StuartO Posted August 24, 2015 Share Posted August 24, 2015 I'm still not sure I understand what these devices do - and therefore whether they have any value to me personally, given my pattern of MH use. Please correct me if I'm wrong but AFAIK a B2B artificially enhances the charge delivered to a leisure battery by the MH's engine alternator, so that you get a more complete re-charge during a period of driving. Even a full day's driving will not necessarily fully recharge your leisure batteries whereas with a B2B fitted you will get much closer to achieving this. Depending on your pattern of using your MH, i.e. if you do enough driving, a B2B might therefore relieve you of the need to fit solar panels or to use an EHU. There is a potential downside in that a faster rate of recharge has to involve applying a higher charging voltage to the batteries and this may not be good for their service life. A B2B is also a substantial and costly piece of equipment, costing £200 or more. A B2B does not charge your batteries unless your engine is running and doesn't charge fast enough to make using the engine while stationary, purely to charge your leisure batteries. As with many MH accessories, the potential value of a B2B depends on the pattern of your use of your MH. If you drive your MH most days while touring and rarely stay in the same place for more than one or two nights, a B2B might provide a better and cheaper option for topping up your leisure batteries than fitting solar panels. If on the other hand you spend more time parked up than driving and if your MH is stored without access to an EHU, solar panels will probably deliver better results. Have I got that about right? Link to comment Share on other sites More sharing options...
Tracker Posted August 24, 2015 Share Posted August 24, 2015 Maybe whether anyone thinks that you are right or not comes down to their own personal experiences and opinions more than available facts? A low current B2B is handy if you have a solar panel and it them to top up the engine battery too - very handy when the van is out of use for a few weeks. As I understand it a modern alternator chucks out a high amperage at low revs so even at tickover you should, I think, get a far better charge rate into the leisure batteries than the measly charge allowed through by most van's built in wiring. Allegedly, they say it is to reduse the risk of gassing but the voltage is not high enough to eliminate the risks of sulphation. You just can't win! I seem to recall Alan of aandn telling us that a powerful B2b can put too much strain on the alternator causing it to fail prematurely. I respect his experience but I don't quite see how a B2B could do that as the alternator cannot output more than it is designed to output and should surely be capable of running for short periods at full output - or not? All of which is why I am still deliberating whether I need a solar panel, a B2B, or just carry on with twin leisure batteries. I used to be indecisive but now - I'm not so sure! Link to comment Share on other sites More sharing options...
Sydney1 Posted August 24, 2015 Share Posted August 24, 2015 Our vehicle is stored remotely and as we have use of a classic VW camper it's only used outside of summer months. Worried that the alarm and GPS tracker would run down the battery, we fitted an extra leisure battery and B2B charger so combined with our solar panel it keeps everything topped up nicely. Batteries have always been full when we needed them Link to comment Share on other sites More sharing options...
Guest Peter James Posted August 24, 2015 Share Posted August 24, 2015 Tracker - 2015-08-24 12:49 PM As I understand it a modern alternator chucks out a high amperage at low revs so even at tickover you should, I think, get a far better charge rate into the leisure batteries than the measly charge allowed through by most van's built in wiring. Correct. I just have the vans original battery from 2008 together with a larger one the same age connected in parallel as leisure batteries. (the main battery is only 3 years old) Connected to the main battery through a voltage sensing relay. I used good thick 25mm2 tinned copper welding cable to minimise voltage drop, and they charge quickly even on tickover as the X2/50 comes with a 160 amp Bosch alternator as standard. Still working a treat with 7 year old batteries. Link to comment Share on other sites More sharing options...
kevina Posted August 24, 2015 Share Posted August 24, 2015 Tracker is correct that the b2b will deliver full output (if required) whilst the engine is ticking over. Also that modern 140A/160A alternators will cope fine with a 50A b2b. Think of the b2b charger as a powerful, sophisticated 3 stage battery charger. More sophisticated than your mains charger because it will have voltage sensing and temperature sensing inputs from the batteries and will have several charging profiles for different types of batteries (flooded/gel/agm1/agm2). It will also be connected with much larger wires. If I didn't already have a solar panel fitted I wouldn't bother now that I have the b2b. That is with my particular motorhome usage; always in autumn/winter, 2 months touring with only 1 or 2 night stops and 2 months skiing with 4 nights to a week stopped (will run van on tickover for 1 hour after 3 or 4 nights). Kev Link to comment Share on other sites More sharing options...
