Thread: Lithium Battery Install Instructions

Originally Posted by Hoges

Sorry to prolong this but I wanted to understand why 8 B&S gauge cable is apparently too thin for this application.
Surely it's dependent on practical requirements which in turn influence the design parameters.

I used 8 B&S for general charging of a second battery: it was more than satisfactory. For a 5m run carrying a max of 15 amps, the difference in voltage drop between a 6 B&S and 8 B&S was a theoretical 0.063V (0.094V for 6 B&S and 0.16V for 8 B&S). In the scheme of things for charging a battery this difference is " in the noise".

In line with this, I wondered why virtually all mains powered battery chargers (including my good mate's expensive CTek collection!) have charging leads of approx 2m of seemingly 3-4mm cable which has about 10 times the resistance of 6 B&S!

So with due respect to all the practical knowledge in these contributions, perhaps 6 B&S isn't necessary as a one size fits all approach. Surely as long as the gauge of cable used ( in this case 8 B&S) is "fit for purpose" ...which I believe has been demonstrated, then why the angst?

Maybe I'm missing something...

Sorry Hoges, I did not see your post at the time.

Yes you can use 8B&S ( 7.9mm2 ) for charging auxiliary battery. You could even charge that battery with something as small as 6mm AUTO ( 4.5mm2 ) and you battery will charge.

I your case, there is a single consideration but with modern vehicles there are two related considerations.

In your case, with a standard alternator, you will have a constant voltage of around 14.0v, so the voltage drop can be easily factored in.

But even with a known constant voltage, if you are just topping up your auxiliary battery 8B&S is more than adequate.

But if you discharge your battery to a low state, you could add two or more hours of driving needed, to get your battery fully charged, over what you could achieve when using 6B&S cabling.

With vehicles equipped with a SMART alternator operation, the potential problem of charing a low battery is much worse because of the voltage drop thinner cabling causes, and NOTE, if you are using a DC/DC device you still NEED the thicker cable because DC/DC devices ( depending on the brand ) can either reduce the OUTPUT charge current to the auxiliary battery when the INPUT voltage is low, or they may continually turn on and off.

As the ladies say "Size does matter"

Originally Posted by drivesafe

While it does not matter, connecting to point on the Ctek would most likely be the easiest.

thanks ver much