We've only had our RV for about 2 months.  We've taken one small trip with no problems.  We retire next week and will head out as fulltimers, but as we've been stocking and making small repairs to the RV we've found the chassis battery dead two times - one week apart, even after running the engine for 20 mins to recharge it.  It's supposed to be a new battery - saw the dealer get it off the shelf to install.  Do you know why it would discharge in a week?  Is there something we can plug in that will keep it charged all the time?  Or do we just need to get a new, better battery?  Luckily, we've been able to jump it with our toad, but as someone mentioned we need to be able to move the RV quickly in case of emergency and we don't want to have to jump it every time.

You probably have something turned on that is drawing down the battery. If not, then there is a short circuit in the system. It would probably be best if you take it back to the dealer and have them tell you what is wrong

I think we need a lot more information to help starting with brand and type of RV.

Since we weren't able to sell our house without giving it away we had to go with an older RV.  We got a 1997 37' Itasca Suncruiser, 480 Ford engine, with one slide.  It only has 36,000 miles on it and we got it for $25,000.  Blue book was $37,000, so we figured even with some repairs that would be necessary - new tires, brakes, etc., we were still money ahead.  It's fully loaded with all the best equipment so we're very happy.  I'm thinking we need to just buy a better grade of battery, but Roger thinks if there's a short it will ruin a new battery too.  So, we'll probably do as suggested and take it to get it tested for a short.  In the meantime, we'll probably disconnect it while it's parked to save whatever charge it does have.  Would this work?

Older Winnebago and Itasca motorhomes did not charge the chassis battery while hooked to shore power or generator, they only charge when the engine is running. Many places that service RVs know how to put the $10 part and wiring in that allows the chassis battery to be charged when on shore power or generator. You also might have a battery boost switch, which links the chassis and house batteries together while you hold it down so you can start the motorhome. But many Winnebago and Itasca owners do not find their chassis battery discharged when only sitting for a week or so, only for much longer times. That means you do have a problem. Either your engine is not doing a good job of charging which would be an alternator issue, the chassis battery is weak, or you have something discharging the chassis battery while you are sitting still. Does it only happen when camping or when the motorhome is just sitting still? If only when camping then something you are using is hooked to the chassis battery, maybe a radio or 12-volt connection. Any auto parts store or other place that sells batteries can test your "new" battery to see if the battery is good and many do this for free. 20 minutes is not enough time to really charge a dead battery, more like a couple hours. If you have a car battery charger it will work fine on your chassis battery. Use it to top the battery off before your next trip. Then when you next stop then hook up the battery charger and see how long it takes to fully charge the battery. If the alternator and battery are fine it should charge up quickly, under 15 minutes. If it takes longer then either the alternator is not doing its job or the battery is toast. If you don't have a battery charger I would recommend getting one, they do come in very handy.

So much wonderful information!  Thank you!  We're still so new at this and have so much to learn.  We will check out everything you mentioned.  You're the best, as are all the learned people on RV Dreams!