Arco Zeus regulator - first impressions and a look inside

[IanD]

14 minutes ago, dmr said:

I suspect the "current shunt amplifier on a chip" does temperature correction if required. I suspect this is what Victron uses I have wondered if the smartshunt suffers from temperature issues, the standard BMV looks to have no electronics on the shunt mounted pcb. I also note that both the BMV shunt and smartshunt obstruct any airflow over the shunt.

I belive that shunts are made from some clever alloy that has minimal temperature co-efficient.

 

Expensive precision lower-current shunts are usually made from manganin, a copper-manganese-nickel alloy.

 

But this is *way* more expensive than copper for big high-current shunts like the 500A ones commonly used in boats, which I suspect use copper because the tempco is low enough given the required accuracy.

 

With a smartshunt it would be much cheaper to go down the temperature sensor/correction route than using manganin -- but I expect this isn't needed anyway... 😉 

[dmr]

Look at this:

 

https://uk.rs-online.com/web/p/shunts/8233570?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_PMAX_Catch+All-_--_-8233570&matchtype=&&gad_source=1&gclid=CjwKCAiA_5WvBhBAEiwAZtCU7wqeb5xPrgGzfxTClWFNIKLSpiebdsIrkalvCC-zXfUhHCU-lJmMRRoCrhkQAvD_BwE&gclsrc=aw.ds

 

Manganin 500 amp shunt, 0.25% accuracy and only £35 and thats at RS prices.

 

Thinking about this, a shunt is used for amp-hour counting and the amps go in at 100amps or so, and often come out at just an amp or two, so it does require accuracy. Probably ok for lead acids that are unpredictable beasts, but might be more significan with Lithiums.

[nicknorman]

47 minutes ago, dmr said:

Look at this:

 

https://uk.rs-online.com/web/p/shunts/8233570?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_PMAX_Catch+All-_--_-8233570&matchtype=&&gad_source=1&gclid=CjwKCAiA_5WvBhBAEiwAZtCU7wqeb5xPrgGzfxTClWFNIKLSpiebdsIrkalvCC-zXfUhHCU-lJmMRRoCrhkQAvD_BwE&gclsrc=aw.ds

 

Manganin 500 amp shunt, 0.25% accuracy and only £35 and thats at RS prices.

 

Thinking about this, a shunt is used for amp-hour counting and the amps go in at 100amps or so, and often come out at just an amp or two, so it does require accuracy. Probably ok for lead acids that are unpredictable beasts, but might be more significan with Lithiums.

I would say that absolute accuracy (gain accuracy) is not that important provided it is proportional both ways. It doesn’t particularly matter if it thinks 101A has been taken out for an hour, and 10.1A for 10 hours put back in again, when in fact it was 100Ah both ways. What is important is that the zero is accurate and errors are symmetrical about zero, otherwise the integration errors will accumulate rapidly.

Edited March 4 by nicknorman

[IanD]

50 minutes ago, dmr said:

Look at this:

 

https://uk.rs-online.com/web/p/shunts/8233570?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_PMAX_Catch+All-_--_-8233570&matchtype=&&gad_source=1&gclid=CjwKCAiA_5WvBhBAEiwAZtCU7wqeb5xPrgGzfxTClWFNIKLSpiebdsIrkalvCC-zXfUhHCU-lJmMRRoCrhkQAvD_BwE&gclsrc=aw.ds

 

Manganin 500 amp shunt, 0.25% accuracy and only £35 and thats at RS prices.

 

Thinking about this, a shunt is used for amp-hour counting and the amps go in at 100amps or so, and often come out at just an amp or two, so it does require accuracy. Probably ok for lead acids that are unpredictable beasts, but might be more significan with Lithiums.

 

It's not the absolute accuracy that manganin is used for, it's temperature variation. Copper tempco is about 0.4%/C, so the shunt reading could vary by several percent over normal temperature ranges, but in reality that's probably OK for most boat applications. It's the kind of thing that gets left off specs if adding it would reveal that they've skimped on materials.

 

The fact that current goes in at 100A and out at 1A isn't affected by this, both readings would change with temperature (ignoring self-heating) -- what this needs is good resolution and linearity.

