Battery & Charger Advice Needed

I need a 12 volt battery somewhere between 100 - 250Ah for powering some PC equipment during power outages. For my requirements I've been told to get:
1. 600 watt modified sine wave inverter 2. 'Leisure' type open lead-acid battery (not a starter battery) 3. Good quality charger
I have sourced a few inverters and suitable batteries but am still in a quandary about the charger. I would like a charger that can be left on all the time. So what should get for charging open lead-acid 'leisure' or what they seem to call 'traction' or 'semi-traction' batteries.
Would this product be suitable?
http://www.amperordirect.co.uk/prod_spp_probud12v-10a_charger.asp?MSCIDS
Is there a formula for working out the correct charge rate for any given ampere hour battery? For example would a 20Ah charger suit a 230 Ah battery and a 10Ah charger a 110 Ah battery?
Would I be better with 2x110Ah batteries as opposed to 1x230Ah type? Could one person actually lift a 230Ah battery?
It's one thing listening to dealers and manufacturers but I would welcome the unbiased expert opinion in this group.
I shall be very grateful for any advice received. TIA.

Why not just get an off-the-shelf uninterruptible power supply (UPS) designed specifically for PC equipment?
Perce
On 09/30/05 10:45 pm Mark Stevens tossed the following ingredients into the ever-growing pot of cybersoup:
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we all have out biases :)
i use a similar system to what you describe. it consists of two 100 AH deep cycle batteries (12v) in parallel. they are charged by a tripp-lite inverter (400W).
I have added a second inverter, a 1200W Coleman.
if I were to us a separate charger I would use a voltage regulated and current limited unit.
the voltage regulation would prevent overcharging (boiling out the electrolyte) and allow direct operation of 12V equipment such as radio transceivers.
current limiting would be set as per the battery MFRs recommendations
despite this set up (which sometimes operates PA systems) my computers hook to an off the shelf UPS unit.
some of the drawbacks of my system are.
weight: the batteries are heavy potential for leaks (they sit in plastic tubs) safety: something could short the terminals and cause a fire or explosion ( I use the orig cardboard boxes until I acquire marine battery boxes) possible outgassing.
my official recommendation for both residential and commercial users is to obtain a UPS of sufficient size and runtime. someone else has done the engineering all you have to do is hook up the battery and plug it in.

TimPerry wrote:
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What he said..
I hope that you don't mind me piggy-backing the rest - aimed at the OP rather than you!
The starting point for the OP has got to be to design the system - not just put together bits that seem a good idea at the time.
So, he needs to know the maximum off-supply load and the maximum duration of power outage that he is designing for. Then the type of load will determine the type of inverter needed.That lot will determine the size of inverter and the stored energy needed.
Then the OP needs to know the minimum designed recovery time - the time needed to recharge the system ready for the next outage. That will determine the battery charging capability needed.
If there are commercial, off the shelf, systems that will meet the requirement - as you say, it has to be the best option.
UPS, with or without external battery packs, are often excellent value for money. They tend to be ideal for relatively short, infrequent, outages.
"High wattage inverters" are typically used for longer duration, frequent outages and often have a high-amperage charger built-in.
What follows are just my personal favourites. They may, or may not, be suitable for the OP's application! (See notes above about actually designing the system, rather than picking "good bits").
My favourite battery: Personally, I can just about lift a 6v 225AH battery. I have lifting straps and isn't going far (Like 12"). So I guess that is why I have a preference for series/parallel 6v battery chains. My favourite are Trojans T105 (no jokes please)
My favourite charger is a XANTREX TRUECHARGE 40 +, because it charges at full rating off a cheap generator. It can be left connected permanently.
My favourite inverter is a XANTREX DR2412, 2400W that charges at =<120A. I like to use a battery temperature probe with it, for fastest re-charge. Like most inverter built-in chargers, it is total pants charging off a small generator and need at least a 6kVA one to charge effectively. You can add a boost transformer - but I prefer using a Truecharge unit.
-- Sue