Guest RonB Posted January 1, 2006 Share Posted January 1, 2006 I have recently installed tubular heaters to provide electric between-floor heating to give frost protection (and preserve gas)down to approximately -10C to the water tanks residing there. However, I often read of owners de-frosting their equipment with hair dryers,boiling water,etc, which prompts the following question. Setting aside boilers and water pumps, at what sort of temperature can water tanks and pipework be expected to give up and split? Whilst investigating the frost prevention subject, via the forums search facility, I came across the advice not to run electric items from the hook-up for long periods without isolating the 12v system. This was to prevent the auxiliary batteries being damaged by overcharching. I must admit that for years I have simply hooked up for weeks on end without problems and in the belief that chargers automatically cut back the charging process when the batteries are up to strength. Indeed, my Burstner manual states that you should 'use every opportunity to charge the living area batteries' and mentions nothing regarding overcharging. As my electrical knowledge is such that I would have been reduced to a cinder long ago if left to my own devices I would be very grateful for further enlightenment on this one. Best regards Ron Link to comment Share on other sites More sharing options...
Guest Derek Uzzell Posted January 1, 2006 Share Posted January 1, 2006 I don't think your first question is really answerable. There may be temperatures below which the plastic materials water tanks and pipework are made from become brittle and break up, but I suspect these are far below anything motorcaravanners will ever experience. As far as what a plastic pipe or tank will tolerate if it's filled with water that then freezes, I would have thought ultra low temperatures are academic - once the tank/pipework has been exposed to temperature sufficiently low to cause the liquid inside to freeze solid, a further lowering of temperature shouldn't make any difference. If the tank/pipe can cope with being frozen at -2C then it should cope with staying frozen at -22C. Obviously if a pipe or tank is absolutely full of water to begin with the chances of harm from freezing will be greater than if there is some expansion room. The main frost-damage trouble is likely to come from fittings/valves within the water system rather than the actual pipes or tanks. A classic example is kitchen/bathroom taps splitting when water inside them freezes. Regarding Question 2, as far as I'm concerned, if the motorhome's battery-charger is designed not to overcharge the batteries (as the CBE-made charger on my Hobby claims to be) then the batteries won't be overcharged and hence won't suffer damage if the charger is operating for extended periods of time. Depends on what sort of charger one has, I guess. (By the way, I failed Physics 'O' level!) Link to comment Share on other sites More sharing options...
Guest Roy Hamilton Posted January 1, 2006 Share Posted January 1, 2006 The chargers on my Lunar 720 and on my previous Swift 590RL have/had a switch on them to turn them off, but on the current Lunar the 'van or cab battery selector must also be switched on to to connect the charger and supply a charge to the respective battery. Merely connecting the 230v supply does not charge anything, just supplies juice to the 230v system. Link to comment Share on other sites More sharing options...
Guest Mel B Posted January 2, 2006 Share Posted January 2, 2006 On our Rapido 709F we can't turn off the charger, it's on all the time when the mains power is connected, turning itself on an off automatically. We know it does this as we can hear it kicking in - we usually only notice that it's not been charging when we hear it kick in again as we get so used to the buzzing noise! Anyway we don't worry and haven't yet had any problems. There is one query though - when on hook-up when I read on a night time with one small halogen spot light on, the light sometimes goes much brigher and then dims down again, I assume this is just the charger kicking on and off causing the slight surge in power - am I right do you think? Link to comment Share on other sites More sharing options...
Guest Clive Posted January 2, 2006 Share Posted January 2, 2006 Some interesting points in Mel B's post on the charger in the 709F. I don,t know the motorhome intimately but am suprised that the on-board charger turned itself on and off automatically rather than regulating the output voltage. What is normal in motorhomes and caravans and has been so for quite a few years now is that the on-board charger replicates the output of the vehicle alternator, that is supplies a regulated 14 volts constrained only by the current capabilitiy of the charger. This should achieve at least an 80% charged battery with little gassing. If a lead acid battery is to be left on charge for a long period of time (like in emergency lighting systems) then the "float voltage" is lower between 13.6 and 13.8 volts. This to minimise gassing to maintenance free levels. This is why its not good practice to leave a motorhome on hookup all winter, better to plug it in for a day a fortnight or so. If the battery being charged is totally disconnected from the load circuit then a different charging regime can be used to ensure that the battery is 100% charged, this traditionally would limit the charge voltage to 14 volts until the charge current had fallen to a low level, then to allow the voltage to rise quite a bit higher, sometimes above 15 volts (Elecsol's web site state 15.6 for their battery test) but still monitoring the current and time and sometimes the battery temperature, then eventually to lower the charging voltage back to a float charge level. But chargers such as this tend to be restricted to batteries for electric fork lifts and the like. Also this will generate much more gassing and such systems today frequently have semi-automated topping up systems for the batteries. Having said that some regulators for solar panels I have seen adopt a similar regime leaving out the high voltage stage but charging up to 14 volts then reducing the voltage after the current has fallen because the battery is charged. Does anybody have the paperwork for the Rapido 709F charger? Happy New Year Clive Link to comment Share on other sites More sharing options...
