dmr

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.

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 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.

Its interesting looking at the various digital voltmeters and current monitors on eBay, or even looking at the Victron specs. A few do display to two decimal places, 10mV and 10mA, but the accuracy spec is sometimes as bad as 3%, especially on the current, and accuarcy is relative to FSD, so the figures do need to be treated with a bit of caution, but can still be very useful if used correctly. The Zeus and the Victron volts and amps agree well. I have not looked at the Zeus amp-hours capability yet. The current was possibly a little off on the Zeus alternator shunt but I did use a cheap chinese shunt that I had in the parts box. Maybe Arco thought of this as they allow a correction factor to be specified.

Ahhh I always wonderred what a shunt was 😀 I think you missed the smiley in my post. Anyway if you did have two shunts in parallel then the sum of the two currents will indeed be the correct total current, I think it was you who was talking about Kirchoff recently??? 😀 A man who understands the difference between resolution and accuracy 😀, Its surprising how many struggle with this. I note than the Victron displays voltage to two decimal places but Zeus only does one. The Smartgage does one and a half.

I'm sure you know but there are a few chips on the market that do the whole job of shunt measurement (and power calculation) with an I2C interface, I think they are 20bit. I started using one to do my own amp-hour counter (with a positive shunt) but decided it was better and easier to fall into the Victron family.

Thats ok but I think they are llike batteries and must be from the same manufacturer and have the same capacity. and you get an RPi and write some software to add the two currents together 😀

Before the Victron we had the old Adverc BMS/monitor, an old design so they used a higher resistance shunt, 100mV at 100amp I think, and I melted that one 😀. The Victron shunt system is impressive, it resolves 10mA and that corresponds to just 1 microvolt (if my calculation is correct)

The Zeus has a very nice feature where it logs some parameters such as volts, amps and temperature, though only 600 samples which is maybe the most recent few minutes. These time history graphs showed the Zeus ramping duty cycle/current up and down to try to control temperature, so a bit like an unstable loop. Maybe it will "learn" and get better, or maybe my alternator is thermally very different to whatever models it might have built in. Sadly I discovered that the screen grab feature on my iphone does not work so I could not capture this interesting stuff. Will try again another day. The overshoot does look like a bit of bad programming, but then Zeus was done in a rush. As long as Arco fix it I will have no complaint. Shunts in series are a bit like the length of thin cable, rather wasteful of otherwise low resistance cables. As you say, its fine if each device is only using the shunt "signals" to derive current, but if it is using one terminal as a system ground then it gets a bit more worrying.

But, an extra hot day, a bit of belt slip, or a few dog hairs inside the alternator, and you resistance wire will no longer be correct. Measuring the alternator case temperature is a big step closer to doing it right. The new car is very comfotable and sorts of floats along nicely, and the steering wheel and pedals sort of tell it how to float along, but its not like actually driving it 😀. Our old mk1 Focus was a lovely car to drive. At least the boat is nicely mechanical and free of processors........oh bugger, Ive just installed the Zeus.

Yes, shunts are nasty, we spend loads of effort and money on thick cables to get the resistance down, then put a shunt in the circuit. (but adding a length of thin wire as a current limiter is much worse 😀) My view is that shunts are more acceptable in the positive line, but I am totally outnumberred on this so have just redone things to fall in line. The only and "nicer" alternative is a Hall effect current sensor and currently these are just not accurate enough. My new (to me) car reads the speed limit signs, beeps if Im going too fast, and optionaly takes control of driving the car at the correct speed.

How quickly does stuff update on a typical CANbus system?. I suspect the problem is that a sudden increase in engine speed, or more likely a reduction in load current as something turns off, will give an increase in voltage and the Zeus needs to respond to this as fast as possible. I was trying to look at some transient responses today, and will look again next time I need to run the engine (Tuesday).

I think its reasonable that the Zeus needs its own voltage sense. This is a critical bit of info, in fact its the main objective of the Zeus, so it would be risky to rely on some other device providing data over a bus. In addition I suspect that bus issues and delays/slow update rates could play havoc with the control loops (see my post above 😀 ) . It might be good to have an option to take temperature, and maybe current, from CANbus. I have shared the Victron BMV shunt with the Zeus. Arco do not provide a shunt so I assume that this is their intention, and shunts in series is not a great idea. There is a post somewhere on a Victron forum saying that sharing shunts is not good, but I feel that even though the signal is small the source impedance of a shunt is so incredibly low that it must be ok.

Update and a BUG I've got the alternator thermistor on, not looking too horible, but might need to drill and tap the alternator body for a top job. Have also redone the brush box to give a P type (and 6 diode) configuration. (I can see little point in an N type 6 diode config). It was good to see that as I changed the setup from N to P the App gave me a serious warning. This rework (obviously) fixes the excitation issue that I was having. The warning light still does not function as an ignition light simulation, but flashes on a fault condition so I know its working. There is a bug where the Zeus occassionally looses control of voltage regulation, I see 15.2volt transients on my 14.8volt target. Could be an issue with Lithiums????? This happens because the Zeus cycles its duty cycle up and down to control alternator temperature, so switching between a "constant temperature" and "constant voltage" regime. At the transition it sort of takes its eye off the ball and continues to ramp the duty cycle upwards before it gets it back in control and this gives an over-voltage pulse. I am hoping for a good response from Arco.

