Fading Batteries and their Effects

For anyone else in this position the other option would be to fit just one 12v 100ah lithium battery @a cost under €400 this would give the same output as the 2 Halfords units plus they would last the life of the van and weigh in under 10kg pre battery , you would also have the option to fit a 2nd battery in the further if required

Below is a link to very informative guidance about connecting two batteries. It mentions the load when engine starting but the comments are applicable to any loads.
When going from one to two, or from two to one, batteries it's just a simple rewiring job and if done correctly you shouldn't end up with and redundant wires which need to be taped over.

https://caravanchronicles.com/…-parallel/

Picture showing the resting voltage of LA related to the amount of charge remaining. Remember LA voltage will change under load and the size of the load is important so the voltage should not be read until 30mins after no load on the LA battery to get an accurate view.

In relation to charging it's not a simple case of just of having a split charge relay and away you go. Yes it will charge and work for many people but if you are asking a lot from batteries then they need a good charging regime. If your cable on the SCR to the leisure LA is too long and not adequately sized then the voltage will drop and the current and voltage that end up getting through will be low. While it's relatively easiy to get to 80% charge on a LA with enough driving the remaining 20% is not easy to do unless done with the right kit. If you remove 50AHr from your leisure batteries and you're only delivering 6A from your SCR then that's a lot of driving and you may never get about the 80%. Nothing beats a good B2B and good cabling if you use your batteries a lot. If you're using a 500W inverter at full tilt then remember W=A(x)V and therefore 500W=12V x 41A. 41Amps from your batteries in an hour is massive and it's impossible to give you an accuate estimate of how well you can charge given the unknowns of your set up.

Solar works really well and does that 80 to 100% charging really really well with a good MPPT charger. I have 2x90Ahr LA with 60A sterling B2B and 170W solar with short runs of 25mm2 on the B2B and 6mm2 on the solar. It's over speced but intend going to Lithium when the current batteries die.

Good luck with your travels.

Cudnt agree more ,the level of knowledge and xpertise on this forum is incomparable to ringing this guy and that guy,ask any newbies on here including myself or just look at they’re queries and problems answered by seasoned motorhomers is nothing short of outstanding,even if it doesn’t relate to you someone will come in with a problem and be replyed to by the most articulate intelligent knowledgeable Motorhomers in Ireland, no exaggeration there’s boys on here know their stuff

, Jump forward to about 9 min .

I know nothing about the ifs and buts, but have you considered a solar panel

Martin @sprinter is correct.
From experience I find that the majority of power drain on leisure batteries can be from what is known as “parasitic draw”, basically an amperage drain on the batteries that is not being utilised. Over time a parasitic draw of 150mA (not uncommon) will pull a battery down pretty fast (3 Ah every 24 hrs approx). Lots of things can cause this, improper fitment of aftermarket devices, rectifier in chargers faulty, and a host of other things.
Your usage/draw can be passed thru a shunt and be monitored down to +/- 50 milliamps (or better) so you can fully establish where/what/why that draw is being demanded and act accordingly. This can be temporarily done thru a multimeter but bear in mind that the ‘average’ multimeter off the shelf has a max current rating of 10 amps.
A good solar system is worthwhile coupled to a quality MPPT controller & monitor will at least leave you with info on current state of charge, your usage and battery voltage at a given time.

Using a multimeter to measure current ( amps), you have to connect the meter between the batteries and the load, now that's not as simple as it sounds, because if you look at the size of the cables, you cannot connect it to the battery main cable, ok to step trough each individual unit in the van that draws less than 10amps.
A DC clamp meter around the main battery /batteries live cable will give you a max load , and you can probably get it around the feed to the inverter, to check the load and off load current. The difference between the battery reading and the inverter load, is what you may have to find, what is on, and possibly wasting your batteries, using a combination of multimeter voltage and current, remembering to change the leads to the correct position. Remember if the Monitor is not on but the inverter is still running, it's drawing power.
It's not easy and I hope as clear as mud. Jon may very well have other advise, but to be honest, I would suggest, a visit to @JJF and see if he has a solution.
I would be reluctant to advise anyone to buy gear, as I've so come across so much rubbish, In my working life, I've alway had to used a combination of Anolog wall mounted gauges and Fluke Multimeter, Clamp AC/DC meters, the yearly calibrations cost 10 times what you would pay now, on Amazon, with a second set in the van for breakdown's, and cover if one went down.

