Hi. I installed mine using a battery lead connection from auto shop. If I was doing it now (with extra knowledge) I would use 

6 B & S. Less chance of voltage drop. Col P

>what size inverter cable do we need to run 5ft to our 1000w inverter thanks

Let's call it 2m for ease of calculation and to add a bit of overhead.

1000W at 12.5 volts = 80 amps.

First of all... cable size measurement:
Forget all this motor vehicle measurement rubbish which includes the thickness of the insulation - God alone knows why!?

The only measurement which matters is "cross sectional area" (CSA). This is a measurement of the copper and relates directly to the current carrying capacity of the cable. It is quoted in mm2 (millimetre squared but I can't do the notation here).

Have a look at this calculator:

http://www.voltagedropcalculator.com.au/index.php?fldlength=2&fldcurrent=80&fldvoltage=12&fldcrosssection=6&submit=Submit%21

I have no previous experience of it but assume it's correct - it looks about right to me.

Voltage drop in copper is related to temperature but providing the cable has a bit of flowing air around that won't make a lot of difference to you.

Let's assume 6mm CSA cable; plugging that into the calculator indicates a drop of 0V91 for 2m. If we add the drop through connectors and fuses we'll be looking at, perhaps, 1V5?

Using 10mm CSA almost halves the cable drop to 0V54 and would be my preferred size.

Your next problem is where to get some? I suggest you drop in on your local electrician with a six pack and ask if he has an offcut to spare. You could use 2 x 6mm in parallel which would work well too.

80 amps is a lot of current - you will need a large battery system in good condition to support it.

MH

> we have 2x97amp batteries

The amp-hour rating of lead acid batteries can be confusing. The rating given, 97Ah in your case, is only valid when the battery is being discharged at a rate of approximately 5A or "Capacity / 20" (C/20). Similarly a 40Ah battery is only 40Ah when it is being discharged at 2A. A few specialised batteries are rated at C/10 but this is unusual.

If the discharge rate is increased the battery capacity reduces and vice versa. This is due to the chemistry of the battery and may be calculated using Peukert's Law.

https://en.wikipedia.org/wiki/Peukert's_law

Using the datasheet for my own Powersonic PDC-121000 100Ah battery it shows the battery falling to a terminal voltage of 11V0 at a discharge rate of:

5A = 20 hours
9A = 9.5h
19A = 3.5h
35A = 1.75h
58A = 40 minutes
99A = 20m

Given that discharging a lead acid battery below 50% is a bad idea and *will* shorten its life if done regularly it's best not to discharge it to below a terminal voltage of 11V7 which equates to a 20 minute discharge at 58A.

NB. For a 30% depth of discharge my battery has a quoted life of 1700 cycles whereas for a 50% DoD that reduces to 700 cycles.

The situation gets worse as a battery ages (a bit like me really :) and its capacity naturally falls. How much it falls is very hard to put a number on and much depends upon how the battery has been treated but a capacity reduction of 10% per year (of original capacity) is probably a reasonably figure.

High power inverters, which I consider to be anything over about 150W, and camping/caravan situations are not really a good match and, if used often, will significantly shorten battery life.

MH