 

I agree that manganin would be better, the question is whether shunt manufacturers bother spending the extra money, especially cheap Chinese ones for the cheapskate canal boater market... 😉 

 

(this applies to passive shunts only, much easier and cheaper to measure and correct temperature with a smart shunt if accuracy matters that much -- which is what I suspect Victron do, given that accuracy is specified at +/-0.4% and there's also an optional external temperature sensor)

 

6 minutes ago, nicknorman said:

I would say that absolute accuracy (gain accuracy) is not that important provided it is proportional both ways. It doesn’t particularly matter if it thinks 101A has been taken out for an hour, and 10.1A for 10 hours put back in again, when in fact it was 100Ah both ways. What is important is that the zero is accurate, otherwise the integration errors will accumulate rapidly.

 

Agreed, zero error is by *far* the most important thing when you're Ah counting, because this accumulates over days so a tiny offset error in the current measurement ends up as a big Ah error.

 

Fortunately offset error is the easiest thing to fix electronically using tricks like chopping or autocalibration, down to microvolt levels or even lower if required... 🙂 

Edited March 4 by IanD

[nicknorman]

Anyway, Ive said this before and I’ll say it again, I don’t see why an alternator controller needs an accurate measure of its output current. It does need to know SoC but that comes from measuring battery current, not alternator output current. I think the Zeus has the option to specify a max output current but why would you want to bother with that, unless you have a very large alternator and a very small battery or at least very small BMS max current rating? Not really appropriate for a narrowboat installation.

[dmr]

12 minutes ago, nicknorman said:

Anyway, Ive said this before and I’ll say it again, I don’t see why an alternator controller needs an accurate measure of its output current. It does need to know SoC but that comes from measuring battery current, not alternator output current. I think the Zeus has the option to specify a max output current but why would you want to bother with that, unless you have a very large alternator and a very small battery or at least very small BMS max current rating? Not really appropriate for a narrowboat installation.

 

It is a useful thing to have when trying to understand alternator temperature and belt loading etc as its independant of the fridge going on and off etc, and as I said, I had a spare cheap shunt and space (just) to install it and was re-doing the wiring anyway, but I don't think I would have purchased a shunt just for this purpose.

[nicknorman]

2 hours ago, dmr said:

 

It is a useful thing to have when trying to understand alternator temperature and belt loading etc as its independant of the fridge going on and off etc, and as I said, I had a spare cheap shunt and space (just) to install it and was re-doing the wiring anyway, but I don't think I would have purchased a shunt just for this purpose.

 

I am not complaining that you have purchased a cheap shunt / found a dusty one in a cupboard. It is more the issue of why Arco bothered to include the ability to measure alternator current and what they proposed to do with that data. That will have cost money, and wasn't necessary. Certainly as you have already paid for it, you might as well install it.

Edited March 4 by nicknorman

[IanD]

3 hours ago, nicknorman said:

 

I am not complaining that you have purchased a cheap shunt / found a dusty one in a cupboard. It is more the issue of why Arco bothered to include the ability to measure alternator current and what they proposed to do with that data. That will have cost money, and wasn't necessary. Certainly as you have already paid for it, you might as well install it.

 

To allow the user to set an alternator current vs. rpm curve to keep the alternator cooler and reduce belt/engine loading at low rpm, like I believe you do? Particularly useful if you want to fit a big alternator, which is one of the applications the Arco is targeted at...

Edited March 4 by IanD

[nicknorman]

24 minutes ago, IanD said:

 

To allow the user to set an alternator current vs. rpm curve to keep the alternator cooler and reduce belt/engine loading at low rpm, like I believe you do? Particularly useful if you want to fit a big alternator, which is one of the applications the Arco is targeted at...

No. In order to set an alternator load vs rpm curve, you use the rpm and a max field current limit as the axes on the curve. Otherwise, if you were foolish enough to use the alternator current instead of the max field current, when there was a sudden load on the alternator there would be transient overswing on the alternator current and hence on the mechanical load. Which is bad design.
Why go for the added complexity of requiring a shunt to measure alternator current so that you can make a bad design, when instead you can use a field current limit that doesn’t require an external shunt, and make a good design with no load overshoot?

Edited March 4 by nicknorman

[beerbeerbeerbeerbeer]

3 hours ago, nicknorman said:

What is important is that the zero is accurate and errors are symmetrical about zero, otherwise the integration errors will accumulate rapidly.