keninpalamos Posted August 24, 2015 Share Posted August 24, 2015 I Fitted my B2B charger to run with my solar panels not instead of. The panels are connected to the input side of the B2B charger via a Steca regulator. When the sun comes up they turn on the B2B charger which in turn does what it does when you start the engine. It ensures the starter battery is fully charged then diverts the power to the auxiliary batteries and I've noticed that the voltage output is always greater than the voltage at the solar regulator ie the voltage input. When the sun goes down the B2B turns off. The Sterling BB1250 is in fact a 4 step charger and puts a greater voltage charge out than it is taking in. It doesn't "artificially enhance" the charge, it actually does it and I quote "In a nutshell it charges your extra battery system about 5 times faster than it would otherwise charge, doubles the useful power subsequently available, and increases battery life by de-sulphating them. For best effect use open lead acid batteries" etc etc etc. The words of a very experienced electrical engineer and component designer. Of coarse there are people on the forum who would dispute the above and we all have a different point of view and some would sooner listen to Burt in his shed up the road. I will say my 'van is quite old and the electrical system reasonably simple but it works for me. I will add that I use Trojan 2 x 6v 250amp hr traction batteries wired in series to give 12v and 250 amp hr which I have had for 8 years now not 6 as I stated elsewhere on the forum. :-S Link to comment Share on other sites More sharing options...
aandncaravan Posted August 26, 2015 Share Posted August 26, 2015 Yes StuartO your summary at the beginning is pretty much spot on. However, some of the more sophisticated units like Reich, Schaudt, Arsilicii are designed to handle ALL power coming in and going out. For example the Schaudt Elektroblock EBL 220 will not work correctly if you charge the battery via an outside source. When you put on a light that draws 0.1A it knows the current being drawn, it can watch the battery voltage drop. So if at 0.1A draw the battery drops by 0.1v in one hour it can calculate the size of the battery bank. This allows it to predict how long the battery will last at a set usage, etc. So imagine what would happen if you put on a Halogen light, just as a Solar panel wakes up and starts charging the battery directly? The EBL will see the battery voltage rise, which as far as it is concerned is impossible. It can shutdown thinking there is a issue. Best case is that the figures will not be accurate. If a B2B is wired to charge the batteries directly, you can see the same potential issues as the EBL will be completely unaware of any charging taking place directly to the batteries. B2B's work in different ways, the Stirling version 'Tricks the Alternator to work at it's Maximum', within the confines of the B2B capability. It doesn't 'enhance' the charge, just sticks a whacking great load on the Alternator and passes the resultant amps to the batteries. The one thing that you missed off about B2B's is that they increase fuel consumption. People believe that the energy is free because they are driving anyway. But it isn't, if you place a higher load on the Alternator it will load up the engine to supply those extra amps. The engine has to work harder so you use more fuel. The more amps you draw the greater the penalty in MPG. You will sometimes hear a B2B Motorhome 'squealing' as it drives off from site after a heavy battery drain because the loading on the Alternator is so high it places an abnormal load on the drive belts/pulleys which slip. People think the running cost of a B2B is zero, but it isn't. The loss in MPG on a long run South can be significant. Add on the toll on the batteries and their replacement costs, The shorter life of the Alternator, etc and it works out more expensive compared to other power sources. The Stirling B2B was designed for boats. But remember a boat usually has a 100A Alternator for the starter battery and ANOTHER 150A Alternator for the Habitation batteries. The habitation battery bank is usually twice the size of a Motorhome bank, so even though the output from the Alternator might be 130 amps, spread across 6 batteries it is 'only' about 22amps per battery so they stay pretty much within tolerance. As we say on the website a B2B can be useful on Motorhomes with less sophisticated electronics. They can be the right choice for some people but generally create issues with many Continental built Motorhomes. We have just restored a Citroen H van for the Wheeler Dealer TV show, goes out 28th September on Discovery, for use as a catering vehicle. See the 11th Photo?? of it being loaded on a Trailer outside our 'shed' after completion : http://www.citroenhyonline.co.uk/gallery.php They initially wanted the Ford Transit Engine transplant we do for the H van, but then asked us to do a Rally spec 2.1 engine. That then snowballed to doing a lot more as can be seen in the photos. After we delivered it they contacted us to say that they were going to do some Interior changes on screen, one of which was to fit a Invertor. We suggested they did not as we said it would not work on a H van. The Salesman assured them it would all work ok so they went ahead and fitted it anyway. A 4KVA Inverter running from a 290Ah AGM battery. They thought it would be something other H van owners could do. The Salesman said it would allow the new owner to run the 240v Fridge, water Heater, etc while he was trading and then charge up the battery on the drive home. The thing is the 'uprated' Alternator on this particular van is 45amp so has a maximum 30amps spare after the engine and ancillaries take their bit, assuming its not raining or dark. If you ran the battery down half flat, to put back that 145Ah would take a five hour drive, assuming the Alternator would run flat out without catching fire. Most H van owners drive short distances when they trade, typically less than 30mins. The most ridiculous thing is that a standard H van up to 1963 has a 6v Dynamo with about 16amps output!!. Even the later 12v vans had only a 30a Alternator which rarely gets beyond 25a output. Subtract 15amps for the engine, etc and 10amps isn't going to charger a big battery this side of a 20 hour drive. They just didn't do the maths, but listened solely to the Salesman who happily drove off with nearly £6k. After filming we noticed a tortured squealing noise from the Alternator belt. I suspect it won't be long before the Alternator comes in for a rebuild. Watch the TV show and check out just how big this box of tricks is. Link to comment Share on other sites More sharing options...