I have a battery monitor like the one above that was part of the solar setup installed by campermedic.co.uk

I'll learn how to read it one day

On a slightly different note, during the really good days we had here, (as a test) I ran my fridge off 300watt of solar and a 3kw inverter whilst the sun shone, batteries never went below 12.9, it's a three way absorption fridge.

I have a switch to make the van 240 from the inverter.

Thanks guys. had no idea what a clamp meter was, found

https://www.hioki.com/euro-en/…meter.html

which gives a good intro

Try vanderlust in Ennistymon, Anchor point or Derek Walsh, Cara MH in Limerick ,

It is a parallel 12V arrangement but because it is factory built cables run under the floor. And everything is wired into the charger unit. I can only assume it was done right and hadn't changed in years. When I replaced the batteries 2 months ago I was careful to connect them the same way as the old ones.

One thing that does bother me is the way I connected the inverter. It sits nicely behind the driver's seat just above the battery and I wired it directly into that battery. Ideally I would have run the earth cable to the battery under the passenger seat but the cables lengths which came with it were short and anyway I didn't want cable on the floor between the two seats. I would imagine I could have wired the inverter into the charger unit but was reluctant to disturb that as there is a huge number of cables running into it and it could be easy to make things worse. But running the inverter of one battery would cause an imbalance which could be the source of issues I'm seeing.

Likewise I probably could have disconnected the passenger seat battery at the charger unit but the cables would need to be identified. This may well need to be something I bite the bullet with and look at

For now I was trying to see could I get a reasonable single battery setup. Because if that works I'd be quite happy to replace it with one Lithium battery but couldn't see myself buying two of them (to start with).

I've seen conversions using a single battery and it seems easy enough to figure where cables run but the compact setup is more complex than that.

Am I correct in thinking, that under your passenger seat, you have one cable ( red ) with a positive + battery connector on the end, and another negative - battery connector with two leads ( black ) going off it.? or is there two black - cables going off the other battery,?

"Running the inverter of one battery would cause an imbalance which could be the source of issues I'm seeing"
That could be where the some of the problem is.

I would have wired the inverter with the live of one battery and the neutral off the second one. even if it meant increasing the length and size of the cabling.

The wiring diagram has:

14) 9 poles connector for the batteries system:
1-2) earth, batteries and chassis
3) /
4) in + starter battery (50A fuse protected)
5) /
6) in D+ engine alternator
7-8-9) in + services battery (50A fuse protected)

If I am understanding correctly the black negative cables from both batteries should be in 1-2 with the positive cables in 7-8-9)

If I do go at it, I guess the 9 pole connector will pull out and there are small screws for each connection

"Under the passenger seat there is just one black cable which was connected to the negative terminal and a blue (I was wondering why not red) which was connected to the positive terminal. Just the 2 cables, no more."
Q?. do you know where the other end of these cables are connected to. and is there any slack/ movement.

"If I am understanding correctly the black negative cables from both batteries should be in 1-2 with the positive cables in 7-8-9)". This is why I cant see that your batteries are in true Parallel ( only in Tandem ). If you use the system with one battery I think you are going to get a similar result to what you have. another thing of note, the general color scheme in crazy, you have
( brown to red ) ( brown to brown ) ( blue and brown to black ) then ( large red to double brown)

Q?. what is the color of the cables on your starter battery., and where is it fitted. the reason for asking this is, on your 9 block at position 4 it would appear you have a blue wire, which is the position for the starter battery.
Q?. where is this blue wire coming from. Is it possible the original starter / engine battery was under the passenger seat?
can you identify the color and position of all the wires in the 9 block
I still think a trip to campermedic.co.uk would be your best bet, and since you work from the van on the computer does it relay matter where you are,I'm sure he will lend you a lead.

Yes the engine battery positive terminal has a blue cable in addition to a cable conduit with who knows what inside.

I charged the single leisure battery last night and the control panel is now reading correctly again. And the readings seem to agree with those taken directly from the battery using the topdun battery tester.

I had charged both batteries before taking out the passenger seat one and this may have confused the control unit. But it seems to have corrected itself with the latest charge