nicknorman

Fogstar BMS has a "balancing start voltage" which allows you to set the voltage at which balancing starts (as well as the delta v to start balancing). As we know, you don't want to set this too low as balance differences can reverse as the knee is climbed. But I think you could reasonably have it at 3.55v which means that you only have to go just over that for balancing to start. There is also a setting to say whether to only balance during charge, or to continue balancing after the charge voltage is reduced/removed. That is set to the latter by default. Also the BMS SoC estimation is not just a current integral and therefore doesn't have the slowly increasing without limit error that it otherwise might. It uses a table of cell voltage vs SoC, so the SoC estimation is a hybrid of that and the current integral. I think it is this table of voltages vs SoC that is not properly populated on delivery, hence why you need to cycle it a bit for it to "learn" the entries. You can manually set them as well if you like. I'm sure you won't have damaged them at 14.37v for many hours. One should bear in mind that Fogstar don't make cells, almost certainly haven't done any tests to support their opinion, and that the science is a bit vague, but I think that holding them at 14.37 for a long period - by which I mean weeks or months - is going to shorten the life. As is taking them up to 14.37 every day without any significant discharge in the meantime. But I don't really know, there is not much rigorous evidence out there other than opinion, but the opinion seems to be shared by the key players in the early adoption of Li, and there were examples of expensive Victron etc batteries wrecked by prolonged exposure to the maximum voltage.

If you want to get 100% SoC then yes, you need 14.6v. But if you go for 14.3 or 14.4v you still get 99.something% and personally I don't see the need to stress either yourself or the battery by ramming that last Ah in. If you charge at 14.3v, virtually nothing is lost and if the cells are out of balance, the balancing algorithm will still be invoked. I think there is slight confusion between balancing the cells within a battery, vs balancing two batteries in parallel. For the latter, the shape of the charge curve with its "knee" means that if both batteries are at 14.3v, they will be at the same SoC give or take a very small % (less than 1%). It might be that the internal SoC estimations are not identical, but that doesn't really matter as it is just the indication, not the reality. The BMS parameters can be adjusted so the SoC estimation resets to 100% at a voltage quite a bit below the maximum cell voltage of 3.65. I can't remember what mine (Fogstar) is set to but the BMS doesn't struggle to reset when the batteries are reasonably close to, but not at, the maximum allowable SoC. Setting a lower voltage just makes it take slightly longer to get to full due to the soft regulation of the charger, but the difference between 14.3 and 14.6v is negligable. If you go down to 13.8, then yes it would make quite a difference and would not be appropriate for charging with a generator or engine, if the aim is to minimise engine running time.

In my own boat, before we got the Li batteries, I installed a Mastershunt (blind Ah counting SoC meter) - shunt in the negative but also has a built in 500A megafuse in the positive. So I felt smug about that -well until we installed Li and now probably the fuse's max interruptable current is exceeded! So I am inclined to agree with you but on the other hand, how many serious issues have there been as a result of an alternator cable shorting the battery out? As I said, you have to look at the risk which is consequences x probability.

Convention says no. I agree that there is a danger from short circuiting the battery via thick cable and 1000s of amps, but in reality such cables are short and routed carefully. For example take a look at the standard wiring for the ubiquitous Beta 43 - there is no fuse between alternator and battery, just the battery isolator switch which can be turned off when working on the engine to prevent that pesky spanner short. Changing to Lithium presents an even more alarming scenario in terms of fault current, but also brings in the consideration that putting any old fuse in the wiring is probably pointless, unless the maximum breaking current of the fuse is taken into account. An ordinary megafuse etc probably won’t break the current in the case of a dead short on a big Lithium bank, it will just be arced over. But safety is about risk assessment and risk is the combination of severity of outcome and probability of it happening. Hopefully in a well installed unfused alternator system, the probability of a wiring short circuit is extremely low.