kevina Posted August 26, 2015 Share Posted August 26, 2015 OK, so a 1000 mile drive south takes, say 30 hours. The engine is working at, lets say 50Kw, so it produces 1500Kwh on the drive. A battery stores about 1Kwh of energy, lets say it needs a 50% recharge 6 times during the trip (that is a lot) so the engine needs to produce an extra 3Kwh to keep the batteries topped up. Cost in extra fuel = 0.2% which would be used even if you didn't have a b2b charger. Link to comment Share on other sites More sharing options...
StuartO Posted August 26, 2015 Author Share Posted August 26, 2015 aandncaravan - 2015-08-26 2:07 PM Yes StuartO your summary at the beginning is pretty much spot on. Thank you Alan. I suppose if I try enough times I'm bound to get something right occasionally! Link to comment Share on other sites More sharing options...
Curtisden Posted August 26, 2015 Share Posted August 26, 2015 aandncaravan - 2015-08-26 2:07 PM Yes StuartO your summary at the beginning is pretty much spot on. However, some of the more sophisticated units like Reich, Schaudt, Arsilicii are designed to handle ALL power coming in and going out. For example the Schaudt Elektroblock EBL 220 will not work correctly if you charge the battery via an outside source. When you put on a light that draws 0.1A it knows the current being drawn, it can watch the battery voltage drop. So if at 0.1A draw the battery drops by 0.1v in one hour it can calculate the size of the battery bank. This allows it to predict how long the battery will last at a set usage, etc. So imagine what would happen if you put on a Halogen light, just as a Solar panel wakes up and starts charging the battery directly? The EBL will see the battery voltage rise, which as far as it is concerned is impossible. It can shutdown thinking there is a issue. Best case is that the figures will not be accurate. If a B2B is wired to charge the batteries directly, you can see the same potential issues as the EBL will be completely unaware of any charging taking place directly to the batteries. B2B's work in different ways, the Stirling version 'Tricks the Alternator to work at it's Maximum', within the confines of the B2B capability. It doesn't 'enhance' the charge, just sticks a whacking great load on the Alternator and passes the resultant amps to the batteries. The one thing that you missed off about B2B's is that they increase fuel consumption. People believe that the energy is free because they are driving anyway. But it isn't, if you place a higher load on the Alternator it will load up the engine to supply those extra amps. The engine has to work harder so you use more fuel. The more amps you draw the greater the penalty in MPG. You will sometimes hear a B2B Motorhome 'squealing' as it drives off from site after a heavy battery drain because the loading on the Alternator is so high it places an abnormal load on the drive belts/pulleys which slip. People think the running cost of a B2B is zero, but it isn't. The loss in MPG on a long run South can be significant. Add on the toll on the batteries and their replacement costs, The shorter life of the Alternator, etc and it works out more expensive compared to other power sources. The Stirling B2B was designed for boats. But remember a boat usually has a 100A Alternator for the starter battery and ANOTHER 150A Alternator for the Habitation batteries. The habitation battery bank is usually twice the size of a Motorhome bank, so even though the output from the Alternator might be 130 amps, spread across 6 batteries it is 'only' about 22amps per battery so they stay pretty much within tolerance. As we say on the website a B2B can be useful on Motorhomes with less sophisticated electronics. They can be the right choice for some people but generally create issues with many Continental built Motorhomes. We have just restored a Citroen H van for the Wheeler Dealer TV show, goes out 28th September on Discovery, for use as a catering vehicle. See the 11th Photo?? of it being loaded on a Trailer outside our 'shed' after completion : http://www.citroenhyonline.co.uk/gallery.php They initially wanted the Ford Transit Engine transplant we do for the H van, but then asked us to do a Rally spec 2.1 engine. That then snowballed to doing a lot more as can be seen in the photos. After we delivered it they contacted us to say that they were going to do some Interior changes on screen, one of which was to fit a Invertor. We suggested they did not as we said it would not work on a H van. The Salesman assured them it would all work ok so they went ahead and fitted it anyway. A 4KVA Inverter running from a 290Ah AGM battery. They thought it would be something