How thick should the wires be? (1 Viewer)

[irnbru]

Hi all you knowledgeable lot. Alan is wiring up a battery bank of 4 batteries. How thick of diameter should these wires be bearing in mind at a later date I may want to add a 2k inverter....or should it be moms I order in. A bit confused and I like to run things past funsters first.

Thx

 

[andy63]

35mm square should do..if cable runs are not excessive...

 

[TheBig1]

35mm sq is about right,as using undersized cable will introduce resistance between the batteries

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[andy63]

Well I've just had a look on line... they suggest double that ie 70mm square for a 2kw inverter... that''s with load at up to 2 m distance... I'll look again

 

[andy63]

Interesting and confusing read lol

I have never had an inverter so don't know what the possible surge currents etc can be... the advice on wire size always seems to be follow the manufacturers recommendations. .
So 35mm square cable is capable of 200A dc.. and I'm sure capabe of a higher surge current so that's what I would use unless told differently..
Andy.

 

[Gromett]

I wouldn't want an inverter mounted 2 meters from my battery especially the high power ones. The close to the battery the better.

Losses in cables are I²R so (current x current) x the resistance. The thinner the cable the cable the higher the resistance, the longer the cable the higher the resistance.

You can't affect the current used, so you need to reduce the resistance as much as possible by either using bigger cables or shorter lengths or both.

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[Gromett]

The other thing to think about when choosing cable size. What type of terminals are on the device. If it is the screw type there might not be a big enough hole to fit the larger cable into. If it is a bolt then some crimp terminals might be too big to fit without touching each other.

 

[Abacist]

I used 70mm2 multicore welding cable with crimped and taped ends that were all bolted down to the battery terminals and the same cable to my 1500w inverter that can draw up to 3000w and obviously a big fuse between the batteries and the inverter. The cables between the battery terminals are no more than 1 foot long and the 2 lengths to the inverter is no more than 15 inches. I only have 2 180amp hour batteries linked together which made life a bit easier.

 

[IanF]

Get intelligent ones Sandra thick ones are never much good!

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[funflair]

I used 10mm dia or 50mm square on ours but again less than 2 metres from batteries.

And no I dont have big hands, the 10mm is the copper conductor diameter.

Martin

 

[andy63]

I used 10mm dia or 50mm square on ours but again less than 2 metres from batteries.
View attachment 129432

And no I dont have big hands, the 10mm is the copper conductor diameter.

Martin

That's fair size cable... if it's 10mm diam (is that overall or just the copper core ) it would make it about 78.5mm square...
Andy
I should read more closely. .. it's the cu conductor as you said

 

[irnbru]

Thx I will get Alan to read the thread after dinner.

What I can tell you is the battery bank is all 4 batteries going under the seat so no long wires (says me)

The future inverter would be around there too.

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[Camping Gaza]

What I can tell you is the battery bank is all 4 batteries going under the seat

What about weight issues on just one side of the van, Is this something to consider?

 

[irnbru]

What about weight issues on just one side of the van, Is this something to consider?

Shouldn't be as the cooker and fridge are on other side.

 

[gus-lopez]

I used 10mm dia or 50mm square on ours but again less than 2 metres from batteries.
View attachment 129432

And no I dont have big hands, the 10mm is the copper conductor diameter.

Martin

I bought jump leads from Wilko's when I needed some in the UK. 2m in length & some as your photo's. £10
home here I use welding cable

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[rupert]

hi and thanks all, for your input. the cable size sandra is talking about is for linking the 4 batteries together. i thought these cables would not need to be as heavy as the load cable to the inverter, as this is shared by the 2 longest cables ,as per the diagram.
or have i got it all wrong..........again

also i'm intending to box in the bank of batteries to stop them moving around. do they need air to be able to circulate around them to prevent over heating
thanks alan /rupert

 

[funflair]

That's fair size cable... if it's 10mm diam (is that overall or just the copper core ) it would make it about 78.5mm square...
Andy
I should read more closely. .. it's the cu conductor as you said

You are right Andy, I was thinking it was 50mm sq but it is good chunky stuff.

