nicknorman

True. However in our case we get round the problem by having a fridge with an ice box compartment. Many do!

Something I hadn't really thought about is the self-discharge rate of the actual cells, vs the self discharge rate of the battery including BMS. The JBD BMS quotes a running current of 25mA and a sleep current of 0.3mA. Sleep mode is entered when the there is no current or other stuff going on. So 0.3mA sounds quite small but is still 2.6Ah a year or 2.5% of my battery. But the bluetooth module is an "extra" which is probably not included in that 0.3mA and it has to remain vaguely active so it can connect with the phone app at any time. So I wouldn't be too surprised if the actual sleep consumption including the bluetooth was not more like 3mA or 26Ah (25%) a year. Whereas I think the self discharge of the cells themselves is much lower. I was careful with my own BMS design to minimise sleep current - all the peripherals (canbus transmit, microprocessor clock etc) is shut down when it's sleeping and it just wakes up every 20 seconds or so to sample cell voltages (which takes a few milliseconds). That way the sleep current is under 100 microamps. But of course if I want to interact with it, I have to wake it up with a button, not with my phone!

If the cell just topped out early during charging, loss of capacity would be an explanation. But I first noticed the problem when the other 3 cells were nearly flat, whilst the rogue one still had loads of charge. So I don't think the capacity has been lost, it is just that more charge has been put in or less charge taken out of cell 4, than it has from cells 1-3. Which bearing in mind they are in series, is weird!

OK not on my boat where I have a "proper" lithium battery system, but in my caravan. One 105Ah LiFePO4 Fogstar Drift battery charged by solar in summer and a genny in winter. I use a BMV712 to stop the solar charging at 90% SoC as I didn't want the battery to be continually rammed full every day by the solar when I wasn't there. It's been in for a couple of years now I think. I fully charge it on occasion to sync the BMV712, every 3 months or so (not that fussed about the accuracy of the BMV). It seemed OK when I got it but one cell (cell 4) was always a bit odd. But I haven't paid much attention until recently when the SoC got quite low due to excessive electric blanket use! Cells 1,2 and 3 are always within a few mV and they started going down the knee. Meanwhile cell 4 was way up. Hmmm, big imbalance. So I fully charged it but cell 4 topped out very early. I left it connected to a power supply for a few hours whilst the balancing thing was going on. But it was not touching the sides. The balance current is only about 50 or 100mA I think. So in the end I decided to investigate further and opened up the case. Firstly, the BMS is reading the cell voltage correctly. So I then disconnected the cell connections and connected a resistor across cell 4 to give around 0.8A. This has now probably been on for at least 10 hours and probably nearer 15, but Cell 4 still overtakes the others as full charge is approached. I am discharging it more as we speak. So somehow, cell 4 has managed to accumulate at least 10Ah (out of 105Ah) more charge than cells 1-3. This is a crazy amount of imbalance and I am wondering how it happened. I notice that the BMS which is a JBDSP04S034 can be used with either 3 or 4 cells in series. So I am wondering if it is so crappily designed that it actually takes the power to run the BMS and the Bluetooth, just from cells 1-3 and cell 4 has no parasitic drain. Thus over 2 years this 10 or more Ah imbalance has built up. I can't think of another explanation and I certainly can't see how 3 cells can be perfect and one cell has far too much charge. I could understand it if one cell was low - knackered cell. But when cells become knackered they don't gain charge! confused.com

If the boat has a steel cabin sides/roof then most likely it is seeping in around the window frames. A common problem. If it was colder I might suggest condensation but I don’t think it’s been cold enough, unless you are in the habit of raising the internal humidity by drying washing inside or endlessly boiling potatoes with the windows closed. If the boat has wooden (on the outside) cabin sides and roof, then all bets are off, could be leaking anywhere!

2.5m is a lot more than 5ft, more like 8ft. Did you mean 2.5m?

True, but then you will also have no idea when the lights are about to go out…

You can see the relay state in default mode, it’s on the “front page” if you scroll down a bit. The relay is a changeover bistable relay, so it doesn’t exactly have an open or closed state, because at any one time the NO or NC contact will be connected or not, so it just depends on how it’s wired.

No I’m not saying that. The cell voltage is the cell voltage! But if everything is normal and settled, the cells would all be at pretty much the same voltage, regardless of whether the batteries were connected together or not. Yes the SoC measurement is rubbish, certainly at first. But it does seem to improve with significant cycling.

We leave the water tank (stainless, under the well deck) nearly empty, turn off the stopcock and disconnect the pump inlet. Then run the pump with all cold taps open - the pump sucks air into the pipes, displacing most,of the “higher up” water. I start the washing machine so air is pumped through the inlet valve (plastic, high up), ditto the toilet. Disconnect the shower hose and push air through the thermostatic valve. I don’t drain the calorifier but it is well insulated and fairly low down, not been a problem so far… The basic consideration is that stuff at the bottom of the boat won’t freeze (eg pipes under the floor) whereas stuff higher up might. I can turn on the Mikuni remotely, which I occasionally do if there is a particularly cold spell, this heats the radiators and the calorifier.