There’s a lot of communicational confusion between the participants in this conversation! If you want to charge to 100%, you first have to define what 100% charge means. Most cell manufacturers say that 100% charge is when the cell voltage is 3.65v AND the charge current has decreased to 5%. But then despite being at 100% charge, you could subsequently squeeze a tiny bit more charge in if you held the voltage at 3.65 whilst the current subsided further. But the extra charge, as a %, is tiny. This is the way to fully charge a battery is a fairly short time eg when running a generator or engine But does it matter what 100% is - not really because as long as you get quite close as in you 3.5something volts, you are not missing out on any significant capacity. You might be losing 0.5% worst case. The other way to charge is to apply a lower voltage for much, much longer. Days weeks or months at a time. 13.5v, given enough time, will get the batteries pretty close to 100%. It’s the sort of charging you might do from solar when there is not much taken out between days. Overall I thin you are overthinking it. What you are doing is fine - don’t fret!

No, you don’t need to charge to “trip” (disconnect) the BMS for the balancing process to start, it happens a little before that. But anyway from the sound of it your battery cells are balanced which is why the balancing is not activating. I would just continue as you are, it sound fine to me. With lead acid equalisation it’s hard to know when it’s needed and for how long. But Li balancing is a completely different thing. The latter will trigger if there is more than 15mV (or whatever is set in the BMS) difference between the cells. If there isn’t the balancing won’t trigger. IMO cells in good condition don’t go out of balance so the fact that it isn’t being triggered is a good thing.

Yes, and I would strongly advise against inserting anything between the alternator and the domestic batteries. Should something go wrong with something inserted there, there is the possibility of a fault disconnecting the alternator whilst it’s charging, and this can be fatal for the alternator.

The voltage would rise rapidly if the charger voltage was set a bit higher. The current is dropping off because the charger regulated voltage has been reached, not because the batteries don’t want to take any more current. However I would leave it as it is. If all the cells are balanced and hitting 3.58 at more or less the same time, there is no need for balancing. If the cell are not balanced, then out of the 14.3v some will be lower than 3.58 and one or two will be higher, triggering the balancing. The fact that it’s all reaching 14.3v without any drama means the cells are balanced. If you have 2 batteries in parallel and both are at 14.3v (as they must be, if the wiring is faulty-free) then both batteries are fully charged or at least 99.9% fully charged. There is nothing to be gained by longer charging. It’s an interesting point. If the charge voltage rises too high then the BMS will turn off the MOSFETs and the battery will effectively be disconnected. However with a further rise in voltage there will come a point when the maximum permitted voltage across the MOSFETs is exceeded and they will break down to short circuit, ie the Full and very high voltage will be presented to the cells. Which would be very bad! So it will depend on the maximum solar open circuit voltage vs the rating of the particular MOSFETs that the BMS manufacturer has chosen to use. Having an independent over-voltage alarm would be a good idea especially if you have series solar panels that present a high voltage to the controller.

This is a great piece of wriggling. Ever thought of taking up politics! Well maybe not because I don't think anyone is taken in! "it's not discharging, even though discharging is enabled" So you are saying that when there is no load on it, it is not discharging even though discharging is enabled. Well that is astonishing. I really thought that if you turned on discharging when nothing was connected to the battery, all the charge would still leak out. I mean, that is what happens with water and a tap after all, and everyone says water is just like electricity when it comes to those volt and amp thingies! This is why I always ensure that sockets in the house are switched off when nothing is plugged in. Have you any idea how expensive it is to have all the electricity leaking away into the atmosphere!!! Anyway it is a good outcome because I think you have finally worked out how MOSFET BMSs work and I am just here to educate.

No you still don’t get it. More practice with the eggs required. If you (or the BMS) untick charging and tick discharging, you can (surprise surprise) connect a load and the battery will power it, but if you connect a charger the battery won’t take any current. If you (or the BMS) untick discharging and tick charging, you can connect a charger and charge the battery but if you remove the charger the battery won’t discharge into a load. Have another read of the link I posted earlier.