Martin

 

[movan]

Gosh Sandra ... respect woman... I wouldn't have a clue what you are talking about!!! Hope it sorted for you.

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[andy63]

Gosh Sandra ... respect woman... I wouldn't have a clue what you are talking about!!! Hope it sorted for you.

Don't worry joy... nor has she..that's Sandra I mean.. @irnbru
Andy

 

[irnbru]

I dont @movan I just want to make sure its done the best way possible and thats where the funsters come in. 2 heads better than one and all that ...

 

[rb62]

Don't worry joy... nor has she..that's Sandra I mean.. @irnbru
Andy

I thought I'd leave it to you!

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[funflair]

hi and thanks all, for your input. the cable size sandra is talking about is for linking the 4 batteries together. i thought these cables would not need to be as heavy as the load cable to the inverter, as this is shared by the 2 longest cables ,as per the diagram.
or have i got it all wrong..........again
View attachment 129434

also i'm intending to box in the bank of batteries to stop them moving around. do they need air to be able to circulate around them to prevent over heating
thanks alan /rupert

Hi Alan

The 4 shortest that are just carrying one battery load could be 1/4 of the main cable cross sectional area, call it 5mm or 6mm in my opinion.

Martin

 

[irnbru]

I found this. Thought it might be helpful.

Use the table below to convert between wire square mm and diameter mm:

Wire
mm2 .... mm IN DIAMETER
0.75 = 1.0
1 = 1.1
1.5 = 1.4
2 = 1.5
2.5 = 1.8
4 = 2.3
6 = 2.8
10 = 3.6
16 = 4.5
25 = 5.6
35 = 6.7
50 = 8.0
70 = 9.5
95 = 11.0
120 = 12.4
150 =13.8
185 =15.4
240 =17.5
300 = 19.5
400 =22.6
500 = 25.2
630 = 28.3
800 = 31.9
1000 =35.7
1200 =39.1
2000 =50.5

 

[andy63]

Hi Alan

The 4 shortest that are just carrying one battery load could be 1/4 of the main cable cross sectional area, call it 5mm or 6mm in my opinion.

Martin

Martin should the minium wire size not be at least half the total current draw..
Ie two batteries in parallel . Paralleled with a further two batterie's in parallel. .
Think that's it... so each bank of two will supply half the total draw
Andy

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[funflair]

Martin should the minium wire size not be at least half the total current draw..
Ie two batteries in parallel . Paralleled with a further two batterie's in parallel. .
Think that's it... so each bank of two will supply half the total draw
Andy

Hi Andy

Just talking about the 4 short wires. each one will only be taking 1 battery load.

Martin

 

[rupert]

should the minium wire size not be at least half the total current draw..
Ie two batteries in parallel . Paralleled with a further two batterie's in parallel. .
Think that's it... so each bank of two will supply half the total draw

yeah thats what i'm figuring andy. can anyone confirm that for me pleeeese
or shoot me down in flames.... so as not to cause a fire lol.

 

[andy63]

I thought I'd leave it to you!

You needn't. .. Richard. . Feel free... relieves me of some pressure..

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[andy63]

Hi Andy

Just talking about the 4 short wires. each one will only be taking 1 battery load.

Martin

Yes think I've got what your saying... but if it was me I'd be wiring them all up with the max current draw cable...
It's possible one battery goes faulty and that leaves the connecting cable taking a higher current possibly half the total.... for peace of mind I'd do them all in the heavier cable..
Won't cost that much more... they are short runs... even for a tight Yorkshire man... @rupert and she's a jock so nearly as tight..

 

[andy63]

yeah thats what i'm figuring andy. can anyone confirm that for me pleeeese
or shoot me down in flames.... so as not to cause a fire lol.

Will you change that dam avatar picture... I keep thinking it's herself posting...
I've given my thoughts on cable size Alan. .. have a look... we can argue on what's app lol...
Andy

 

[rupert]

Will you change that dam avatar picture...
Andy

ok ok

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