other H van owners could do. The Salesman said it would allow the new owner to run the 240v Fridge, water Heater, etc while he was trading and then charge up the battery on the drive home. The thing is the 'uprated' Alternator on this particular van is 45amp so has a maximum 30amps spare after the engine and ancillaries take their bit, assuming its not raining or dark. If you ran the battery down half flat, to put back that 145Ah would take a five hour drive, assuming the Alternator would run flat out without catching fire. Most H van owners drive short distances when they trade, typically less than 30mins. The most ridiculous thing is that a standard H van up to 1963 has a 6v Dynamo with about 16amps output!!. Even the later 12v vans had only a 30a Alternator which rarely gets beyond 25a output. Subtract 15amps for the engine, etc and 10amps isn't going to charger a big battery this side of a 20 hour drive. They just didn't do the maths, but listened solely to the Salesman who happily drove off with nearly £6k. After filming we noticed a tortured squealing noise from the Alternator belt. I suspect it won't be long before the Alternator comes in for a rebuild. Watch the TV show and check out just how big this box of tricks is. Agree with most of that. My East Neuk is fitted with a Amperor Power Interrogator which does the lot. Inputs the solar panel output in storage first to the Van Battery then when 80% full to the leisure and maintains them. Fools the alternator into maintaining higher charge direct to the Leisure battery charging on a 3 stage system quickly while driving and will also if needed take the output from a wind turbine or extra solar panel. Been running for 3 years trouble free. Solar panel went down but that may have been as it was a flexible type. Never need to hook up, In fact I can only think of a couple of times when we have to run a fan heater in - 4 temperature. Oh yes our fridge is also 12 volt only but my battery is a 230 Amp Banner? East Neuk are now using a Sargent EC328 which seems to be more high tech but does the same job. Hope that helps. http://www.amperorassociates.co.uk/c-DC_power_supplies/PowerS-PI.html http://sargentshop.co.uk/EC328-Power-Supply-Unit Link to comment Share on other sites More sharing options...
aandncaravan Posted August 27, 2015 Share Posted August 27, 2015 The Amperor is a nice bit of kit and flexible, but only has a 25A (max) output so not in the high power battery bashing category. As for an Alternator not taking a lot of power? See here : http://www.dslreports.com/forum/r24644940-how-much-horse-power-is-needed-to-power-a-alternator They write an Alternator can be a very inefficient 'Charger', particularly so when powered by expensive Diesel. They quote, "Because the alternator is around 60% efficient, it consumes about 1 horsepower for every 450 watts of load. In a 13.8-volt charging system this means our alternators draw one horsepower for every 33 amperes of load current". So a 150amp Alternator could draw 5 Horse Power?. That is an extreme example but shows how it's not free like some think. Link to comment Share on other sites More sharing options...
kevina Posted August 27, 2015 Share Posted August 27, 2015 I didn't bother with alternator inefficiencies but the bottom line is that, over "a long run south", a b2b will cost no more than without. (The b2b itself is very efficient, doesn't get very hot and looks after the batteries with a clean supply). It will cost more on a shorter trip with an empty battery but then the alternatives are: campsite hookup, generator or invest in solar and hope it's sunny. You have to pay to recharge one way or another. Link to comment Share on other sites More sharing options...
keninpalamos Posted August 28, 2015 Share Posted August 28, 2015 kevina - 2015-08-27 4:13 PM I didn't bother with alternator inefficiencies but the bottom line is that, over "a long run south", a b2b will cost no more than without. (The b2b itself is very efficient, doesn't get very hot and looks after the batteries with a clean supply). It will cost more on a shorter trip with an empty battery but then the alternatives are: campsite hookup, generator or invest in solar and hope it's sunny. You have to pay to recharge one way or another. We know nothing, I'm throwing mine out and buying a caravan., even though I've had the B2B for many years and my batteries for 8 years and the fan belt doesn't squeal (because it is adjusted correctly) and they don't get hot and I've never had a fire or a new alternator, and my cassette has never blown off.....sorry wrong thread. Anyone want a B2B charger free... :D Link to comment Share on other sites More sharing options...
