I have done quite a few of these types of set ups.
First, I am assuming that 1400VA (1400 watts-ish) is a lot more than you really need, and therefore, you are wasting a LOT of power to run this monster (unless you have a power hungry laser printer). Example my Sony Vaio, 17" flat panel, inkjet printer, cordless phone, and fax will run eaisly from a US$45 Vector 400W inverter (mid-quality, more efficient than most, easy to get, and cheap).
Second, forgive me, but I don't know anything about a 40V Ametec, but you said 12 volts, so I'll go with it.
You are going to find it cheaper and better to start over.
Get a 12 volt battery the right size, and a little bigger. Wet is much cheaper, but any sealed is nicer in the home. Battery sizing information is available and specific to you situation. Deep Cycle only, look for AH or amp hour rating. If it lists 'Cranking Amps', it's probably a half-breed or just a car battery with a different sticker. If you have the Ametek, you probably alredy have enough batteries.
Figure how much power you really need to keep your equipment running, multiply it by 1.2 (20% extra). Maybe go up a step for future expansion. Most run about 90% efficient at 90% capacity, too big is a Huge waste, and too small won't work. Get the inverter.
Connect it all together. Almost plug and play.
Here is why I say to start over.
- st- 12 to 24V is not too easy, cheap, or efficient.
- nd- Most 12 volt stuff is readily available, and cheaper.
- rd- I think the efficientcy of going 12 to 24V rules it out, not to mention cost and reliability (more fancy parts = more failures).
Big 4th- you may have the chargers and batteries already. You need a $40 inverter with a switch. You can sell the UPS.
About the 10 watt panel. It's going to make about 0.58 amps, or about 7.4 watts, almost negligible. In comparison, your UPS is probably using 18 to 25 watts when it's not even running anything. If you already have it, or if it's free, by all means hook it up! But here (US), for about double the money, you can get a panel 5X bigger that will count for something. A 10 watt panel into batteries used often, or over say 40 AH, won't even need a regulator, just a diode (use the diode, the diode discussions about not using it are flawed).
I've seen this dozens of times. Someone has plenty of solar, but can't keep up with there needs. Turns out they are running a 1000, 1200, and once even a 2000 watt inverter to recharge drill batteries needing 32 watts peak, for 8 hours. The inverters were actually using several times more power than the batteries! A $30 inverter fixed the problem. The guy who sold them the inverters, said they needed $thousands more of his solar panels.