... if you consider the useable output from a
battery is about half of its rated value, ie. 110AH gives approx 55AH useable the heater alone would run your
battery down in a little over 5hrs. Add on the other usage and a
battery "life" of 3-4hrs each is all you could reasonably expect. ...
Although thier has on here and on other threads a lot of talk about inefficient charging and low
battery power much of this is irrelevent and often inaccurate. It is true that vehicle and the on board charging systems do not achieve 100%
battery charge it is in real terms better than the 65-70% quoted and has proved itself over many years to be cost effective and above all reliable, Quite simply if you wish to increase the available power you have the best method is to add greater
battery power, weight and space permiting.
...
I suspect that if you restricted the time that you run the heater as much as possible and conserved power elsewhere, provided that you don't stay put for more than 2-3 days at a time you should not have a problem.
...
Finaly having checked out the link given in a previous post I would like to point out that the source seems to be from Australia, and not only is much of the information about 20yrs out of date but does not apply to systems used in Europe. ie. Use of blocking diodes to isolate batteries went out of use about 25 years ago.
Geoff, you are trying to have a both ways bet here. You agree that charging systems found on many motorhomes are pretty rubbishy and won't charge the
battery beyond about 70%, but claim that this is irrelevant and also claim that this lousy system is cost effective and efficient.
If you have a system that you (correctly) say can only safely provide 20% of the
battery capacity, then adding another
battery in a motorhome that is already pushing the limits of space and legal weight (as you agree is often the case) is still not going to achieve as much as would be gained in charging the
battery up properly in the first place. If you just don't have room, then the only way to overcome the problem is to use the available room more efficiently and the only practical way to do that is to use as much of the
battery capacity as possible. Money is almost an irrelevant factor in this case.
Collyn Rivers is quite thorough in the research he does for his books and there are few sources that cover the field as well. The electrons that flow in Australia are subject to exactly the same physical laws as the ones flowing in Europe and unlike in some countries, Australia is happy to import the latest technology from whatever country produces it. Some of it even comes from the EU.
Whether they are the best way of doing it or not (and electromechanical switches also have problems), diodes are still commonly used in
battery isolation systems and Collyn discusses their limitations and also ways that the inherent voltage drop can be eliminated. Use of Schottky diodes with their much lower voltage drop overcomes some of these limitations anyway.
What is 20 years out of date is MH manufacturers supplying units that do only allow 20% utilization of a costly and heavy
battery, especially when doing so invariably results in the
battery failing well before its design service life. If they were to clearly state the limitations of the installed systems so that purchasers could make an informed decision, that would help a bit, but since most people never bother to read the instructions anyway, I guess the average purchaser is only going to worry about the things they can see. If, as seems to be the case in most countries, 95% of MHers and Vanners never wild-camp anyway, I guess it doesn't matter. However since this IS a wild-camping forum, I would have thought the members realise they MUST spend extra money to pursue their chosen activity - or if they don't spend the money, they must be content to just follow the crowd into the nearest camping ground with full services.
You said the solution to the OP's problem was "if you restricted the time that you run the heater as much as possible and conserved power elsewhere, provided that you don't stay put for more than 2-3 days at a time you should not have a problem."
Better advice, but even less practical would be to fit an isolating switch on the
battery so by turning it off, the power use would drop to zero and they could stay in one place forever.
I chose the other course and built a system that can quietly provide all the power I need almost indefinitely so that I never have to use hookups. It is possible but very expensive - or seems that way until you add up the cost of staying in van parks every night. Then it works out cheaper.
could your radio be draining the