Dr Bob

Thank you, Tony.

Fully agree but I didnt consider my application to be critical to operation. Put it into perpsective. Sailing across Biscay in a Force 6 was critical to life. A quick and dirty approach via trending can give you a reasonable assessment. You also dont need to look at amps back in. Just measure Ahr out. Would you like me to fully define how you do it by trending? No I thought not. By the way, "Just measure Ahr out" should not be taken literally. I should have said, Just measure Ahr out and multiply by 1.25. Oh sorry, I should have said, Just measure Ahr out and multiply by 1.25 to get an estimate of the Ahr you would need to put back in. I dont want to be criticised for writing 'shorthand'.

Er...Yes, I do understand. The bit I have highlighted says that the point that you dont think I understand, I do understand. Of course SoC is not related to voltage, but you dont have to be a rocket scientist to work out how to use voltage at rest to calculate capacity. Wotever obviously understood it. I was trying not to write the ultimate detail so as to bore the guys who arent interested. I measured the voltage at rest when full - ie 12.8 ish, discharged during the day (but not on a known load). Measured voltage at rest again and noted the amps out. You can then do what you want with the numbers - ie work out difference in state of charge between the two values and thus estimate capacity. Would you like me to show you the calculations one needs to do? It seems that you lot want all the gorey details. If your maths isnt up to it, then I can happily oblige. I did this maybe every couple of months but mostly just noted the Ahr used to go from say 12.8 to 12.5 and if the number was the same and not trending down, then I knew the batteries were ok. I cant remember the exact numbers I used. There are two problems with the above approach which I am sure Tony will charge in with. 1) Voltage at rest needs a couple of hours to stabilise the voltage. Not always easy. On our yacht it was more easy to do this with no inverter. With experience you could see the difference between a light load and at rest. That wasnt rocket science either. In a 'single' system, where you do the same things all the time and the number of inputs is low, it is not difficult to understand the difference between light loads and at rest. 2) Normally the accepted way is to put a known load on the batteries to calculate the Ahrs taken out. Great if you need an exact number. I was looking for a trend of decreasing Ahrs out (not in - not needed) with varying voltage at rest so an individual accurate reading was not necessary. Over a period of a year if I saw the 12.8-12.5 range use 80Ahr ( a guess as I cant remember) +/- 10Ahr, then I was happy as long as the trend wasnt downwards. Over 5 years it didnt go down much - again cant remember. I was not after an exact number. For battery charging you dont have to be exact. +/- 10% is good enough. Watch the trends and you dont have to worry too much over individual readings as long as they are near the trend line. Whilst part of my career was spent on materials, ie plastics, paints, sealants etc I spent 10 years managing computer modeling teams, modelling a range of refinery/chemical plant applications. The models here were to predict operation of processes - viz monitor inputs and outputs and hence predict performance. Modelling a battery is no different. I made a comment in a post above about Smartguage (which I didnt elaborate on - yet it got some very negative vibes- so here is more detail). It would not be difficult at all to write a model based only on voltage that would predict a part of the charging process - After 5 years of watching batteries and charging/discharging, I could have written something similar for my set up given my knowledge of computer modelling, going from techniques such as the simple regression models up to more challenging methods of Topology or sparse data/others. I have read all the comments on here about Smartguages which is why I have not done any modelling myself and rely far more heavily on the Amps in/Amps out but following voltage does give you a lot of information if you use it in comparison with the other inputs. What would be interesting is to take a model based on voltage only (something similar to Smartguage) and add in the extra inputs of Ahrs change, plus inputs from the alternator (and or controller) plus solar, type/size of battery. Maybe the Ahr counters do some of this but I dont think they go far enough as they have their own model built in. Each system is diferent so you have different inputs/outputs. It would be possible to write a model for your own system and then this may be transferrable to other systems where a knowledgeable user could input his own data. Has anyone here done this? Apologies for such a long post but I am getting tired of a number of you trying to tell me I am thick.

Ah, very useful. So for a 100-50% cycle, these Trojans will do 1500 and for 100-80% they will do almost 3 times more. I will do a bit of searching on wet lead acids. This is why I was always told to not drop below 80% when we first started sailing.

