cheesegas

You don't, in an ideal world. Also, in an ideal world, the BMS never does a charge/discharge disconnect because all the charge sources have a lithium charge profile programmed into them; the BMS is there as a last resort. The batteries wouldn't sit at 14.4v etc for an extended period of time because each charge source would hold it at say 14.2v for 30 min to an hour to allow the balancers to work, then drop the voltage to 13.35v to maintain the state of charge. The system would be designed to never rely on the BMS doing an over voltage disconnect to terminate the charge cycle.

You can do if you'd like, at the expense of some lost capacity. It's debatable quite how many extra cycles keeping it below 80% gets you, before the battery's total capacity drops below 80% of new - if it goes from something like 4000 to 5000 cycles, there's little point. The JBD BMS in the Fogstars use 14.8v by default, and 3.7v per cell. At this high a voltage, they're not designed to be triggered to end the charge cycle, it's there as a last resort cutoff.

None of the drop-in batteries have a BMS which can cut off charge at 100%. They all use volts or amps to trigger the charge connect/disconnect, the SoC % isn't used in any of the disconnects at all. It's totally voltage based - when the cell voltage or pack voltage goes above a certain voltage, it disconnects charge until it drops below a certain threshold.

As I was the one who was responsible for the PAT testing for the business’s hire stock and office bits, I did indeed test my partners power bank when I took it in to charge. Usually it’s outsourced; you’d be surprised at how many companies offer paid per item PAT testing and make an absolute hash of it. Classic one is testing everything as a Class 2 so you don’t have to bother with the earth bond test… And I’ve heard of fragile IT equipment being done on the standard class 2 high voltage preset which doesn’t do it any good.

I think it's time for my obligatory fortnightly battery nomenclature blurb, sorry... The term li-ion covers a wide range of battery chemistries. Lifepo4 or LFP batteries are a type of li-ion. The chemistry used in phones and laptops are NMC or NCO cells, which are also a type of li-ion. However...it's passed into language to call NMC/NCO batteries li-ion, and call LFP/lifepo4 batteries just that. It's rather confusing, as insurance companies also cover a lot of lithium chemistries with the term li-ion, as that refers to both LFPs, NCO and NMCs amongst others. On the power bank issue though, only the smallest Jackery uses NMCs, the rest use LFPs. It's the same for Bluetti too, I expect it's because the power density of NMCs is better than LFPs. On that note, it's best to use watt-hours rather than amp-hours to describe battery capacity, particularly when comparing li-ion packs as they come in a variety of voltages. Indeed, airlines and insurance companies all talk in watt-hours. A 48 volt 40ah battery is much bigger than a 13 volt 40ah! The UKCAA limit is around 100wh, purpose and chemistry dependant. I have recently dealt with insurance companies (well, 3 years ago) on insuring a hires warehouse where up to 500 wireless LED uplighters are charged at once. These use a 150wh li-ion NMC battery charged by an internal mains-powered board. Safety records on these is pretty good; the previous generation which used lead-acid AGM batteries used to fail and explode on a much more regular basis. I remember the stainless steel shell of one being deformed pretty badly by one such incident! Anyway, both the premises insurers and also the liability insurers (for when they're used on site) didn't care about the charging at all, and it also didn't matter whether they were LFPs or NMC/NCO. All that mattered was that it was inside the device it was designed for, no bare cells were charged and the devices were given a visual inspection annually, which incidentally happens during a PAT test. Most laptops have an 80-100wh NMC battery in them, which the insurers also don't care about as long as it's in a laptop and not bare cells. There's plenty of these in your average office - probably in a stack somewhere - which easily equal a 1kwh Jackery in terms of stored energy. Safety records of brand name, genuine NMC/NCO li-ions is pretty good. There's millions of these in laptops and phones with a very low failure rate. Generally speaking, you get more issues with recycled packs made from recovered cells of varying ages; these tend to be big packs in scooters and e-bikes, which increases the damage when they go wrong.

According to @Machpoint005, that doesn’t matter - the fact you’re taking electricity for personal use is the issue. Whether it’s for your car battery (which would otherwise be recharged at home) or a powerbank isn’t relevant. However, ethically, I’d argue that doing the HMRC out of a few pennies doesn’t matter at all.

This is a really good example of how much solar yields vary with location - I have slightly less than you, 1kw of panels, but have been getting 1.3kwh per day for the past 3 days. I'm currently moored in a semi-rural area but there's a big tree about 30m away which just so happens to shade my boat until the afternoon, so I miss out on the morning sun.

I used this stuff, in my opinion bitumen isn't the way to go - it leaches into the water and has a short lifespan. https://www.acothaneuk.com - it's the same thing they paint potable water towers with in the UK but it's not cheap. It's a two pack which has quite a short curing time of around 20-30 minutes, you need to be quick with the roller or it'll start to thicken up and be too difficult to apply. One 2.5 litre can did one coat on my 1000 litre tank, don't buy a single 5 litre can and try to split it, the paint has the consistency of thick yoghurt before it's mixed with the hardener!

