Cable To Connect Batteries

[Darren]

im looking to purchase some cableto join to 110 amp batteries together. I will need around 3meters to do this, what size would be best and where can I purchase it from?

 

[johnp10]

I simply went to my local Auto Electricians and bought (his advice) the cables used as battery cables for HGVs.
More than up to the job.

 

[DavidG58]

I don't think you can have too thick cable, but you mustn't have too thin

 

[Gellyneck]

Old set of jump leads?

 

[tonyidle]

im looking to purchase some cableto join to 110 amp batteries together. I will need around 3meters to do this, what size would be best and where can I purchase it from?

Broken Link Removed

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[jockaneezer]

Old set of jump leads?

I chopped up an old set of jumpleads when I fitted my second leisure battery for the Chester rally

 

[SomeoneElse]

Plenty of advice from the (way) over-engineer it brigade, but to do any sort of design work on the situation you need to explain what you intend to do when you have the two batteries connected together.

If its just increase the battery capacity, say you know you can last out a two night meet with the current situation but you wish to attend four night meets, then the simple advice is to use the same size cable that is connected to the first battery. The logic being that the existing cables carry the load ok and when you have two batteries the inter connecting cable will only be carrying half the load. Having said all that, because of the distance between the batteries, I would probably go up a cable size as I usually over-engineer things.

However if you intend to increase the load on the batteries, by say adding an inverter, then the size of the cables between the batteries and to the inverter must be based on the inverter load as well as the length of the cables.

 

[Gizmouk]

Firstly - I wouldn't use jump lead cables. They are designed to handle large currents for very short durations, and are generally poor quality cable.

So,
I used 50A continuous load in the cable calc:

50A
3m run
0.5v drop
= 10mm (10mm2 / 10mmCSA)

 

[tonyidle]

Cable sizes vs current using any information from suppliers is based on the current the cable can safely carry. This is not the information on which to base cable size when used for low-voltage DC supplies where the issue is voltage drop. Voltage drop, simply put, is the loss incurred whenever a supply and load are connected together by a cable. It is affected by the current you intend to draw and the length of wire. So .......... be aware of the minimum cable size needed to safely carry the current but don't consider it a target. If the run is lengthy use thicker cable than if it is short. In the case of a link cable between two batteries the advice offered above to use a thickness at least the same as the existing battery connection is sound.

Edit: see post by Gizmouk above.

 

[funflair]

Some cheap jump leads are alloy cable and quite large diameter strands I would avoid this but heavy multi strand copper is OK.

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[Peter A Forbes]

You need something like a flexible multi-stranded cable of between 35sq mm and 50sq mm.

Something like welding cable is highly recommended. Type 0361TQ, Orange or Black sheathed and most are dual-covered.

If you are anywhere near our works, we'd be happy to cut it to size and crimp some terminals on for you.

Peter

 

[Darren]

Thanks everybody for their input. I'm trying to increase the length I can stay of grid by joining the two together.

 

[Techno]

My Rapido has the leisure batteries at the front but the distribution board at the back. The factory cable routing involves at least 6 metres maybe 7 of 10mm cable before each circuit gets off the ground.
The original alternator charging system involves double that length of cable as the battery parallel relay is in the distribution panel. Quite a rubbish design!
Is there no way you can relocate the original battery so you can have both side by side? two lengths of 35mm welding cable amounting to 6 metres is quite heavy.

 

[Darren]

No wat to relocate the battery. I have a homer 534. The original battery is fitted at the side of the passenger seat in a footwell room enough for one battery ,the other one has the same well along side the drivers seat so I presume it's ment to go in there.

 

[thehutchies]

...
The logic being that the existing cables carry the load ok and when you have two batteries the inter connecting cable will only be carrying half the load.
...

Apologies in advance if I've misunderstood your post (it has been known )but the interconnecting cable will still be carrying the same load irrespective of how many batteries are connected.
A load that draws, say, 20 amps will produce a 20 amp current in all parts of the circuit.

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[SomeoneElse]

If you have a load of 20Amps in your MH then the cables from the battery to the control/distribution panel will each be carrying 20Amps.
When a second battery is added by connecting positive to positive and negative to negative from the first to the second battery. Then each battery will only need to supply 10Amps. The second battery will be sending 10Amps along the inter-connecting cables to the first, where 10Amps from the first battery will be added, the resulting 20Amps will then flow to the control panel.

 

[thehutchies]

If you have a load of 20Amps in your MH then the cables from the battery to the control/distribution panel will each be carrying 20Amps.
When a second battery is added by connecting positive to positive and negative to negative from the first to the second battery. Then each battery will only need to supply 10Amps. The second battery will be sending 10Amps along the inter-connecting cables to the first, where 10Amps from the first battery will be added, the resulting 20Amps will then flow to the control panel.

The current in all parts of the circuit, including the interconnecting cables, will be 20amps.

 

[Techno]

Batteries in parallel provides two paths and 10 amps flow through each
If they were in series and thus only one path then yes the current would be the same throughout

 

[SomeoneElse]

The current in all parts of the circuit, including the interconnecting cables, will be 20amps.

Then we must disagree with each other.

Batteries in parallel provides two paths and 10 amps flow through each
If they were in series and thus only one path then yes the current would be the same throughout

Correct, but the voltage would be 24Volts, not what is wanted I fear.

 

[Techno]

Yes but that isn't the way I meant it and why I didn't add figures to that scenario

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[Techno]

Current takes the path of least resistance
If you provide two equal paths the current will split 50/50

 

[Techno]

Incidentally the best way to ensure a true 50/50 split is to take the load connection from the +ve of one battery and the -ve of the other

 

[thehutchies]

Sorry!
Complete misunderstanding on my part, as I suggested it might be.
A qualification in electrical engineering and a Physics degree specialising in electrical theory still doesn't prevent a temporary short-circuit between the earlobes.