nicknorman

B2B current flows one way, but of course a box of tricks might well have 2 B2Bs in reverse parallel. And of course faster than light travel of information is already available, just awaiting a firmware update. I think what is relevant about that is that the B2B continues to charge the engine battery even after the van engine is stopped. So if the engine battery is running at a deficit for a few hours, this will be recouped overnight or whatever, by being charged from the domestic Li battery. It would be interesting to know if the van could tolerate very long drives without lengthy periods of the engine being stopped (overnight etc).

So as I said, it is unidirectional. No doubt it could in the future be made to be bidirectional. Along with faster than light travel, coming soon…

If it is MOSFET switch then it’s the same as a relay. A direct bidirectional connection. A B2B is not a direct connection even though the circuitry might contain MOSFETs amongst other things. Input and output voltage of a B2B are likely to be quite different, unlike a relay or VSR. And current can’t flow bidirectionally.

I would say it’s more like a VSR. Probably with MOSFET switching rather than a mechanical relay.

I think it was probably a combination of bungs left in AND voltage sense wire on the wrong terminal. Like most accidents, more than one contributory cause. Eliminating just one of the two causes would have prevented the accident.

But in my experience Li cells, once properly balanced, never go out of balance unless they are faulty. The algorithm mention by the OP implies 2hr absorption every time SoC goes below 70%, which could be every day.

Maybe it was a typo?

A proper system! I would just say that 2hrs absorption seems excessive even bearing in mind the caveats you mention. Once the voltage has hit 14.0v (which is presumably when the absorption timer starts), I would have expected the current to have fallen below 5% in 15 to 30 mins, and holding the voltage up at 14v after that doesn’t really achieve anything, and does slightly stress the batteries. Might be worth observing the behaviour / charge current during the absorption phase after you have discharged below 70%.

I think it is reasonable in theory. It’s the same idea as connecting the boat alternator to the domestics and then using a split charge relay to charge the starter - because the domestics need the most charge. 4A does seem quite low but led lights on modern vehicles don’t take much current. It seems to work for them, anyway.

Yes. Although personally I have enough reasons already!

There is a stoppage notice about it. Definitely not available to passing boats. https://canalrivertrust.org.uk/notices/30146-fazeley-mill-marina-facilities-birmingham-fazeley-canal

New signs at the entrance say something like “welcome to Fazeley mill marina” “private marina, no entry”, which is somewhat oxymoronic. I guess it would still be possible to rock up in a boat and use the elsan, but that is verboten by the “head of marinas”. And not on Thursday or Saturday when the office is manned.

It is. And FMM is not really a marina any more, it is a moorings with very intermittent services, no caretaker/supervision for 5 days out of 7. And although they have finally partially sorted it after 6 months, no security. One could walk in under the bridge and walk onto our pontoon. Not great for an urban “marina”. They cut down the protective vegetation under the bridge and declined to fix the pontoon gate lock. Now 6 months later they have just installed fencing under the bridge but still no pontoon gate lock. One thing which really tickles me is FMM’s new website. See screenshot below. Slight problem, FMM is not in Warwickshire, it is in Staffordshire. Oh and it is not on the Coventry, it is on the Birmingham and Fazeley. So they don’t seem to actually know where their new marina is! That website has been up for about 6 months, they haven’t noticed!

It’s certainly closer to Aberdeen, but since my mother lives near Stratford on Avon, we still need to drive the same distance when we go to the boat because I feel obliged to visit her as well - she is after all 102 now!

Will be in Aston (Stone). But currently we are homeless , in transit. I suppose that makes us Continuous Cuisers!😱. But only for 3 days😇 Probably not😱

Yes same as previously mentioned. We are still in transit but popped into the new marina to deposit car and then get train back to collect the boat. Although the marina office person was different from last time, we received the same very warm and friendly reception. Chalk and cheese from the new order in FMM. Although to be fair, FMM has a new chap in the office (just 2 days a week) and he is great, but above him is the hostile regime so I doubt he will last long, he is too nice!

After 14 happy years in Fazeley Mill Marina, we have departed. Since Rothen Group bought it last autumn, the atmosphere from “the management” has been hostile, derogatory and we feel despised. Everything done is about the needs of the Rothen group, moorers needs do not seem to figure at all. Not the slightest concept of customer service or being in the leisure industry. Not prepared to put up with that so we are moving to another marina which as well as being much, much nicer and massively friendlier, is also £500 a year cheaper. It’s a no-brainer. FMM now looking very empty since lots of people have left. Maybe they have a plan to fill it in and build houses once those pesky moorers are got rid of? Or maybe it is a tax loss vehicle? Who knows, it is all very odd. It’s hard to believe they are not being deliberately unpleasant. Lengths of empty pontoon, this is just a small sample…

Yes.

Set at that when I received it.

My 105Ah Fogstar drift is set to about 14.3. Which is quite low.

It was certainly the case that when I first got my Fogstar the SoC was absolute rubbish. First time I put on the microwave (just under the max current) the SoC plummeted to zero almost instantly. And when I put on the 0.4C charger, it jumped to 100% very quickly and long before the battery was full. But after a few cycles it became OK.

In my experience - of which zero is with a kestrel reg - decent modern alternator controllers bring big advantages in lead acid charging. So whilst a standard 14.4v built in reg is OK, a good modern (digital) alternator controller is much better.

That’s interesting, I didn’t think it could do that. Must have come about in a firmware update… Always something new to learn!

Not necessary, but beneficial only in that it can be useful to have a backup/alternative/independent indication of SoC. For example if for some reason you need to disconnect the BMV display from the shunt (as I did when I stupidly dropped something heavy on the shunt and damaged the RJ45 socket on the shunt) - when you reconnect the previous SoC is not remembered and goes to 100% (by default). An ability to look at the BMS SoC and copy the value to the BMV gives a reasonable starting point pending the next sync to 100%.

But set against that is the temperature coefficient of the BMS MOSFETs - MOSFET on resistance increases with temperature, so there is a degree of current balancing between batteries in parallel. And interconnect resistances are very small unless there is a poor connection. My 12 cell Li battery (3P4S)doesn’t have equal interconnect lengths (due to battery box space constraints) but I am unable to detect any difference is current flow from the groups of 3 cells in parallel under heavy load. This is why battery manufacturers tend to allow perhaps 4 batteries in parallel.