I gave a greenie, more to congratulate myself for there was something I finally understood!

 

I like to read and persevere with electricity threads even if I quickly get lost with what your on about, 
(but really of course I’m rooting for Dmr to get his set up working proper 👍)

[dmr]

22 minutes ago, IanD said:

 

To allow the user to set an alternator current vs. rpm curve to keep the alternator cooler and reduce belt/engine loading at low rpm, like I believe you do? Particularly useful if you want to fit a big alternator, which is one of the applications the Arco is targeted at...

 

The Zeus current vs rpm curve looks to work in % terms and I'm not sure if this refers to current or duty cycle...but Im pretty sure its field duty cycle as I dont think Ive told the app how many amps my alternator can produce.

 

Much more exciting, I've been exploring the app a bit and just found a data logging option, might investigate this tomorrow.

[nicknorman]

1 minute ago, beerbeerbeerbeerbeer said:

I gave a greenie, more to congratulate myself for there was something I finally understood!

 

I like to read and persevere with electricity threads even if I quickly get lost with what your on about, 
(but really of course I’m rooting for Dmr to get his set up working proper 👍)

Well done for just continuing to read this thread. It is a geeky thread for geeky people, but spectators are of course welcome!

[beerbeerbeerbeerbeer]

Just now, nicknorman said:

Well done for just continuing to read this thread. It is a geeky thread for geeky people, but spectators are of course welcome!

spectators are very important,

we learn a lot, 

and getting to a truth about something matters,  

 

[nicknorman]

7 minutes ago, dmr said:

 

The Zeus current vs rpm curve looks to work in % terms and I'm not sure if this refers to current or duty cycle...but Im pretty sure its field duty cycle as I dont think Ive told the app how many amps my alternator can produce.

 

Much more exciting, I've been exploring the app a bit and just found a data logging option, might investigate this tomorrow.

Yes the rotor is a surprisingly resistive load (bearing in mind all the whirly round magnetic bits in an alternator). Of course it has inductance too but in the longer term, the current is based on ohms law. So if eg you want to limit the alternator output to about half, you could specify a max of 50% duty cycle. Certainly this would work fine for an rpm vs load map to reduce mechanical load at low rpm, or to control max temperature.

 

In my case the chip had field current measurement built in (measuring the voltage drop across the FET probably) and I use that, having identified that the alternator max field current was about 4.5A with 13v across it. Obviously that made it “tuned” to my specific alternator, but that isn’t a problem for me. In fact having just checked, I see I can read the instantaneous duty cycle but I can’t set a duty cycle limit. Only a field current limit in amps. This seems to be the industry standard for a LIN interface alternator controller. Anyway, it works fine for me!

[dmr]

1 minute ago, nicknorman said:

Yes the rotor is a surprisingly resistive load (bearing in mind all the whirly round magnetic bits in an alternator). Of course it has inductance too but in the longer term, the current is based on ohms law. So if eg you want to limit the alternator output to about half, you could specify a max of 50% duty cycle. Certainly this would work fine for an rpm vs load map to reduce mechanical load at low rpm, or to control max temperature.

 

In my case the chip had field current measurement built in (measuring the voltage drop across the FET probably) and I use that, having identified that the alternator max field current was about 4.5A with 13v across it. Obviously that made it “tuned” to my specific alternator, but that isn’t a problem for me. In fact having just checked, I see I can read the instantaneous duty cycle but I can’t set a duty cycle limit. Only a field current limit in amps. This seems to be the industry standard for a LIN interface alternator controller. Anyway, it works fine for me!

 

Mine is 3.5ohms 😀 but I can't measure the inductance (well I suppose I could if I really really wanted to).

Can we assume that 100% rotor excitation just about gives full alternator output (at maybe 13 volts)???? or will there be quite a safety margin?  But then with Zeus and a half hour (and the alternator shunt 😀😀) I could answer this myself.

 

Zeus has the "limit vs rpm" option and also has a "maximum duty cyle" option which is a bit of duplication but useful.

Even though I am having a couple of software issues I am very impressed with the potential of this thing.

[nicknorman]

18 minutes ago, dmr said:

 

Mine is 3.5ohms 😀 but I can't measure the inductance (well I suppose I could if I really really wanted to).

