Sunday, Feb 18, 2007 at 22:18
OT, not looking to challenge your advice, but for balance I though I'd follow up on the issue of a dual battery system.
First, this bit is copied from the
Rainbow Power Company web site (an excellent site):
7.1.8. What Are the Differences Between Car, Marine Starting and Deep Cycle Batteries?
'Car batteries are specially designed with thinner (.04 inch or 1.02 mm) and more porous plates for a greater surface area to produce the high amps required to start an engine. They are engineered for up to 5,000 shallow (to 3%) discharges, which works out to over four engine starts per day. Car batteries should NOT be discharged below 90% State-of-Charge. They use sponge lead and expanded metal grids rather than solid lead. Marine Starting batteries are a comprise between a car and deep cycle battery and are designed for starting and prolonged discharges at lower amperage that typically consumes between 20% and 50% of the battery's capacity. Motive and Stationary deep cycle batteries have much thicker (up to .25 inch or 6.35 mm) plates, more lead, and weight more than car batteries the same size. They are normally discharged between 20% and 80% at lower amperage. deep cycle batteries will typically outlast two to ten car batteries in a deep cycle application'
A more practical approach. Say you arrive at
Manning Gorge at 3.00 PM. Set up
camp and spend the night. In the morning after breakfast (say 7.30 AM) you walk to the falls, have a swim and morning tea, then walk back (about 4 hours total). You have lunch and pack up. It is now at least 1 PM. You have been stopped for 22 hours.
A 40 litre Engle _Affordable_Storage_Drawers.aspx 2.5 amps form a fully charged battery. In the 22 hour period, with likely ambient temps it's not unreasonable to expect that the fridge compressor will run for 11 hours. Thats a minimum of 27.5 AH, not counting any additional power consumption like lights etc. Now I don't have enough information (or knowledge) to say for certain that there will be enough power to start the vehicle after this, but there is a serious risk that there won't be.
One basis for this is the many posts on this site from people with 3 way fridges that draw 10 amps. There have been many post suggesting that an hour without engine running (10 AH) is OK, but 2 hours (20 AH) is too much and the vehicle won't start. I have no personal experience with this (I've always had a dual battery system). Just repeating the experience of others.
Now you could improve things a bit by running the vehicle at fast idle for at least 30 mins before going to bed and as soon as you rise. But that's a pain, very inefficient and a real PITA to other campers around you. Might even get you some abuse. But will this be enough?
Well I don't know and I don't think I'd want to
test it.
Just thought I'd post this info so that Outback tourer has both sides of the 'do I need a second battery' story so he can seek out enough info to make an informed decision. Up to him then.
FollowupID:
483388