This was originally posted on APC forums on 3/30/2008
While we are at it:
Despite the fact that APC started out as a company with focus on solar applications, that focus has been lost completely.
I consider APC to be the best manufacturer for small to mid-size UPS systems. Period. The expertise should be there, the market is definitely there and growing. Xantrex and Outback etc. can't quite fill the ticket, either.
I'm pretty happy with APC's solutions if there is AC power around, but in case there isn't, APC has nothing to offer.
A simple real-life scenario:
Take a Smart-UPS 750XL, fit it with a management card like the AP9617, hook up several external batteries, hook up some solar panels and/or wind generators that charge the batteries via an external charge controller, unplug the AC power to the UPS and watch what the management card reports...
Although the Wind/Solar system keeps the batteries at 100% charge, the UPS will report an ever declining remaining capacity of the Batteries down to 0%. That's the way the firmware is programmed. Not to speak about the impossibility to adjust float charge voltages or scheduled equalization charges if your external batteries happen to bet wet-cells.
I absolutely love the remote management capabilities of the SmartUPS line. I guess that it only takes minor hardware/firmware modifications to accomodate an off-grid (inverter-only) operation of the SamrtUPS. In our case, we operate remote telecommunications equipment and would like to supplement battery charge levels with solar/wind, but that seems to be a no-no with the current way the UPS evaluates battery charge levels.