Adding Leasure Batteries

Dave Scadding

Dave Scadding

Joined
Jul 20, 2018
Posts
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Location
Bridport Dorset
Funster No
55,041
MH
Swift Kontiki 655
Exp
Trailer tent for 10 years Motorhome since 2018
Hi all,
I have a Swift Kontiki 655 which has a single leisure battery, I want to add an additional battery to give me power for longer periods. However the cables on the existing battery are quite small ie about 8 - 10mm nowhere near the size I was expecting (ie 16mm jump lead size). Can I just buy a 110ah battery and wire it in next to the existing in parallel + to + and - to - with a similar sized cable? As far as I'm aware the wiring system hasn't been modified in anyway with the exception of a solar panel which is supposed to charge both the leisure and vehicle battery. The mains charger in the rear of the van is the standard Sargent EC200 2007.
 
Yes, as they will be neighbours use the same gauge wire.
If there's ANY chance of the linking positive wire being damaged put a fuse at BOTH ends next to the batteries.
If there's no chance put one 30amp fuse next to one battery.
 
I wonder why you want to add a second battery? If it's because the present capacity is insufficient, it could be because the current battery is on its last legs. I believe that adding a brand new one alongside an ageing one is not such a bright idea. The poor one will reduce the performance of the good one and might even take it down when it fails. How about just replacing the existing battery?
The wires should be spec'd for the current demand. Unless you are planning to consume more, there should be no need to 'fatten them up'.
 
Thanks for your prompt reply Pappajohn, you always seem to come up trumps with answers and its appreciated. So I can just add another leisure battery and inline fuse. I'm assuming this will then provide the same amount of power but for a longer period?
 
Ahh ok, so buy a new one and if that doesn't perform then add another?

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Yes, if you add a second 110ah battery it will give you, theoretically, 220ah.
Twice the reserve power you had.
All depends how good your old battery is as posted by two above.
 
Have you read the threads about additional leisure batteries? They should ideally be matched - the same make, capacity and age.

If not, you can have problems. I did. I put a new Varta LFD140ah battery in parallel with a two years old Varta LFD140ah Battery and two years later the older battery burst, probably as a result of over-charging from solar panels in summer. Not a nice happening but predictable by the battery experts.

Incidentally, though not the ideal way to wire them in parallel, the original habitiation positive and negative wires were left on the first battery, and the two batteries parallel joined +ve to +ve and -ve to -ve with 100mm(?) diameter copper wire. It would have been better to take the habitation +ve to one battery and the habitation -ve to the other but the cables wouldn't reach.

After the burst battery episode, I put things right by fitting two new, identical batteries and by extending the habitiation negative cable so it reached the second battery. Worth considering.
 
OK thanks both Papajohn and two,
I spent my first night "off grid" and was unable to have the heating running as the leisure battery wouldn't support it. After returning home and plugging the van in and re charging the battery I set off again (the next weekend) and didn't put the heating on, however even just having the TV and one light on the battery was drained to 10v after about 20mins and then woulkdnt support even just a light. hence my thoghts of adding another battery. However from response it looks like my current battery may be on its last legs. i'll replace it with a new one and see how that performs and add additional if duration is not extended.
thanks both for taking the time to reply.
 
Hagstrom said:
the same make, capacity and age.
Click to expand...
Don't know why this keeps cropping up.
The only definate is age
Make doesn't matter
Capacity doesn't matter.

A 70ah and a 130ah will become a 200ah battery as far as the charging system is concerned, it doesn't know how many individual batteries there are... It just sees 200ah capacity.

Age only matters as the older a battery is the less efficient it is at accepting and holding a charge and eventually will fail to hold at all.

The only other definate is battery chemistry.... Battery types, lead/acid, gel, lithium, must not be nixed.
 
Thanks Hagstrom, noted basically split the existing cables across the two batteries.

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Dave Scadding said:
OK thanks both Papajohn and two,
I spent my first night "off grid" and was unable to have the heating running as the leisure battery wouldn't support it. After returning home and plugging the van in and re charging the battery I set off again (the next weekend) and didn't put the heating on, however even just having the TV and one light on the battery was drained to 10v after about 20mins and then woulkdnt support even just a light. hence my thoghts of adding another battery. However from response it looks like my current battery may be on its last legs. i'll replace it with a new one and see how that performs and add additional if duration is not extended.
thanks both for taking the time to reply.
Click to expand...
Time for a new battery, that one's had it.
Fitting a second at this stage won't do it any good as the old one will drag its efficiency right down.

Edit.... You should get £8 to £10 from a scrapyard for your old one, takes a bit of pain out of the cost of a new one .
 
That's what I'd do, and I think you'd notice the difference. If you consider that the extended capacity is still insufficient, then add another identical one.
It will work with different sizes/ages of battery but not for as long as if they are matched.
 
pappajohn said:
Don't know why this keeps cropping up.
The only definate is age
Make doesn't matter
Capacity doesn't matter.

