nicknorman
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Posts posted by nicknorman
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1 hour ago, hoopdriver said:
Thank you for that very enlightening explanation. I really appreciate your taking the time and effort to write it all out like that, I found it very useful. I have noticed that I have to rev the engine up quite a lot - far more than ever before to get the alternator light going on the BMS. It needs to get to 1600 - no less - before the light comes on. I never needed to rev the engine nearly that high before to start the charging.
As you say, once that light does come on, I can drop the devs down to idle and the charging, such as it us, continues. But I really have to rev it up quite high to initiate charging.
Ah one other general point I meant to make: although charging will happen at idle, it is not a good way to charge the batteries either for the engine, for the drive belt, or for the alternator. It is better to run the engine at a faster speed, say 1000 to 1200 rpm because:
There is less tension on the belt and less side force on the engine pulley / crankshaft
The engine is happier when there is load, to run a bit faster than idle (in the same way that it is kinder to change down a gear in a car going uphill, rather than having the engine labouring slowly in a higher gear)
If the alternator is spinning faster, its fan is spinning faster and thus the cooling air is moving faster and thus the alternator runs cooler.
Probably the maximum alternator output is not achieved at idle anyway, even with a good alternator you would get more charge current if you run the engine above idle. You could try increasing the rpm slowly and gradually, noting the charge current on the BMS App, and stop increasing the rpm shortly after the current reaches a maximum %.
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12 minutes ago, hoopdriver said:
Thank you for that very enlightening explanation. I really appreciate your taking the time and effort to write it all out like that, I found it very useful. I have noticed that I have to rev the engine up quite a lot - far more than ever before to get the alternator light going on the BMS. It needs to get to 1600 - no less - before the light comes on. I never needed to rev the engine nearly that high before to start the charging.
As you say, once that light does come on, I can drop the devs down to idle and the charging, such as it us, continues. But I really have to rev it up quite high to initiate charging.
I would say this is as close to categoric proof as one can get, that the alternator is defective.
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1 hour ago, hoopdriver said:
I have turned the engine on to try to give the batteries a little charge. This time I kept a sharp eye on the alternator starter voltage. It was 1.27v when I turned the key to the heater position. It remained at 1.27v when I turned the engine on and it was at idle. When I increased the revs (in neutral) it rose to 1.40v up to 1600 revs when it went to 13.6
when I brought the throttle back down it remained at 13.6 increasing slowly to 13.69v at 46% charge
Battery voltage went to its usual 13.34v and remained there. All cells balanced - at 3.33,
This is not too inexplicable. First a bit of theory for bedtime reading ...
Alternators work by having a spinning magnetic field (the rotor) adjacent to some stationary windings (coils of wire) called the stator, and this induces ac current in these windings. The spinning magnetic field is an electromagnet, ie current has to flow through the windings to create the magnetic field.
The type of alternator you have is a "nine diode machine", there being 6 diodes that rectify the ac from the stator windings and convert to dc to output to the battery. The other 3 (smaller) diodes, often called "field diodes", rectify a small portion of the generated ac which is used to power the field windings that are on the rotor (the bit that goes round!). These generate a rotating magnetic field which induces the ac current into the stator windings. The regulator adjusts the current in the rotor windings to control the alternator output.
So in summary the alternator works by spinning windings containing self generated current that produces a magnetic field, near the stator windings, and this causes power to be generated in the stator windings, some of which is used to power the spinning rotor windings. You can see the chicken and egg situation - when the alternator first starts, there is no current in the stator windings, so no current in the rotor windings, so no current in the stator windings etc etc. It is never going to work!
To get around that problem, when you put the ignition on it connects battery power to the alternator warning light and the other end of that warning light is connected to the alternator to feed a small amount of current into the rotor (field) windings to get things going. Once the rotor is spinning fast enough, enough power is generated in the stator to fully power the rotor and off it goes happily generating power without any external input.
So in other words, if you gradually increase the alternator rpm, at first nothing much happens, then suddenly there is enough power to increase the rotor current and this increases the stator current which increases the rotor current etc etc - the thing is now "self sustaining" and no external current is needed. rpm could be reduced and the alternator is still working.Normally the speed at which this happens would be, with a modern engine and alternator, below idle speed. So once the engine is started and at idle, the alternator will be working. However if there are blown diodes or other problems (melted wiring in the windings etc) then the efficiency of the alternator is much worse and thus it will take a lot more rpm to get the alternator to self-sustain. But once this is happening, the rpm can be reduced and still there is enough current being generated to self sustain. In other words, the rpm necessary for the alternator to cut in is much higher than that needed to sustain it. So again, the high revs needed to get the alternator going points to a damaged alternator.
