Charging batteries

I have a 2720SL on order and the dealer suggested that the stock 12v batteries (there were to be two with the unit) be changed to two 6 v deep cycle golf cart type batteries. He indicated something like 30% more useful time out of them although they are heavier. I agreed and he is supplying these at no extra cost.
Is this a good idea or are there downsides of which I am unaware?
Also (real newbie question) how does one charge up these batteries prior to a trip? My sense from reading these boards is that the TV will not charge batteries in route. So, I have to charge them up in advance of a trip. Do I just plug the TM into household current? If so, how long does it take to charge 'em up?

[Bill]

You're getting two golf cart batteries at no extra cost?? That's a good deal!! Congrats!

Your tow vehicle will maintain the charge on TM batteries, and will also handle light loads while you drive. But you are right - if your TM batteries are discharged when you leave home, they will still be discharged when you arrive at your campsite. So make sure they are charged up when you leave.

Again, you're right - the easiest way to do this is simply to plug in the TM for 24 hours (or more) before you leave home. The TM's built-in charger will top them up.

When you get back and put your TM into storage, assuming you have no shore power, just disconnect the battery. Easiest way is to pull the 30-amp main fuse, which is located in the + line about 6"-12" from the battery. This ensures that there is no parasitic load on the battery, and it will maintain its charge for quite a while.

Hope this helps

Bill

Thanks to you both for the info.
Bearing in mind that I know near zero about electrical -- is there a gizmo in the TM that monitors things so that being plugged into household current won't fry the batteries? Or, is this something I have to buy, and then plug the household into it, and it into the trailer? Something that will fast charge first, and then fall back to trickle charge -- and at the same time protect the batteries from over charging? Seems to me that should be built into the TM already but then again, what do I know? :-)

I occasionally use a "battery tender" on my motorcycle's battery and it does just that. Cost about $40 too!