Linking 2 leisure batteries??

Robmac

Full Member
Posts
26,383
Likes
34,424
or are you talking about two batteries connected in parallel which provide both cab & hab services.I've never seen this in a professional build

I've seen this in boats many times and my present boat has such a setup. In fact they make dual purpose batteries for this. But it wouldn't really be suitable for a motorhome.

But the way I read it is that the OP wants to add a second leisure battery in parallel l to the existing one. But I could be wrong.
 

Wooie1958

Full Member
Posts
14,511
Likes
11,787
I've seen this in boats many times and my present boat has such a setup. In fact they make dual purpose batteries for this. But it wouldn't really be suitable for a motorhome.

But the way I read it is that the OP wants to add a second leisure battery in parallel l to the existing one. But I could be wrong.

That`s exactly how i read it as well Rob however it could have been worded better and it`s the last phrase really worries me :eek:

They simply want to add a second leisure battery but it will not be right next to the original so ..............................

1, What size cable do i need to use to connect the two leisure batteries together ?

2, Is the alterator capable of charging all three batteries, i.e. starter battery and two leisure batteries ?

Now the worrying bit

3, How to connect the two leisure batteries together ?

This is the worrying bit, they have got that completely wrong because to keep the voltage at 12 volt they need connecting in parallel and NOT in series.

To keep the system at 12 volts they need connecting in parallel, positive to positive and negative to negative which is correct for the OP`s motorhome

To make the system 24 volt they need connecting in series, positive to negative and negative to positive which is NOT correct for the OP`s motorhome

The OP does not have a clear idea on how to do it so it would be better and more importantly safer if someone else who is qualified does the job for them.

It`s pointless and achieves nothing just having a go at them.
 

Tookey

Full Member
Posts
1,252
Likes
1,987
I for one hope Chris gives it a go. One of the best things about this forum is the assistance members will offer to each other. I believe if Chris does he research, presents his plans for scrutiny and then shares some clear photos once completed it can be done correctly. Chris will gain both knowledge and satisfaction and those that helped can give themselves a little pat on the shoulder..........job well done.

Chris can always go 'belt n braces' and show his work to an auto electrician if it will help him sleep better at night.
 

mistericeman

Full Member
Posts
3,118
Likes
6,661
Frankly it's a good job some folks actually try to do stuff themselves or this (along with a lot of other forums)
Would be a very boring read.

Yes it's important to take advice....
BUT it's also important to realise that NONE of us were born experts.... We've all been taught, either by ourselves or others.

Information and advice are freely given on here and combined with books (remember them) and YouTube videos, all sorts of things are possible.
 

chrishunter

Full Member
Posts
32
Likes
58
Is there a danger of leisure batteries gassing off when charging. I remember when we charged the generator batteries at the hospital when we turned on the charger they were in a sealed room with extractors on. So isnt it dangerous to have the batteries in a cupboard in the van when on charge at night when sleeping.
 

chrishunter

Full Member
Posts
32
Likes
58
just had a look online for a bigger ah battery .problem is I'm limited to the size of the compartment,which is L300 x h220 x w170... I'm trying to make sure I've enough in the leisure battery to last ,we probably go away for a week stopping for 3days ,no hook up. only other thought is 1 leisure battery and buy a solar panel any suggestions..???
 

winks

Full Member
Posts
1,617
Likes
2,264
Batteries do give off small amounts of Hydrogen which can easily be vented, usually through the floor of battery housing, using small bore plastic pipe like that used in fish tanks etc. This is lead acid batteries.

As for the choice of battery that 300mm is a bit tight for most on Alpha Batteries and there are choices to be made around technology and budget. I have always found Alpha to be very good value especially with our member discount. There is a load of help available from here with regards to solar and battery management but the basics are, get yourself a good quality MPPT controller. Everyone has their favoured manufacturers but Victron, Epever and Votronic are well regarded. Also go for as big a solar panel as you can fit on the roof or carry and stand outside to face the sun which will greatly increase the energy harvested.