In your case, once you had revved the engine, the system is charging at around 40A but since you have no means to monitor battery state of charge, and since the voltage of a lithium battery remains very static during much of the mid-charging period, it looks as though nothing is happening. But it is, albeit slowly, Bear in mind that at 40A it will take 8 hrs or so to charge the battery. Only in the latter part of that will the voltage gradually rise. And of course if you are using power on the boat, it will take longer than 8 hours.
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4 minutes ago, hoopdriver said:
It’s back to 13.4v now
Weird, but I suspect it's a red herring.
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Just now, hoopdriver said:
The engine was not cranking. Just the shrill beep
OK well I think that demonstrates that the domestic and starter alternators are not connected in parallel. So there must just be some leakage current from somewhere that is raising the voltage on the alternator input to the BMS.
I can't think of a scenario to explain it since the domestic alternator should be completely isolated from the starter engine system, save for a relay feeding the domestic alternator with power when the ignition is on. And if anything that would result in an increase in voltage on the alternator BMS terminal, not a reduction. It is odd, but probably inconsequential to the problem at hand.
Is the 1.27v just with the ignition on, or just with the heaters on, or both? And does it go back to the 13.5v or whatever, when you turn the ignition off?
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do you mean 1.27v or 12.7v? Screenshot?
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39 minutes ago, hoopdriver said:
This just gets weirder …
I’ve just looked at the app and in the BMS it us showing 13.44v from alternator starter current - and this more than three hours since I shut off the engine
It does fit with a starter battery being in circuit. A fully charged lead acid battey will hold well above the nominal fully charged lead acid voltage of 12.7v for a long time if there is zero load. So 13.44v is not too surprising as the starter battery voltage.
You could try one thing to prove the point. Does the engine have a separate heater position on the ignition switch? If so, turn on the ignition and operate the heaters for about 10 seconds but don't start the engine. Then, with the ignition still on but the engine not started, have another look at the voltage on the BMS app. If we are seeing the starter battery voltage on the BMS alternator input, then draining some juice by using the heaters should make the voltage reduce to around 12.7v
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10 minutes ago, hoopdriver said:
No, it’s a new build. A year old - I moved in last year at this time.
The same electrician did the entire installation
Then I don't understand where the 13.5v is coming from!
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Is this a new built boat, or a second hand one that originally had lead acid batteries and you then had modified for the lithium system?
If the latter, it is conceivable that previous owner decided to connect the starter and domestic alternators together, either directly or via some sort of relay, to increase the maximum charging current. And when your Lithium installer came along, he wasn't aware of that and didn't realise they were already connected together. I am just hypothesising of course!
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20 minutes ago, Tony Brooks said:
Remember, take more notice of Nick and Peter F than me. They are probably far more conversant with that BMS and how it works than I am.
Nevertheless you had a valid point. It was something I had thought about earlier, if you remember the original problem was that the green "allow alternator charging" LED on the BMS was not illuminated when it should have been, due to a fault in the BMS which was then replaced, and now the green "allow alternator charging" LED is on, but the alternator is only producing limited power. Both the BMS failure and the alternator problem occurred at the same time, which suggests they are linked. Once scenario is that a fault in the BMS caused a sudden interruption of alternator current which generated a transient which blew diodes. The only contrary indication to that is the presence of 13.5v on the alternator input terminal of the BMS, a voltage higher than the Li battery. And thus I can't see how that could come from anything other than a lead acid battery (the starter battery) being in parallel with the alternator. Alternators, since that would suggest both alternators were paralelled.
What Mr hoopdriver could do is to get his mate to check the voltage on the starter battery, the starter alternator main positive terminal, and the domestic alternator main positive terminal - with the engine switched off. If they are all exactly the same voltage (to within 0.1v) it tells us that the alternators and starter battery are all paralelled. Which would not be a bad way to install the system, it's just not the way we were expecting.
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19 minutes ago, Tony Brooks said:
... until the Li charge is cut off by the batteries BMS, a separate BMS, or a big manual switch I would have expected the low resistance of the Lis to keep both alternator voltage below the value at which the regulator started working so both should have delivered maximum charge. I wonder if a single B2B was limiting the charging current. This is just musing on my part, you found what you found and it seemed to work, practice must beat theory here.
