Col_T

Quite right, Alan, but in both the cases you cite, the metal that is heated will expand in three dimensions. My question is, if a steel tank is heated, and therefore all sides expand in three dimensions, would the capacity of the tank actually decrease slightly?

Sorry to backtrack, but there are a couple of things I don't understand here, mainly around the 'expansion' topic. Firstly, get a block of steel, heat it enough to measure how much it has expanded and you will find that all three dimensions have increased e.g. it is wider, and deeper and higher. If that is case, wouldn't heating a tank cause it's volume to decrease a little? Secondly, in the scenario where a mooring dolly includes a fuel breather, and a tube extends down from the dolly into the tank. If I've understood it correctly, the suggestion is that expansion of air within the tank will cause a noticeable amount of diesel to be ejected through the fuel breather. Doesn't this require an amount of fuel to be trapped above the air so it can be expelled? If so, how does that fuel get trapped above the pocket of air in the first place?

Your first post says " I have 4 X 6v batteries and I check them to see if fully charged and it seems so.... They are reading at close to 6v when I checked them." The state of charge table, below, suggests that your batteries are not fully charged which may well explain why the Combi is permanently showing charger on fast mode. There is the chance that, if the batteries have not been fully charged for a long period, their capacity has been permanently, severely reduced, through a process known as sulphation. The only heavy load you talk about is the domestic, not 12v, fridge. When you are on shore-power, this will be powered from the shore-power, via the Combi, as long as the Combi has pass-through functionality built in. When not on shore-power, you will need the inverter function of the Combi switched on, to convert the 12v from the batteries to the 240v the fridge requires. The inverter is another load, and is not 100% efficient so will get hotter the longer that it has to work. Given that the fan is now on almost permanently, it's reasonable to say that the Combi thinks it's working pretty hard pretty much permanently - this may not be good for the life expectancy of the Combi. There is a chance that your little trip to Bath and back has taken a set on batteries that were dubious to start with and finished them off. I'm no expert in this electrical stuff, so hopefully the thoughts above will prompt someone who knows what they are talking about to intervene and educate us both! Hope this helps. There you are - Wotever and Old Goat beat me to it, and both know far more than I. Rejoice.

First time we came back leaving Bristol moorings at 8:30 and moored on the BOA side of Bathampton Bridge (183) at about 19:00. That included lunch on the hoof, but about 30 minutes for tea by the bus station in Bath. I thought that we were pushing on a bit, going against the stream at about 1600 revs, BETA 1505, but then I'm a bit of a wuz (that spelling looks well dodgy!) when it comes to flogging the engine!! Unless something has changed pretty radically, you'll encounter moored boats pretty much solid from BOA to Avoncliff Aqueduct, clumps of CCers between Avoncliff and Dundas Aqueducts, with the section between Dundas and Claverton seeming to be nothing but moored boats. After that, well, it's just Bathampton and Bathwick to look forward to! I think your best bet might be to get onto the river at Bath, and see the time is like, at least you'll have done the deep lock, the gates of which are flippin' heavy, and folk like watching but not helping! Have fun!

We've only done that section twice, but from our experience there is a short pontoon (3 boats?) just under the Bitton Railway Bridge (no. 211) on your right as you head towards Bristol. There is another short pontoon on your left, which also has water and Elsan (I think) but I neglected to make a note of exactly where in our copy of Nicholsons, so that's not much use, I'm afraid. There is also moorings at Hanham Lock, but these were occupied by what looked like long-termed a when we went past last year. On the two occasions we've gone down to Bristol, we've done the deep lock late in the afternoon, and moored by Bath bus station (pretty much opposite what look like old warehouses, which'll be on your left after four bridges) overnight so that we have all day to get to Brizzle. We motor on down to Hanham, phone the keeper at Netham Lock, which is where you pay and get a key, for the water points if I remember correctly. The Netham keepers will point out the mooring spots, opposite the Great Britain being our preferred spot, and you'll be on your way. We prefer Bristol to Bath - we think it has a better feel to it, and there's only so much sandstone this old fogey can stand!! Hope this helps, and that you enjoy your trip.

Not quite sure if I'm being sarcastic, pedantic, or humourless, but you'll be wanting a question mark at the end of your second sentence.

Not so much a thought, more a question. If one dip pipe has corroded, why wouldn't the other dip pipe be corroded?

Okay, thanks all for continuing my education. I've only encountered snap-head rivets to date so didn't realise countersunk rivets existed.

Wouldn't the countersink be inside the hull, rather than underneath the rivet head?

It was the Bimble site that gave me the idea to be honest, @Reg. As for swapping between solar-powered and mains-powered immersion heaters, I wouldn't bother, to be honest. We don't have an immersion heater at all at the moment, and swapping between two would be just inviting leaks I reckon, particularly with my plumbing skills!

