is it possible to plug in the surge protector to the UPS ?

Can the UPS power the phones, laptops?

Yes, that's the point of a UPS.

It has an internal sealed lead-acid (SLA) battery and a pure sine wave inverter. All the ones I've seen use a 12-volt battery, which is charged when plugged into the mains. The batteries do not have a lot of capacity, so don't expect a long run-time.

I see no reason why a solar panel couldn't be connected to the battery to extend the run-time. And in theory (I haven't tested it), connecting to a car battery should also be possible.

The catch is that some models shut down once the battery is low, and will not restart until reconnected to the mains. I've tried restarting by plugging them into a modified sine wave inverter with no luck; maybe I need to attach an earth ground.

My UPS battery lasted for about 8 years. Now, it won't hold a charge. I only found out when I had a power outage, which is exactly when I needed it.

What's an inexpensive maintenance routine for a UPS? For example, is there a brand that allows replacement of the battery only? If so, what's a good brand?

Most decent brands will allow replacement of just the battery, I don't think I've ever seen one that didn't, unless apple makes UPS's now.
Look up your model on a site like batteries plus and see the replacement battery and cost.
My $60 UPS needs two $20 batteries

Unless you get the more expensive UPS systems, most of the ones for home computers are modified sine. You can't plug them into another modified sine wave UPS, because it sees an irregular waverform and automatically switches to battery, which is what it's supposed to do.

Really? That's surprising, though it makes sense from a cost POV. It must be a much better modified sine than I get with my other inverters. There's no noise, buzzing, or overheating at all, which is why I like them for my low-draw, sensitive gear.



I'm not entirely convinced of that, though I confess my research is incomplete. For example, I have two older ones (a Belkin and an APC) and have plugged them into a modified sine inverter in an attempt to clean up the power on the non-UPS outlets. That side works, though not all the noise is gone.

Both UPS units have dead batteries, so I'll need to swap them out to see if a modified sine will charge the internal battery. It doesn't matter much since it's easier pull straight DC from an external battery and solar panels. The only issue is a reset if I lose a connection (IIRC it's the APC that locks up).

Yup, I was surprised to find out it put out the same waveform as my cheap 12V inverter. If anything, the inverter modified sine was a little bit cleaner. On most devices I don't notice any difference either way, but connect an electric motor or LCD TV to them and you can hear the difference immediately.



I had no luck chaining APC units together (I also have a belkin but I haven't tested it). There is a sensitivity adjustment on them, but even at the lowest sensitivity I couldn't get it work. Older ones might be different, but I think currently only the APC smart UPS have true sine wave. During normal operation it just passes the regular line voltage straight through. Not until it's on backup power does it change to MSW. So if the first one is plugged into an outlet it would probably work, but as soon as you lose power both of them would stop charging.

During a windstorm last year I lost power for one week. I had to learn a lot about backup power very quickly.

Most of your small home/office UPS's are this offline type, as you said they just pass line power through normally. They will have a set high and low voltage threshold where they will switch to using the inverter and battery. If you want something that is always using the inverter and therefore always conditioning the incoming power you look for the "online" type.
The difference is cost, the online needs the battery charge circuit to be able to carry the whole load plus extra to recharge the battery, the offline type has a small battery charger just sufficient to charge the battery.

For UPSes in datacenters, we tell our customers to replace the batteries every two years. For home users, and if you have sufficient capacity, you might get away with three years betweeen replacements.

APC and Tripp Lite are the only brands I'd use professionally. At home, both are excellent and I'd also consider Belkin. Don't chain them together unless they are designed to do so -- APC in particular makes external battery packs for their UPSes.

Most are SLA batteries, not much for maintenance, just test and replace regularly.