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Dr Bob

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Dr Bob last won the day on February 18 2021

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  1. Well of course they (the CRT) could, but they could also just ban them. What is the CRTs intention? We dont know. When they brought in the restrictions a few years back, the wording says that fat boats can make a passage if they inform the CRT first. I thought at the time I heard that they were trying to discourage fat boats and they would only allow 'essential' trips (ie not lesiure trips). The wording on the restrictions however allows any trip. I have asked the CRT in an email to clarify and they have not responded to me. We need to know their intentions - do they encorage leisure trips or not, up and down the North Oxford?
  2. Yep, someone saw it leave this morning crewed by a number of blokes wearing life jackets - looked like a boat moving company I was told. Hopefully one way trip only.
  3. Well it's not Miles Away. They are still here. It looks like it is the new Aqualine fat boat that was launched 4-5 weeks ago for commissioning. It has been sat near the slipway since it was put in with the occasional 'visitor' - presumably to kit it out. I've just noticed now that its gone - and was defo there this morning. I would guess therefore that this is a 'once only' transit and it was at Dunchurch just to be launched.
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  5. Tony, I am probably one of the few people with direct experience of what you are doing as I have a very similar system, a hybrid LA/Li set up with B2B's, long wires controlled by a BMV 713 and a BEP switch. I do think you are overcomplicating it a tad! There is two sides to this i) the technical set up and ii) how it is operated in practice. Lets look at these separately. Firstly the technical bit. For me the first level of control has to be the charge source reducing its input when a set level is reached, rather than the isolation switch activated. You say your first line of defence is the isolation activated when you get to 80% SoC. If you are using solar, then the MPPT will work fine to turn down to float so your isolation switch will never be needed. If you are on the alternator for charge then the B2B's will turn down once the set level is needed. I assume your isolation switch is the BEP. In the 4 years I have operated my system, my BEP has not activated once (on its own). I test it infrequently. For me the first level must not rely on the isolation switch. You then say you need 3 BMVs. Why are you controlling on SoC? On my BMV, SoC is pretty useless after a couple of weeks since sync. Why not use voltage? My BMV is set to trigger the relay for high voltage at 13.9V. This is an absolute value. My state of charge limit is always the same – when the alternator gets to 13.9v at circa 50A (drops from 120A at start). The SoC reading could be anything. One advantage of using voltage is that the BMV has a high level and low level relay so the one BMV does both. That removes your 2nd BMV, and also allows your charge sources to shut down rather than relying on the BEP. The BMV voltage is my second line of defence but as above it is never normally triggered. My third defence is the BMV sounding an audible (just) alarm at 14.0V volts, then a fourth - a cell monitoring device that activates the BEP if an individual cell goes above 3.8V and then a final audible alarm if the whole lot goes over 14.4V. The automated isolation is all via the BEP switch which is a vulnerability in the way Tom's Tyco bipolar relay could fail, but shutting down the charge sources in normal operation has to be the way to do it. I think though that you have to look at normal operation. I very rarely get anywhere near isolation events. I see 2 modes of operation, moving and stationary. An example from this summers 3 months trip out. In the stationary mode, we are tied up not going anywhere. Our 200Ah of power has gone out overnight (and previous 24hrs) and the BMV is showing -200Ahrs. The sun starts charging, we run the engine for an hour to warm the water (putting circa 100Ahr back in). The sun does the rest and the mppt goes into float at the end of the afternoon. No intervention at all. No B2B running – just straight from the solar to Li's. Lack of sun one day and I run the engine for an extra 30 mins. Never any chance of getting near full charge with the engine. I will turn it off after the time I estimate. If I died in the interim, the BEP would isolate it. In moving mode, we are down -200Ahrs at the start of the day. I know we will be charged enough after circa 60 mins and the B2B will shut down the charge then. In practice though I have given up with the B2B's (2* 60A) as they consume so much power and heat up the boat! …..and I just manually isolate the Li's when the voltage gets to circa 13.8V. If I want it automatic then the B2Bs are fine but I am always watching the instruments as we idle along so spending 10 secs to turn a switch is not a chore. It really is so simple. Now the solar is loosing its efficiency, when stationary, we just run the engine for 90 mins instead of 60 – but we are a very heavy power user. I do use 2 BMVs, one on the Li system that does all the controlling and one on the LA system. Both are needed to understand battery health for the two banks. Anyway, well done on setting up your system. It sounds complicated to the non initiated but it isnt. I would certainly encourage you to move to isolating the charge sources at source and then using voltage to control the BMV rather than SoC in an emergency situation. How do you monitor your system with the 3 BMVs? I have mine wired into a Raspberry Pi which dumps all the data to the Victron server (data 24/7) so can see all of the data from the last year from my armchair. For peeps new on here who dont know me, (who can you trust on the internet these days?)my electrical knowledge is significantly lacking when compared to Nick and Simon (MP) so my system was developed from a 'user' approach rather than a technical approach and one where I could marry 2nd hand Li's to a new boat where I didnt want to void any warranties – hence the hybrid. I do however consider myself an expert on Li batteries, particularly in their safety as I am director of a company working closely with the aviation industry setting standards (via destruction testing) on their transport on passenger aeroplanes and also developing new technology for early warning of battery failure leading to ignition or explosions (ie during dendrite failure).
  6. I didnt ask for sources of LiFePO's from cars. It's obvious that the new car sources are out of the question. You do realise do you that there were a number on here before you got interested that sourced Li's from the EV market - not just Peter? That is why I asked Peter (who knows about the sources) rather than you (who doesnt know about the sources). Those sources are still there with batteries 4 years older - and likely in much larger quantity as they are now 4 years older.
  7. Well said. A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter? That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.
  8. .....er how can I be here frequently if the last post before this current round was 2nd July? I frequently look for infrequent postings but frequently am disappointed. My infrequent red thermometer has been infrequently used since May as the stove has been in dormant mode awaiting the injection of some solid fuel and an ignition source. That cant be more than 3 or 4 weeks away....EEK!!!! Sorry to hear about Tom's blow out but 2 blown alternators sounds expensive. I'm using the BEP switch for charging and discharging (rather than the latching relay) but my strategy is for the charging source to back off or be isolated before the isolation switch activated so it is only to be used in an emergency. I do test it from time to time (infrequently - every 3 months or so) and do have an audible alarm if there was a failure. Tom, why did the alternator blow? When the tyco activates, the 12V LA in your system takes the surge. What happened when the relay blew?
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  15. I was trying to think how this relates to the subject of the thread but then realised that it hasnt got the word 'away' in it.
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