Leisure battery charging problem

Thanks all for that.  I have just been looking in the pile of paperwork I got with the van for something else and have found a Zig X7 manual so it probably had that originally - it is now a X70.

The wiring diagram is the same as the one I have in whats left of my manual, the only difference between what is on paper and what is in the van is that the van has an extra 30 amp fuse.  There are two in the bonnet near the main battery and one under the drivers seat.

It all looks like its working so will leave as it is now.   

The only other question I have is if I leave it on EHU with the charger running is the Zig charger intellegent enough to know the leisure battery is full and stop charging it or will it keep going and boil it dry?   The manual makes me think it is intellegent to stop the charging...

Richard

Hi  

A bit of marketing hype on Zig's part there I think. The charger has no intelligence of any sort. Once the battery comes up to 13.8V (the same as the charger) there is no more current flow and so no more charging. An intelligent charger would go well over 13.8V and then cut back.

It’s simply a 13.8V power supply so it can’t overcharge the battery unless (as Zig say on page 1 of the manual) the battery is faulty.

Brod

I do have an intelligent (Sargent) charger but would not dream of leaving it on for long periods. A fully charged battery is 12.8V so 13.8V will carry on trickle charging. I prefer to let the EHU charge the leisure battery for a couple of days and then the vehicle battery for a couple of days and then it is switched off for a few weeks until voltages drop just below 12V before I repeat the exercise. It is important not to let either battery drop below 11V.

Hi

inspiredron wrote:I do have an intelligent (Sargent) charger but would not dream of leaving it on for long periods. A fully charged battery is 12.8V so 13.8V will carry on trickle charging. I prefer to let the EHU charge the leisure battery for a couple of days and then the vehicle battery for a couple of days and then it is switched off for a few weeks until voltages drop just below 12V before I repeat the exercise. It is important not to let either battery drop below 11V.

 
That’s a good point and there will be much disagreement about the details. Here’s my take on it (other opinions are available). 
In this case I think we need to differentiate between trickle charge and float charge. Trickle charge refers to forcing a small continuous current through the battery and float charge refers to holding the terminals at a specific voltage. There is a subtle difference.
 
Float charging is a well known technique that has been used for years to maintain full charge and ensure long battery life.  After all, many electrical systems (even safely critical) have a backup battery that needs to be maintained at full charge. Until recently they were nearly always lead acid and maintained by a float charge system. The secret is to find a voltage that ensures full charge is maintained but doesn’t result too many negative effects (e.g. excess gassing).
 
To that end I will admit that 13.8V is at the high end off acceptable, my copy of  “The Handbook of Batteries and Fuel Cells”  recommends 13.5V but it’s an old copy( 1984). That said, many manufacturers seem to have settled on 13.8V, Zig being one of them. One variable that a fixed voltage can’t take into account is temperature and the maximum float voltage is temperature dependent. In the UK I wouldn’t be particularly concerned about leaving a battery at 13.8V for long periods except perhaps if the weather was exceptionally hot. 
 
Thinks have moved on and now more often than not we use “intelligent” chargers. I know some people are suspicious of them, I think mainly due to some rubbish products that really shouldn’t have been marketed as intelligent. A properly designed charger can be left on permanently without fear of damage to the battery. 
 
Obviously if you don’t trust the charger and prefer to control it manually that’s fine I just don’t think it’s really  necessary.

Brod.

Hi
I have been watching this thread with hope of learning from the replies.
I have 2 motorhomes and the newer one as a hab battery under the drivers seat , this battery type is new to me, it is fitted on its side with the 2 large terminals sticking out the front of the seat, my concern is would it be possible to use this type of battery to jump to the starter battery which is closeby under the cover by passenger seat should i need too.
anyone tell me the type of hab battery and likely replacement cost.
I have no problems just intrested to learn something.
regards
John Dean

I've been watching this thread with interest whilst on my travels and was pleased to see Richard seems to have got a resolution to his problem that he posted at the beginning.

Now the debate has moved onto charging strategies. The way I read the last two posts by Ron and Brod is that Ron is talking about maintaining battery condition whilst not camping and Brod is talking about maintaining battery condition whilst camping. If that is the case I agree with them both for the different scenarios.

Just to throw in a wild card..it occurred to me whilst on site for two weeks in September that what I had thought was a float charge scenario was not. I discovered, having been prompted by the forum, earlier this year that the Sargent EC325 (and only that specific model) that is fitted in my van has a different charging strategy.

When the charger is switched on it disconnects the habitation electrics from the battery and connects them instead to a 12v power supply. The battery is at the same time connected to the charger. They do this so that high charge voltages can be used that would potentially damage the habitation apparatus. The charge strategy is therefore an initial fast charge followed by a trickle to maintain condition.

Constant trickle charging can start to cause deterioration of the battery (although over months rather than weeks) and I therefore decided to switch the charger off every other day to let the battery do a little work.

Peter

johndean wrote:the newer one as a hab battery under the drivers seat , this battery type is new to me, it is fitted on its side with the 2 large terminals sticking out the front of the seat, my concern is would it be possible to use this type of battery to jump to the starter battery which is closeby under the cover by passenger seat should i need too.

