bcope01 wrote:
Instead of running your generator just to charge batteries, why not start the engine to charge your batteries (both coach and chassis at the same time) at much higher amps than any converter/inverter can supply? Wouldn't this charge the batteries faster?
Just asking. This is what I do.

Now if you need to run your microwave or AC, you'll need to run your generator if not connected to shore power.
Bill
As long as you just dry camp or boondock overnight or for a couple of days and just use the lights and water pump, running the engine for an hour or so works just fine.
However if you run the furnace in 35*-45* or lower temps for 12-16 hours, just running the engine for an hour won't charge the batteries well enough.
Additionally if you have an inverter and run a TV & satellite receiver, and a couple of laptops in addition to the lights for several hours, running the engine for an hour won't recharge the batteries enough. Do this for 2-4 days and you will have dead batteries. Repeat this process for 20-30 times and you will kill your batteries so they won't accept a full charge and you will need new house batteries.
Doing either of the above will use 50 to 90 amp hours (AH) in one day.
To quickly charge a lead acid battery pack you need to apply 14.6 volts (Bulk Mode charging voltage) at about 25% of the total battery capacity. My Born Free house batteries have a capacity of about 200 AH. So I can charge at 50 amps. If you push say 100 amps at 14.6V or even 13.8V for the needed hour or so you can damage the batteries.
To get 50 AH back into the batteries you need have the 50 amps at the 14.6V continuously for 1 hour.
Auto or truck alternators put out about 13.6-13.8, possibly 14, volts and are designed to recharge the starting battery, and are not set up to quickly recharge the house batteries. This means it will take even longer to recharge than if it was at 14.6V
We probably have #10 wire from the alternator to the house batteries. With that small wire going to the house batteries, pushing high current down that wire causes a voltage drop. So instead of getting the 13.6-13.8 volts you could be getting 13 volts at the battery. Now it takes many hours to get 50AH back into the house batteries. Running #0 or #00 (one "0" or two "0") wire, which is 5-10 times a thick as #10 would really help.
If you want more info here is a link to very good RV battery info
http://www.rvcruzer.com/electrical/chapter7.php
Here is a link to Trojan Battery's website where they detail the proper daily (bulk mode) charging voltage as 14.8V.
http://www.trojanbattery.com/BatteryMai ... rging.aspx
Lots more info about batteries & RV electrical system on the above websites.