Hiya.
The Morningstar Sunsaver MPPT-15 controller they sell now isn't powerful enough for your requirement. It's a 15A controller that does 12/24V batteries.
They've got a 45/60A Tristar MPPT controller in the pipeline but the shipping date keeps slipping. It was September '09 and now is November '09 (I've been watching their web site as I'm interested in it).
When they get it out the door, I'll probably get one to replace one of my MPPT-15 Morningstar controllers, as I've already overloaded it with about 600Wp of PV (it's only rated to 400W) and it's capped the battery current at 15A.
Someone I know has been using the Outback MX-60 MPPT for years without problem. See here:
www.mrsharkey.com
Personally, I like the Morningstar design as it's fanless and seems bulletproof. I've had my system running about a year and at first was using a 12V bank but kept buying more and more panels so hit the 15A limiter on the controller. Then I reconfigured for 24V and that allowed me to buy a pair of Sharp ND-170 panels that work at 42.6V in series on a second controller (as the MPPT voltage is too different) and connect all my other 17V panels in series pairs for 35V on the original controller. This cut down the need to upgrade the wiring as the volt drops are much less of a problem at 35/42V.
As I said, one of my Morningstars still gets quite a lot of abuse from too much PV input but it caps the battery current at 15A so it doesn't overheat or blow up and just sits there for like 4-5 hours a day pegged at 15A. Even so, they don't need a fan as they don't get hot at all - just warm to the touch and the mounting plate is also the heat sink. Just don't mount them in a sunny place! I mounted mine indoors on a north facing wall.
The Tristar MPPT will be a bit more flexible than the 15A one as it can go up to 150Voc (whereas my one is limited to 75Voc). My controller didn't like it when I connected my amorphous panels in triplets as they can put out up to 26Voc even though their Vmp is only 17.5V. With my cheapskate approach to DC wiring, it's just as well that I'm only dealing with relatively low voltages (35-58V).
I also like the way that with the serial interface on the Morningstars, you can hook them up to a laptop and fully program all the charging set points and timers to suit any type / size of lead battery bank. The new Tristar MPPT-60 will also have an Ethernet port on it so it can be plugged into a LAN for remote monitoring. You could easily make that a wireless LAN as the transmitters usually work on 12V DC so you can just power it from the solar batteries with a regulator instead of the mains cube they usually come with.
So at 48V nominal, you can go up to about 3kWp on a single Tristar and they can be run in parallel to make a modular system as big as you like. I think they will communicate with each other by their serial ports but even if they don't you can run them in parallel. The MPPT-15's don't communicate with each other but they charge my bank just fine. All I did was make sure that they both had the same set points and timers programmed and disabled EQ charging on one of them so that only one charger decides when to EQ the bank. They do it on low discharge events or monthly (whichever happens first) so I didn't want them to independently decide to do calendar EQs on different days. If my bank was too big this might be a problem as one controller might not be enough to "boil" the bank. I guess that's where the communication between controllers comes in.