I hope anyone who reports someone who is ‘stealing’ the taxes on 50p worth of electricity from the HMRC as a benefit in kind has a good hard look at themselves in the mirror before realising what a terrible human being they are.

As long as the employer is aware of it I don't see an issue. Not everyone works for a massive multinational with a huge chain of command to pass things through. I used to work full time in a hires warehouse, small company of 10 people, and would routinely take things in to work to charge, including my partner's Bluetti power bank. I'd borrow a van and plug it in in the warehouse. They were totally fine with it; at 20p per kwh (at the time!), that's around 50p to charge even a big 2kwh power bank. Pales in comparison to the 32a 3ph electric heater that was run in the winter! As to charging lithium in a warehouse and insurance - that company had a few hundred wireless uplighters with li-ion NMC cells in them which were charged daily, as well as two lithium forklifts. All approved by insurance. I agree it's cheeky if you work in some massive companies office as it wouldn't get approved and some brown-noser would probably delight in informing someone as to what you're doing...

I've only seen the Bluetti version of these, but you can set the charge current via the app to avoid the overheating. They aren't the most efficient way to charge a battery, but they do work rather well. The maximum output is only 500w, which is well within the capabilities of a 70a A127, even if it spends a bit of time charging the boat's leisure bank. To be honest, these power packs are expensive per kw/h, but for a very basic boat with only rudimentary electrics, it's often easier, quicker and cheaper to dump one on a shelf and hook it to a conventional rigid solar panel on the roof. It doesn't have to be a proprietary panel, most have a fairly wide voltage input - Bluetti for example are fine up to 140v I think. Comparing it kwh for kwh to a bare battery like a Fogstar isn't a fair comparison; even including the costs of the inverter, if someone doesn't have the expertise or tools to install it, the cost of paying someone brings it up dramatically. If it's a basic boat with little in the way of busbars or high current domestic wiring and it's got a little 35a alternator, then it'll all need to be upgraded first before even thinking about installing a lifepo4 battery. I've seen them used quite a bit by people on an online mooring without shore power - they can park their car nearby, pop the battery in the boot and charge it at work etc to avoid having to run a generator or engine. One chap has the Bluetti DC-DC installed in his van so he can charge it whilst he drives, as he goes between sites a lot for work. He then returns to the boat and has a fully charged battery. I agree it's definitely not as neat as a properly installed electrical system, but for someone with not much on board who needs a quick, cheap solution then it's perfect. Everything has its place! Check the spec first. Most of these units have a floating output, the same as smaller inverters and inverter-generators. Bonding neutral to earth to enable an RCD to function correctly might damage the unit if it's not designed for this. Some may have a centre tapped earth which will work though. A circuit breaker isn't strictly necessary as in my experience, the unit will go into overload and shut down long before the breaker trips. However, when charging from the mains in pass-through mode, the shore power earth is linked directly to the output's earth so whatever you charge it from must have an RCD. Generally, these portable power stations are designed to be used with appliances connected directly to the mains sockets rather than using an extension lead etc. This

Exactly. It's a compromise between incomplete battery charging causing sulphating and reducing capacity, and diesel costs and engine wear. However, repeatedly charging a heavily discharged 400ah bank for an hour or two until the tail current is still around 20a is proven to dramatically reduce their lifespan in most cases. For an average liveaboard, this usually corresponds to one winter's usage before needing new batteries.

Those hours are important with lead acid; short periods of high current charging with no extended periods of low current charging dramatically reduce cyclic life. You'll end up with sulphated batteries rather quickly. It might look like a waste of time in theory, but it's critical. Your average 400ah flooded lead battery bank is really only full around the 12hr mark, no matter how much current the charge source can output. Most people charge for less time as a compromise between battery lifespan and engine wear/fuel usage.

I'd say Tony's numbers are correct; lead acids charge at a remarkably low rate. I can't find the logs from my system when I had 3 x 100ah flooded lead acids but @T_i_m's graph is rather good at illustrating how quickly the rate reduces. High output alternators came about to enable people to run high power appliances from the inverter whilst the engine's running. A 400ah battery bank that's heavily discharged may be able to absorb 100a, but not for long, usually a matter of half an hour.

Yep, as I said - it'll always be correct when it reads 100%, as it'll sync to full charge when current is below a certain threshold and voltage is above a certain threshold, for a set amount of time. However, counting from 100% down will get incrementally less accurate as the batteries lose capacity over time. To work out the SOC below 100%, there's no algorithm, just amp-hour counting with adjusting for charge efficiency and Peukert. And yes, I'm sure that volts are not taken into account to calculate SOC at any point other than at 100%. There's no algorithm there.

