Leisure battery confusion (1 Viewer)

[kelpbeds]

Good point, I think Jon is going to take his aux bat out when his Ford warranty is up and I am going to take mine out to give room to put in my sterling charger which won't have space when my new Trojans arrive.
I have also read what you say about mixing batteries with diff ah, not being a good idea. Cheers

 

[Popeye]

Well Kelpbeds, thank you for asking the question, and johnandshell thank you for the line diagrams which as you say worth a 1000 words.

I'm sure many half useful individuals will better understand the set-up now.

Happy New year and appreciate your efforts..........Griff :thumb:

 

[jonandshell]

I have perused the diagrams with interest in a couple of cases the "Aux" battery is in parellel with the engine battery to give it more oomph and in others it is in parellel with the leisure batteries and therby causing a problem. Batteries in parellel will charge to the level of the smallest battery and no more so 85 amp/hr + 2 x 115amp/hr = 3 x 85amp/hr batteries. All leisure batteries should be same size age and capacity or all will be pulled down to the lowest one resulting in much less capacity than you expect and premature failure of the bigger batteries.

Yes, it is usually best practice to ensure all batteries are of equal size/type.
However, the part about a smaller battery making the larger one only charge to the same amount is an old wives tale..........
A fully charged 115 Ah hour will perform as a 115Ah battery whatever the size of other battery it is connected to. The 85Ah to which it is connected will behave like a 85Ah one. Both will charge to the same voltage and discharge at the same voltage. The only difference between them is the amperage flowing through each, both during charge and discharge. This will be in proportion to their rated capacity, assuming all batteries are in equal condition.

Let me explain further........

The batteries are connected in parallel right?
Both positive terminals are having the same voltage applied to them during charging.
When the resistance in the batteries reaches sufficient level for current flow to nearly stop, the batteries are fully charged right?
If the bigger battery wasn't fully charged, the voltage at that battery would be lower, but it can't be! The batteries are connected together in parallel!

Both batteries will be fully charged together, they will discharge together. The only difference is the current through each and therefore the Ah!

All of which is immaterial in our MH at the moment because the small batteries are charged directly by the alternator, the traction ones by the sterling unit. They are isolated from each other during charging.
What does happen though, is that the smaller batteries are in effect charged by the traction batteries initially when the engine is stopped and the batteries reconnected because the Sterling unit charges the traction batteries to a higher voltage than just the alternator alone. This happens until all batteries are in the same state of charge, ie. voltage.

The statement about linked batteries only being as good as the smallest DOES apply to batteries in SERIES, so there is an element of truth in that old wive's tale Wildman!

In reality, my setup works fine. Like I said earlier, I expect the Ford battery to give up the ghost first!
Once the Ford warranty is up, there will be rewiring of the cab to run just the traction batteries in the back for habitation purposes.
I had the Sterling charger and batteries from the last MH and they had to go somewhere, but without disturbing the Ford-fitted stuff!
Hence the nightmare circuit I have at the present!!!!!

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[jonandshell]

Understand the general gist of that Jon but must admit my layman's mind is a little overwhelmed by the finer details! I've got a mate who is an electrical engineer so will get him to have a read me thinks!
And just a wild shot in the dark (and cheap shot at a solution) but does it make any difference whether the distribution board is on or off when the engine is running to the potential prob with sterling and fridge?
Cheers
Tim

No!
Your fridge is connected directly to the battery via the PCB on the distribution panel! The fridge 12v output cable from the PCB is to be found on one of the white plastic multiplugs on the PCB. I assume you have a CBE system similar to ours, after looking at photos of your model on the web.
If you undo the two screws on the distribution board (either side of the fuses) and look inside its one of those!

 

[jonandshell]

Back to the dissimilar size battery discussion again. Sorry to go on!

If it were true that a larger battery only gets charged as much a smaller battery connected to it in parallel, consider this...........

In a conventional split charge system, the starter and leisure battery are connected in parallel by the slit charge relay when the alternator is charging them.

If we apply the logic behind the above mentioned theory , it would be a waste of time having a larger leisure battery than your starter battery because, the theory says, it would only hold the same Ah of the starter battery!

I rest my case M'Lud!

 

[kelpbeds]

No!
Your fridge is connected directly to the battery via the PCB on the distribution panel! The fridge 12v output cable from the PCB is to be found on one of the white plastic multiplugs on the PCB. I assume you have a CBE system similar to ours, after looking at photos of your model on the web.
If you undo the two screws on the distribution board (either side of the fuses) and look inside its one of those!

Well it was worth a try!

Oh and we like it when you go on, most interesting stuff!

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[kelpbeds]

Jon, next episode in the saga!

Well you've inspired me now! Spend half the day in the van, tidied up all my wiring, was crimping away, cable tieing etc... Looks like an electrician has been in there now!
Took out the auxillary battery and installed the Sterling charger in its place, as we talked about, which is when something interesting happened.
I disconnected the auxillary battery which left me with the earth and positive leads that were attached to it. The earth I used to connect to the sterling, obviously, and was going to use the live to connect to the leisure battery pos terminal on the sterling as I thought the cable was connected to 2 my other leisure batteries - but when I tested it I found that it was not, which surprised me, so I just blanked it off. I fed a wire from the leisure batteries direct to the sterling and then connected the starter positive terminal on sterling to the 60amp terminal connection by starter battery as you suggested. All good so far!
Then, for no particular reason, I went to switch on the control panel and it wouldn't come on! So after I finished crying I figured it must be something to do with the old aux positive lead(which was now blanked off). So when I connected that back to leisure battery pos terminal on the sterling it all worked again, hurrah!
What this leads me to, and I realise I may be off the mark again here!, is should I put the relay you mentioned re fridge problem, between the sterling leisure positive terminal and the old aux positive lead i.e. where I have drawn the arrow on your diagram I have attached (tho note I don't think the cable is attached to the leisure batteries anymore - not sure where it leads to other than control panel)
I'm starting to enjoy all this a real learning curve! And I suspect it's informing quite a few others too!
Cheers
Tim

 

[jonandshell]

Hi Tim

Just to establish that your split charge relay hasn't been disconnected by the changes......