I was actually asking the question as I am intrested in understanding the answer? I know 100% down to 50% will knacker a battery (but after 300 cycles or less?) and 100% down to 80-90% is pretty frugal (???) but then long life. What is the effect of 100 to 60%, 100 to 70% etc? You guys seem to profess to be the experts? All I know is how to keep bog standard wet lead acids in good shape and dont profess to know more. I do see the adverts saying 600 cycles, 1200 cycles and upwards.

What is a cycle? Is it is 100% down to 50% and back up again? It is certainly not 100% down to 80-90% and up to 100% again as over a 5 year period we must have done 1500 cycles. To me, looking after your batteries is to try and not fall below 80% which means having a big battery bank. On the yacht we could only afford 400 Ahrs (to keep weight down). On our NB we have 700Ahrs. If you run from 100% down to 50% and back all the time, then you will knacker them. Surely that is common sense? On the yacht our batteries lasted 5 years because of the SoC I kept them in, not because of reduced capacity.

There seems to be a theme from a number of you here that I dont know what I am talking about - and that my SoC was much lower than I was thinking (particularly Wotever)....ie I was keeping it between 80-100%. Also Mike referred to total capacity in one of his posts. I did monitor voltage at rest as I have said on a couple of posts. If you have 12.8V (almost) and it doesnt go below 12.5V then things are fine. I managed the system to keep it at these levels most of the time although the accuracy of the voltage measurement I have no idea of. Rest means a couple of hours with no load - I did test this now and again. Each morning you could see the voltage under load and see that everything was normal. I probably had enough information after the 5 years to build a model (like Smartguage) for what that is worth. In terms of capacity I did check from time to time the amps in/out versus voltage at rest and was happy that I wasnt loosing capacity big time. Ref your other post, spending £350 on solar will be very advantageous for the summer (and certainly better than an AtoB - if you have space) but very little advantage in the winter.....and winter is when you need the power as your existing solar will not be working nearly as well. I am very surprised you made that recommendation.

Mike, I didnt mean to insult you and apologise if that is the way it came over. Your experience is real and shows that it doesnt always go by the book. There is more to it than the chemistry that has been documented here. In our case we hadnt lost 50% of our capacity in years 2,3 etc as the voltage at rest showed more capacity than that but cant remember the exact number. We started with 440Ahr so a 50% decrease would have had a significant effect on days when we used 80 Ahrs.

Tony, I usually read your stuff with reverence both here and in the magazine.........however, I very much doubt the two sentances you quoted. Dont be so presumtive. My batteries lasted 5 years+ with no problems whatsoever - and it was not frugal use - you (a general you) cannot and we cannot do frugal use living aboard. The cabling was all fine. If I was mislead and the SoC was 80% not 100% when charged then the batteries would have died long ago. If my batttery and charging knowledge was suspect then again they would have died long ago. The only potential weakness was the brand new Volvo alternator which was only 70A but was matched OK to the size of the battery bank. Finally I do take offence in the comment posted above. That sentance suggests that I had a problem with my charging/batteries. I did not. They lasted 5 years plus on a brand new boat and performance was better with the Sterling unit. If there was a system defect with the original layout - ie the alternator, then the problem was certianly cured with the AtoB. Hence the AtoB was certainly worth buying. Interesting that ALL those throwing bricks at the Sterling unit HAVE NEVER USED ONE (and maybe never even seen one). Looking after batteries is not Rocket science but you seem to be making that way. A bit of common sense and it is easy with the right tools.

I am quite astounded by the vitriol poured out here about Sterling products. Whilst the canal world seems dominated by Victron, the sailing community see Sterling as premium products. Funny that a 5 year battery life span seems normal in sailing yachts whereas less than a year seems possible for canals - how can you destroy your batteries in 5 months? Certainly this is NOT down to different suppliers but maybe you have something to learn from the 'other side'. Someone seemed to be saying I was a gullable fool for having the AtoB. Do your bog standard cheap batteries last 5 years+? I am out of here.

