Cable sizing for additional battery

Braunston

Free Member
May 21, 2008
1,413
7
Funster No
2,762
Hi,

I have been thinking about installing an additional leisure battery and i have been trying to find the cable size that i need as the new battery will be approximately 4-5 metre away from the existing.

The majority of the new cable will be exposed running along the chassis, can anyone tell me what cable size i need or point me to a site where i may obtain this information, also i would like to install a in-line fuse on the same cable can anyone tell me what size it should be or how to calculate and where i can purchase the in-line fuse holders from.

any other information that i should take into account would be very helpful

Thank you

Braunston
 

scotjimland

Free Member
Jul 25, 2007
32,020
29,507
.
Funster No
15
MH
.
Exp
.
Hi

AEI Cables have a cable sizing 'wizard'

AEI Cables - Cable Sizing Wizard - Disclaimer


JIm


PS.. you need to register but it only takes a couple of minutes


PPS

I used a distance of 5mt with a max load of 50A

The result is 25 sq mm

Cable Type6491B-6181XLPE (90°C Single cores)
Supply voltage (V) 12
Phase:Direct current
Cable load (Amps)50
Cable length (mtrs.)5
Ambient temperature (c)30
Average efficiency1.00
Power factor1.00
Cable grouping factor1.00
Temperature correction factor1.00
No.of circuits:1
Maximum allowed volt drop (%)5.00
Selected installation CABLE TRAY FLAT & TOUCHING (IEE Table 4E1A Method F)
Cable Requirements.
Cable size (sq.mm):25.00
Max. current rating over 5 mtrs. 64.86
Actual voltage drop over 5 mtrs.0.46
Estimated conductor temperature (c)35.79
Related Information.
 
Last edited:
OP
B

Braunston

Free Member
May 21, 2008
1,413
7
Funster No
2,762
Hi, Jim

Thanks for the link and the calculation, I signed up and ran the calculations and my results are the same as yours.

However, I am not to sure of the outside diameter of a 25 sq mm cable but i have assumed its similar to a normal ? battery cable, is that correct , if it is, the existing cables that connect the leisure battery are quite small in comparison albeit i don't know the actual size,

Is it possible to determine the cable size from measuring the outside covering, only if i go for the 25mm and i am correct in my assumed outside diameter size it would look far to big against the existing, hope that makes sense

any suggestions would be welcome

Braunston
 

scotjimland

Free Member
Jul 25, 2007
32,020
29,507
.
Funster No
15
MH
.
Exp
.
However, I am not to sure of the outside diameter of a 25 sq mm cable but i have assumed its similar to a normal ? battery cable, is that correct , if it is, the existing cables that connect the leisure battery are quite small in comparison albeit i don't know the actual size,

That is correct, it's about the same size as the cable used for the engine battery, the existing cable to the leisure battery may be a bit smaller, the constructor would size according to the van's max load and charging current which may be less than 20A but when connecting two or more batteries in parallel the cable should be sized for the max load and length to reduce volt drop .. otherwise they won't charge nor discharge equally.
If you use the wizard and change the max load to 20A the result is the same.. 25 sq mm

Is it possible to determine the cable size from measuring the outside covering, only if i go for the 25mm and i am correct in my assumed outside diameter size it would look far to big against the existing, hope that makes sense

It is possible but not easy to determine, yes it will look bigger than existing cable to the leisure battery

I would go for 25 sq mm cable and fit a 100A in line battery fuse at both ends of the cable..

I can't remember the supplier, but you can get battery connectors with built in fuses .. I'll keep Googling


Jim


PS

Found this supplier .. fuses, terminals and cable

Single core heavy duty electric cable
 
Last edited:
Oct 15, 2007
1,623
254
Five Roads Alyth
Funster No
633
MH
A class RV
Exp
since 2005
Thanks you lot, not only do I not need to ask the questions I now have the answers and sources:Smile:

Simply put, battery dieing and I want to replace with two new and tidy up dodgey wiring etc etc etc!!!!

Happy new year to all:thumb:
 
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