arthur49 Posted February 21, 2014 Share Posted February 21, 2014 Currently have a 110Ah leisure battery charged from Sargent EC155 Power Control and Charger Unit. The User Instructions (copy attached) for this states that its a straight 13.8v charging - so not 'intelligent' - and battery size recommended up to 120Ah. Issue: I want to add a 2nd battery giving me 220Ah. The existing charger will never get these up to 100% Ah so thinking of a CTEK MXS 7.0 to supplement charging. 1. If I wired the CTEK straight into leisure batteries (via 20A fuse) would this cause a problem to the existing EC155? Would have thought not but .... 2. On hook up with CTEK on would it apply intelligent charging if EC155 was also on. Or would I have to switch off EC155 to enable CTEK to do its job? Arthur Link to comment Share on other sites More sharing options...
lennyhb Posted February 21, 2014 Share Posted February 21, 2014 At 13.8volts it will never fully charge the battery whatever size it is, sound like the type of charger they used to fit to caravans 25 years ago. NO you can not connect the output of two chargers together, you would be better wiring in the CTEC and disconnecting the the charging both mains & 12v from EC155, you will need to ensure the battery remains connected to the distribution side of the EC155. Alternately a high power Schottky Diode in line with each charger would isolate the chargers from each other, but my first suggestion is the one I would favour. Link to comment Share on other sites More sharing options...
sshortcircuit Posted February 21, 2014 Share Posted February 21, 2014 The Ctek is a multistage charger and you cannot run another charger with it at the same time as it would become totally confused. The CTEK MXS 7.0, 7 amp output is not very much and if you discharge your leisure batteries quite a bit, its going to take a long time to recharge. Did not read all the Ctek stuff but the word "maintenance" came up a few time ????? Hopefully battery expert will come on, but I certainly would not purchase at this stage. I use a Ctek D250S which is powered from the alternator when engine running giving up to 20Amps and also solar panel, which you may wish to consider for future. I can also power it when on hookup so making full use of the multi stage charge function to the benefit of the batteries. There are other similar chargers. Link to comment Share on other sites More sharing options...
Guest Peter James Posted February 21, 2014 Share Posted February 21, 2014 I have a self converted X2/50 van. I added 2 extra batteries - 115AH and 95AH connected with 25mm2 copper cable via a 100amp relay to the main battery 95AH. May not charge the leisure batteries 100% I don't know. But it seems to charge them quickly enough even on tickover (has 160 amp alternator as standard) and is still working well enough after 4 years :-D PS:I wouldn't recommend the sort of split charging kits you buy in Halfords - its very light duty. At best it will be slow to charge, at worst blow fuses or burn out. Link to comment Share on other sites More sharing options...
Tracker Posted February 21, 2014 Share Posted February 21, 2014 I know nothing of the theory of all this but in practical terms as we never use mains hook up I have always connected a second battery as detailed below and let the alternator keep them both charged which if you do enough miles it will. Then we graduated to a solar panel with split charging relay which has the added advantage of never letting any of them go flat when you don't use the van for a few weeks. I don't know why the inboard charger would have a limit on the capacity it can handle and how would it know anyway or what would happen if you exceeded that alleged capacity particularly if it never has to charge from flat, so I would just add another battery using at least 30 amp cable and suck it and see? If you use sites a lot and are on hookup a lot I wonder whether you even need a second leisure battery? My way of connecting them is to use the existing van wiring connected to the positive on one battery and the negative on the other with both batteries then being linked together with 30 amp cable, pos to pos with red cable and fused and neg to neg with black cable unfused. My understanding is that makes both batteries share equal use and prevents one being a slave to the other which I am told is what occurs when you simply add another battery without separating the pos / neg input / outputs and is allegedly not conducive to longevity - it may well be true as it sounds reasonable - but every time I research it I find conflicting advice and opinions? Just like a forum! Link to comment Share on other sites More sharing options...
arthur49 Posted February 21, 2014 Author Share Posted February 21, 2014 sshortcircuit - 2014-02-21 5:52 PM The CTEK MXS 7.0, 7 amp output is not very much and if you discharge your leisure batteries quite a bit, its going to take a long time to recharge. Did not read all the Ctek stuff but the word "maintenance" came up a few time ????? . Oops I did look at the CTEK and dismissed it because of the 7A limit. I meant to say the Sargent PX300.. To answer some of other points made, yes we do use sites and EHU but rarely in mainland Europe which is where our travels are mainly Yes 120W solar panel fitted Thank you all for input Arthur Link to comment Share on other sites More sharing options...