Not quite right but not far off. Yes typically the motor would be run first thing to get us out of a marina or off an anchorage, but the solar was a panel that had to be taken off when sailing so maybe only used every other day. Wind/water gen, used only when sailing fast enough. I will be guided by what you say on our SoC but if it was only typically 80% then there is no way the bank would have lasted 5 years. I was paranoic about keeping it above 'My' 80% and it went below only on a few occasions, once on a North Sea race from Aberdeen to Stavanger where we couldnt run the engine and likely we went to 50% SoC (by amps out and voltage at rest) and another couple of 2 day races when it went below 'my' 80%. On a sailing yacht with no inverter it was pretty easy to see the voltage at rest as a lot of the time when racing everything was turned off.

1) Agreed 2) Agreed. I used 500% as that is what Sterling say..... 3) It is interesting that most of my friends with Sailing Boats who were also live aboards (so Yachts from 35-45 ft) were not changing batteries that often. 4-5 years seemed the norm. Our set up was pretty typical with 400Ahrs and only a very small inverter - fridge was 12V and electrical appliances (hair driers, curling tongues, coffee machines etc) only used on shore power. The main drain on power were the chart plotter (circa 4Ahr), fridge (3-4Ahr when on - I think), anchor light and tricolour at the top of the mast plus the only big draw was the anchor windlass which drew 80Ahr if I remember correctly. Some boats had a Girlie Button which also took big power. Only the biggest, heaviest boats had a washing machine!!!!! On this forum it seems the norm that batteries last a very short time. Could it be that it is the use of big inverters (2KW and above) that is killing the batteries? It will be interesting to see how mine last as our One Pot and Coffee maker are both taking 1.2KW and Washing machine that keeps tripping when the wife does a 30deg wash - told her to do cold washes for now.

I am going to disagree. In an earlier post, you said my first statement was wrong in that the AtoB fools the alternator into charging at a faster rate. The Sterling charger reduces the voltage from the alternator - not increases thus fools it - and not increases voltage as you say. It is not the same as other Ato B units. It is a fact that we got more amps into our batteries with the Sterling unit. Probably 25% of the boats we knew had these units and the owners saw the benefit. No one in the NB world seems to use Sterling which is surprising considering the number of sailing boats that use them. I doubt Sterling would be in existence if your coments above are true as they would have been hammered by Trading Standards. Sterling do not quote at what stage of charge their Ato B units are 500% more efficient but for us we saw a big efficiency change at the higher end of charging. Rather than continually saying the chemistry doesnt allow faster charging, why not consider the facts that people who actually use this kit see a benefit. If I had another yacht I would certainly add a Sterling AtoB. I am holding off doing so on my NB as I run the engine far more and it seems to charge far better at tickover than the Volvo unit I had.

Right let's rewind. After a night at anchor we had used 40 A. 30 mins to an hour of engine with An AtoB brought that up to a state of charge a lot faster than no AtoB. Battery bank 440amp. Maybe the state of charge was not 100%. Let's assume it was only 95%. Maybe it was even less. Maybe I should be saying how long it took to put 40A ( as per the meter- which may only be 35 A true) back in. The AtoB was faster. Voltage at rest was fine. The batteries lasts 5 years and more. I am looking at a comparison here. Have you tried an AtoB? I lived with one for 4.5 years.

Thanks for the link. Yes, I had read this before. We also had some solar to top up and a wind/water genny which did achieve full charge at least every other day so mainly we were 'nearly' fully charged.

I was referring to 80-90% charge. I also said the AtoB started at 40A and kept it at this for much longer. Therefore to go from 90 towards full was not much more than an hour. OK, maybe only 95-97%. The point I was trying to make was that the AtoB was far better to get to that level of charge than the straight alternator which within a short time was charging at less than 5 amps. It then took a few hours more to put back in what had gone out. Maybe you are right that I wasn't getting to full charge as I was using amps in vs amps out (as well as charging Amps down to 2-3) but I was looking at the comparison to that state of charge, whatever that state of charge was - to me it didn't really matter as long as state never went below 80% (which was likely less given all the flack I am taking here on state of charge) but the strategy worked as they lasted at least 5 years and possibly more. The AtoB worked better. The battery monitor, if I remember rightly was a BEP one, which 10 years ago seemed to be pretty sophisticated.

