Linking 2 leisure batteries??

[Fisherman]

I have been watching this thread, and quite frankly it scares the S—t out of me.
I brings back memories of a neighbour who was about to wire up a 10.5 kw shower with some 1.5mm cable he had in his garage.

Chris this is a simple job for someone who knows what they are doing, you don’t.
I would seriously advise you not to mess about with electricity. But if you do insist take a look at this. Take my advice listen to wildebus, I do. Take care, be really careful.

Pardon our interruption...

 

[harrow]

Where I used to work we had huge solid copper busbars 8 inches by 2 inches some were doubled up.

But we have to live in a real world, why use 2 cables ?

 

[colinm]

But we have to live in a real world, why use 2 cables ?

See post 7

 

[molly 2]

I have been watching this thread, and quite frankly it scares the S—t out of me.
I brings back memories of a neighbour who was about to wire up a 10.5 kw shower with some 1.5mm cable he had in his garage.

Chris this is a simple job for someone who knows what they are doing, you don’t.
I would seriously advise you not to mess about with electricity. But if you do insist take a look at this. Take my advice listen to wildebus, I do. Take care, be really careful.

Pardon our interruption...

These cables look to thin you need cables like short jump leads

 

[chrishunter]

Hi Chris,

Like you I am a novice and after your first post understand why those that are knowledgeable are now hesitant to give advice. Can I suggest doing your own research on youtube and then coming back here and asking for confirmation that what you've figured out will work, is safe and then do the project.

Some replies do seem brutal but that is only cos nobody wants you stuck in a moho on fire

yes your right..

 

[molly 2]

Doing it wrong could be horrendous , follow trevs Drawing .look on you tube lots of advice ,iinstructions,

 

[Fisherman]

These cables look to thin you need cables like short jump leads

I would reckon 10mm would be required, I am sure wildebus would know.

To be honest I never really looked at the photos, I assumed as this is supposed to be for a Motorhome it would be fine, but looking at the photos I would agree, they look to thin.

 

[wildebus]

Its done like this using proper battery cable & clamps which can be bought at any good car shop, do get someone else to do the job.

That's the way to cable up. In terms of cable length, equal gauge & length cables (to give equal resistance) are advised BETWEEN the batteries, but once out of the battery bank, equal length is not a factor as far as I am concerned, so the note above about equal length cables in the picture at the "To +12V" and "To Ground" point is not relevant (IMO)

Additional advice ....
If the batteries are separated by any significant distance then you need to incorporate fuses into the inter-battery wiring to protect against shorting (with two batteries there are two sources of energy remember and so both sources need protected from/against )
Cable size, I would usually not go below 16mm2 cable generally and quite possibly higher if there is any likelyhood of high current draws (say from an inverter).
Some people add more batteries for longer off-grid time; some people add more batteries to allow them to have more power. If it is the latter, beefier cables are definately needed. The Battery interconnects (between the three batteries) on my Campervan were 50mm2 in order to allow a 2400W inverter to be used reliably.

 

[wildebus]

I would reckon 10mm would be required, I am sure wildebus would know.

To be honest I never really looked at the photos, I assumed as this is supposed to be for a Motorhome it would be fine, but looking at the photos I would agree, they look to thin.

In the link you posted to those cables, they initially looked fine. But when you look closer (which I did following a couple of comments), it looks like the cables are around 4mm (guessing here) and have some sheathing over them which I am sure is not the intent but makes them appear much thicker.


Also there have been some comments about using Jump Lead Cables. Generally they are not good enough either. You might think if they are ok for jumping a engine they must be pretty hefty and they look good and thick? Well, the typical jump lead cable is actually not very good at jumping an engine and if you feel one after being used they can be pretty warm! and you feed that heat despite the insulation on them usually being twice as thick as proper cables (which is why they LOOK thick but are not in reality when it comes to the central core.

Best cable to get is generally UK/European (NOT Chinese) made Welding Cable. It is flexible and high quality and not expensive for the amount of cable that is required.
If anyone has bought a Far East supplied Inverter which comes with cables, they will know why I have said "NOT Chinese" when it comes to Cable!