Thanks for the comments, folks. Lots of useful stuff there, and certainly much to be thought about. That's it for now.

Thanks for this, @Robbo. The solar setup has yet to be specified, but will definitely include an MPPT charge controller, probably one of the Tracer family. @mrsmelly, our travelling pattern, to date, has been very much like yours is now - motoring every day. However, we've been down to Bristol a couple of times and were lucky enough to find electricity bollards at the mooring site opposite the Great Britain that even had credit left on them! It seemed a shame to have to run the engine just to get hot water, and my guess is that electric bollards on the majority of the canal network are few and far between - as someone before me once said "you can't plug into to a hedge", hence the investigation into alternative ways of generating hot water. I dare say someone will suggest a Whispergen, that can generate electricity and hot water at one and the same time, but I suspect those are even more rare than a hedge one can plug into! Thanks for the opinions, chaps.

We have a narrow-boat with hot water supplied by either engine or Mikuni diesel fired boiler, which is fine for our present 'holiday boating' pattern of use. However, we will soon be setting off on a series of 'mini-cruises', each of 4 to 6 weeks in length, and will be fitting about 500W of solar panels so that we don't need to run the engine every day to keep the batteries topped up. We are not power-hungry boaters - no TV, electric kettles, coffee-makers or hair-driers(!), and I estimate that we'll be using about 60Ah over-night (mainly the fridge) out of a 450Ah battery bank. The solar array should get the batteries recharged by mid-morning most days, and I'm thinking of installing an immersion heater into the calorifier as an additional source of hot water, the idea being that the excess capacity of the solar panels can be busy warming / heating water whilst we are away from the boat, exploring the local area. The options seem to be either a 240v immersion, which will require the Sterling 1500W modified sine wave inverter to be on, or a 12v immersion. All / any advice and / or experience would be much appreciated. Colin T.

We had two lighting units in the kitchen of our boat, both of which consisted of two 12v fluorescents. I have put 1 odd Bedazzled LED tubes in each lighting unit. A single LED is much brighter than the 2 fluorescents. Hope that helps.

Your original post said I read this and think you are saying that, if the 12.1v reading was taken from a remote gauge, the voltage at the battery terminals would be less than 12.1v. I don't understand your original post as I would expect a reading taken from a remote gauge to show a lower figure than a reading taken direct at the batteries.

Sorry chaps, but I don't understand this. If the 12.1v reading is taken at the battery terminals then that's the true reading, but surely any reading taken at a remote gauge would show less than 12.1v due to voltage drop along the cable run? How long a cable run would it need to be to give a significant voltage drop?

A question on 'C' rating. In the video, Jono says that charging his Victron lithiums at 0 degrees centigrade can be done, but the charge has to be within the range 0.05C => 0.1C. I'm not sure that I understand C ratings, so I'm really struggling to understand where he got the 5 amp number from. Any explanation would be welcome. On the discharge side, does a statement saying discharge at 5C mean apply a load that will discharge the battery in 5 hours?

Another vote for Craig Allen.

Thanks for this, Nick. You had me confused until I realised that meant that current would decrease by more than voltage would increase, at which point the penny dropped!

There is a formula that says Volts times Amps equals Watts. During the first phase of battery charging, voltage rises as current falls. If I understand it, this is because the battery itself is limiting the amount of charge it receives. Does anyone here know if the voltage rise and current drop are aligned during the first phase of charging so that the watts 'input' as charge is pretty much constant? If they are aligned, is there a way of predicting what the input charge would be, in watts, based on, for instance, battery specs?

Thanks for this, Tony. Much appreciated.

If the above is true, why is 12.7v usually quoted as the fully charged voltage of a 6 cell 12v battery? Indeed, why is 13.2v often referred to as surface charge? Not being funny, just trying to understand.

Johny, ISTR you threatening to get a battery de-sulphation gadget - I think it sent low current, high voltage pulses into the battery to break down the sulphation. Did you ever get that? Did it work? Was it rubbish? Just curious about it!

Good stuff, Dr. Bob. I got the missus one of the Baby Equaliser 5 Blade fans for Christmas, based on your recommendation. We've only been on the boat once since, the night before New Year's Eve as it happens, so have used the fan only once. The layout of our boat looks the same as yours and both the wife and I found the warmth from our Morso Squirrel seemed to be spread more evenly vertically. Certainly there was no overly hot layer of air at head height! The lady is more than pleased, which makes my life easier, and we're looking to using it much more in the days to come.

Our boat (4 x 110Ah sealed lead acid batts) also spends most of its life on shore-power, and it always seems as though the batts don't function particularly well for the first couple of days of a cruise e.g. as though they are down on capacity. My guess is that being on trickle charge for weeks at a time makes them 'lazy' and they forget what they are there for! Re your batteries, might be worth a quick look to see whether they are low maintenance or open lead acid batteries. If the latter, this might help explain why they seem to have lasted to well.