His alternators are not directly connected to the Li battery. He has a lead acid "buffer" battery and then B2Bs to push the current into the Li battery. The rating of the B2Bs is such that the alternators never work more than around 60% of max output, to avoid overheating.
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Anyway all this chit chat is speculation! What we need is a categoric check and (almost certainly) repair of the domestic alternator. The rest is of less consequence other than perhaps the much smaller starter alternator is doing all the work at present and may thus have a short life if the domestic alternator isn't repaired pronto!
2 minutes ago, Tony Brooks said:For clarity, how many alternators? If it is two then perhaps the start alternator is charging it's own LA battery, while the domestic alternator feeds he Victron BMS, but if so that is not what the diagram shows, I would expect another LA battery.
There are 2 alternators.
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Just now, Tony Brooks said:
but the diagram sows the start LA battery directly connected to the alternator, so current could flow from the start battery through the alternator. I think we need a diagram for the system as installed.
But don't forget that diagram is for a vehicle with a single alternator.
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Just now, hoopdriver said:
He definitely meant the lithium battery.
I may not be tech savvy but even I wondered how you could flow “uphill”
There has got to be a connection to a lead acid battery in there, even if the installer doesn't realise it! If there isn't a domestic lead acid battery, it must be the starter battery.
Just now, hoopdriver said:It’s connected to the BMS
Yes, hence I said "directly". And as you said, current doesn't flow up hill so it can't be the Lithium battery that is holding the alternator terminal voltage up.
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4 minutes ago, Tony Brooks said:
Through a shorting diode(s), quite possibly. The alternator should also be warm to the touch
But only if the alternator is connected directly to a battery, which we are told it isn't.
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8 minutes ago, hoopdriver said:
Thank you! Im remembering now that when the guy checked the alternator he checked the connection at the BMS (I might not be phrasing that correctly) and was puzzled about why there would be current there with the engine off.
I mentioned this to the guy who installed it and he said it would be current coming from the battery. Could that be right?
"The battery" - but which battery! In your screenshot of the BMS after engine shut down, you can see that the alternator voltage is slightly higher than the Lithium battery voltage. It might be concievable to put that voltage down to back-leakage from the lithium battery if the voltage on the alternator terminal was slightly lower, but not feasible since the voltage on the alternator terminal is slightly higher. Current always flows "down hill" ie from higher to lower voltage.
A lead acid battery, just having been taken off charge, will have a voltage of around 13.5v. Seems an unlikely coincidence!
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3 minutes ago, hoopdriver said:
Thanks. When I started the engine this morning the BMS reading was 13.22 and then it rose to that 13.67
I don’t think my guy rounded up to 14 - I think he saw 14. This wasn’t the installer but another boater - an engineer with 16 years living in boats - with a multimeter
OK but we don't know that. It seems a bit unlikely that it was exactly 14.0v. Not impossible though. You could ask him.
In any case, what is relevant is the voltage today, which is 13.67v and that is too low at 40% load to be a healthy alternator.
Just going back to the lead acid thing, I notice that with the engine switched off, the voltage on the alternator input terminal ("Alternator/Starter voltage" on the BMS display) is 13.5v in your screenshot. This strongly suggests to me that the BMS is not simply connected to the domestic alternator - if it were then with the engine off, this voltage would be zero. There is something holding the voltage up and I can't think of anything other than a lead acid battery just off charge.
So there are a couple of possibilities:
1) There is in fact still a small domestic lead acid battery in parallel with the domestic alternator, or
2) The BMS alternator input is wired to both the domestic and the engine alternators, and with the engine alternator comes the starter battery in parallel.
If it is 2) then what could be happening at the moment is that the domestic alternator is completely dead and all the charge current is coming from the starter alternator - it is running flat out and thus getting very hot.
Once the engine is cold again, it would be interesting to start the engine, run for 5 minutes, shut it down and then check (very cautiously, don't burn yourself!) the temperature of the starter alternator casing. If it is very hot, that would point to the wiring being as per 2).
Really, your installation chappie should have presented you with a wiring diagram of what he has done, even just a pencil sketch. You could ask him for it!
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9 minutes ago, hoopdriver said:
Sorry if this is a dumb question but would an alternator with a blown diode still produce 14v? When the guy tested the alternator he said it was producing “a healthy 14v” Coukd it be doing that and still gave one or two blown diodes? I want to be armed with as much knowledge as possible when I confront the installer
The devil is in the detail of the voltage. 14v suggests a rough measurement, whereas 14.0v would be more precise. 14v could mean 13.6v rounded up, or 14.4v rounded down. There is a massive difference between 13.6v and 14.4v in this context. What we do have to go on is the BMS reading which showed 13.67v with the engine running. That could be (inadvisedly) interpreted as 14v. But 13.6v at 40% output is not healthy for an alternator.
