Batteries connected correct

[Trout bum]

Hi up at the van today to get some stuff done to the van , had a look at the liesure batteries and I don't think they are connected properly to allow even usage , I always thought that when two batteries were connected you took the positive connection from one battery and the negative from the other this gives you even usage , am I correct the pic is how they are connected just now from dealer.

 

[Tombola]

Wired as a bank but cables seem a but weedy? and draw leads will over draw formt he 1st battery.
Id be tempted to get some good thick cable to bank them up (25 or 35mm) and then put the draw leads correctly as you say.

 

[Jimbohorlicks]

The positives don't seem to be connected together,but the negatives are,unless the positives are joined somewhere else

 

[Lenny HB]

Doesn't make much odds with two batteries close together.
As Tombola says the cables look way undersized.

 

[Trout bum]

Thanks guys I have 35 mm cable I'm going to join them with as in near future I'm fitting an inverter, and I'll connect the positive on one battery and negative on the other to get an even fill and draw from them , as I said this was the cable the dealer fitted .

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[Scully]

How thick should the cables be?

I've 2 x110ah leisure batteries about 1m apart (1 under each bench seat) . I've 160w solar. The outside diameter of the cable connecting the 2 batteries is 3.5mm, I guess the cable length must be about 1.5m. The thicker "load" cables (on one battery only) are 10mm diameter. The most I'm running at one time is 42w compressor fridge, couple of Led lights, 12v telly and truma fan for hot air ( heated by gas). I was planning on rewiring the batteries "correctly" as per the OP's issue but using 10mm diameter connecting cables.

This talk of needing 25-35mm cables has me wondering about the safety of the rest of the van electrics. Is there a formulae for calculating required thickness based on current draw / cable length etc?

 

[Trout bum]

The positives don't seem to be connected together,but the negatives are,unless the positives are joined somewhere else

Positives are connected together jim, but as you see think cable and drawing of the same battery I've been told it should draw positive from one battery and negative from the other so I'm going to do this and I'm connecting them with 35 mm cable .

 

[Trout bum]

How thick should the cables be?

I've 2 x110ah leisure batteries about 1m apart (1 under each bench seat) . I've 160w solar. The outside diameter of the cable connecting the 2 batteries is 3.5mm, I guess the cable length must be about 1.5m. The thicker "load" cables (on one battery only) are 10mm diameter. The most I'm running at one time is 42w compressor fridge, couple of Led lights, 12v telly and truma fan for hot air ( heated by gas). I was planning on rewiring the batteries "correctly" as per the OP's issue but using 10mm diameter connecting cables.

This talk of needing 25-35mm cables has me wondering about the safety of the rest of the van electrics. Is there a formulae for calculating required thickness based on current draw / cable length etc?

Hi not 100% sure but longer the run of cable the thicker it should be , guys on here are more knowledgeable they will advise better , my batteries are next to each other but I'm going to use 35mm cable both cut to same length as in future I want to instal an inverter hence the heavier cables

 

[Lenny HB]

With Brit built vans cable size is a joke.
For normal use 25mm sq is fine but it's no good just uprating the cables joining the batteries you need to look at the system as a whole.
To start with the cables from the batteries to the distribution unit also need to be 25 mm sq.

Then you need to look at the cables feeding appliances around the van, no need to worry about lighting as they are all low current LED's now. You need to look at the heater, TV supply, 12v sockets etc.

When buying single core cables it is best to buy standard auto cable Thin Walled cable is best avoided for two reasons, stiff and awkward to work with, sizing is different and includes the insulation so unless less you understand it you will end up with undersized cables.

You need to aim for a max volt drop of 3% the lower the better, link to a calculator below.

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

 

[xsparks]

When talking about cable it's the cross sectional area not the diameter. So a 35mm cable is not as fat as you might imagine.

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[Scully]

When talking about cable it's the cross sectional area not the diameter. So a 35mm cable is not as fat as you might imagine.

Thanks, that's reassuring, that means 35mm ,assuming it refers the copper area, equates to about 7mm diameter copper, and adding on say 2mm sheilding, means around 11mm thick wire.

Thanks LennyHB for the link to the cable sizing site, really interesting, I will study in more detail. I now see that it can be quite common to omit the 2 or mm2.

Appreciate TroutBum, that much thicker wires are required for the current draw of an invertor.

Thanks for your help guys.

 

[xsparks]

Approximately 10mm dia for 35 mm and 8mm for 25mm cable.

 

[denisejoe]

Hi up at the van today to get some stuff done to the van , had a look at the liesure batteries and I don't think they are connected properly to allow even usage , I always thought that when two batteries were connected you took the positive connection from one battery and the negative from the other this gives you even usage , am I correct the pic is how they are connected just now from dealer.

Your thinking of connecting in series check should be parallel
Broken Link Removed

 

[pappajohn]

I noticed the existing link wires are long enough to hang washing off..... Keep both new ones as short as safely possible.

 

[Trout bum]

Went up to the motorhome today and done first phase of tiding up the batteries, fitted new battery terminals with 3 connection points on each (would have liked to use connecting strips for negative and positive wires but not enough room) , batteries are now in parallel with positive coming off one battery and negative off the other..

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[Lenny HB]

A good start except for the battery terminals, they look like pressed steel ones. Much better to use solid brass terminals.

 

[Trout bum]

A good start except for the battery terminals, they look like pressed steel ones. Much better to use solid brass terminals.

Thanks Lenny I did try to find the brass ones with the take off points on them ,I'll keep looking and change them when I find them .

 

[Tombola]

Looks far more pro than before

 

[Trout bum]

Looks far more pro than before

Thanks Tombola , everyday is a school day , and you guys help with your knowledge .

 

[autorouter]

This talk of needing 25-35mm cables has me wondering about the safety of the rest of the van electrics. Is there a formulae for calculating required thickness based on current draw / cable length etc?

Usually it's not a safety issue. The idea of thick wires is to keep the voltage drop low - below 3% for example. The voltage drop depends on the amps and the length. Wires sized for low voltage drop are usually two or three times thicker than would be required for safety.

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