Submitted: Wednesday, Mar 08, 2017 at 01:33
ThreadID: 134430 Views:2424 Replies:6 FollowUps:12
This Thread has been Archived
Hi All,

The battery compartment in the caravan is only big enough for one N70 sized battery. This limits the amount of amp hours that I have available. I have noticed that 6v batteries have bigger amp hour ratings. There were 2x 6v batteries (dead) in it when I bought it & now that it is time for a new battery is there any disadvantage in using 2x6v instead of a single 12v one? Bill
Back Expand Un-Read 0 Moderator

Reply By: Member - Boobook - Wednesday, Mar 08, 2017 at 06:12

Wednesday, Mar 08, 2017 at 06:12

While a 6V battery may have more AH than a 12v battery for the same physical size, you will need 2 of them. Therefore to fit in the same space, each 6V battery would have to be about half the size of the 12V one.

Use as big a 12v one as you can. It will be cheaper and easier to replace.

AnswerID: 609235

Reply By: Sigmund - Wednesday, Mar 08, 2017 at 07:52

Wednesday, Mar 08, 2017 at 07:52
That's done often enough when space is tight, and of course two 6v wired in series gives you 12 v.
AnswerID: 609240

Reply By: qldcamper - Wednesday, Mar 08, 2017 at 08:00

Wednesday, Mar 08, 2017 at 08:00
the disadvantage of running two 6 volt batteries is that if you lose a cell in one, your whole system is down as well as there being extra wiring and connections. connections.

If you insist on using two batteries use two 12 volts in parallel, then if you drop a cell you can isolate the dud battery and still operate on one till you get to somewhere to pick up new batteries.
AnswerID: 609242

Follow Up By: The Bantam - Sunday, Mar 12, 2017 at 00:15

Sunday, Mar 12, 2017 at 00:15
Sorry but this makes no sense .... regardless of the battery being made up of 1 x 12 volt battery package or 2 x 6 volt packages ..... dropping a cell will have the same result.

Using batteries in series is more relaibale and easier to manage than using them in paralell.

batteries of matched size and age will oppeate fine in series, and the cell capacities will equalise with a stiff charge.

Batteries operated in paralell will often not load share properly especially if particular attention is not paid to the wiring arrangements.


FollowupID: 879194

Follow Up By: qldcamper - Sunday, Mar 12, 2017 at 08:51

Sunday, Mar 12, 2017 at 08:51
Im sorry it makes no sense to you, maybe if you had a little more practical experience with batteries.
Using batteries in series may be easier to manage but what is the advantage, you said yourself that if you lose a cell in one of them it results in an inoperative system.
As i said, if you have 2 in parallel and you lose a cell, if you isolate the dud battery you still have one to continue operating with, which is better than none don't you think?
If you pay the same attention to properly matching type and age to a parallel system then it will give you the same reliable service until they are getting near to the end of their service life, or until one shows singes of poor assembly, pretty much similar to a series set up.
Wiring arrangements? Poor design will bring any system down.
Yes there is a need to regularly check them individually like the end of each trip as they age but that is recommended with any system.
Maybe you should inform Toyota of the mistake their engineers have made running all those landcruisers with parallel systems and not two 6 volt in series.
Hopefully this will help you see sense in my post and you might consider not beginning replies to my posts in such an aggressive manor.
happy camping.
FollowupID: 879202

Follow Up By: Allan B (Sunshine Coast) - Sunday, Mar 12, 2017 at 09:43

Sunday, Mar 12, 2017 at 09:43

Telling The Bantam "maybe if you had a little more practical experience with batteries."

You're new here aren't you Qldcamper?

My Profile  My Blog  My Position  Send Message

FollowupID: 879203

Follow Up By: Bob Y. - Qld - Sunday, Mar 12, 2017 at 09:56

Sunday, Mar 12, 2017 at 09:56
I don't think Bantam was being aggressive Qldcamper, all he did was disagree with you. Try Facebook if you want abuse, aggressiveness or bullying. LOL

Bantam will debate you on any subject, especially batteries, for as long you like!


Seen it all, Done it all.
Can't remember most of it.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 879204

Follow Up By: qldcamper - Sunday, Mar 12, 2017 at 12:22

Sunday, Mar 12, 2017 at 12:22

How long does it take before a NEW member can make a post with some honest advice without being challenged?

And to start a post with.....that makes no sense at all, I'm sorry if i miss interpreted it, but i think it is dis respectful.

Not here to debate, here to hopefully learn a few things, as you are aware if I don't know something I will ask. I prefer to ask people that have real experience in a field rather than just read up on it on the net and hope the authors of what I read actually know what they are writing about.

