nicknorman

February 7

Hello Tony. You are not very subtle!

February 4

8 minutes ago, Mark R said:

I'm assuming the quality might not be al that great on the one I linked to, it was more used as an example. Would I be right in thinking the 'heat' position on ignition of the purpose built narrowboat panels is for glow plug heaters?

Yes the heat position is for the glow plug heaters. Not all engines with glow plug heaters have a separate heat position though - eg some Listers have a timed relay such that the glow plugs come on automatically when the ignition is turned on, and go off when the timed relay opens, thus making it "transparent" to the user.

On your first comment just be aware that if you do go for a generic panel, you need to be confident that the gauges match with the senders on the engine, either because they are directly compatible, or because the gauges are configurable.

February 4

Instrument panel gauges are not really specific to the engine they are attached to but they are specific to the senders that are attached to the engine for the oil pressure and coolant temperature. That said, the description does imply that this panel can be configured to suit a variety of senders. Ditto the tacho would have to be adjusted to match the pulley ratio and number of pole pairs on the alternator.

So it would probably work, but it is hard to know the quality and robustness of the panel without seeing it in the flesh. And what about glow plug heaters, there doesn’t seem to be provision for that?

February 4

I think it’s a case of the excessive side force wearing the bearing which allows a bit of play which wears the seal. Not really a reversible process.

February 2

34 minutes ago, MtB said:

Curious. I've never heard of a "lithium polymer" battery.

I'm off for a Goggle!

Ok back now. Looks like they are a new(ish) type of mobile phone battery:

"Lithium-polymer technology again uses a positive and negative electrode but with a dry solid, porous chemical, or gel-like electrolyte, rather than a liquid. As a result, polymer batteries can offer a lower profile, flexible, and more robust designs. They also have a lower chance of leaking electrolytes resulting in thermal runaway. In a nutshell, they’re a fair bit safer. However, they aren’t completely immune from issues arising from being punctured, stressed, or overheated."

https://www.androidauthority.com/lithium-ion-vs-lithium-polymer-whats-the-difference-27608/

They've been around for quite a long time. Often referred to as LiPo. Used in most or all mobile phones, model flying things etc. Fairly unstable compared to LiFePO4 but not as bad as the cobalt ones.

February 1

Yes for long term ie weeks, months etc it is better to use a voltage of around 13.2v which keeps the batteries nearly fully charged but minimises “positive plate corrosion” which can shorten the life of a battery left on charge for long periods. In your case, float at 13.8 would be a better option since you are only there for a few days.

February 1

As I explained, the propensity to slip is related to the load on the alternator which is related to the size and state of charge of the battery. So it seems that the pulley that was slipping badly, is now spinning ok despite being worn and polished, as the load is minimal. The one that was previously not loaded and hence not polished and worn from extensive slipping, is for the time being working better. Did you tighten the belt at the same time? Anyway, I would get a new belt and stay on top of keeping it correctly tensioned. Clean off the black dust. If it recurs this indicates the belt is slipping.

February 1

10 hours ago, MtB said:

Even with the raging belt-slip evidenced by insufficient belt wrap and black dust plastered all over everything?

No. My point was that the reported voltage was too low to be explained away by a fully functional alternator being pulled down by low batteries.
The reported voltage indicates something is wrong. Quite possibly belt slip.

January 31

From your description I’d say slightly over tightened. Twisting 90 degrees is a fair way to assess but only using moderate force. If you say “I can just twist it 90 degrees using maximum force” then that is too much. Put it another way, it needs to be just tight enough to avoid slippage, but not more. So back it off until it just squeals under max load at low rpm, then tighten slightly. Then note how much force is required to twist 90 degrees for future reference.

January 31

23 minutes ago, BEngo said:

If the AGM batteries are at 12.2 Volts after standing for an hour with nothing switched on then they are roughly half discharged. Even knackered half-discharged batteries will hold the voltage of the alternator down below its regulated voltage, so it is quite possible that your alternator is not duff.

N

I disagree. OP reported 12.8v which is too low for a reasonable size of alternator. Yes of course low batteries will reduce the alternator voltage, but not by anything like that much. Mid to high 13s would be reasonable.

January 31

The other option would be to restore the Travelpower and use it to run a battery charger.

January 31

2 minutes ago, Roberto Conigliaro said:

Hi, yes correct - the 2 alternator (starter and leisure) are run by one belt, the other belt is part of a third alternator which doesn't have any purpose anymore as it was giving to a travel pack not in use anymore.

