Let's start off with a few questions?
What type of batteries are they?
They're custom made by Shen Zhen YKX Battery Energy Co. They make a lot of the LiFePO4s being rebranded in the states, I believe.
Do you have a BMS?
Yes, batteries each have a built in BMS
Do you have an inverter/charger?
I have a 3000W "pure sine" inverter that was $315 off eBay (PUGU is the brand) and I was using a Bioenne Power 14.6V charger model BPC-1520C
Will the van every be anywhere below freezing?
Absolutely. Van is designed for four seasons, one of those being winters in Wyoming where it's regularly -20°F or colder. Van has ~R30 on the walls, R20 on the floor and ceiling. Has electric heated floors and a gasoline powered Webasto furnace. I'm not sure that will keep the batteries above freezing at all times, but the BMS is supposed to not let them charge when they're below a certain temperature.
Most good inverter/chargers have a custom setting to allow for custom charge profiles. If you just have an inverter, then as others have said you'll need a dedicated charger. However if you don't even have an inverter yet, just bite the bullet and go with a nice inverter charger. Xantrex just released a pretty nice inverter that's a good value. It's their XC line and has an 80A charger.
http://www.xantrex.com/power-products/inverter-chargers/freedom-xc.aspx. Slower charging helps with longevity, but with 600ah, slow charging isn't always an option.
My solution to all of my inverter and charging issues was going to be exactly that: bight the bullet and buy a ~$700 charger/inverter combo. It's actually not nearly as pricey as I thought. When you consider that my cheap chinese "pure sine" 3000W inverter (Keep quoting that because I can prove it's always putting out a steady sine wave) was ~$315 and the 20A charger I got was $115, so $430 combined. For an extra $300 or so, I could have gotten an all-in-one solution from a reputable brand based in the USA (customer support, warranty, etc.) that would charge at four times the rate and, presumably, put out a steady sine wave at its rated wattage.
My van has 400ah of lifepo4 and I've been doing research on these batteries for a while, but I'm not an expert, but feel free to ask any questions and I can help where I can or point you to the right place.