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I think it’s pretty unlikely that the RCR guy damaged the alternator, much more likely that he dislodged a wire. So hopefully it will be a cheap fix.
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I say again "Lancashire Rotating Electrics", in case it is lost in the many posts!
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3 minutes ago, hoopdriver said:
This really rings true. I know you’re an expert so affirmation from me is meaningless, but I am grateful.
when I fire up the engine the initial charge reading is usually 68-71% then drops over the next 10 to 15 minutes to 36-40% and there is stays. Likewise the voltage on the batter never rises above 13.34v
One thing to be aware of with Lithium, there is much less difference between "on charge" and "off charge" voltage - ie the voltage doesn't initially rise much when being charged, compared to lead acid. This is why you should get a SmartShunt installed once this immediate problem is fixed, things will be much clearer and you will know how much battery juice you have left and be able to watch the SoC rising when charging.
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I've been thinking about the alternator again, the existing alternator, assuming it is actually the problem, is repairable. So one possibility is to take it to Lancashire Rotating Electrics in Leyland - not a million miles from the L&L - and get them to test and or repair it. That company is nationally renowned amongst boaters for being very good, competent and helpful and you just happen to be close - lucky! They could probably source you a replacement at a fraction of the price of a new one from Vetus too.
You can either source a replacement alternator first, or check into a marina etc for a few days to use shore power whilst they check and repair it. I suppose you will need someone to remove and re-install it though. Watch what they do, so next time you can DIY!
2 minutes ago, Tony Brooks said:Oh boy, I do hope the installer did not wire as per that diagram. If they did, then expect the hull to go porous over time. Boats should NEVER be wired earth (chassis) return as shown.
Please make sure the boat is wired insulated return. That is only one negative connection to the boat hull, with that being linked to the engine bock acceptable.
It's an example of a van install.
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2 minutes ago, Tony Brooks said:
I agree, but 40% of what? I would prefer to see it in amps. I suppose one could guess at 40% of the 90 amps the fuse set the Victorn kit to, so 36 amps, and that seems remarkably close to 1/3 of 90 amps. As it is a three-phase alternator, this seems to reinforce the possibility of one phase not working - a blown diode.
Yes it does seem odd displaying it as a % - and yes it will be a % of the preset max current, 90A in this case. But I suppose equally, to a non-technical person, % is quite meaningful whereas amps probably isn't!
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Thanks for the display pictures, they are helpful. They show that with the engine running, the battery voltage is slightly raised and some charging is happening, albeit rather slowly. Again this suggests to me that an alternator diode (or two) has blown and the alternator is still working a bit, but well below par. This is entirely consistent with the way the system has been set up -> alternator overheated and after lengthy exposure to excessive temperature, it has become damaged.
Another mildly interesting poing is that with the engine shut down, the "alternator/starter voltage" is showing 13.5v, which implies to me that there is a lead acid battery connected directly to the alternator. We don't know how the system is wired up but perhaps it is not as straightforward as the leisure alternator simply being connected to the BMS input. Perhaps you could ask your installer how the alternator is connected and if there is another lead acid battery in parallel?
Finally having read the manuals I see that neither the BMS nor the battery have a State of Charge (SoC) display. This seems a major omission in the system design - it would be like buying a car and finding out that there was no fuel gauge! With lead acid batteries, one can deduce the SoC by looking at the no-load voltage, but not so with lithium since the voltage of a lithium battery remains virtually constant over a wide range of SoC.
I think this is why you think nothing is happening when you run the engine for long periods. In fact the battery is charging slowly, but nothing on the display is changing because there is no SoC display.
In terms of "where to go from here", here is my suggested plan of action...
Someone needs to categorically say that the alternator is goosed, by testing it in situ. Really I think this should be your installation chap. Vetus stuff is renown for adding a zero to the end of the price, so I would get your electrican guy to source a replacement alternator not from Vetus. It will be much cheaper and just as good! Change the fuse to the 80A one and adjust the setting in the BMS, to prevent a recurrence of the alternator early death.
Get a Victron Smartshunt fitted, these are not particularly expensive, around £70. This will give you another display on your phone that shows the state of charge - ie how much "fuel" there is in the battery. IMO this should have been part of the original design.
Electric/Battery gremlins
in Boat Building & Maintenance
Posted
Do let us know the outcome when it is fixed.