Yes also correct, the belt of the 2 alternators seems quite loose - I guess it's worth tightening it? or just replacing it? It is still an option that this might simply be the problem right?

Yes it could just be a loose belt. You can try tightening but it may be worn. V belts are designed to contact the V shaped sides of the pulleys. If the belt or the pulleys get too worn, the bottom of the Vbelt can contact the bottom of the pulley and so there is no force on the V sides (which have a much better contact area). So even if you tighten it correctly, it can still slip. Have a close look at the bottom of the V on the pulley - if it is shiny, this indicates the belt has been bottoming out on it due to being too worn. New belt required.

This design of alternator drive with 2 alternators on 1 belt (and a water pump) is not a great design as the “wrap” (% of the pulley in contact with the belt) isn’t great and it can be a bit marginal at the best of times even with belt and pulley in good condition.

January 31

It would be an interesting test and shouldn’t cause a problem, but don’t disconnect anything with the engine running.

But see my post about belt slip, it could just cause the other alternator to slip on the worn belt when it is loaded up by the flat domestic batteries. Only one way to find out!

Edit: actually I’m not clear what you would be swapping. Are you going to end up swapping which alternator feeds which battery by this swap? Or just swapping the alternator and battery combination between domestic and leisure supplies? If the former, good test. If the latter, not sure what it would achieve.

January 31

I’m a bit confused about your setup as the photos aren’t great. I think there are 2 alternators run by one V belt? Is one for the leisure batteries and one for the engine battery? And there is a polyvee belt in the picture, what is that for?

Anyway, I would say that the leisure alternator is most likely knackered BUT as was mentioned, there is a lot of black dust which is indicative of belt slip. Can you rotate the leisure battery alternator pulley without the engine turning? If so it is slipping too much and probably the belt is worn to the point it’s not gripping due to being bottomed out in the pulley.

It is worth bearing in mind that the propensity for the belt to slip depends on the electrical load on the alternator. Starting the engine uses probably less than 1 amp hour which is rapidly replaced and hence the load and propensity to slip on the engine alternator is minimal. By contrast low leisure batteries can take the full output of the alternator, maximum electrical and hence maximum mechanical load and hence could just be permanently slipping.

January 31

No that isn’t suitable for measuring any significant current, and you have to disconnect wires and insert the probes in series. A good way to blow the meter, or at least its fuse! The clamp meter MtB mentioned is the easiest way to measure current from alternators etc, you just clip it over the wire and hey presto! Or you can still get the slightly cheaper Uni-t ut203.

As I routinely say on here, electricity is invisible and so without adequate test equipment, we and you are just guessing. Lots of time is spent on guessing and false actions, when the solution is a £40 meter! Does not compute!

January 31

BMF I think - British Marine Federation

January 30

32 minutes ago, Tacet said:

To remake the immersion heater joint, it needs to be removed from its boss. The boss remains joined to the cylinder

It's unusual for this joint to start leaking if it has been dry for a good while. If it looks to have started to leak only recently, I suggest a careful examination to make quite sure where the trouble lies before fiddling further.

However that is exactly what happened to our boat after 10 years. I thought the calorifier had split, but I finally traced it to the immersion threads. I replaced the fibre washer, but it still leaked. I then applied PTFE tape to the threads. This fixed the problem.
However it’s worth bearing in mind that the seal is/should be the fibre washer. The PTFE tape helped primarily because it lubricated the threads and allowed me to tighten the immersion more - well, it went further round for the same force, crushing the fibre washer more. It felt quite different with the tape on the threads, a nice sliding of metal on metal gradually getting tighter, rather than jerky catching unlubricated metal on metal.

January 30

34 minutes ago, IanD said:

I wondered if anyone would get that joke... 😉

We were trying to ignore it.

January 30

Calorifier can of course be heated by 3 sources (at least), the engine - which is "free", an electric immersion heater (if you have shore power or a genny) or by whatever you use for central heating (diesel, gas or solid fuel stove). Instant gas water heater is a solution that doesn't require any electricity or engine running or diesel, and you only heat what you need, but the downside is a fairly slow flow rate making winter showers a bit miserable.

January 29

19 minutes ago, Mark R said:

@magnetman The fan moves freely by hand, I can see the fan blades are turning when the engine is running, I could measure the rpm using a tachometer to get an idea of numbers, but it definitely is spinning around.