I’ve got Fogstar Drift in my caravan - heating bit of it is useful as the caravan is in highlands of Scotland and gets cold! For a narrowboat sitting in water and depending on where you locate the battery (lower down is better) it’s unlikely to get below zero but still, the automatic heating is reassuring. Victron is top notch with a price tag to match but I suspect the actual cells are no better than Fogstar. Victron universe is great for open source data interconnectability but for a simple system, probably overkill. Don’t know about Renology, probably more aligned with Fogstar. Granny, this is how you suck eggs. And don’t make a mess. They can and do block charge sources whilst permitting load drive. Or vice versa. I don’t understand why you deny it. To be clear, we are talking about current flowing in and out of the battery which is what a BMS controls. We are not talking about whether once the BMS has cut off charging, the charge source can still supply the load. There, I have given you a chance to redeem yourself, I would grab it if I were you! Here you go granny, look at this https://diysolarforum.com/threads/bms-mosfets-explained.29318/ Dont suck too many, you will get constipation.

You’ve said that before, but I can’t think of an electronics person on TV. Intrigued. Perhaps it was “Brains” from Thunderbirds?

Although it doesn’t turn the charge source off, a BMS in the likes of a Fogstar Drift has bidirectional control, in other words in the even of a cell overvoltage, current flowing in charge direction is shut off, current flowing in discharge direction is allowed. Similar for a low cell voltage event but the other way round. My own system uses a bidirectional relay which completely isolates the battery, but since that is a “last resort” disconnection which has never yet happened, I don’t think it’s a big deal. As you know, in normal circumstances my BMS controls the charge sources so the “last resort” event should never happen. Do you know anything about electronics? Current sensing -> polarity of current -> MOSFETS on or off. Incorrect.

Yes, should do.

If you buy a Li battery (collection of cells in 1 case) then it will have a BMS - Battery Management System - built in. The BMS monitors cell voltages, temperature, current and can isolate the battery if any of these parameters reaches values that can damage the cells. If you buy individual cells then you also need to buy a BMS to go with them, for protection. Since you are talking about “self heating” I would imagine you are considering something like a Fogstar Drift, which has built in BMS. he configuration you have, you should be able to swap the gel battery to a Li battery with no problem, provided you adjust the charging parameters appropriately. I would get some kind of battery state of charge monitor such as a BMV712 to keep track of the State of Charge (SoC) of the Li since unlike lead acid, it is hard to determine the charge state by just looking at the voltage. It might be that the Battery has Bluetooth and you can use an App to see the SoC which would be an adequate substitute for an external SoC monitor.

Yes. However there are a couple of issues, one is that most people don't have the battery capability to drain 2.8kWh in a few hours. Yes you and I do, but we are the minority. The point being that if you intend to fit a washer dryer to your off grid live aboard, you need to start by having a "non-typical" electrical system. Secondly a lot of off grid live aboard people are very frugal with power. They regard the fridge as the main consumer of power, don't leave the inverter on when not in use, don't have a router, rarely use the microwave if they have one, have on 1 led light at night and go to bed early in winter etc etc. They can just about cope with the 0.4kWh for the fridge in summer (when solar is good) and probably turn it off in mid-winter and store perishable food outside. Doubling the weekly energy demand by adding a washer dryer, which contrary to the fridge will be more energy hungry in winter than in summer, is a massive (near 100%) increase in energy required to sustain them. Which is why I said "a lot".

To be fair he said "who cares on a boat" in the context of the time it takes to run the complete cycle. He wasn't commenting on the energy consumption which is of course "a lot!" for most people. However one should also bear in mind the context of the OP who said he intended to do a lot of cruising, so 3 hours of cruising during which the thing is on, is not a big deal. When we run the washing machine and then the tumble drier, that is probably around 3kwh but we always do it when cruising. As with anything narrowboat related, a lot depends on how the boat is to be used.

Vapour is invisible too!

