Fitting two leisure batteries

[Guest Patricia]

The Zig charging unit on our Auto-Trail Cheyenne has stopped working and we were advised by the firm that we should not use two 85ah batteries but fit one 110ah instead. These leisure batteries were fitted at the Bath and Western Show so we presumed they were done correctly. I imagine they are connected in parallel i.e. live to one battery and negative to the other from the charger and linked together. We will of course have the batteries tested (due to ill-health my husband is unable to scrabble about underneath the vehicle at the moment)and have a competent engineer to diagnose the cause of the breakdown but also wonder whether the rating of the engine battery will have any bearing on the problem (88ah) as the batteries failed to recharge on a long journey. The charging rate from the alternator was checked in January. We have had problems using the motorhome off the mains hence having the two batteries fitted. We would be grateful for any helpful comments and advice.

[Guest PeteC]

Hi Patricia When you say 'live to one battery and negative to the other' Do you men that the negative of one battery is connected to the positive of the other If so the batteries are in SERIES and will only charge up to 6V each The LIVE should go to BOTH Batery POSITIVES and The NEGATIVE to BOTH batery NEGATIVES This puts them in Parallel. Then they should charge up to 12V each We have a 95Ah for the van and 110Ah for the leisure batery

[Guest Clive]

Sometimes its hard to sit on ones fingers! "LIVE" only aplies to AC mains supplies. On batteries you have a POSITIVE (+) terminal frequently marked with a RED sleeve around the connection. The other connection is the NEGATIVE (-) terminal. If these terminals are round and slightly tapered then the smaller one will be the NEGATIVE. Alternatively they can be rectangular with a bolt hole. Although its better to fit two 6 volt batteries in series to achieve more capacity I have to accept that this is not the norm. Most people just connect one 12 volt battery in parallel with a second similar 12 volt battery. That's one link joining the two battery POSITIVES together and a second link joining the battery NEGATIVES together. (presuming they are mounted adjacent to each other) If the batteries have been used for several days and are well discharged you cannot expect the vehicle alternator to recharge them significantly in a couple of hours of driving. The ZIG unit should not be damaged if you increase the capacity of your leisure battery pack, but it will take twice as long to charge two batteries as it will to charge one presuming the two batteries are similar. I think that whoever said that this is why the ZIG is damaged is applying bulls..t! The ZIG charging unit has to be mounted such that it has adequate ventilation and will stabilise at a working temperature within no more than a couple of hours if the battery is very discharged initially. After this it is just the time taken to put in sufficient ampere hours until the battery terminal voltage reached 14 volts. After this the ZIG unit will progessively reduce the charging current so that the battery terminal voltage does not go in excess of 14 volts. Leaving the ZIG unit connected and working for 24 hours should achieve some 75% - 80% of full capacity in your batteries. I have two 160 Ah 6 volt batteries connected in series. Have a look at the April 2005 MMM page 258

[Guest Derek Uzzell]

Auto-Trail is another converter that re-uses model names and "Cheyenne" has been used continuously for at least 10 years, covering smallish petrol-engined coachbuilts to long tandem-axle diesel-powered biggies. (Some present Cheyennes even come on Fiat or Mercedes chassis.) The year of manufacture of the vehicle can be significant, as the older the 'van the more chance of a component failing due to old age. Patricia: assuming your Cheyenne is recent, it appears from Auto-Trail's 2005 brochure that the same output (16A) charger/transformer is used on all Cheyennes and, dependent on the model, standard fitment is either a single 85Ah leisure-battery or a pair of 85Ah batteries. This suggests that adding a second battery to your vehicle shouldn't have presented problems as far as the charging-system is concerned. It also seems logical to assume that the batteries were linked together correctly, otherwise the consequences should have been obvious immediately. I can't really see why your 88Ah engine-battery should make a contribution to your charging problem. For some unaccountable reason, I thought that Auto-Trail didn't use Zig products now, but clearly you know what's fitted to your motorhome and Clive (another Auto-Trail owner) also talks about Zig chargers - so I guess I was wrong. I do notice that Zig said about their X-Series chargers: "NB. If a battery is not used, or is heavily discharged, the load drawn by the accessories must not exceed the rated output of the charger." but nothing is revealed about what happens if the load is excessive! It's possible that some chargers may have an overload fuse or reset button, but if yours has the instructions should say. Assuming the obvious (that 230V power is actually reaching the charger), then there's a fair likelihood that the unit has developed a fault, and it's merely coincidence that this has occurred not long after a 2nd battery was installed. I'm sure you are right to get a skilled technician to look at this problem as the solution may well be quickly apparent to someone with the necessary experience.

[Guest Clive]

Sorry Derek, I used ZIG like housewives use "Hoover". You are correct, my Autotrail does not have a ZIG unit but one from Plug-IN-Systems. I just used the words from the previous posting. But the logic of the arguement remains the same. Someone is taking advantage of their lack of knowledge and trying it on!