tonyg3nwl Posted February 22, 2014 Share Posted February 22, 2014 I wonder if Clive has seen this post. He is the expert on battery connecting, but in his absence, I would not recommend joining 2 batteries unless there is some protection between them. If one battery has a faulty cell, short curcuit for example, the the other battery will be dragged down, and heavy current will flow from the good battery throught the dud one, and in worst case could overheat the interbattery wiring.. you must ensure that each battery has protection in the form of a fuse or heavy current diode to isolate one from another. secondly, the charger will try to bring up both batteries to same voltage, and if one battery is faulty the charger may well be overloaded, and cant fully charge the good battery. Each battery must be isolated from the other to prevent circulating current between batteries. .both batteries should be of same rating in amphours, or assuming one is smaller than the other, then the smaller one will be fully charged before the larger one, but a common charger will still try to bring both to same charge state, resulting in possible overcharge of the smaller one, resulting in gassing..a dangerous state.. my recommendation is dont do it ..keep batteries separate, and change from one to the other as needed.. Clive may have other suggestions as well. tonyg3nwl. Link to comment Share on other sites More sharing options...
sshortcircuit Posted February 22, 2014 Share Posted February 22, 2014 Interesting article on multiple battery connection http://www.smartgauge.co.uk/batt_con.html Link to comment Share on other sites More sharing options...
Brambles Posted February 22, 2014 Share Posted February 22, 2014 A few explanations needed I feel. Yes, you can add another battery and Tracker has mentioned the ideal wiring method of Positive from one, and negative form other. Both batteries must be protected by fuses, which also protects one from the other as well. Trackers method is fine for adding an extra battery, However if the batteries are next to each other or close by and because loads are not heavy ( i.e starting currents) it is easier just to sling it in parallel with a fuse between the positives. Job done. Battery size. - They ideally should be within one size of each other. This is a safety thing should one battery develop a shorted cell. It is unlikely to blow the fuse but all the power from the good one will dissipate in the bad one. Trying to charge the duff battery from the alternator may well blow the fuse in this case. Imagine if the faulty battery was 1/10 the size. It will boil its head off and overheat dissipating the power from the good battery. Hence the one size difference max recommended. It has absolutely nothing to do with one charging before the other. They will both charge up at the same rate %age capacity wise. Think about it, If the big one takes longer to charge than the small one it will keep the voltage dragged lower. The small one with a higher %age charge level requires a higher voltage so it waits for the big one to catch up so to speak. As long as they are the same chemistry and type they will follow each other both charging and discharging. There is more to it but basically not an issue. Both Batteries should ideally be within a years age of each other. In other words they should both be in similar condition. This is so they both have similar charging and discharging characteristics v voltage. And also so one does not fail way before the other and risk damaging it as well by constantly dragging its voltage down, although if they are full calcium batteries such as dual purpose type ( which most people seem to have) then they should fail high resistance and not with a shorted cell. Often goes unnoticed until eventually plates buckle enough to cause a short. Both batteries should be the same type. They do not have to be the same make. 13.8 volts is fine for charging the batteries, it will reach 80% capacity fairly quickly and then start to slow down much more as it approaches 90% and take ages as in days to get to 100% but will get there eventually. However your solar panel and it's controller will help here as will driving and charging from the alternator. To summarise the general rules are. Same type, within a year of each other in age, and within one size difference. e.g. an 90Ah with a 110 , or a 75Ah with a 90, is fine. A 50Ah with a 100Ah is possible but not recommended without additional temperature monitoring and system to isolate the failed battery. All battery positive interconnection cables must be protected by fuses. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted February 23, 2014 Share Posted February 23, 2014 arthur49 - 2014-02-21 7:12 PM ...Oops I did look at the CTEK and dismissed it because of the 7A limit. I meant to say the Sargent PX300.. To answer some of other points made, yes we do use sites and EHU but rarely in mainland Europe which is where our travels are mainly Arthur Presumably your inquiry relates to the brand-new Devon Aztec motorhome you mentioned in a January 2014 forum thread that you were getting in the near future. I note from the Devon website that an Aztec is fitted as standard with a "110Ah carbon fibre" battery, so (if my assumption above is correct) there should not be an 'age' mismatch if you added a new 2nd battery and, logically, you'd choose to fit an identical battery to the standard one. Clive Mott-Gotobed deals with adding a 2nd leisure-battery on this part of his website http://www.motts.org/second%20leisiure%20battery.htm Sargent's EC155 system (as you are probably aware) not only charges at a maximum of 13.8V, but has a relatively