Can we assume that 100% rotor excitation just about gives full alternator output (at maybe 13 volts)???? or will there be quite a safety margin?  But then with Zeus and a half hour (and the alternator shunt 😀😀) I could answer this myself.

 

Zeus has the "limit vs rpm" option and also has a "maximum duty cyle" option which is a bit of duplication but useful.

Even though I am having a couple of software issues I am very impressed with the potential of this thing.

The inductance doesn’t matter for steady state, it only affects the max dI/dt.

100% duty cycle will put the battery voltage (13.whatever) across the rotor. Which is fine and will give max alternator output for the rpm. There is a reasonably close correlation between % duty cycle and % rotor current.

 

The limit vs rpm is to reduce load at low rpm by reducing the duty cycle (very useful if you have a large alternator) whereas the max duty cycle puts an overall cap on the max output. Not sure why you would want to do that other than to establish a rough max current into a battery in the absence of a shunt, although as I said before it seems unlikely that you would want to put a blanket reduction on max output regardless of eg alternator temperature.
 

Then again I do remember when I said our alternator (before the advent of my controller) could stuff in 180A into our 450Ah of Trojans at the beginning of charging. You said I was cruel! Trojan of course recommend a max of 20% C charge current and that was 40%.
But that was crappy old lead acid batteries, who uses them these days?

Edited March 4 by nicknorman

[dmr]

19 minutes ago, nicknorman said:

The inductance doesn’t matter for steady state, it only affects the max dI/dt.

100% duty cycle will put the battery voltage (13.whatever) across the rotor. Which is fine and will give max alternator output for the rpm. There is a reasonably close correlation between % duty cycle and % rotor current.

 

The limit vs rpm is to reduce load at low rpm by reducing the duty cycle (very useful if you have a large alternator) whereas the max duty cycle puts an overall cap on the max output. Not sure why you would want to do that other than to establish a rough max current into a battery in the absence of a shunt, although as I said before it seems unlikely that you would want to put a blanket reduction on max output regardless of eg alternator temperature.
 

Then again I do remember when I said our alternator (before the advent of my controller) could stuff in 180A into our 450Ah of Trojans at the beginning of charging. You said I was cruel! Trojan of course recommend a max of 20% C charge current.
But that was crappy old lead acid batteries, who uses them these days?

 

For the first run with the Zeus I had not yet installed the alternator thermistor so I myself was part of the temperature control loop, feeling alternator temperature with my hand and setting current by adjusting the "maximim duty cycle" option". The "limit vs speed" is difficult to use as I only have a very little iphone and big fingers 😀.

 

Although we now have a home/winter mooring we are still off grid so any electrical upgrades have to be done in small doses so that we can still run the engine every second day. A landline is now an option but thats maybe too close to living in a house? 😀

[nicknorman]

8 hours ago, dmr said:

 

For the first run with the Zeus I had not yet installed the alternator thermistor so I myself was part of the temperature control loop, feeling alternator temperature with my hand and setting current by adjusting the "maximim duty cycle" option". The "limit vs speed" is difficult to use as I only have a very little iphone and big fingers 😀.

 

Although we now have a home/winter mooring we are still off grid so any electrical upgrades have to be done in small doses so that we can still run the engine every second day. A landline is now an option but thats maybe too close to living in a house? 😀

Limiting the max duty cycle is one way of avoiding alternator overtemp, but it doesn’t take into account the ambient temperature of the engine room - which even with your setup could probably vary by at least 20C - or the fact that the alternator can run flat out for a short while before overheating. Using a temperature sensor is of course the better way to do it.

[dmr]

14 minutes ago, nicknorman said:

Limiting the max duty cycle is one way of avoiding alternator overtemp, but it doesn’t take into account the ambient temperature of the engine room - which even with your setup could probably vary by at least 20C - or the fact that the alternator can run flat out for a short while before overheating. Using a temperature sensor is of course the better way to do it.

 

Yes, I think I said in an earlier post that the sensor has an 8mm hole (its a thermistor potted in a copper tube terminal) so did not easily fit onto the alternator so was not installed for my initial engine run, so I had to set a quite low duty cycle.

I have now carefully reshaped it a bit so that it can fit over one of the long bolts (m4 or m5?) that hold the two halves of the body together. I really need to drill and tap the alternator body but this is a bit more complicated.