My comments were all about the later stages of charging as it sounded like the OP was talking large battery bank and a useage of 100A per day (my interpretation of the numbers that had some dubious values in them). On our yacht, we therefore got away with charging for 30mins to an hour rather than 2-3 hrs -which was important as we were sailing not motoring (ie your one to two hours a day). The AtoB worked well for us. The batteries (cheap end 110A lesiures) worked well for 5 years until we sold the boat. Only once went down to 50% charge and only below 80% a few times so they were looked after. Never saw the negative effect of overvoltage.

The Caly canal is hardly a place to take a narrowboat. Useful to have Steel boat in the locks given all the Hoseasons boat that dont have a clue but a Narrow Boat would be well out of place on Loch Ness. We took our 40ft Yacht with 60ft mast and 2.4 metre draught through there 3 times. It's more 3 big lochs (ie Scottish Lakes) joined by very wide canals. Defo a place for GRP.

Combination of replacing the amps that had been taken out overnight - as measured by a amp hour counter, and then the alternator amps in dropping to 2-3amps which usually seemed to co-incide. We also had a Sterling battery charger that was used when we were on shore power that achieved 100% (I assume) so we had a base line from which to measure Amps out. I was a bit of a power nerd, and watched and plotted the volts and amps all the time. Probably had enough data to write a model for the voltage (similar to the Smartgauge!). I prefer amps in and amps out, but of course that doesnt tell you the capacity of the bank if it has deteriorated.

I was trying to keep it simple and not get too technical. In my experiencethe AtoB did work very well and was 5 times faster than without. Our system was 420 Ahr of batteries (new at first) being charged by a 70A alternator. The boat was new, using a Volvo Penta engine - so new alternator/wiring. My comments were about the ability to charge the batteries from circa 85/90% to full - which is where the OP is going to be if he has upwards of 600Ahr capacity. Before we fitted the AtoB, at 85/90% capacity, the alternator would start by putting in 25amps or so but this would fall very quickly to 5 -10amps and take over 5 hrs to get to 100%. This was on a Sailing yacht were you didnt want to have to run the engine for more than half an hour to get out of your berth. We fitted the AtoB and found that the initial charge was 40 amps but it was sustained at this level for much longer. Less than an hour was needed to get up to 100%. In our case it was 5 times faster and it was new kit (albeit smaller capacity etc). We lived aboard for 3 years and in the 5 years we had the boat, the battery performance did not seem to deteriorate. I am sure you are right in saying a modern Beta with 175A domestic alternator is the bees knees, but not everyone will have that. Our current boat doesnt but with 700Ahrs of capacity and a 90A alternator, I am happy to run it a few hours to put the amps back in.

I think you may be getting a rather skewed picture from the replies in this thread. There are a number of folks saying NB's are the best for canals and a number of folks supporting GRP. It almost sounds like is pretty even. You need to look at reality. As I said before, we have just done the Warwick ring in a week (ie 130 locks - with a detour into Brum) and NOT ONE Grp boat passed us. NOT ONE. Yes you may be seeing them near rivers (where GRP is by far the best choice) but in a the muddy ditch areas - people are not using them - less than 1% on this route in the last week. Does that tell you something? If you decide not to share locks with NB's then you will be slowing down the lock process and waste water which by the levels we have at the moment is important. Whilst you may be happy to wait till the NB in front completes the lock, what about the guy behind you, and the one behind him. If you were doing 99%+ of you time on canals, IMHO you would be daft to buy a new or 'modern' grp cruiser. Most other people in this neck of the woods think the same (viz not passed one all week) I'm out of here!

...but all the GPR boats I am seeing are looking extremely tatty. Our GPR sailing boat was bought by us new. We had here for 5 years. We lovingly protected her from all sorts of potential damage. You just cant do that on the canals. We loved our GRP boat on the sea. I firmly believe a GRP boat on the canals is a bad idea. The laminate may hold up over many years but not if you are going in an out of wide locks with steel boats. What are you going to say when you motor into your first lock on the GU and then you are followed in by a steel NB who clouts your back end. It happens all the time.