A lot to learn but keep asking questions.


Cheers

H
 
Last edited:

Bigshug

Full Member
Posts
178
Likes
361
Absolutely get a solar panel, if you intend to be off grid for three days, the bigger the better! I would also suggest using a good quality controller, I originally had a Ring combined solar and B2B controller, which was adequate. I later changed to a victron MPPT solar controller and a Sterling B2B charger, and the improvement was amazing!!
I have just noticed that the Sterling B2B charger now incorporates a solar controller, which when the leisure battery is full diverts a small charge to the vehicle battery.
 

chrishunter

Full Member
Posts
32
Likes
58
Absolutely get a solar panel, if you intend to be off grid for three days, the bigger the better! I would also suggest using a good quality controller, I originally had a Ring combined solar and B2B controller, which was adequate. I later changed to a victron MPPT solar controller and a Sterling B2B charger, and the improvement was amazing!!
I have just noticed that the Sterling B2B charger now incorporates a solar controller, which when the leisure battery is full diverts a small charge to the vehicle battery.
I think thats the way to go.
 

brian c

Full Member
Posts
161
Likes
234
I agree with mistericeman. Thread 44. Also not everyone has the ability through age/ disablement to do the tasks that some people say it’s easy .you just do this then this etc i for one have learnt a lot reading the threads . A lot completely lost me . But still read them. Brian. The
 

trevskoda

Full Member
Posts
23,768
Likes
27,183
I would never buy all in one box, if one bit fails you are stuffed, yoy will at least want 2 100ah batts and 200w solar running through a mppt regulator, go for votronic as there is a take of for the engine battery, good luck.
 

Nabsim

Full Member
Posts
3,191
Likes
2,978
just had a look online for a bigger ah battery .problem is I'm limited to the size of the compartment,which is L300 x h220 x w170... I'm trying to make sure I've enough in the leisure battery to last ,we probably go away for a week stopping for 3days ,no hook up. only other thought is 1 leisure battery and buy a solar panel any suggestions..???
Solar is good for so many months of the year so much depends on when you use the van and where you go. Where I am today has been overcast and frequent rain and most I have seen is 4W off 300W of solar panels. Dont confuse charging with storage, if you need two batterys then fit them, you can use solar to get some charge on good days/summer. Of course if all you run are a few led lights then winter may not be a problem for you
 

maingate

Full Member
Posts
10,490
Likes
11,725
I THINK I`LL CARRY ON SWOPPING THE BATTERIES OVER WHEN I`M AWAY..THOUGHT IT MIGHT SAVE MY BACK..

You can do what you wanted as long as you connect as shown by Trevskoda. The connecting cable should be fine with 2.5 or 4 mm sq. cable (my second battery was connected by thhee dealer using the official Autotrail kit for the job. The wiring was about 1.5 mm sq with a 30 amp fuse inline on the positive lead. I actually returned it and made them fit something better than 1.5 mm wire).

Remember that you will need a fuse on the positive lead and a vent tube through the floor on the new battery. A 30 amp fuse was (in my opinion overkill). I would fit a 15 or 20 amp fuse myself unless you use a large inverter. If you do use an inverter then your cable size and fuse rating needs ramping right up.
 

clarkpeacock

Full Member
Posts
250
Likes
138
You can do what you wanted as long as you connect as shown by Trevskoda. The connecting cable should be fine with 2.5 or 4 mm sq. cable (my second battery was connected by thhee dealer using the official Autotrail kit for the job. The wiring was about 1.5 mm sq with a 30 amp fuse inline on the positive lead. I actually returned it and made them fit something better than 1.5 mm wire).

Remember that you will need a fuse on the positive lead and a vent tube through the floor on the new battery. A 30 amp fuse was (in my opinion overkill). I would fit a 15 or 20 amp fuse myself unless you use a large inverter. If you do use an inverter then your cable size and fuse rating needs ramping right up.