@nicknorman I did try to measure the heat in the alternator with the engine cold, didn't notice a change but maybe I didn't do it for long enough! I'll try a clamp meter on the positive cable between the battery and alternator, I'm assuming that if functioning correctly that I'd be measuring in excess of 35 amps (dependant on alternator output)?

Is there a RPM that I need to get the engine running at to ensure that the alternator kicks in?

A few months ago I was travelling the Aire and Calder at a 'good speed' for a fair number of hours, had to jump the engine before the journey and next time I turned it over again, so it's not through lack of motoring!

When you say “the fan moves freely by hand” do you mean with the belt taken off, or as it is now? You should not be able to move the fan if the belt is on, otherwise it is far too loose. Just because you can see the fan rotating doesn’t mean the belt isn’t slipping madly and the fan turning at 1/4 speed.

January 29

20 minutes ago, Mark R said:

Thanks for all your input. Just to add to my original post (and possibly answer some questions raised), the boat did a journey of around 2 and a half hours a week or so ago, it was certainly revved during this journey. I went to the boat today and checked two things, firstly I started the engine, let it run for a good 5 minutes with some revs for good measure. I then isolated the battery and measured voltage across the negative terminal on the battery and the positive of the alternator and got nothing. I also tried leaving the isolator off with the engine not running. I didn't detect any heat in the alternator but did notice a reduction in voltage across the battery terminals afterwards.

I'm at the boat again tomorrow, is it worth me giving it one more go with even more revs for longer?

Mark

I wasn’t quite clear from the above whether the engine was completely cold when you turned on the isolator and checked for alternator warming. The test would be to start off with a completely cold engine, since the alternator is only going to get slightly warm from back flowing current. If it is already warm, you probably aren’t going to notice the difference.

As usual we are up against the fact that electricity is invisible! Without proper test /measuring equipment it is very difficult to now what is going on. And yet adequate test equipment is so cheap! I would recommend getting a multimeter that includes a DC current clamp-meter (be careful, lots only do ac current). The Uni-t UT203 is the old favourite from ebay, used to be £30, now seems to be £40 (that’s inflation for you!) eg https://www.ebay.co.uk/itm/334520176779

You can clip the meter around a cable, eg the battery to alternator cable, and see if there is any current flowing. Or clip it on elsewhere in the hunt for where the current is going. Takes seconds! It is not super accurate as it works on magnetic field, you need 1/2 amp or so at least. But in the context of boat electrics, it is very useful.

January 29

2 hours ago, magnetman said:

A question for you Nick as you seem 'up' on electronics.

I know a little bit but not a lot.

What I am intrigued about is the potential high current degradation of FETS.

IF the alternator was providing a high charge rate lets say 1C to the lithium battery then the BMS suddenly switches off could this cause degradation of the FETs?

What I am getting at is the BMS has originally been engineered as a rarely used backup for cell protection rather than an 'on/off' switch.

If the original design had been intending to regularly cut off a high current would the specification of the FETs be the same?

Heating and cooling (thermal management) of FETs is a significant issue when large currents are being switched.

The devil is in the detail. At a high current, provided the gate drive voltage is adequate, there is fairly low power dissipation. Obviously you would choose MOSFETS that have sufficiently low Rds(on) (on resistance) to keep power dissipation to a safe limit at max rated current - and taking regard for the relevant temperature range.

When the MOSFET is off, there is no significant current and thus no power dissipation.

Bearing in mind power = V*I, you can see that when on we have lots of I but no (very little) V, and when off we have lots of V but no I.

But half on we have quite a lot of V and I and thus a very large power dissipation. So it is important to drive the MOSFET hard and fast to pass through this "partially on" phase as quickly as possible. Bearing in mind the actual semiconductor junction is very small and its thermal capacity is very low.

Then we have the possibility of avalanche breakdown, which occurs when Vds is too high. No problem you say, we are using MOSFETS rated at 25v and the system voltage is never more than 14.6v. Except that we have to take into account inductance. Even a wire leading from a cell to the BMS board has some inductance, and the wires leading from the alternator to the battery, a lot more. The property of inductance is to resist rates of change of current, by creating an opposing voltage. V = LdI/dt. So with a fast dI/dt, which you need to avoid the power dissipation problem, you can generate a momentary transient voltage that exceeds the MOSFET rating. By "momentary" we are talking a few microseconds.

"But I have a LA battery in parallel" you say. Yes, but again we have inductance in the wires and the battery will take more than a few microseconds to absorb the transient as a result.

Well you did ask!