 

[molly 2]

My comment on jump leads was for the physical size ,not a recommendation ,.awg and mm2 can be confusing

 

[r4dent]

Easiest solution is to fit a bigger capacity battery.
When fitting two they should be same age/ make & model/ capacity so buy a big one instead of.s two identical smaller ones.
Cable size required depends on length of cable runs and acceptable voltage drop.

If determined to go to 2 batteries I support those who believe you need to find an auto electrician.

For either 1 bigger or 2 batteries you check the charger is us up to it.

This is a must read http://www.WEBSITE BLOCKED BY ADMIN/add-a-second-battery.php

 

[trevskoda]

My batteries are about 6 feet apart and fuses ar both ends, one is in the passengers footwell & the other is in a locker where the sink pump and heater are half way down the van.
Follow wildbuses advice and dont let any tom dick or harry poke at the wiring.

 

[SimonM]

Look at what you end up with if you think you know what you’re doing

 

[Robmac]

To be honest, I don't see a problem with the OP doing this himself.

He has taken steps to ask advice here and not just gone ahead and done it, and there is loads of stuff online including diagrams and tutorials to guide him. I would imagine that many of the self builders here are not qualified auto electricians but have wired their vans without endangering themselves. I've done basic wiring myself without knowing much at all, but with help and advice and a bit of double/treble checking I have managed to do it safely. The more complicated stuff I've got a mate on here who helps me out by doing it for me!

 

[trevskoda]

Yes if he is happy then go ahead, if not leave alone.

 

[n brown]

trouble is ,i'm a fervent believer that everyone should have a camper, and a lot of people can only afford to self build . and of those , many can only afford second hand and found/recycled materials . so paying a sparkie or a gas fitter etc might be out of the question.
as Rob says , the OP has the sense to ask a very valuable source of info ,us , and hasn't been offended by the ,shall we say ,robustness ,of some of the answers ! so ,given that ,let's make sure he's asked all the right questions and been given the most useful answers

 

[Fisherman]

Found this on eBay

Pardon our interruption...

 

[wildebus]

My batteries are about 6 feet apart and fuses ar both ends, one is in the passengers footwell & the other is in a locker where the sink pump and heater are half way down the van.....

Always best to be safe
On the installation below, the two batteries were only what? 2 foot apart? but I still fitted a fuse to each battery as the connecting cables ran along the floor between the bases, as potential for shorting in the case of an accident

Seats Bases by David, on Flickr
(the RHS +VE battery connection shown was temporary while waiting for the multi-fuse block)

The only time you might not need to fit fuses is if the cables were so short the chance of shorting is near-impossible (on my current bank, the cables are like that and they wouldn't even reach to an opposite terminal or any ground point to create a problem - but there is still a 'master fuse' for the bank as a precaution)

 

[r4dent]

My batteries are about 6 feet apart and fuses ar both ends, one is in the passengers footwell & the other is in a locker where the sink pump and heater are half way down the van.
Follow wildbuses advice and dont let any tom dick or harry poke at the wiring.

Are you talking about two hab batteries connected in parallel which is what the reference to cable size being dependent on distance apart is about

or are you talking about one cab battery (often located in footwell) and one hab battery (usually located in a locker in habitation area) which are not connected to each other
.
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

 

[trevskoda]

Are you talking about two hab batteries connected in parallel which is what the reference to cable size being dependent on distance apart is about

or are you talking about one cab battery (often located in footwell) and one hab battery (usually located in a locker in habitation area) which are not connected to each other
.
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

No two les batteries, truck cam with only one in the footwell and a long cable to run the rear chairlift, I shortened the cable as to connect to a second service batt in a cupboard, from new there was one fuse at diode take of under the bonnet, I now have a second at other end. I also had to do a part rewire of the van as the split diode unit only let 13.7 volts to batts, I now have bypass relays on a switch going round the old unit, but if one fails I will still get a charge.