StewartJ Posted September 27, 2010 Share Posted September 27, 2010 Apologies for yet another newbie question, tomorrow I'm driving our new MH (Auto-trail Tracker) almost 30 miles to a gold rated Cassoa site for storage whilst I'm away at sea. On this occasion I'll be leaving it 2 weeks, I'm tempted to disconnect the batteries (2 x 110AH) so they don't run down. Will I cause myself any problems or even worse damage the charging systems by driving this distance with them disconnected??? Again I appreciate your advice and input. ATB Link to comment Share on other sites More sharing options...
fred22 Posted September 27, 2010 Share Posted September 27, 2010 Why disconnect them, you will need them to maintain your alarm system. Even though you may be on a secure storage site your insurance company may require the alarm to be active. I would have though the batteries you have can last two weeks Link to comment Share on other sites More sharing options...
StewartJ Posted September 27, 2010 Author Share Posted September 27, 2010 Hi Fred, my normal working pattern is 4 weeks on 4 off hence my query, as an engineer I realise as winter progresses and temperatures dip below zero the batteries will discharge quickly. Sub zero temps will shorten battery life and probably result in premature expensive battery failure. Stewart Link to comment Share on other sites More sharing options...
davew Posted September 28, 2010 Share Posted September 28, 2010 StewartJ - 2010-09-27 10:37 PM Hi Fred, my normal working pattern is 4 weeks on 4 off hence my query, as an engineer I realise as winter progresses and temperatures dip below zero the batteries will discharge quickly. Sub zero temps will shorten battery life and probably result in premature expensive battery failure. Stewart They won't discharge quickly at all and in 2 weeks they'll be pretty well as good as when you left them. I don't know anyone who removes them from their vans. My 2 batteries are 3 and 5 years old respectively and have seen some pretty low temperatures! If you are really concerned about them, think about fitting a solar panel in future for keeping them topped up. Link to comment Share on other sites More sharing options...
Steve928 Posted September 28, 2010 Share Posted September 28, 2010 I thought that the self-discharge rate becomes lower at lower temperatures? Wiki seems to confirm this: Store batteries at a low temperature if possible, 5°C is ideal. Although capacity goes up with temperature, the life of a battery goes down. The self discharge rate goes down with temperature. At room temperature, recharge stored batteries every 6 months; storage at 5°C lets you wait 18 months before recharging. We leave our boat leisure batteries connected all winter whilst laid-up ashore. Last year hit -20c. The batteries never seem to lose any appreciable charge over the 2 or 3 months between visits. Link to comment Share on other sites More sharing options...
Brambles Posted September 28, 2010 Share Posted September 28, 2010 Hi, You can disconnect the batteries without a problem and drive. Disconnect the negative lead and place out of the way from shorting to anything. If you disconnect the positive then you risk shorting to the chassis etc as it will have 12 volts on it when you are driving. So disconnect negative. If you have a solar panel and regulator fitted then some you need to watch because they auto select 12 or 24 volts and get confused. They normally require the batteries to be connected before the solar panel but trust this does not apply in your case otherwise you would be happy to leave connected. It is surpising how fast batteries can drain when left connected even with thngs switched off as so many items can draw standby current. The contol panel itself, the boiler, and goodness knows what else you may have. 2 weeks should be fine, but you mentioned 4 week cycles so I personally agree and disconnect. What you could consider is ftting a switch in series with the batteries, then you can just switch off when you park up. To clarify another point which may be asked, most habitation chargers/suppies are just that and can act as a charger or a stand alone power supply. So no problem there with batteries disconnected....and you will not be on hook up anyway. As far as the alternator attempting to charge it just switches the split charge relay and 12 volts appears at the leisure batteries. Because you have disconnected the negative cable no current flows into the battery, but whilst engine is running you will have 12 volts available to power lights etc. Engine battery. If you have alarm fitted this will drain it over time. All depends on your vehicle and alarm fitted how long it will survive. I am confused over drain on X250's and seems extraordinarily high, but on older models it is low and 4 weeks should be OK, certainly 2 weeks, but not necessarily if you have had the radio modified to work of the liesure battery as then the vehicle management system can get confused it seems and not go fully into standby. Agian no hard explanation as to why or what is happening except it seems to keep auxilliary circuits active. but some people have the problem. Hope this helps. I am great believer in disconnecting battereis when laid up. They self dicharge slowly and a good battery will certainly last 6 months if fully charged 1st, and the best batteries will go 18 months if in good condition. I really do not see the point of fitting solar panels wher teh sole purpose is just to keep batteries topped up in storage. Powering an alarm as well is different, but there are many cheapish small solar panels (10 watts or even less) which for many will be enough to extend the time before batteries drain too much. Jon. Link to comment Share on other sites More sharing options...
rolandrat Posted September 28, 2010 Share Posted September 28, 2010 A solar panel is a good investment in the long run especially if you do some wild camping or use Aires on the continent. I have a 120 fitted which has a splitter to keep the engine battery topped up as well. Link to comment Share on other sites More sharing options...