Point 1. Yes, you are right that older boats were made with much thicker laminates - not denser. No that has no difference to osmotic blistering. Blistering is caused by air pockets in the laminate. Water migrates to these pockets by osmosis. It is mainly the gel coat which will stop this ingress so the gel coat is key in looking at osmosis. The older method of hand lay up of the laminate caused a lot of the air voids hence a lot of evidence of osmosis on boat made in the 70's and 80's. Thickness of laminate has zero effect on the progress of osmossis When the manufactures swiched to vacuum infusion or resin injection, the air voids were less and the glass was better wet out and hence osmosis is less. I would forget osmosiss. It is not a problem. It never sank anythink. I would be far more worried about a big gash in the front of my boat, or a load of very fine cracks caused in the gel coat caused by a 'casual' bump against the lock entrance - as that will let water into the laminate ....and that is not osmosis. Point 2. Fine, see you on the GU in a few weeks in one of the wide locks. I wouldnt like to be crushed in there with a 20te steel boat next to me - dont forget, I dont have fenders out. Rivers yes, canals no.

What are you asking? GRP stands for glass reinforced plastic. That is a composite made from a fibre (ie, glass or nylon (ie kevlar) or carbon fibre) bound together with a thermoset matrix, (ie unsaturated polyester, vinyl ester or epoxy etc) From your other post, you seem to suggest one sort is better for osmosis. Epoxy/ Carbon is by far the best with glass/polyester the worst ....but almost all GRP boats are made with glass/polyester. You then have to think about how it is made, ie glass to resin ratio, type of glass (chopped strand mat, spray roving, or woven roving) lay up method ( vacuum, resin injection, hand lay up etc). Your average buyer will not have a clue about the above. All the above will have an effect on lifetime - and osmosis which you referred to earlier.

NO, NO, NO. A scratch on a GRP hull will cause a tear of the gel coat and therefore expose the glass fibre laminate underneath. Water will therefore have access to the glass mat and water will wick into the laminate causing damage. Scratches must be repaired. With Steel, at the next lift out, you can just monitor corrosion and get it welded. GRP is FAR, FAR less forgiving. Trust me, I'm a Doctor (with 10 year developing GRP). We lived aboard a 40ft Sailing Yacht sailing it from Scotland to Greece over 3 years so know all about how GRP hulls work. We have recently bought a solid, steel, heavy, long, wont sink, narrowboat. We have just completed our first month aboard doing the GU, the Staford, the Birmingham and Fazely, the Coventry and Oxford canal, and there is NO WAY I would try and do this in a GRP boat. The locks, bridges, other narrowings, are just not wide enough to traverse without contact. Yes, you can get 100% contact free, but just one bump and you will need to check the hull for damage. Just one lock approached at the wrong angle would see an impact on the front that could cause load of micro-cracks which will weaken the hull. On our recent trip round the Warwickshire ring, I did not see one grp boat going in the opposite direction. It would be very interesting to share a lock on the GU with a plastic boat. If I had a GRP boat I would never go in a lock with a steel narrow boat. I am not sure where your comment on osmosis comes from. All GRP will suffer from it to greater or lesser degrees. It is caused initially by poor lay up techniques introducing air voids in the laminate, which water is then driven into by osmotic pressure. The speed it will be driven into will be a function of the water transmission through the gell coat or laminate. Some gel coats are worse than others (I spent 4 years developing gel coats for one the UK's polyester manufactures many years ago). Osmosis is not something you should worry about as it is unlikely to sink a boat made over 10 years ago when the laminate thickness was usually good. Far worse is the effect of a cracked gel coat which then allows water directly into the laminate. Water will wick up the glass fibres and reduce the strength of the fibre to resin bond weakening the structure. This is not osmosis. To be honest, most grp hulls were so overenginered that they will never sink anyway - just look at the much reduced thickness's now.....but would you like to be in a lock with me. No, GRP hulls for oceans and rivers......Steel narrowboats for the canals.