StuartO Posted August 28, 2015 Author Share Posted August 28, 2015 The problem we all face, human nature being what it is, is the tendency to want the gadget you've chosen to back up your judgement, so you have a bias towards praising its merits and perhaps even being blind to its constraints or limitations or faults. For example it clearly must cost some money in extra fuel to extract more energy from the alternator to charge the battery more quickly. It may not cost enough extra to be worth worrying about to you personally but arguing that it won't cost extra at all is to show that you don't understand the laws of physics. This thread, and a couple of other electrical ones recently, should be enough to persuade anyone with an open mind that there are pros and cons in every case and that an individual pattern of using a motorhome can make a big difference to which choice or combination will be optimal for you personally. B2B chargers, solar panels and even portable wind generators are all of potential value to a motorhomer, depending on what sort of motorhoming they do. But if you store your MH plugged into an EHU an always use sites and an EHU, none of them are likely to have any value at all. Link to comment Share on other sites More sharing options...
kevina Posted August 28, 2015 Share Posted August 28, 2015 Nobody was arguing that charging a battery wouldn't cost any extra. Aandn said: "People think the running cost of a B2B is zero, but it isn't. The loss in MPG on a long run South can be significant". I was making the point that on "a long run south" the batteries will be fully charged with or without a b2b so there is no overall extra power through the alternator needed to run a b2b except a tiny amount because it is only 95% efficient (similar to solar regs). Therefore there is no "significant" extra cost. The fact that the alternator is inefficient applies equally to split charge relay charging and b2b. Link to comment Share on other sites More sharing options...
StuartO Posted August 28, 2015 Author Share Posted August 28, 2015 I'm sorry if it sounded like I was having a go at you because that wasn't the intention. Alan had made the point that there's no such thing as a free battery charge and I was simply reinforcing that. One way or another it's always costing you, even if only in depreciation costs of your equipment, and loaded alternators do increase fuel costs - the more the charging load the bigger the fuel cost. With a B2B you might well get a full battery recharge from a full day's driving but there would be a fuel cost and, as I understand it, a forced fast charge of that sort is far from ideal for the service live of some leisure batteries. You may have a different view about this or that and that's OK by me. But I remember a full day's drive we did after a couple of nights on the leisure batteries and I was disappointed to see that (without a B2B) I only got about two thirds charged. It was quite a surprise and struck home the idea that batteries have finite capacity to accept a charge from an alternator, so driving doesn't automatically top them up. (This was before I got solar panels, which I subsequently discovered work just as well when your driving as when you are parked up and do seem to give me a full recharge in a day, more or less every day.) Link to comment Share on other sites More sharing options...
Curtisden Posted August 28, 2015 Share Posted August 28, 2015 kevina - 2015-08-28 6:30 PM Nobody was arguing that charging a battery wouldn't cost any extra. Aandn said: "People think the running cost of a B2B is zero, but it isn't. The loss in MPG on a long run South can be significant". I was making the point that on "a long run south" the batteries will be fully charged with or without a b2b so there is no overall extra power through the alternator needed to run a b2b except a tiny amount because it is only 95% efficient (similar to solar regs). Therefore there is no "significant" extra cost. The fact that the alternator is inefficient applies equally to split charge relay charging and b2b. The point you make is interesting as long as what benefit the choice brings is weighed against any cost. In my case I like to wild camp nearly all the time in this country and Europe. So what ever the cost of running the kit is offset against the much larger cost of sites with EHU? But other aspects come into the equation. Carrying the full range of kit (Kitchen Sink!) also has a large effect on MPG and the drive train. A B2B comes into its own with Solar Panels when EHU's become surplus in most situations. If you will benefit from a B2B have one. If not its a luxury you will not miss. Link to comment Share on other sites More sharing options...
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