Obviously trying to identify a battery from a description like that is difficult, but it sounds like it's a gel/AGM battery. These are designed for deep cycle applications and can be very expensive in large capacities.

Unless you can get to the side of it and see what manufacturer's marks are on it, I would not use it as a starter battery. AGM batteries are not designed for that type of load, and if I were in need of a jump start, I would rather wait for my chosen recovery company to come out than risk damaging what is ~probably~ a very expensive battery.

Back to chargers: like Cymro, I leave my car/van batteries on float on intelligent (CTEK, but other good ones are available) chargers all the time they are not being driven, and I get 10+ years life from their batteries.

Thanks for that Mojo I retired 12 years ago from Peugeot chief engineer and hadnt seen this type of battery during my time, wont try any jumping from it and will tell my sons not to as well
regards
John Dean

I'd like to thank everyone for the help and I now have a working charger and a leisure battery that works.

In the process I have now discovered another previous owner modification that I could do with dome advice about!

Attached to the leisure battery terminals where two black wires (one on + and one on - terminal. I traced these and they go to a cig socket plug that is in the centre footwell behind where the gear cables are. There is enough cable to let the plug reach and fit in the van cig lighter socket.
Before I remove this mod I am wondering it it's purpose is to charge the van battery from the leisure battery/charger. The cig socket is live when ignition is off so it could work.

Is this a possibility and something safe to do or I better to remove it?

Cheers
Richard

TAKE IT OUT! 

That is one of the stupidest mods that I can think of. Why would anybody want to connect the two batteries together?  As far as I remember from my looking at the manuals there is a switch on the ZIG that allows it to charge either the leisure or the vehicle battery. The extra lead could only be justified if that switch doesn't work. Does your control panel allow you to use the vehicle battery for habitation electrics if the leisure battery is totally dead?  If it does not, or if a fault in the ZIG stops that happening, then the bodge would provide an emergency get you through the night.  Maybe there was a fault with the original Z7 and the lead was left behind when it was changed to a Z70? 

And it's not good practice to use black for both wires - the postive should be red.

AND if those wires shorted together at any time the lack of a fuse at the leisure battery end could cause a fire in the van.



Having found the two examples of poor DIY, you may want to be watchful for any other amateur work by the previous owner(s)

I'm not going to disagree with what Inspiredron says (except for the option to use/charge the vehicle battery on EHU, which older ZIG and similar installs seldom have). However, this is a modification that has been suggested here before, despite several of us trying to point out why it isn't a great idea.

As already pointed out, if you leave the wiring in place, you ~must~ add a fuse on the positive lead next to the leisure battery. Having a fuse in the plug is not good enoguh - if the trailing cable gets trapped in a door, seat runner or whatever then fire is very likely without one.

The arrangement does have a couple of good points. It has an advantage over other methods of linking two batteries together, in that the connection is some distance from both batteries - so it practically eliminates the risk of explosion from battery gases. It is also very simple, with little to go wrong.

However, it probably won't be much use in an emergency, when one or other of the batteries is flat, because the van's cigar lighter socket will be served by a fuse (probably 7.5 or 10 amps), and this will almost certainly blow as soon as you connect the two batteries together.

As I've also pointed out in the past, my VW owner's manual also states that the van battery MUST NOT be charged via the cigar lighter socket. If you get this wrong, the cost to replace the relevant body control module will be an unwelcome surprise (in excess of £200 on my van last time I looked).

I need a lie down in a dark room, me ed urts

Hi  

You mean you have a live plug floating about in the foot well?  

inspiredron wrote:TAKE IT OUT!

I agree, it sounds like a right bodge. If you don’t know what it’s for you probably don’t need it anyway.

-mojo- wrote:my VW owner's manual also states that the van battery MUST NOT be charged via the cigar lighter socket.

Cymro wrote:[ for the last 15 years I've been charging my vehicle battery on my VW T4 Clubman by using the Airflow battery conditioner (which comes with a cigar lighter plug as one of the options for connecting to the battery) via the cigar lighter socket. That may simply be good luck, or the difference between an intelligent battery conditioner and a charger.

I assume (possibly wrongly) that mojo is talking about his new van. I’d be surprised it that applied to a 15 year old Clubman, but then maybe I’m about to be surprised.   It’s certainly quite possible to charge via the cigar lighter socket on the Duetto.

Brod.

brodco wrote:I assume (possibly wrongly) that mojo is talking about his new van. I’d be surprised it that applied to a 15 year old Clubman, but then maybe I’m about to be surprised.   It’s certainly quite possible to charge via the cigar lighter socket on the Duetto.

Yes - I'm fairly sure this applies to any VW T5 made in the last 10 years, but I suspect that the previous T4 will have simpler control systems.

TBH I suspect that it would take a significant voltage surge to cause any damage, so ~probably~ only battery-to-battery charging or the use of a fast charger into a flat vehicle battery would be a problem.

Thanks again all - I am sure at the time it was probably a good idea, but in light of not knowing exactly what it was there for, I have removed it.
In the course of doing so I was looking in the bonnet and can see that after the last few days of torrential rain there is water all over the gearbox and the scuttle drain is not working so thats the next job!

Richard