Guest Derek Uzzell Posted January 3, 2006 Share Posted January 3, 2006 I don't know what make of charger Rapido uses, but Scheiber, Schaudt or CBE are popular choices for Continental European manufacturers. My Hobby has a switched-mode CBE "CB 516" charger and the charging regimen is described thus in the CBE brochure: "The charging system is carried out in 4 stages: 1. Battery charging with maximum current until the end-charge voltage is reached. (Note: the end-charge voltage is reached only if the battery is efficient.) 2. When the end-charge threshold is reached the charger continues to operate for 90 minutes (lead batteries) or 8 hours (gel batteries) with constant voltage. 3. Constant voltage holding 13.8V (gel batteries) or 13.5 (lead batteries). 4. After 10 hours, the battery charger reaches the stand-by mode and begins to operate again only when the battery charge voltage is lower than 13V." Just in case the motorhome owner is actually perverse enough to read the literature that comes with his/her vehicle the Hobby User Manual provides the following advice: "CHARGING PROCEDURE. The charging procedure is dependent on the battery voltage of the caravan battery: - Charge until the battery voltage has reached 14.4V. - Switch off the battery charger until the battery voltage has sunk to 13.8V. - Recharge when the battery voltage sinks below 13.8V. - Make a parallel connection and charge the engine battery as well as the caravan battery when the battery voltage sinks below 13.5V. - Separate the engine battery and the caravan battery when the joint battery voltage sinks below 12.5V." Despite a photo of the CBE system's control panel appearing in Hobby's User Manual, it's more likely that the 'Charging Procedure' information above applies to the different system used on the more expensive Hobby motorhome models. Either way, it appears that the battery chargers are cutting in and out in the manner Mel B describes. For what it's worth, our Hobby's charger is reasonably accessible beneath the front of the passenger cab-seat (the distribution/fuse box and gel leisure-battery are also located there). The charger is switched on by a push-button on its upper surface. When pressed, the button illuminates and a brief whirring noise comes from the charger after which it stays silent. When the battery charger has been switched on an LED illuminates on the above-door control panel (which is nice!) Link to comment Share on other sites More sharing options...
Guest Clive Posted January 3, 2006 Share Posted January 3, 2006 Thanks Derek for that comprehensive description of the CBE "CB 516" system as fitted to your Hobby. It certainly is quite comprehensive. I did in fact atimmediately before Christmas email Rapido requesting data on the charging system on the 709F for another reason. Now that I guess they are back to work I may have an answer soon. If anything is relevant I shall post it here. Happy New year to all Clive Link to comment Share on other sites More sharing options...
Guest Derek Uzzell Posted January 3, 2006 Share Posted January 3, 2006 Last time I e-mailed Rapido for information it took 3 months for them to reply and the answer was wrong. Hopefully you've asked in French!! Link to comment Share on other sites More sharing options...
Guest RonB Posted January 3, 2006 Share Posted January 3, 2006 Thanks for the replies chaps. It looks like I have no alternative but to consult my dealer as to how my particuler charging system works (Burstner 681). I hate doing this - the last time I requested info on the spare weight capacity on the individual axles, ex works, in habitation mode. They directed me to the body plate. When I explained that this wasn't what I asked they thought what I really wanted was quite bizzarre. Incidentally, I dont have a charger anymore but an E-Box and mini computer called an E-Control!! You have no doubt seen these and marvelled at modern technology. Why all I have to do to turn my water pump on is; Press a knob - Turn knob three clicks right - Press the knob - Turn the knob one click - Press the knob - Turn the knob one click - Press the knob - Job done. This is progress? To think that I used to have all the trouble of just flicking a switch. Have fun Ron Link to comment Share on other sites More sharing options...
Guest Clive Posted January 4, 2006 Share Posted January 4, 2006 Re rapido, I hope I don,t have the same experience. I have in fact spoken to the bosses secretary at Rapido UK but the boss is off because of familly illness. He was initially expected back in work yesterday afternoon but my late phone call revealed he never made it. So far I believe them. The French Rapido web site does not give up an email address for the factory. If anybody has one please reveal and I will try a two pronged attack for information. Regards Link to comment Share on other sites More sharing options...
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