I also wont advise people on anything I am not sure about.

I simply pointed out what i feel is the major disadvantage of running two 6 volt batteries over two 12 volt batteries to be basically told that I don't know what I am talking about.

So how long do you think I should be a member before I offer any advice to someone asking for it?
FollowupID: 879205

Follow Up By: Allan B (Sunshine Coast) - Sunday, Mar 12, 2017 at 13:03

Sunday, Mar 12, 2017 at 13:03

"How long" etc? Well, and with respect, it may be better to observe the forum for long enough to determine who has expertise before getting stroppy. Bantam did begin with "Sorry but..."

And one thing you may need to learn is that electrical and battery subjects are always controversial on here, possibly because everybody considers themselves to be expertly knowledgable about the subject.

Hang in there mate.


My Profile  My Blog  My Position  Send Message

FollowupID: 879206

Follow Up By: The Bantam - Sunday, Mar 12, 2017 at 15:32

Sunday, Mar 12, 2017 at 15:32
qldcamper ........ heh heh .. ..... mate Ive been dealing with batteries large and small most of my working life ..... yes I have been formally trained and I try my best to keep up with the issues.

while there are some matters of personal opinion and there are many strongly held just plain wrong beliefs about batteries ..... the issues of series and parallel battery banks are very well known, very well documented and not a matter of opinion.

It is very well known that in a single supply situation, it is by far better to use a series bank of batteries than a parallel bank.

In my apprenticeship we where trained on and maintained very large banks combined in series and parallel in battery rooms bigger than most peoples lounge room..... these batteries where supervised extrordinarily stringently, with voltages and SG of individual cells taken and recorded weekly ...... the informaion and polocies of this organisation alone where built on decades of records over thousands of sites ....... I think they knew what they where doing when they trained me over 30 years ago.

In more recent times I have had experience with lead acid batteries from 1.2Ah to 200Ah on a regular bassis ..... on a busy day of preventive maintenence these days I will test and or replace batteries on between 8 and 15 sites in a day.

I don't claim to know it all ....... but I have a pretty good "background" knoweledge.

The issues of series and parallel banks are very well known as I said.

IN ALL batteries of all types no two batteries or cells are identical or have identical charge discharge behaviours.

In a series bank ... .... ALL standard off the shelf lead acid family packages BTW are series banks of cells if they are not single 2 volt cells.

In a series bank of cells .... current that flows flows equally thru all cells ..... without question ...... thus the whole bank load shares equally the entire life of the battery ........ individual cells WILL charge and discharge at slightly differing rates ..... but in series as long as the bank is fully charged those cells will equalize.

In a parallel bank of batteries ........ the two banks WILL NEVER (in lead acid,can't won't does not happen) load share equally ...... if the wiring is correctly configured and the batteries are well matched, this can be done with reasonable results but ....... one bank WILL ALWAYS take more load than the other ........ as the batteries age this will get worse and worse ...... maximum life WILL NEVER be achieved out of either battery.

In bad cases one battery will fail long before the other and well before it's best life ..... in bad cases the failing battery will will prevent the better battery from charging and or take it with it.

what automotive manufacturers do with batteries and electrics in general can not be held up as best practice ...... there are many priorities before best battery practice. ....... in some casses they simply did not have space for a big enough battery or in the case of landcruiser, (it is commonly argued) the single battery did not have sufficient capacity to crank in cold climates, so a second was fitted.

Most Japanese trucks run 24 volt systems and run 2 x 12 volt or 4 x 6 volt banks as factory fitted. Likewise many european trucks and busses.

Many of the American trucks , Mack, Kenworth, Freightliner run 12 volt systems with some with parallel batteries.

WHY they try to crank 12 litre diesel engines off a 12 volt system is beyond me ..... yes and most these days ARE electric crank.

Some models of Freightliner, run a 4 x 12 volt in paralell battery rig ..... this battery carrier runs the full width of the truck just behind the front wheels ....... the positive comes in one end and the negative in the other with a very heavy loom connecting all 4 batteries.
INvariably ..... 2 of the 4 batteries fail long before the other two.

It is well known, well proven and well documented, over many decades, that a series combination of batteries is by far a better option than a paralell arrangement if it can be implimented.

FollowupID: 879210

Follow Up By: qldcamper - Sunday, Mar 12, 2017 at 16:35

Sunday, Mar 12, 2017 at 16:35
Thanks for taking the time to explain your post, and your qualifications to make such a statement. I do agree with most of what you say, well all of it if the application requires a near perfect condition, which in many cases is impractical.

