Tuesday, Sep 06, 2011 at 23:20
Hi Stan,
Simplistically, you need to put back in what you take out. Getting more batteries will not help you put back in, it will only delay how long you can keep taking out for.
Also, having a ~95A alternator doesn't mean you can recharge at 95A. There are many reasons why, but you will be very unlikley to charge at more than 15A to a rear mounted battery, the size cables needed for this will be very large and their cost will virtually buy a dc-dc charger!
But having two batteries (if you can fully recharge them) is good as it increases the SoC for a given load. The longer you stay put, the more batteries you will need to maintain a decent SoC, or run the vehiicle to recharge, or go solar!
A 100a/hr battery at 50% SoC will give 50a/hr, about what most people use a day - give or take a bit. Go lower than this and you strt affecting long term battery life. How long do you intend to stay put? (I know, how long is a piece of string!) This will help decide whats the best way, but then the best is not the cheapest!
The way I see it, you have several options;
1. one AGM, alternator charging - will be cheapest but will likley have the battery struggling to last more than 2 years - but cost effective!
2. one/two AGMs, dc-dc charging - will give good 100% recharging (if you drive ~3-4 hours) and should give good battery life. But you will be limited to 2-3 days between driving for recharge.
3. add solar and depending on how many panels, increase to 5+ days before driving (if sunny!).
4. add a generator to account for cloudy days.
I have been thru all the above steps over time and in that order. I have 2 x 120a/hr AGMs, 40A dc-dc charger, 160W solar with MPPT controller and a Honda genny.
From my experience, getting the dc-dc charger was perhaps the best move as my type of camping is moving on after a few days. Adding the solar makes a 5-6 day stay possible without any motor running (sun dependant) but after that i need to run a motor, either the vehicle or the genny. My power consumption is ~80a/hr day, but I have a party of 4 and am a relatively big power consumer.
Trying to read into what is most cost effective for you would arguably be a dc-dc charger on a single AGM battery. If you can get a second AGM, even better. Hopefully I haven't confused you further!
Cheers
Captain
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