nicknorman

In the case of the 3 bobbin regulator, the 3 bobbins are cut-out, voltage control and current limit. Setting aside the cut-out one which has the double winding, both the voltage control and the current limit operate by PWM-ing the voltage applied to the field windings, and hence modulating the field current. This adjusts the output current, so that the output current will be such as to maintain the regulated voltage across whatever the load is - unless the current becomes excessive in which case the voltage is allowed to droop. So in this particular case the field voltage is adjusted so as to adjust the field current so as to adjust the output current so as to maintain the desired output voltage (unless current limiting is invoked). But that is an electromechanical system. A linear electronic regulation system (series transistor etc) throttles current in order to get the desired output voltage at the present load. Less clear perhaps is a boost/buck converter such as is found in a B2B, where the input supply is PWMd to control the output current so as to give the desired output voltage. Both voltage and current are PWMd. But I would still say that it is the output current that is adjusted to maintain the desired voltage into whatever the load is. Hopefully that clears things up!

Wow you have a long memory! But I don’t remember that. It would be interesting to see the dialogue but I suspect it will be difficult to find. I suspect my comment would have been in a specific context, not a general comment.

Well to be entirely pedantic, an electronic device such as a B2B or pretty much any analogue regulator, controls voltage by controlling current. But its aim is to control the current so as to achieve a certain voltage, rather than to achieve a certain current.

The other option is Droylesden marina at Ashton top lock. We had a friendly reception there when we spent the night, and there are reasonably OK moorings just outside the marina too.

The alternator is designed to charge lead acid batteries long term, so no harm will be done especially since the domestic alternator only puts out 13.9v, which is on the low side to satisfy LA. If you wanted to be nice to the new owner you could replace the regulator in the domestic alternator with one that puts out the more standard 14.4v. Not an expensive thing to do and much cheaper than some A2B. But be assured that LA batteries are quite happy to be kept at 14.4v for many hours. They like it! They will end up not really taking any significant current. So are you selling up then? To become a land lubber, or to upgrade to a swankier boat?

It means that relays or contactors that, for at least part of the time, directly parallel different battery chemistries, should not be used. However a B2B does not fall into that category since there is no direct connection, so would be OK. MP’s diode slightly muddies the waters.

But you do say "I expect to replace the diode pack every few years". You are capable of doing that, many people aren't. So for most people that would be a replacement alternator every few years. And what about the BMS disconnect / alternator transient thing? Or do you have the (frowned upon by the establishment) lead acid battery in parallel?

There are a few ways of fudging it, the long wire and the B2B both need a LA battery to smooth the supply and/or absorb an Li battery switch-off induced transient. There is only one way to do it properly and that is to control the charging source properly such that it is compatible with Li. In other words fit an appropriate alternator controller such as the Wakespeed, Zeus or Mastervolt Alpha Pro. By the time you have bought a couple of B2Bs you have probably spent nearly as much as a decent regulator, and whilst the B2Bs are quite inefficient (turning a good bit of your precious charging current into waste heat), an alternator controller doesn’t waste any power and is simply the right way to charge Li batteries, and has added features such as avoiding overloading an idling engine. So when you say there is no off the shelf solution, this is incorrect as there are several.

I think the later Webastos are better at running at variable speed rather than just turning on and off.

Yes we find our Mikuni keeps the boat warm. But of course it does use electricity while it’s on, so you’re going to need a lot of battery juice if it’s on all the time, unless you are on shore power. If you go that way I would keep the squirrel for emergencies if the CH breaks down or it’s a particularly cold spell (or you run out of diesel).

I think that generally the actual discharge C limit is greater than the charge C limit, because cells can more easily be damaged by charging too fast than discharging too fast. But manufacturers probably find it easier to just stick with the one figure. And I would suspect that figure varies with temperature as well, beyond the usual "not below zeroC " thing.

I’m not familiar with this particular cooker but we have a gas oven on the boat with the burners underneath in the middle, rather than right at the back. Even though it’s a fan oven it does tend to heat from below and burns stuff on the bottom. So we put a baking tray on the lower shelf to protect stuff being cooked from the fierce heat. Stops getting a burnt bottom!

Does the flame size reduce as it gets up to temperature? If not maybe the thermostat isn't working.

Ah but all that used food slopping around in a big tank under the bed keeps one warm at night as it slowly ferments.

