Quote:
Originally Posted by Azriel  exactly, and if you wanted to use more batteries in a single battery ups, throw as many as you want at it and wire them parallel. If you want to add more to a larger UPSs you add series wired pairs in parallel. |
I'm guessing you didn't read my article, or at least didn't read it all the way through.
While it is certainly true that IN PRINCIPLE, you can simply add more batteries in parallel with the existing battery in order to increase your run-time, in practice, at least with the SmartUPS 1400 used here, it doesn't work that way.
See, the SmartUPS 'knows' how many batteries are attached, based on information you give it via configuration commands. You can put as many batteries as you like on there, of whatever capacity you desire, and your run time won't change. Why? Because, if the Smart-UPS only thinks it has one 36 AH of capacity (one battery) it's only gonna run that long. I'm guessing this is done as some kind of safety feature, since it is obviously also sensing the battery voltage.
Because of this fact, you MUST add capacity in 36 AH increments, or the UPS gets screwy ideas about how much capacity it SHOULD have versus how much it actually DOES have, and you'll end up either not using your available capacity, or getting 'Bad Battery' warnings, AND you MUST configure the UPS so that it knows how many batteries there are. Further, the UPS will only allow you to plug in a maximum of (I believe) 4 battery packs. I think this is also done as a safety feature, to limit the surge current for charging when the cells go flat.
As for being unnecessarily complicated, I suppose that rather depends on how you look at it. It is true that you could simply use some alligator clips and jumper the batteries together. I was going for something a little more 'polished' than that. In addition, simply jumpering the batteries together doesn't prevent an internal short in one battery from destroying the entire array, and maybe the UPS too. That's why there's a 100 amp car fuse in there.