😀 As I said, the App gives the option of "require Tacho" so I assume it can all work fine without a tach if required, and indeed it does because I initially failed to scroll down far enough to find the tacho option, its in amongst all that CANbus stuff. I suggest its Arco who are thinking 9 diodes, that are making their warning light a direct replica of an olde worlde alternator 😀 Took the TravelPower down to that nice (but expensive) Mr Cox yesterday. He claims that he can also rebuild my cooked Iskra alternator for less that the price of a new one. Do you think he will give me a discount if I ask him to leave three of the diodes out ? 😀

As AdE says, the tanker will have a hefty pipe that gushes out fuel at a huge rate, they do not have petrol pump style nozzles. You will likely need to sign a red diesel declaration when you order the fuel stating what the fuel is going to be used for and why you can use red. They will not like boats. 200 litre drums work out much more expensive than bulk deliveries, and as said, bulk starts at 500 litres.

The light never comes up (or never came on 😀)....... I've just created an error by disconnecing the alternator thermistor and the light is flashing. So, it must be my 9 diode install thats upsetting things. This suggests that rather detecting "ignition on, no alternator current" the software is measuring field current flowing and no output current?. I cant decide if this is a good or bad way of doing things. Actually its correct....its assuming the field circuit is open circuit so not lighting up, just like a conventional alternator system.

Yes, and I assume it comes on when the ignition comes on and goes out when the engine starts (alternator starts), just like a standard ignition light, but also flashes error codes. I could try to create an error code tomorrow. Just maybe my "diode trio" supply is upsetting it but thats unlikely. The feature-in is purple, the lamp output is purple with a pink trace, maybe there is a harness building error?

If you are correct then I have done it wrong and this could explain the problem. But if you are correct tthen the Zeus instructions are misleading or just plain wrong.............. "This output acts like a switch between your load (light or fan) and the internal ground in the Smart Regulator. It can switch uo to 48V at 1 Amo."

Ive already connected the Zeus output1 to the old Adverc light which is functionally identical to the ignition light (same positive feed). This is not currently working and I can't work out why not, but thats a separate issue. There are software options as to what the light does but I've tried the two obvious choices.

Yes, the field positive supply to the Zeus is fused, and when its not running (transistor off) there is no live feed to the field. I am not sure how much current limiting the Zeus provides and if its transistors can survive a short but that doesn't really matter as its fused. An N install with a fixed/permanent live feed to the rotor just puts more user added live wires inside the alternator and makes the field wire permanently live (via the rotor resistance) so now has no advantages at all over the P install. The regulator is suitably disabled, its just a case of cutting a couple of wires. The Adverc can of course run without an internal regulator (which is what I did) as sometimes the internal regulator voltage is greater than the Adverc low voltage. So I have done an Adverc style install with the Zeus using the diode trio to supply the field positive. This works fine as long as the duty cycle is not set too low. I now appreciate that Arco intend an N install to have a direct feed to the top brush and feel that a P install is just the better way to go.

I think you are correct that Arco intend the N system to have a live feed added to the top brush, this will explain why they suggest putting a fuse in the field wire, I have been puzzling over that. However unless some physical layout of the alternator internals makes a P install difficult I can see no advantage at all in an N install with a live feed to the rotor, and the P arrangement becomes the obvious way to go.

In N mode the Zeus takes the field wire from the bottom brush and "connects" it to ground via its internal (lower) transistor, it has no means to supply current to the top brush so this must come from the diode trio or ignition light? In P mode the Zeus uses its (top) transistor to supply the top brush, with the bottom brush grounded and so the Zeus has full control over the current????? Ahh I see what you are saying....in an N install, and unlike the Adverc, I should connect the top brush directly to the main supply, in effect joining B+ to D. I don't like that idea but not sure why not, I think going for a P scheme is better.

I'm pretty sure that I'm right, and setting the duty cycle limit back to 100% sorts it out. Its all down to doing a N install while the Zeus (and Wakespeed), are really aimed at P installs. The Zeus has a lamp output (which is not working yet but thats another issue) but I have connected that to a separate indicator lamp which was previously used by the Adverc. I left the old ignition lamp connected to the D terminal hoping that it would still work, and it does, but the start up delay and ramp makes it a bit useless. With an N install the Zeus has no access to the positive brush, only the negative, so it can't supply any current itself, it can only control the current flow between negative brush and ground. With a P install the Zeus does supply the current (via a positive field wire) and it now looks like this is another reason to favour the P system. I want to be 100% certain of this before pointing it out to Arco, so any thoughts???? The Zeus works nicely (almost) with a W input and there is an option that the delay and ramp-up only start when speed is detected rather than detecting ignition. This will be good for those old vintage engines that take a lot of cranking. The linitation is that the speed resolution is only 50rpm which is not so good for slower revving engines. Don't get a Zeus if you have a Kelvin 😀. The alternator remains a 9 diode machine with N wiring, but becomes a 6 diode machine in P mode???????

I've just hit a very interesting problem with the Zeus. I have not installed the alternator thermistor yet so have set the maximum field duty cycle to 55% to limit the current and temperature. Performance is random with often no charge at all from the alternator. I thought I had a bad connection but its more fundamental.... I have stuck with an N type alternator install. This has the advantage that the ignition light still works (I thought) but this is negated by using a switch-on delay and ramp up. (Note the Zeus has a "require tacho" option so the delay does not start till the engine starts which is rather nice.) What I believe is happening is that with initial excitation coming via the ignition light and with a limited duty cycle there is just not enough current to start up the alternator 😀. Tomorows first job is to get back into the alternator and convert to a P type system,