Again, this has never been a problem for us - never spilt anything more than a drip from the nozzle when removing it. Why would you have splash and splutter? As you said earlier, if the pumpout connector is on the gunnel it means the boat has to be facing the right way to get a pumpout, or you have to hang off the side whilst connecting it and operating the lever.

It seems to me that the OP is just a (badly formatted) list of all available Vetus parts trawled from their website.

We have cabin top pump out fitting. Within the fitting is an O ring, so the seal is always good. It’s never been a problem.

Grade B cells. There is only grade A and grade B.

I think there might be some confusion between being “in balance” for cells in series (very important) vs being “in balance” for batteries in parallel (of zero consequence). I think it’s likely that most of this SoC difference is to do with the BMS rather than an actual state, however it doesn’t matter. If you fully charge the batteries, by the time they are approaching fully charged they will in reality both be at more or less the same SoC (regardless of what the BMSs might say), and when the first battery is fully charged, the other battery will also be fully charged. Once the voltage is up around 14.2 or so, and the current has decreased to perhaps 5% of capacity, both batteries will fully charged. This is an important point - cells in series don’t “automatically balance” (the BMS has to engineer that state), whereas batteries in parallel do automatically balance where it matters ie approaching high or low SoC. I don’t think you should be too shy of fully charging from time to time. As the other “faction” mentions, plenty of people do this and it’s fine. Although ultimately it shortens the battery life, the life is still very long and there isn’t an alternative to occasional (every few weeks) fully charging, if you want to know the SoC (ie to synchronise the Ah counting battery monitor). I sometimes fully charge our batteries if eg I know we aren’t planning to move for a couple of days, it saves having to run the engine when moored, which I rather dislike. So I think the point is to try to avoid getting close to 100% (or 0%) as a matter of routine, but doing it occasionally when necessary is fine. What people struggle to get their heads around (due to decades of lead acid mindset) is that hitting 0% is not as bad as hitting 100%. But neither is in any way catastrophic.

Unfortunately with the new ones, the "Pause" expires after quite a short time, 3 minutes I think, so the days of arriving at a pumpout and finding it on pause with enough "free" time left, are over.

It doesn't really work like that. Best thing to do is to fully charge the Li, and then connect the BMV712 (Hopefully it is a 712, not a 702?) and set it to 100%. Or fit it, and sometime later fully charge the Li so that Li and the BMV will be at 100%

Someone with lead acid mentality drew that one! Green for fully charged, amber below 50% -shock horror, and red below 20% PANIC! In reality it should be green from 20 to 80, amber 80-90 and 20-10, and red below 10 and above 90. Or something like that!

However as I understand it, the ISO standard for installing Li batteries in small craft, requires the charging source to be controlled so it doesn’t try to charge a battery under inappropriate circumstances. It considers the BMS to be backup safety, as I do. Lots of unqualified people know better than the people who wrote the ISO, and good engineering design practices, but eventually they may come unstuck.

In series, but with a bypass that I could open if necessary. However it has never been necessary, including during hours of high rpm operation on the tidal Trent.

These plate heat exchangers do have a kw rating but it is misleading. Bear in mind that the rate of heat transfer is proportional to the temperature difference between the hot side and the cooler side. In a Combi boiler doing hot water, the incoming water is very cold, and the circulating boiler coolant is very hot (80c or so) thus there is a big temperature difference. Therefore a given size of heat exchanger transfers a lot of heat and thus has a high kw rating. Use the same heat exchanger for central heating where the circulating CH water is already quite hot, and there is much less temperature difference and hence much less heat transfer. So you need a heat exchanger with a nominal rating much greater than you might at first think. Put it another way, the bigger the heat exchanger the less difference there will be between the engine coolant and the radiators. Since the engine coolant on many engines including Betas is only around 75C, you want to drop as little temperature as possible across the heat exchanger, and therefore you want a big heat exchanger rated at what seems like far too much kw! The bottom line is that the bigger the heat exchanger, the hotter the radiators will be and since the maximum temperature is only about the same as you would get with a diesel boiler, the rads can’t really be too hot. Diminishing returns though, so no point in being absolutely huge but I’d suggest around 30 plates would be a good compromise. Incidentally, I would advise connecting the heat exchanger to the main flow to the skin tank (which is what I did). Lots of people do it to the calorifier circuit but IMO this is sub-optimal. If you have another heat source such as a diesel heater, you can use 2 low opening pressure one way valves / flap valves, so that hot water from one source doesn’t back-flow into the other source and waste the heat.