With that aux battery lead DISCONNECTED at the Sterling, do your caravan electrics work when the engine is RUNNING?

Also can I just confirm that there are no other cables connected to your leisure batteries other than the one you ran from the Sterling and the earth obviously.

Once we've established that, I might be able to guess where those runs of cable go and give you a definite answer!

I suspect at this stage though, you need to put that 5 pin relay between that aux positive lead and the Sterling output, leaving the cable you ran from the Sterling to the leisure batteries in place.

Happy new Year!

 

[B-well]

Hi to all reading this saga, finding this an interesting article. would there be any need to upgrade alternator output at final outcome?

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[jonandshell]

Hi to all reading this saga, finding this an interesting article. would there be any need to upgrade alternator output at final outcome?

Tranny has a 120A, ours hasn't gone up in a puff of smoke yet!!!!!!

 

[kelpbeds]

Hi Tim

Just to establish that your split charge relay hasn't been disconnected by the changes......

With that aux battery lead DISCONNECTED at the Sterling, do your caravan electrics work when the engine is RUNNING?

Also can I just confirm that there are no other cables connected to your leisure batteries other than the one you ran from the Sterling and the earth obviously.

Once we've established that, I might be able to guess where those runs of cable go and give you a definite answer!

I suspect at this stage though, you need to put that 5 pin relay between that aux positive lead and the Sterling output, leaving the cable you ran from the Sterling to the leisure batteries in place.

Happy new Year!

Right again! When engine is running caravan electrics all work fine.

As far as other cable connected to the leisure batteries, the only others are the main ones that clamp to the terminals i.e. the ones that Chausson fitted (plus I've also fitted a battery condition meter and solar panel).

I have checked out the 5 pin relays. There are terminals marked 85,86, 87,87a and 30. So I figure I need to connect the switched live to 85 and 86 the earth and then the output of the sterling to 30 and the other side of that to the leisure batteries to 87?

Am I learning well master?
Happy new year
Tim

 

[jonandshell]

OK then!!!!!

It sounds like that is where that relay has to go!
30 is connected to your sterling output, leaving that new cable to the batteries in place.
87A is where that 'aux' cable needs to be connected!
The choice of ign live is up to you, I used an ign live already connected at the CBE distribution panel.

The idea is, that when the ign is switched on, the relay BREAKS the circuit, leaving the leisure batteries connected to the Sterling unit and nothing else!
Don't worry about the solar kit.
This ensures the Sterling unit reads the battery voltage correctly during charging and also that none of those 50 precious amps goes elsewhere!
Meanwhile, the split charge relay has closed and the caravan electrics (including the fridge and Webasto, if it is on) are run directly from the starter battery. This, you have already demonstrated.
The starter battery, of course is also supplying the Sterling unit!

Meanwhile, your alternator is generating current, keeping your starter battery charged!

When you stop the engine, your aux lead which powers the panel is reconnected to your leisure batteries by your new relay being de-energised and CLOSING the circuit.

The split charge relay is de-energised and OPENS the circuit between your panel and the starter battery, thus isolating the starter battery.

Oh! By the way, what size relay are you using? 30A is the norm, but you should consider that all the current required by your habitation systems will be going through that relay. I fitted a 70A heavy duty version to ours as a belt and braces approach, improving, I hope, reliability.

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Any probs from there on, please don't hesitate to ask!:thumb:

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[kelpbeds]

Fantastic, all my questions answered, looks like the epic saga is now finally over!

I will get hold of said relay and get wiring.

And it all makes sense to me now as well!

Plus we've had over a 1000 views- think how much knowledge has been spread! (nearly all by you, must be said!)

Many thanks again Jon, hope I can buy you a pint or two at sometime in the future.

Tim

 

[jonandshell]

LOL!

Hopefully we'll meet one day at a rally to compare our circuitry!!!

I do wonder though how many people out there aren't getting full benefit from their Sterling battery to battery chargers.
They only work as designed when connected to the leisure battery only. When I first bought ours, I had a lot of head scratching before fitting it in our old Elddis. Because the CBE panel in the Elddis had an INTEGRATED split charge relay on the CBE panel, I had to remove it's cover and insert a bit of tape between the tips to disable it! I then had to fit an additional relay to power the fridge from the input side of the Sterling! All just to ensure the leisure battery was being totally isolated!

Just replacing the split charge relay with a Sterling doesn't work! If you do that, 20amps from the Sterling is lost powering your fridge and it will never reach end of charge because it sees the fridge as being a flat battery! Therefore, you will never get the benefits of that £300 odd quid you spent on the Sterling unit.

I hope this isn't a common mistake made by installers, but I fear it is!

Bye for now Tim, hopefully Jim our ringleader won't need an additional server to store anymore replies to this thread!!!!!