Guest Tracker Posted September 28, 2010 Share Posted September 28, 2010 If you disconnect the negative leads rather than the positive be sure to reconnect BEFORE starting the engine because some control panels prefer to be disconnected by the positive leads to prevent what is known as 'residual' voltages in the system cauing all sorts of charging and voltage anomolies. I don't fully understand why but I had this problem early in the year and was close to buying a new control panel before Sargent's (control panel makers) pointed out the error of my ways. Brambles understands all this techy stuff - don't you Jon - and with luck he will clarify! Link to comment Share on other sites More sharing options...
Brambles Posted September 28, 2010 Share Posted September 28, 2010 Hi Tracker, yes supposedly understand, but there is always the odd spanner in the works like your control panel. Thing is if these manufactures designed right then these problems would not arise with some. I think in your case it is because you have other equipment fitted like the solar panel contoller which remained connected when you switched off the battery negative. If you isolated the solar contoller as well then you had a problem with it getting confused as panel was still generating volts. It is a case of looking at every sytem set up and working out what is what. However on a basic setup it should not be a problem, but as you mention the contol panel may still be getting 12 volts from other parts of the system such as the engine battery and the solar system and mucks it up. So yes I understand these things and yet at same time it is not possible to understand every setup and if something can go wrong it sure as heck will. Link to comment Share on other sites More sharing options...
Guest Tracker Posted September 28, 2010 Share Posted September 28, 2010 Thanks Jon - but should he disconnect poitive or negative when in storage! Link to comment Share on other sites More sharing options...
Brambles Posted September 28, 2010 Share Posted September 28, 2010 I would say if you do not have a solar sytem then battery negative. Remember if you are isolating the battery totally, then it does not make a difference electrically. Positive or negative you have broken the path through the battery so it is now out of circuit. Where problems arise is if other equipment is left connected to the battery, in other words you fit a switch for the habitation supply negative but leave the battery connected to the chassis. No no no, you must diconnect the battery terminal or all cables going to it. It knows no difference between +ve or -ve. If the positive lead is left loose and you start the engine it has 12 volts on it and could short say to the chassis. The negative lead shorting to the chasis is no problem because it is already connected to the chassis. An also remeber the rule when disconnecting batteries, negative 1st and then positive. A spanner between +ve and chassis makes large bang if the negative is still connected. Link to comment Share on other sites More sharing options...
StewartJ Posted September 28, 2010 Author Share Posted September 28, 2010 Many thanks for that Jon you've confirmed what I was thinking, I'm an engineer in the merchant navy and we always disconnect any equipment batteries when laying it up. MH into storage for a couple of weeks today and on this occasion left the batteries connected. Watch this space. Thanks to everyone else for your contributions all very much appreciated. Cheers Link to comment Share on other sites More sharing options...
Guest Tracker Posted September 29, 2010 Share Posted September 29, 2010 The fitting of a simple and inexpensive heavy duty battery isolator switch is the easiest way to isolate a battery! Link to comment Share on other sites More sharing options...
Brambles Posted September 29, 2010 Share Posted September 29, 2010 Hi Tracker, does not even have to be that heavy duty - just 40 Amps domestic heavy loads switch is fine and some are quite compact now. For engine battery, a proper battery isolation switch would be needed. Link to comment Share on other sites More sharing options...
Guest Tracker Posted September 29, 2010 Share Posted September 29, 2010 Appreciated Jon - but if you use a 650 watt inverter a heavy duty one won't get hot! Link to comment Share on other sites More sharing options...
Brambles Posted September 29, 2010 Share Posted September 29, 2010 Ok, fair enough, throw a spanner in the works. If I had an invertor I would have a seperate switch for it anyway, probbaly in the positive line to it, so yep all sorts of issues could arise ...so lets just say a switch suitable for all the loads on the battery negative. Arrrrrrrgh! This is the problem answering remotely, you never have all the information. Cheap option is one of these isolaters that fit on the battery posts, most being sized for the +ve post, but hey ho fit in positive, it has a hand (thumb) knob on it so spanner shorting or loose lead is not an issue. Basically it is two connectors that clamp together by screwing down the knob. Link to comment Share on other sites More sharing options...
Guest Tracker Posted September 29, 2010 Share Posted September 29, 2010 Sorry Jon - apologies for the wind up! Link to comment Share on other sites More sharing options...
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