A 70ah and a 130ah will become a 200ah battery as far as the charging system is concerned, it doesn't know how many individual batteries there are... It just sees 200ah capacity.

Age only matters as the older a battery is the less efficient it is at accepting and holding a charge and eventually will fail to hold at all.

The only other definate is battery chemistry.... Battery types, lead/acid, gel, lithium, must not be nixed.
Click to expand...

Don't know where you have got your information from, but its contrary to what I have been told by several battery manufactures and suppliers. They have all said the batteries should be the same make, power and age. Different brands have slightly different make ups which will effect performance and charging times. If you want to get the optimum performance from your batteries I would stick to same brand , age and power. Hope this doesn't come across as an argument, its not intended too, but I think the information you are giving is not correct.
 
I think it's to do with the internal resistance of each battery, which ought to be the same.
 
I think if a little difference in internal resistance etc is going to sway your opinion you should skip the idea of multiple batteries and opt for one large capacity battery.
It isn't that long ago a leisure battery didn't exist and any old car battery was the order of the day and people survived.
The whole battery issue is becoming far too technical for what it is... A means of providing 12v for the sole purpose of using 12v appliances.
If a good 12v battery can't last a couple of days there's only one reason.... Your using too much power.
I have never had a problem with mixed manufacturers or capacities though I may have got an extra day had I got a battery 'expert' to perfectly match batteries for me, but why bother.... I never had a problem mixing them and I don't think I EVER ran out of battery power.

Of course battery manufacturers are going to tell you to only use matched batteries, they have an interest in telling you that...they make and sell batteries
Someone who sells nails won't tell you to use screws will they.
To many it's just becoming an obsession, what with battery monitors and such, what's it going to prove... Their batteries are being charged or discharged...
Many don't even understand what they're looking at judging by many of the battery threads
it's nothing more than something else to worry about.

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I tend to side with you PJ.
The internal resistance thing I picked-up over 50 years ago. Since then, and after killing several batteries (probably for other reasons), I started to heed the advice being issued.
It seems to make sense not to mix 'n match and I've had more success keeping them the same (but probably as a result of better management).
Once a battery (or a cell within one) fails it has often taken the rest with it, so I'd avoid mixing quality batteries with cheap ones. It looks neater, anyway, to have them all the same (although I'd usually vote for function over form).
 
Mikescuba said:
Don't know where you have got your information from, but its contrary to what I have been told by several battery manufactures and suppliers. They have all said the batteries should be the same make, power and age. Different brands have slightly different make ups which will effect performance and charging times. If you want to get the optimum performance from your batteries I would stick to same brand , age and power. Hope this doesn't come across as an argument, its not intended too, but I think the information you are giving is not correct.
Click to expand...

I worked with batteries for 26 years of my working life and "pappajohn" is correct.

I stopped advising on here about batteries because so many people know better than someone who worked with batteries for a living..........
 
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Mikescuba said:
Seems to be mixed views on the subject.
This is Optima batteries view.
https://www.optimabatteries.com/en-us/experience/2014/04/can-i-connect-dissimilar-batteries-parallel

I have recently upgraded my two leisure batteries and gone for two 110 amp Gel batteries which served me very well in our previous MH. As they are quiet expensive I prefer not to take any chances and prefer to play safe.
https://www.alpha-batteries.co.uk/12v-110ah-leoch-powabloc-tubular-gel-battery/
Click to expand...
But at the end they say if you need say 8 batteries connect them in 3 banks of 3 which to me seems to be just the same thing!!!!!! I recon its a sales ploy
 
The Wino said:
But at the end they say if you need say 8 batteries connect them in 3 banks of 3 which to me seems to be just the same thing!!!!!! I recon its a sales ploy
Click to expand...
I don't know what the answer is. As my batteries have a 6 year warranty I prefer not to give them an excuse to invalidate the warranty.

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The Wino said:
But at the end they say if you need say 8 batteries connect them in 3 banks of 3 which to me seems to be just the same thing!!!!!! I recon its a sales ploy
Click to expand...
What they really need is a couple of night classes in mathematics.
Three banks of three batteries always made nine batteries, not eight. :doh:
 
pappajohn said:
The whole battery issue is becoming far too technical for what it is... A means of providing 12v for the sole purpose of using 12v appliances.
If a good 12v battery can't last a couple of days there's only one reason.... Your using too much power.
Click to expand...
Quite agree. In my early impecunious days with my first m/h I fitted a starter (i.e. not a 'Leisure') battery which was no longer up to starting my lumpy diesel car engine. It worked fine in the m/h for 3 or 4 more years, admittedly only running the water pump, lighting and fridge igniter.
As far as the connecting cables are concerned they only have to be of a size appropriate for the current being drawn or the charge rate, whichever is the greater. Just because you increase the battery (electrical storage) capacity it doesn't follow that more current will be drawn.
 
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