limited 12 Amperes output. The Sargent PX-300 battery-charger has a 25 Amperes output and a 3-stage 'intelligent' charging regimen that can charge at 14.4V. Plainly, if a motorhome has a high-capacity leisure-battery arrangement that's used fairly 'hard', a PX-300 will recharge the batteries more fully and more quickly than an EC155. When there's a factory option that allows extra leisure-batteries to be fitted at the conversion stage, it's quite common for this option to be paired with a higher peformance battery-charger. It's also not unknown for motorhomes to be factory-fitted with more than one battery-charger and for the chargers to operate simultaneously. For example, Carthago's "Highliner" model comes as standard with 2 x 140Ah batteries and 2 x 16A chargers, with the option of adding two more 140Ah batteries and uprating the chargers to 4 x 22A units to produce 560Ah of leisure-battery capacity and a battery charging output of 88 Amperes. However, those battery-chargers will have the same technical specification and the motorhome's electrical system will have been suitably tailored to accommodate them operating together. Although the PX-300 is a 'multi-stage' charger and the EC155's charger is not, I'm uncertain whether (as lennyhb and sshortcircuit advise) they could not be successfully operated simultaneously, but I wouldn't want to experiment (or at least not on my own motorhome) as neither equipment will have been designed to be operated in that manner. I would have thought that Devon should be able to advise you about doubling up the battery capacity, as it's likely other owners will have wanted to do this. Also, as you are considering using an EC155 and a PX300 together, and both are Sargent products, the best and most authorative opinion you'll get regarding the advisability of doing this must come from Sargent itself. Link to comment Share on other sites More sharing options...
sshortcircuit Posted February 23, 2014 Share Posted February 23, 2014 Hmmmmmmmmmmmmm? Fuses? Whilst I respect the input of the "experts" I find the fitting of inter battery fuses a bit confusing. Doing a search for "battery bank" I find connections for RVs, boats, solar panels etc and not one has a fuse fitted in the link between batteries. All use heavy cable, with mechanical protection if necessary, but none have fuses. Why do we suggest fitting them in motorhomes? Link to comment Share on other sites More sharing options...
Brambles Posted February 23, 2014 Share Posted February 23, 2014 sshortcircuit - 2014-02-23 10:19 AM Hmmmmmmmmmmmmm? Fuses? Whilst I respect the input of the "experts" I find the fitting of inter battery fuses a bit confusing. Doing a search for "battery bank" I find connections for RVs, boats, solar panels etc and not one has a fuse fitted in the link between batteries. All use heavy cable, with mechanical protection if necessary, but none have fuses. Why do we suggest fitting them in motorhomes? Very good point SS. Mainly because some people connect batteries with a longer cable running from say under one seat to the other seat,so is really protection for the cable shorting to the chassis. The fuse will not protect one battery discharging into another with a shorted cell as votlage will rise on the fauty battery in the other cells and limit the current. A 30 Amp fuse will not really offer any protection here from one battery discharging into the faulty one. As you say many battery banks are not fitted with fuses. Some people are not very good at interconnecting batteries and will have cables which possibly rest against metal surfaces , wear through with vibration and short hence fusing helps here. With care and good cables, mechanically protected there is indeed not much reason to fit extra fused. But people are daft, when replacing a battery it is surpisng how many will actually connect reversed. The fuse protects these people. Or indeed disconnect the positive on one battrey 1st and lay cable doWn on the chassis, or indeed undo positive 1st with a spanner and short the spanner to chassis. ( Always disconnect the negatives 1st and reconnect last) Next is usng cables which are not heavy enough. As the load is unlikely to be above 30 Amps and the main protection fuse is 30 Amps we do not eally need to use cable capable of a couple of hundred amps. We could just use lighter cable capable of 30 Amps to interconnect the battreis but here it is prudent to fit a fuse....just in case something major does go wrong in a battrey ( say 2 shorted cells) or a spanner is dropped on top of the termimals of one, or god forbid an acident where the battery breaks loose and shorts its terminals against something conducting..e.f the chassis of a seat, or case of a metal locker. Summary. Heavy cable, properly installed with no risks of shorts (e.g. mechanical protection around batteries) . Fuses not requred. Lighter cable then fuses required or Installations with risk of batteries being shorted. Link to comment Share on other sites More sharing options...
Billggski Posted February 23, 2014 Share Posted February 23, 2014 I'm assuming "same type" batteries means gel->gel or similar? Link to comment Share on other sites More sharing options...
sshortcircuit Posted February 23, 2014 Share Posted February 23, 2014 Thanks for the excellent reply Brambles. I would emphasise the point that when lighter cable is used, not mechanically protected, then a fuse is required AT EACH END of the interconnecting wire at a current rating less than the current carrying capacity of the cable. Hope that's clear. Link to comment Share on other sites More sharing options...
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