nicknorman

Can I just mention JLCPCB in Hong Kong for bespoke printed circuit boards? There is no need for breadboard or rats nest things when you can get a top quality pcb with unlimited plated through vias, silk screen and solder mask top and bottom, for peanuts - literally £3.50 for 5 boards double sided or about £7.50 for five 4 layer boards, including shipping and import taxes. This is the latest board I sent away from, a 4 layer board for a PIC microcontroller thingy with a bluetooth module. And personally I would always use a PIC and not an Arduino, because the latter are quite limited.

Ours is a Clesse. Been OK for 10 years of leisure use. I see BES sell them, so they are probably of adequate quality.

Consider yourself mocked. Regarding JonathanA's point, it is a fair one but set against that, many people's inverters including ours are left on 24/7 when quite likely there is no-one around to notice the smoke coming out of it, let alone operate an isolator switch.

You can have 2 shunts in series. Each shunt drops a max of 50mV at it’s rated current, so with 2 you are only losing 0.1v and that only at the full rated current of the shunt. However I would argue against putting a 100A shunt in a circuit that can pass 200A or more. It would likely overheat. And bear in mind power dissipation is I^2R, ie double the current = 4 times the heat generated.

I just used the bus bars supplied with the cells. Although they are solid copper (with a huml), not several strips of thinner copper. But the supplier didn’t provide enough strips for my configuration so I made some more from copper sheet which was quite thin so I used 3 or4 layers. I did wonder whether several layers was a good idea in terms of electrical conductivity, but if this is the new gold standard then I guess it’s ok.

I’m not clear what you mean by flexible busbars. My interconnects (bus bars if you like) are copper strips with a hump - the hump being there to allow a small amount of movement. Since the problem has never recurred in that or any other cell (and we are about 3 years further on now) I don’t think it was an installation issue, more like a manufacturing issue.

I’m not sure what the point of putting stuff between the cells is. I certainly didn’t. I have a wooden battery box and my only aim was to ensure the cells couldn’t move, so there was a bit of packing out the box with thin ply, but just to take up a bit of clearance.

No. Lots of people get arrested on suspicion etc. But they were released, and so far have not been charged with any crime never mind found guilty of it. Only if the issues relates to their work.

Well BSS does not require a battery isolator for the connection to an inverter. I think it used to, which is perhaps where the confusion arises. A fuse is required. I wouldn’t bother with an isolator, it’s just another thing to drop voltage and get hot under heavy load. If you want to work on the inverter, remove it etc, you can undo the megafuse.

It depends on whether you believe in innocent until proven guilty and due process, or trial by social media. As I understand it no-one has been charged with any offence yet, never mind found guilty in court. There are suggestions of a hate campaign from disgruntled ex band members. Personally I don’t think people should be “cancelled” purely by the power of social media and without the backing of fact.

They charge faster than ordinary LA, less prone to sulphation and have a better cycle life. But starting from a low bar, "faster, less and better" may not be saying much. I think Li will be far better in all these parameters. And they are only marginally cheaper than Li, probably more expensive if you grow your own Li.

The damage mechanisms for low and high temperature are quite different. At low temperatures it’s about the slowness of the charging reaction resulting in “free” lithium getting plated on the electrode. But it is certainly not a binary thing. At low temperature Li can still be charged without Li plating, provided the current is kept low within the ability of the reaction to absorb the Li. A cheapo BMS with FET switching can’t unilaterally regulate the charge current, it has to be on or off. But a in a better designed system the BMS a would instruct the charge source to charge slower at low temperatures. I think around 10% of normal max charge rate is ok down to about -10c which is way below what a narrowboat installation is likely to encounter. In my case max charge rate is already only about 0.33C and the normal rate is about 0.15C, so I allow that down to zero and below that charge voltage is reduced to give a trickle charge. I have never found the batteries below zero though, as the inside-ish - modern aft engine compartment in trad stern boat.

I haven't looked at it in detail, but I would have thought a cheap BMS could be used to monitor cell voltages whilst not passing the main current through its MOSFETs. So the over and under charge built in disconnect would not work, but perhaps there is a digital signal output that could be used to send the stop charging command when there is a cell high voltage? Edit. Then again maybe not. Well the JBD BMSs that I looked at dont seem to offer any sort of digital "disconnect" output. Shame.

I built my own battery because at the time the alternatives were things like Victron and Mastervolt, which were very expensive. Now with the likes of Fogstar there is probably less reason. But apart from cost, I didn’t want MOSFET switches in the circuit, I wanted a relay. And I wanted to have a BMS that did exactly what I wanted it to do. If you are going to buy cells and an off the shelf BMS then I can’t see much advantage other that more confidence in build quality (if you are competent!) and an ability to determine the shape. Hence my idea about inserting a soft copper washer…

yes there would need to be some compression. Enough but not too much! But my point is that for a given compression (bolt torque), conductivity would be improved by having a soft copper washer. But this is only conjecture, I have no evidence!