My brother ordered an optional 2nd battery with his brand new Burstner, and this is how the dealer fitted it. To me, the wire seems far too thin, and the take off is from the original battery only.
IMG-20210107-WA0002.jpg
. A poor job in my opinion, and an example to the OP of how not to do it!
 

harrow

Full Member
Posts
6,933
Likes
8,038
My brother ordered an optional 2nd battery with his brand new Burstner, and this is how the dealer fitted it. To me, the wire seems far too thin, and the take off is from the original battery only. View attachment 91118. A poor job in my opinion, and an example to the OP of how not to do it!

I have seen a few of these why are the positive terminal uncovered on the second battery, far more risk. :mad:
 

chrishunter

Full Member
Posts
32
Likes
58
Solar is good for so many months of the year so much depends on when you use the van and where you go. Where I am today has been overcast and frequent rain and most I have seen is 4W off 300W of solar panels. Dont confuse charging with storage, if you need two batterys then fit them, you can use solar to get some charge on good days/summer. Of course if all you run are a few led lights then winter may not be a problem for you
I'm using led lighting, probably only one on at a time ,and the TV and water pump as required.Got to sort something before getting away hopefully in March , for a week stopping for 2/3 days then moving on ,with no hook up.
 

Brockley

Full Member
Posts
225
Likes
394
I'm using led lighting, probably only one on at a time ,and the TV and water pump as required.Got to sort something before getting away hopefully in March , for a week stopping for 2/3 days then moving on ,with no hook up.

It’s amazing what you can learn from YouTube and from the good folk here (although I’m still waiting for someone to get back to me about my split charger question.. lol). You could always get a competent electrician to check your plan before doing the work yourself and then again before you run anything if you aren’t too sure and still save money.

Victron have a great little tool kit app you can download from the App Store. There is a very easy to use cable calculator included. Just enter dc, 12 volts, length of cable and the current in amps and it will tell you the gauge of cable required in mm squared.

Also and sorry if anyone has already mentioned this, but you could ruin the new battery if doesn’t perfectly match your existing one, especially if the existing one has sulphated and lost full efficiency, one will pull the other down.

I’ve messed with lead acid for too long now. The additional 80amp tilting solar panel and a Victron mppt controller certainly has helped me out a lot, but I’m fed up of having to fettle all the time especially at this time of year so I’ve bitten the bullet and ordered a complete lithium system - 200ah Bluetooth Novel battery, 30 amp Victron b to b charger, 40 amp Victron mains charger from Quality Source ltd. Just over £2100 all in posted. Seems a lot but should end all worry of battery management for the next ten years. The battery comes with a 2000 cycle guarantee. Should see me out!
 

Glynno

Full Member
Posts
16
Likes
9
My brother ordered an optional 2nd battery with his brand new Burstner, and this is how the dealer fitted it. To me, the wire seems far too thin, and the take off is from the original battery only. View attachment 91118. A poor job in my opinion, and an example to the OP of how not to do it!
The patch leads are protected via a 15 amp fuse. Don’t forget the main vehicle battery leads are 16mm to cope with starting loads of 120 amp or so. The leads from the first battery would probably be 10 mm to allow for volt drop over the length. To run a 15 amp load would be quite high as the batteries would be sharing this load. The cables look like about 6 mm which could take a higher amperage than the fuse. Therefore it seems safe and workable. Things are not always as they seem. I hope this helps in your worries. 😀 You can buy loops from eBay that are complete with fusecarrier quite cheaply.
Look at the diagram for above. It shows you how to do it and the types of terminals available And also reminds me that I need a fuse on the positive link. Ooops!
It may be worth investing in battery terminal covers to be safer. These are probably covered by a timber seat cover or such. So are normally not accessible without tools.
 

Attachments

  • F295E1E0-212E-4FDF-91A6-CD7EE7B83E39.png
    F295E1E0-212E-4FDF-91A6-CD7EE7B83E39.png
    1.7 MB · Views: 15
Last edited:

Users who viewed this discussion (Total:0)

Top