So to answer your question, if the system is properly designed the MOSFETs won't be degraded by high current switching. If it is not properly designed, each time the MOSFETs switch off there could be a transient that takes the MOSFET into avalanche just for a few microseconds. And each excursion into avalanche takes a little bit of life away.

January 29

1 hour ago, robtheplod said:

Hi All

Prior to our move to Droitwich I'm researching the locks in the Severn. When we came up Diglis lock when we did the Avon Ring i encountered exactly the same issue David does in the video below and wondered is there a correct procedure for these big locks that avoids the embarrassing pull over to the other side?

I'm not quite sure exactly what you mean by "pull over the other side" - in the vid he just seems to struggle to come alongside on the intended side. This is caused by hitting reverse too hard - water is pushed forwards and pushes the boat away from the wall. Come in more in the centre of the lock and turn towards the wall, swing the back in just before it hits at the front, and hit reverse when you have momentum carrying you towards the side. If you come in slowly, you need less reverse and the effect is less.

He was going downhill, if you were going uphill and had problems with the "pull over to the other side" when the lock is filling, it is because you started out on the wrong side! Normally the Severn lock keeps tell you which side to go if there is just the one boat, such that the water flow from the paddles keeps you on that side. Mind you, with the advent of volockies, maybe that is no longer SOP.

January 29

1 hour ago, magnetman said:

Interesting read.

Are the BMS circuits designed to be used as on/orf switches? I don't know, presumably they are but its possible they are only meant for unexpected outcomes rather than being used routinely.

He doesn't say what happens if the BMS over voltage disconnect fails to operate.

Website needs proof reading.

Also the website pages need sorting out. Calling it 'blank page' is a bit naff.

The BMS switches are not mechanical, they are MOSFETs (transistors if you like) so there is no concept of mechanically wearing out. More ageing will occur from high charge and discharge currents than from switching on and off.

34 minutes ago, MtB said:

This post perfectly illustrates the schism that exists between old skool dinosaur engineers on here who see the switches in the BMS (any BMS) as a last ditch backstop and the vast numbers of real world users out there who say the BMS (the JBD specifically) is ultra-reliable and use it on a daily basis for charge control with no problems arising.

I think it is partly if not wholly due the the plummeting price of LFP batteries. Back in the day when LFP batteries cost multiple £ks and BMS designs were not so reliable, it made sense to have separate cell charge control and charge protection devices. But now LFP batts cost hardly any more than decent LAs, the occasional loss of a cheap LFP bank is no longer the big deal it used to be. Hence the willingness to rely on the JBD device to control charge, along with a carefully selected length of thin(ish) wire to cut down alternator current and an LA in parallel to protect the alt when the JBD disconnects.

Not dinosaurs IMO, just cautious based on decades of engineering experience that says a single point of failure shouldn't cause a catastrophe.

That said, it is interesting that they mention the BMS is configured to be used as a hybrid system. I think traditionally, battery manufacturers have set the BMS limits on charge and discharge to be the absolute limit, in order to maximise the claimed capacity. The "dinosaurs" were concerned that taking the cells routinely up to the limit for "just not quite doing serious damage" was a bad thing.

But of course there is nothing to stop a manufacturer from moving the BMS settings to more conservative values and thus one doesn't routinely approach and only just dodge the "death to Lithiums" conditions. This is what these folk have done, and same applies to Fogstar who have set fairly conservative limits in their BMS.

Downside of that is if you want to use the battery in a "proper" system whereby charging is properly controlled and the BMS shutoff is considered the last resort protection - instead of the charging system controlling the charging, the battery BMS might decide to jump in first and thus the concept of "last resort protection" is nullified.

The other thing to mention about the website is no mention of alternator overheating. I guess that doesn't concern them too much because their battery won't be damaged, but it is interesting they have not mentioned the slightly dodgy tactic of the "long wire".

January 28

It is inadvisable to run the engine and then disconnect the battery. Alternator damage may ensue.

from your description it does sound as though the alternator is faulty. The voltage should rise to around 14v straight away, assuming you rev the engine a bit.
If the alternator warning light is on, this means something is wrong and it is not charging. Probably a diode issue.

If your battery is going flat with the isolator in the on position, but not in the off position, one explanation could be failed diodes in the alternator that allow the battery to discharge back into the alternator. You can check for this by turning on the isolator, not starting the engine, and then after 15 mins or so feel the alternator. If it has become slightly warm to the touch, it definitely points to failed diodes.

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