If you look at a junction between two nominally flat surfaces (the battery terminal and the ring terminal) at the microscopic level, you would see a lot of peaks and troughs and generally rough surface. The actual metal to metal contact area is thus only between the places where the peaks align, and thus is a fraction of the apparent contact area. Copper, especially recently annealed copper, is quite soft and so my contention (not proven!) is that inserting a relatively soft and squishy conductor between them will to an extent conform to the rough surfaces and thus increase the contact area. Of course the cable-end ring crimps are notionally made of copper, but I think it’s some sort of alloy and they are tin plated which I suspect increases the surface hardness.

Yes. For a year or two the cells were fine. Then suddenly one suffered this poor internal connection issue. So most of the current went into the other 2 cells and fully charged them to 3.65v. The third dodgy cell was also apparently at 3.65v but this comprised (say) 3.4v cell voltage plus 0.25v dropped in the resistance of the poor connection whilst under charge. The effect was an apparent (though not real) loss of capacity of that group of cells. I remedied it by turning the big nut on top of the cell - the nut that says "do not turn this nut" in the instructions - just by 5 degrees or so, there was a bit of a click and everything has been fine ever since. These are CALB cells with a nut on top, a bit like the Winstons. For some reason the nut was well connected to the cell electrode, but the central bit on which the cable lug sits, wasn't. Which was very odd! Turning the nut must have removed some corrosion thing I guess. So it was not really about the cells being well matched or not, it was about a manufacturing issue that showed itself after a couple of years - some sort of poor internal connection to the terminal. Maybe I was just unlucky, but otherwise the cells have been faultless. Well I have the "NO!" configuration. The text is correct in theory but in practice, with the low C charge and discharge rates on a narrowboat (not having electric propulsion) I don't think it is an issue. The cell resistance is a bit more than 1mohm anyway, especially when you add the interconnects. At rest there will be a degree of self-levelling and the cells never get significantly warm from charging or discharging (just a few degrees when charging) so I don't see it as an issue and it makes life a lot easier.

Yes, however a poor terminal connection is only one cause of high cell temperature. And in fact not really even cell temperature as it is unlikely to transfer the heat effectively into the actual cell. Li cells can overheat for other reasons, not to do with bad terminal connections. For example, a couple of years ago ambient temperatures got close to 40C and that is only 5C below the max charging temperature even with no fault conditions. Put the batteries in a poorly ventilated engine room with a bit of added heat from the engine, and heat from fast charging, and getting over 45 is not unfeasible. I have seen 35C on mine, due to batteries being located in the "engine compartment" of a modern trad stern.

If you imagine 12 cells in 3 rows of 4 I was thinking of having a temperature probe in each of the internal “corners” ie where 4 cells touch ie 6 sensors. They are cheap and can all be on the one Onewire bus. I’ll probably never get around to it though! I’m not clear how voltage would be a substitute as there is very little voltage:temperature coefficient. It is pretty dodgy not having cell-level BMS monitoring. From personal experience I had a cell that developed a poor internal connection, and this was only revealed by the voltage on the other 2 paralleled cells being high - because all the current was going to them and not to the third cell. No problem for me because the BMS stopped charging when the affected cell group hit 3.65v even though the overall voltage was still quite low. But without a BMS monitoring and protecting, there would have been a massive cell over-charge.

Terminal overheating is a bit of a worry, I try to remember to check mine from time to time (12 cells so lots of bolts and potential for poor connections) but so far they have remained cold even at high current. Copper links onto the top of the cell terminals probably helps (copper being soft apart from its other properties, and thus give a good contact area when squeezed a bit)). I don’t think the bolt material is significant. But I wonder if a thin copper washer between the cable lug and the cell terminal might help? I only have 2 temperature sensors, one is pushed down between the middle of cells (goes to my BMS) and the other is on top of the cells (goes to the Mastershunt and is accessible to the BMS via CAN). I have had it in mind to use multiple temperature sensors so that each cell has one adjacent, but it would involve more complicated software (using DS1822 on Onewire bus but with multiple sensors on one bus I’d need to address them individually, not using the “call all” command) and so far I have been suffering from a lack of a roundtuit. What does get quite hot is the bistable relay connection. Fortunately it is connected to 75mm^2 cable which acts as a good heat sink, but it gets too hot to touch at very high currents.

Petrol on its own doesn’t burn. You can strike an arc through petrol, nothing will happen. Petrol only burns when it is mixed with oxygen, and that only happens when liquid petrol turns to vapour and is mixed with air in roughly the right proportion.

Excellent. Just send that off to the commission and tell them their work is done and they can have the rest of the week off.

If it gave 30A out of a rating of 55A then that is probably sustainable. However if the alternator and wiring are in good condition, more likely the current would be 55A. Li holds the voltage down at 13.5 or so until getting close to fully charged, vs lead acid which rises to over 14v pretty quickly.

Well of course it depends on how well charged the batteries were when he set off. Maybe they didn’t really need much charge due to being full-ish from solar or shore power? But also as mentioned it might be a low output alternator, or relatively high resistance in the wiring that keeps the current down.

I can lend you a Ouja board.