 

I will investigate the Zeus data logging later today and see if I can capture the temperature control cycling etc.

[dmr]

Zeus App also runs on iPad which is good, nice big screen.

 

Zeus has a data logger though it looks to only log a few samples each second. I logged a half hour or so to my phone then emailed the CSV to my laptop.

There are a few bugs/oddities so I had to go round the houses a bit but here is alternator temperature.

Zeus is cycling duty cycle to hold temperature but missing my 75degree target by a fair bit.

Can't get Time as the X axis as there is what looks like a software bug (possible severe rounding error). Don't want to do yet another bug report till they have fixed my current ones.

All rather good fun.

 

Geek Warning.

Zeus appears to use "{   }" inside a CSV file to embed additional data that does then not import into Excel, never seen this before and used to use CSV files loads.

[cheesegas]

Finally got mine fitted! Notes below, the way it handles minimum field to keep the tacho alive is very poor. Minimum field is not a problem unique to this unit though.

 

The alternator light, much like @dmr experienced, does not act like a normal light which at first appears like a simple oversight. When you turn the ignition on and the engine isn't running, it doesn't come on. I have forced it into a fault condition to see if it works though and it does flash out fault codes nicely...

 

I wouldn't expect the light to work if the batteries are full and the minimum field % is below what is needed to excite the stator though. The error here is not having an option in the config to enable/disable minimum field % drive - you just set the percentage.

 

With the minimum field at say 5% and the batteries full, the Zeus doesn't actually know if the alternator is spinning or not as nothing comes out the W terminal since the field current is so low! I believe that to avoid the light coming on in error (a full battery/low field state looks the same to the Zeus as when the ignition is on and engine is not running), they've just disabled it under those conditions.

 

The way to 'fix' it as mentioned is to have an option to enable or disable the minimum field percentage option; if it's enabled, the light works like a regular alternator light, if disabled it acts like it does now. The 'enabled' state would allow the Zeus to assume that if it's applying minimum field and it's not getting anything out the alternator, it's not spinning. 

 

I had the minimum field set to 24%, just enough to keep the tacho output alive at idle. Any lower and it becomes intermittent, I've verified this with an oscilloscope to ensure it's not just the Zeus being insensitive/too low an input impedance. This is fine for charging at low RPMs when the battery SoC is low. 

 

However, if the battery is fully charged, the regulator is in float and the engine RPMs are high, it's still maintaining the same minimum field %. This means that the voltage will continue to rise unchecked as it can't drop the field current low enough to achieve the target voltage - 13.35v in my case. It'll rise until the lithium BMS does a high voltage disconnect or the Zeus trips on its own high voltage protection. I highly recommend setting the Zeus's high voltage protection lower than the BMS's high voltage disconnect to ensure it stops trying to charge the batteries with an ever increasing voltage BEFORE the BMS disconnects. It does not have any runaway detection like competing regulators do.

 

 

To summarise...

 

Given the target market for the Zeus, I think the minimum field % urgently needs an enable/disable option, along with a big big red warning in the app if you enable it. If you don't change the factory high voltage trip from 16.0v to something lower, setting a minimum field too high will fry your alternator if your lithiums do a high voltage disconnect, or if you have lead batteries it will boil them. 

 

As an experiment, with 24% minimum field on my 90a Prestolite, I connected an old lead battery to the lithium (hybrid eat your heart out...) and brought the engine up to 2500rpm / alternator 4500rpm. The BMS did a high voltage disconnect at 14.6v, the voltage on the lead battery quickly rose to 16v and the Zeus tripped. However, there is little hysteresis built in to this, and it appears to go into a loop of enabling itself, voltage rising and then tripping over and over again! In my test setup, the lead voltage sat around 15-16v.

 

One fix for this is a dynamically changing minimum field, mapped by the installer against engine RPM, and a big fat warning in the app if you enable that not-present minimum field option. The other way around it is to take the engine speed from a different source so it doesn't matter if the tacho output of the alternator drops to zero.

 

However...