There are many many parallel systems operating out there with many more that two batteries in parallel, maybe not as efficient as a series system but it is hard to find and to afford 100 AH 2 volt cells for use in a motorhome, a UPS in a Telstra installation maybe.

Do you agree that the ability to isolate a faulty battery and continue using the system at a reduced capacity is a handy to have option what your in isolated areas, or is it an option you would forgo just to maximize battery life. Individual opinion I guess, everyone is allowed one, to me it does make some sense.

The twin battery system in the landcruisers is used in colder climates as a series parallel system for 24 volt crank and 12 volt everything else, so I guess they just left the same batteries in there and fitted a different cable option in the warmer climates.

It does seem strange that most American road going trucks stay 12 volt, think it might be a typical American we didnt have the idea so it cant be a good one attitude, a few of the Euro trucks went with the series parallel system for a few years but i think most have gone 24 volt now.

It has been a very long time since I have worked on a truck with four 6 volt batteries, not since the old hard rubber days. ^ volt polly cases were made, and probably still are but industry soon swung away from them for onroad opting for the parallel format, my guess is that it become the cheaper option.

When you get into the larger engines like caterpillar air start are so much more efficient, but are a proper pain in the ass, the electric options on the same trucks are a lot more reliable, with air you only get one go at it so if someone has used an e stop to shut it down and didn't reset it, or if there is a tiny air leak it can be a major problem. But in the really hot environments you get sick of fitting batteries.

Anyway, nice to learn a bit about you, would be a good evening round a campfire topic.

Just remember that you are not the only bloke that has spent their whole career working with batteries. Dont really want to get into pissing competitions.

This is getting a bit removed from the OP's request where i was merely offering an advantage of a parallel system.

FollowupID: 879211

Follow Up By: Tim F3 - Sunday, Mar 12, 2017 at 21:50

Sunday, Mar 12, 2017 at 21:50
So based on the above re multiple batteries if space is available caravanners would be better off with one x 200 amp deep cycle battery than 2 x 100 amp deep cycle batteries ???

Any thoughts gentlemen ??
FollowupID: 879226

Follow Up By: qldcamper - Sunday, Mar 12, 2017 at 22:13

Sunday, Mar 12, 2017 at 22:13
One large battery will, or should be more economic if you have the space and dont need to spread the weight around, there will also be less expense in terminals and cables.

In my first reply to this thread note i said....if you insist on using 2 batteries.

An AGM in an N200 configuration would be rather heavy, I have never needed to lift one, let alone juggle it into a tight place and hope i never have to, a conventional flooded N200 is bad enough considering I normally see them in pairs or groups of four.
FollowupID: 879227

Reply By: Allan B (Sunshine Coast) - Wednesday, Mar 08, 2017 at 08:44

Wednesday, Mar 08, 2017 at 08:44
Bill, you are a bit confused about ampere-hours and energy.

A 6 volt battery may have more Ah than a 12 volt battery of the same physical size but it is only half the voltage so the stored energy will be about the same as the 12v battery. (Energy = Ah x V)

The simplest and most economical arrangement is to use a single 12v battery of a size that suits your space and energy needs.

Sometimes two 6v batteries of half the physical size of a single 12v battery may have been used where the access is difficult and two half-size batteries are easier to lift into position. But it is not a "good" arrangement from the electrical viewpoint.

My Profile  My Blog  My Position  Send Message

AnswerID: 609243

Follow Up By: Kazza055 - Wednesday, Mar 08, 2017 at 09:43

Wednesday, Mar 08, 2017 at 09:43
I agree with what Allan has said.

If it was me I would be looking at another place to fit the battery/s. On our van I have moved them (2 x 100AH) to the chassis rail under the van. Freed up front boot space plus reduced the ball weight.
FollowupID: 879065

Reply By: Batt's - Wednesday, Mar 08, 2017 at 21:00

Wednesday, Mar 08, 2017 at 21:00
I don't know what sort of van it is but what's stopping you from relocating where the battery is.
AnswerID: 609275

Follow Up By: vk1dx - Thursday, Mar 09, 2017 at 02:31

Thursday, Mar 09, 2017 at 02:31
Or add a second 12V one somewhere.

However like Batt said, I don't know the van or your budget.

FollowupID: 879137

Reply By: The Bantam - Sunday, Mar 12, 2017 at 00:19

Sunday, Mar 12, 2017 at 00:19
You may get a little more capacity using either a single 12 v or 2 x 6 volt batteries that have slightly differeing dimensions than the N70 series.

for example golf buggy batteries are significantly taller than an N70.

looking for a taller, or fatter battery may get you what you are looking for if length is the restriction.

AnswerID: 609339

Sponsored Links