As the batteries age, their capacity will reduce from the programmed capacity in the BMV. This does not self correct. Eventually, what happens is that the BMV SOC is only correct at 100% charge when it syncs; this is because it counts consumed amp-hours out of the programmed amp-hour capacity. -10ah from a battery that was 300ah but is now 200ah is a different percentage, which is why it ends up being incorrect. What I'm saying here is from experience, not theory. There is logic in there of course, but SOC is determined through simple amp-hour counting. There's no algorithm working it out or dynamic changes - just plain old static counting, altered by static inputs from the parameters you set on it. Battery capacity loss over time varies greatly on application. I've seen battery banks lose 50% of their capacity in one winter; others may lose only 20% a year. You can't easily work out the true capacity to enter into the BMV without doing a slow discharge test, say at 1/20C whilst watching the voltage - that's beyond the average boat owner. The Smartgauge has its uses, whilst it gets confused by slow charge/discharge, it does remain a degree of accuracy. In my experience, with a brand new battery bank this is less accurate than a BMV. However, with a knackered 3 year old battery bank, the Smartgauge is more accurate. I have real life experience of the Smartgauge so I'd recommend taking some of it in...

There's actually no closed-source algorithm in the BMV - it just counts amp-hours in and out, adjusting for charge efficiency and Peukert (both of which you set in the app), which is pretty straightforwards maths. However, the Smartgauge is all closed-source algorithm; it seems to work off the rate of voltage change, and adjusts itself when it sees less change. My experience is that is it works ok, and low loads tend to confuse it. The issue with the BMV and shunt based meters is that they don't compensate for the decreasing capacity of lead batteries as they age. A 300ah battery bank may only be down to 200ah after a year, but the gauge still shows the % as a proportion of the programmed 300ah. Both devices have their compromises, neither is perfect.

I have no idea too - it seemed to be running pretty well until it was shut down on the stop lever, and the suddenly it didn't want to go again. Seems odd for both things to suddenly fail with the engine off! The company who rebuilt the injection pump said that the scoring was unlikely to be terminal but may have caused a reduction in power, and it was the sticking plunger which was the main issue. It must have been sticking for only part of its stroke as I was able to feel it going up and down whilst the engine was being cranked over. The history before it was tied up two decades ago is largely unknown, although the fuel filter looked clean when I cut it open and the tank is a rather nice new looking little stainless steel affair.

Had a couple of days of work cancelled which worked out well for free time, so I could take the pump in in person. Got it back early this morning, apparently it had a scored barrel and the plunger was intermittently sticking. Fitted it, bled the system and it fired up on the first couple of compressions even though it's pretty cold outside. It's now running happily from the boat's tank, had it tied to the pontoon running flat out in gear for 10 minutes. Thanks all - in conclusion, it was both the injector and the pump at fault! Learned a lot about how injection pumps and governors work too, it was an interesting exercise.

There's no correct answer for a lot of things on boats - there's so many variables. Here's some scenarios. If you're in a marina, never intend to leave, only cruise back and forth to the pump out and have a 32 amp shore power supply - then yes, an electric cooker is fine. If you're in a marina, you go for long summer cruises and only have a 16 amp supply - no, it's not a good idea. If you're off grid continuously cruising, have lithium batteries and a decent amount of solar - yes, it's a good idea for 5-6 months of the year, you'll need a gas cooker for the rest of the time. (this is my setup - cook on free solar power when it's available, gas when not)

Indeed - my new MacBook Pro draws under an amp at idle with the screen on. A fraction of the 3 year old Windows machine it replaced.

I would also say that lead batteries are remarkably tolerant of deep discharge, as long they don't spend much time in that discharged state. Electric scissor lifts and forklifts are routinely run down to voltages that would make people on here cringe, but the difference is they're recharged quickly, often overnight. A set of Trojans in a scissor lift taken down to 10-11v regularly will often last a couple of years. However, if they were left for a week in that state as what often happens in boats, they'd be dead quickly.

This estimate is difficult, and you can't even compare two identical boats moored in different places. Yields in a big open marina with no trees are very much different to those on the towpath; even then, being in the shade of a single tree during a winter's morning sun might mean you get half as much solar yield as your neighbour. I would however say that people who hang around towns/cities generally get a much lower yield than those in more rural locations due to shading from buildings.

Yep indeed - but once the complexity is understood and the peak of the learning curve is over, it makes life so much simpler and easier. More importantly it gives you more time to go boating and less worrying about being near land-based services and whether you're charging your batteries often enough.

Most of these things help us do more boating and do less chores though. A washing machine means I don't have to spend half a day lugging everything to a launderette, I can tinker with the boat or cruise. Wifi means I can work from the boat, spending more time on it; otherwise, I'd have to go and find a library or cafe. Lithium batteries and the associated kit mean I have to think less about when to recharge in winter, I look at the battery gauge less often and can get on with everything else. And the rest of the things are expensive, sure, but for some creature comforts it's so worthwhile for me. Being able to switch on the diesel heater remotely so I can come back to a warm boat after being away overnight is one of those comforts. For others, the above things are maybe less important but everyone uses their boats differently, and there's no correct way to use a boat either. Some sit in marinas only going to the pump out, some go on summer cruises, some cruise year round, some live on the boat, some don't.