulator back to Bill so he can analyze the data.

 

[Dad's RV-10]

Update to above Update:

Bill has been analyzing the data from the regulators I've sent back. I'm sure Bill can explain in greater detail what he found but he made a change to the firmware based on the data.

My latest regulator now performs as advertised.

I can now start the engine with the MZ switch "Enabled" and the master in the "BAT/ALT" position. After engine start, there is no STBY GEN EICAS. After allowing the battery to recharge a bit, if I switch the Primary Alternator "OFF", the MZ will pick up the Bus at 13.7V, as intended, and the EICAS will show "STBY GEN."

Kudos to Bill for figuring this out!