 

This overall problem is not unique to the Zeus, it's something we have to deal with in all external regulators which are capable of reducing the alternator voltage to float. Even with the first fix mentioned above, an MPPT in float with a voltage set to slightly above the alternator's float voltage will disable the tacho output. Communication with all components in the system is really important here - all charge sources need to take battery voltage from not just the same physical place in the circuit but ideally it's got to be one 'thing' (SmartShunt etc) measuring the voltage and sharing that data; it's a shame DVCC isn't supported yet. Small voltage differences can cause havoc.

 

The issue unique to the Zeus is the option to 'wait for tacho'. Bafflingly, if enabled, the regulator will first apply the minimum field current % and then when it sees a tacho reading, it will then ramp up the field. If disabled, it appears to apply (almost!) full field first, then ramp it down like most other regulators. I can see no reason for the 'wait for tacho' option other than avoiding overheating the field winding if you leave the ignition on and engine not running. Another option for engine running detection could be a simple accelerometer you'd bolt to the engine.

 

It's worth noting that not all alternators are the same; some may not have this problem - with bigger alternators it's possible to set the field current low enough for the tacho to work but not for the voltage to run away.

 

The Wakespeed handles the minimum field drive in exactly the same way and is prone to the same problem; however, minimum field % is disabled from factory, and requires going into the advanced config and sending Putty commands to set up which the average user will not do. Before firmware 2.5, if it detects a voltage runaway condition, it will drop the field to zero to avoid a BMS trip. However, as of 2.5.1, it will behave like the Zeus and not drop the field % below minimum until it trips on high voltage. 

 

The difference is that the Wakespeed has a big fat warning in red in the manual about this very situation. The Zeus does not! It's also possible for the Wakespeed to take engine RPMs from J1939 CAN registers, whereas it appears the Zeus is read only. 

 

 

[dmr]

I've had my Zeus running for a while now and have used its data logging feature to try to understand how it works and how well it works.

Its an impressive device but does have a few "features" some of which must be bugs and one or two that are potentially destructive. Arco have not responded to most of my questions/bug reports.

I will write a bit more later/tomorow, but on the subject of the warning "ignition" light. Arco did respond to this and tell me the light should NOT light when the ignition is on but no engine rotation, so this is correct behaviour. I disagree with this, and don't understand why the software gives an option for "fault" or "warning light" when it only shows faults.

So why should it work like a standard ignition light? There are two big reasons. When you turn the ignition on in a car all the lights on the dash light up to confirm that the bulbs are working...without this the bulb or wiring could have failed and you would never know so miss any error flashing. Second, it gives instant feedback that the alternator is working (brushes do eventually fail 😀). Everytime I start my engine I watch for the ignition light going out, I don't always look at the BMV (or the Zeus app) to see what the current is.  I realise that the soft ramp confuses things a litttle bit but still think that light really should light up.

[nicknorman]

Thanks for that detailed description. It does seem very crap for something that cost £800+. You say “This overall problem is not unique to the Zeus, it's something we have to deal with in all external regulators which are capable of reducing the alternator voltage to float.” but I  say that it doesn’t have to be like that. I know that you and DMR probably don’t want to hear this, but the regulator I built around an £8 chip deals with keeping the phase /tacho output “alive” with zero load on the alternator, flawlessly. From the data sheet:

 

 15 Phase regulation This function avoids losing phase signal amplitude for proper regulation when the voltage in the board harness is higher than the set point value (case of load shedding, or set point below battery voltage). The regulator monitors the voltage levels of the phase signal and checks if the phase oscillates between VTH_L and VTH_H, ensuring phase amplitude is sufficient for regulation. Phase failure is detected if there is no PhaseOK rising edge for more than 30 ms. In this case the phase regulation is started. The phase regulation function is performed by applying 100 % duty cycle current to the rotor, so the phase amplitude can build up. This 100 % duty cycle is stopped, either when the rising edge of PhaseOK is present again, or when the maximum duration of phase regulation is reached (this timing is determined by programming the tONBOOST parameter, max on time for phase boost). If the PhaseOK signal recovers, then fails again before the end of tONBOOST timer, another tONBOOST time is initiated. If the phase is still not OK after tONBOOST, the device goes back to regulation mode and starts a 300 ms ‘failure’ timer. When this 300 ms timer has elapsed, if there is still no PhaseOK rising edge for the next 30 ms, the phase boost function is active again for a maximum duration of tONBOOST. The number of retries is not limited.

 

In other words, it increase the field current just enough to keep the phase signal working. The actual min. field current will thus vary according to rpm.