As you say, everything on a narrowboat is a compromise! Firstly to answer your direct question, I have no experience of a heat pump washer dryer. The only experiences I have had of a few "ordinary" washer dryers has been very negative when it comes to the drying bit. They are terrible! They fry and crease clothes without managing to dry them in a reasonable time. I have a few points to offer: As a solo boater you don't need a full size washing machine. We have a compact Zanussi washer and, whilst it would be no use for a family of 4, it is fine for the 2 of us on a boat. Bear in mind that part of being a boater is that you don't shower and put on clean clothes every day, well maybe apart from the heatwaves in summer. If you always smell of soap you will be spurned by fellow boaters as being weird! Lots of people drape their damp washing around the boat etc. I hate this! If you have a bow deck with cratch cover you can hang your washing there, but we don't and anyway I don't really like displaying my knickers to passers by. So we got a compact vented tumble drier, same size as the Zanussi. We sited it in a "lost corner" in the galley so it doesn't take up any visible space. Yes it is therefore slightly dificult to access, and we run a vent hose from it out of the galley window when in use. But in practice it is fine. Oh and I wouldn't worry too much about water consumption, it is rare not to find a water point somewhere during a reasonable day's cruise. Our Zanussi uses less than 1/4 tank of water even with the "extra rinse" button pressed. Get a water tank gauge so you are not guessing how much is in there. We too wanted 57' go-anywhere but after discussions with our builder, we added 2' to the galley and went for 59'. This is in practice pretty much "go anywhere" as the short locks up north are all wide, and a 59' boat can fit diagonally across a 57' lock. Although we haven't attempted the upper reaches of the Calder and Hebble beyond Dewsbury nor the Hud Broad (which I think has the shortest locks) we have done everything else without difficulty. Yes vented tumble driers use plenty of electricity - ours is 2kw on for perhaps 50 mins which is too much to take from the batteries really. But like you intend, we cruise a lot and simply put the drier on when we are cruising so it is powered by the engine alternators not by the batteries. Which brings me to power generation and storage. Solar is great. But only for about 9 months of the year. For 3 months it is virtually useless for running power hungry appliances. So IMO chosing an engine and electrical system with plenty of generating power makes a lot of sense. We have a Beta 43 and opted for the Travelpower which, as well as the ~2kw available from the 12v alternators via inverter, gives us up to another 3.5kw. Or to put it another way, the ability to run the drier AND charge the batteries rapidly at the same time. If I were doing it again I would probably opt for an uprated alternator and a bigger inverter and just use that. See Ed Shiers excellent website at four counties marine. He knows his stuff! Finally I would suggest that it would be crazy to commission a new boat and not use lithium batteries. Again, Ed is your man to advise. Lead acid batteries are the equivalent of the horse to propel the boat, Lithium is the equivalent of the warp drive!

I read it as 80% of the gas emitted is hydrogen, 20% is something else eg ethane.

Sorry to hear that - very annoying is an understatement! And it's not just the financial loss, it is the feeling of invasion of your space, violation of your privacy - even if it was just the engine bay - fretting about when it might happen again etc which is probably worse

Yes, however we don't actually know if the lights flicker with the water pump. One difference being that the water pump only runs very occasionally, whereas the dosing pump (when the heater is on) will cause a disturbance perhaps 3 times a second all the time, and is thus much more annoying. Of course one big difference between LED and incandescent lighting is that the latter has some "thermal inertia" whereas LED doesn't, and so slight and brief voltage fluctuations for LED lights that don't have internal voltage regulation, is much more noticable.

No, I’d say the inductance of the coil is tiny compared to a lighting circuit, and anyway it is normal to use a freewheel diode when switching inductances ie the excess energy just circulates through the device and diode and is dissipated in the devices resistance. It doesn’t “escape” to the rest of the system.

I don’t see how cavitation is related only to speed. Surely it is to do with the low pressure created by the sucking effect of the propeller, which must be a function of speed and angle of attack (ie angle between blade and incoming flow. ie a coarse pitched prop will cavitate at a lower speed than a fine pitch one.

As an aside but slightly relevant, our Mikuni MX40 heater has been annoying me for a couple of years because it only fires up on the second attempt despite the Li batteries sitting at 13.3v or so. So I took the glow plug and gauze thingy out to decarbonise. But there was nothing wrong with them really. Then I put them back in and decided to check the voltage actually on the glow plug. Doh! touched the meter probes together and blew the 40A heater blade fuse. I replaced the fuse and now it lights up almost immediately! So a bad connection at the fuse probably dropping voltage to the glow plug was the issue.