If the batteries are in parallel then the overall (terminal) voltage of each must be the same (unless there is some wiring issue). Within each battery one would expect the cells all to be at more or less the same voltage if the battery is balanced within itself, and it follows that one would expect the cell voltages to be the same in each battery, within a few mV. If one battery is showing 100% then its charge MOSFETs will be turned off (not taking any more current) but the battery at 50% will still be able to accept charge, so I would continue to charge until the second battery gets to 100% and charging shuts off. Then they will definitely both be fully charged. If you find they are going out of balance with each other after this, I would check the inter-battery wiring and have the connections to outside world (charge sources and load) connected on the diagonals - ie + on one battery and - on the other battery. You can also check the charge and discharge currents of the 2 batteries on the App when there is significant current flowing, to see if they are the same. The Fogstar BMS SoC is very inaccurate to start with, and improves with some cycles. Have you cycled it down to a fairly low SoC on several occasions?

Thanks for getting back to us, it’s good to hear that perhaps we helped save you from a lot of wasted work.

I don’t think anyone has posted a link to the Boating Association’s excellent guides to navigating the Trent. I would consider it mandatory to have these guides before a first attempt at the tidal Trent. Here is the link: https://theboatingassociation.co.uk/product-category/charts/ TBH I don’t think you need chart 1, as the non-tidal Trent is just an ordinary canalised river - Nicholsons is fine for that. But Chart 2 is very good at keeping you in the channel etc, with photos of sight lines, shoals marked etc. Chart 3 is only relevant if you are going on the tidal Ouse.

Yes I probably should put it on YouTube, but YouTube is becoming just an advert streaming service so I resent it! OK here is YouTube version

We passed by Barlaston towards Trentham in early June. At a culvert, I noticed that water was leaking under the piling and running down into the field and the stream. I phoned CRT to report it. So here we are in late September, passing the same point, and the leak is still there but worse with more soil washed away and a quagmire in the field. No wonder there is a water shortage! I stopped to take the video below. Moments later a CRT bod appeared walking along the field (the leak was non-towpath side) and I asked him if he was going to check the potential breach. He said he was “Yes, it’s just been reported”. I mentioned that I had reported it 3.5 moths ago. But perhaps that is the expected response time? Or maybe with FTL communication he was responding to the report that I had yet to make? https://imgur.com/a/SWWB2qx

I don’t think that is fair. There was a fire, we don’t know what the source of combustible material was nor the source of ignition. We also know there are millions of LiFePO4 batteries out there which haven’t caused a fire. We also know there is a lot of competent research showing that using a LiFePO4 battery to start a fire is very difficult if not impossible. So I don’t think the possibility that his batteries might turn out to be a death trap or unsellable, is anywhere on his radar.

That is incorrect, it is relevant. That it is not leaking right now is of course important, but also important is that it is unlikely to develop a leak in the next 4 years. Copper gas pipes rarely spring a leak spontaneously, unless abraded or corroded. However every gas fitting carries some non-zero risk of developing a leak when subject to vibration etc. This being rather different from a house where, unless you live in an earthquake zone, there is no significant vibration. Since every gas fitting creates a small risk of leaking and since even small leaks on boats can be catastrophic, it makes total sense to have a policy of minimising the number of fittings. It is simply about probability, and it is bad practice to increase the probability of catastrophe unnecessarily, even if that probability is very low.

Not really. One of the checks is to make sure that there are the minimum number of fittings. So if you can’t see the full length of the pipe you cannot known that there isn’t a coupling fitting in there somewhere, because the installer used 2 shorter lengths of pipe instead of 1 long one. Certainly with a narrowboat, this is not hard to achieve.

It depends on the expected level of safety. In aircraft certification we use “extremely remote” for the failure of a critical thing, which is one in 10^9. If you were to say “there is a remote chance of this aircraft crashing and burning on landing” and that meant 5% ie one in 20 landings, I don’t think so many people would be swanning off to Benidorm for their summer hols.

One thing to bear in mind is the need for the pipework to be visible ( possibly with a bit of contortion, but none the less ultimately visible) over the full length. Although it’s hard to be sure from the pic, it rather looks as though once completed, the kitchen units might hide the pipework. Not to mention the isolation valve. This is not acceptable for the BSS. I’d be more worried about gas pouring out of the open end of the pipe😱 💥

The last testing I did was in May. Not quite summer, but close. The builder of the aircraft tests all year round but mostly in Spring to Autumn - no ethanol in his local Asda supermarket petrol. The only reason for putting ethanol in petrol is to follow some green / renewable agenda. But since growing the stuff to produce the ethanol either takes away from food production, or results in more rainforest being slashed and burnt, it’s not an easy target to fulfil.

No sorry, the home built aeroplane I fly doesn’t run on diesel! But it has a plastic fuel tank so doesn’t like ethanol, hence the testing! No don’t think so, it’s all a greenwashing scam IMO! Where would all this ethanol come from to add 10% to all the petrol we use?

Petrol does not “certainly” have 10% ethanol. E10 petrol can have up to 10%, but in my experience it doesn’t. It is easy to test for ethanol using a graduated test tube and some water. I tested a local BP garage recently, it had an undetectable amount of ethanol in the E10 and about 1% ethanol in the E5. An Asda petrol station had no detectable ethanol in its E10.

Of course not! But slightly better I suppose as we have eliminated one false cause of imbalance. As to the total amount of anode and cathode material, this is not a cause of top imbalance either. It might be a cause of varying capacity which of course leads to a conflict between top and bottom balancing, but I think we are just talking about top balancing. As I said, you send some Li ions one way, then you send the same number the other way, and the result is you are back where you started. Anyway, I think the bottom line is that the cells I got direct from China at somewhat high risk, have turned out to be pretty good. It would be interesting to know if the rapid decline in price of Li cells has any correlation with a propensity to go out of balance - ie whether these days cells are built down to a price rather than up to a quality - like so much other stuff.