None of that is anything to do with my design, I just send the regulator the set voltage and field current limit, along with configuration data for the load ramp. The reg sends back rpm and there are a couple of failure flags for mechanical and electrical failure, which I use to operate the warning light. The reg also sends back the actual field current, duty cycle etc but these aren’t useful, just slightly interesting.

 

It does seem odd to me that both Wakespeed and the Zeus have started with blank sheets of paper and re-invented the wheel, not particularly well. Why do that as a small low budget company, rather than using the cheap tried and extensively tested product from one of the several gigantic automotive electronic design companies with enormous budgets, experience and expertise. I just don’t get why people want to make life so difficult for themselves.

 

Just on you point about the low initial field current, my reg does that too and I think it is a good thing. If you have a large alternator it is helpful to have it briefly disabled or at least creating only a light load whilst the engine is starting up. And as you say, why pump 4A into the field when the engine isn’t running?

 

 

 

[cheesegas]

14 minutes ago, dmr said:

I've had my Zeus running for a while now and have used its data logging feature to try to understand how it works and how well it works.

Its an impressive device but does have a few "features" some of which must be bugs and one or two that are potentially destructive. Arco have not responded to most of my questions/bug reports.

I will write a bit more later/tomorow, but on the subject of the warning "ignition" light. Arco did respond to this and tell me the light should NOT light when the ignition is on but no engine rotation, so this is correct behaviour. I disagree with this, and don't understand why the software gives an option for "fault" or "warning light" when it only shows faults.

So why should it work like a standard ignition light? There are two big reasons. When you turn the ignition on in a car all the lights on the dash light up to confirm that the bulbs are working...without this the bulb or wiring could have failed and you would never know so miss any error flashing. Second, it gives instant feedback that the alternator is working (brushes do eventually fail 😀). Everytime I start my engine I watch for the ignition light going out, I don't always look at the BMV (or the Zeus app) to see what the current is.  I realise that the soft ramp confuses things a litttle bit but still think that light really should light up.

Have a read above, I think I was a bit rambly here and there but the reason why it doesn't come on is that unless the minimum field % is configured, the Zeus has no idea if the engine is running or not when the batteries are full and Zeus is in float mode.

 

The inputs in the above scenario are in the exact same state as when the engine is not running but the ignition is off. All *edit* off the shelf external regulators have the same issue, it's about how it's dealt with.

 

I agree that perhaps like Balmars, the first time the ignition wire is turned on the ignition light should come on though. Once the regulator drops to float mode it would then only come on if there's recognised fault state.

 

8 minutes ago, nicknorman said:

In other words, it increase the field current just enough to keep the phase signal working. The actual min. field current will thus vary according to rpm.

Interesting, I didn't know this was doable in an off the shelf chip! I mentioned that this is one of the potential fixes, a dynamic minimum field current depending on RPM, good it's already been done!

 

Wakespeed and Zeus apply a fixed but configurable minimum field current, Balmar as far as I know apply a fixed but unconfigurable minimum field which in my experience isn't enough. I don't know how Mastervolt handle it.

Edited March 25 by cheesegas

[dmr]

24 minutes ago, nicknorman said:

Thanks for that detailed description. It does seem very crap for something that cost £800+. You say “This overall problem is not unique to the Zeus, it's something we have to deal with in all external regulators which are capable of reducing the alternator voltage to float.” but I  say that it doesn’t have to be like that. I know that you and DMR probably don’t want to hear this, but the regulator I built around an £8 chip deals with keeping the phase /tacho output “alive” with zero load on the alternator, flawlessly. From the data sheet:

 

 

 

Its good, I like to hear stuff like this, maybe I should have talked to you and used your design, but its a lot of time and effort that I don't have, but I am a huge believer in the concept of a "one man band" competing with the big (biggish) companies.

 

I don't really see what the big issue is with float mode and tacho signal, maybe I have not thought hard enough 😀, surely it only needs a volt (or even much less) to deduce speed, so as long as a tiny bit of rotor excitation is applied (well below float voltage) there should be enough voltage. Its a zero crossing thing? Is the residual magnetism not enought?

 

If you wanted to be really pedantic you could apply just enough rotor drive to get a tacho signal but not turn on the rectifier diodes 😀