APC UPS Rs1000 not charging batteries when plugged in on the wall

Have you tested for shorts yet? That would be the first thing I would check. If you verify the only flaw is the circuit breaker then you can remove it and usually pull the numbers from it to search for them directly. You could have a bad connection or a bad wire that is causing your problem though.

That large cap in the center bottom looks like it might be expanding. Hard to tell from the top view. If that top is looking convex, replace it.

There is schematics available here. Of course, they won't do you much good if you can't read them.

Is the battery charging when plugged in?

If it is running on battery, then the DC to AC converter is operating.

If it is charging the battery, then the primary AC is working.

If it does not run on AC, then what changes the relays or the relays themselves isn't working.

I used a charger from Aliexpress.com. There are similar ones at Harbor Freight or Amazon. It automatically detects the type battery and charges it. I think about $20 to $40. It can be used on any type wet battery. A few can also be used on LiPo types.

@alextc to the right of D18

Hi Alex,

Okay, I read through the blog post you found where it seems to describe the same problem you're having and the guy's solution of replacing three capacitors. I've circled the ones that "vasvir" replaced.

From left to right they're numbered C41, C40 and C3. Ultimately, the correct way to test a capacitor is with a capacitance, or LC meter. Since very few of us have those in our toolboxes, you can do a rough go/no go test with an ohmmeter. Capacitors pass AC current and block DC current, so to an ohmmeter (which uses DC current) it looks like an open circuit.

So you'll set your meter probes on the two contacts on either side of the capacitor and see if you have continuity. If there's no continuity, you're probably okay. If there is continuity, that doesn't necessarily mean the capacitor is bad, because there could be other connections in the circuit that the ohmmeter is testing instead of just the capacitor. So if you get continuity, the only way to verify whether the capacitor is bad is to remove it from the circuit; for C41 you can unsolder one of the legs and leave it dangling in space while you test it. The others are surface mount and will be difficult to remove just one leg; you can try, but you'll probably end up having to remove it completely from the board to test it.

On the other hand, those parts are really cheap; you'll generally pay far more for shipping than you will for the parts themselves. If you're going to go to the trouble of unsoldering C40 and C3, you might as well have replacements on hand and just put new ones in anyway.

For all three vasvir used 50V 22 uF capacitors, which is fine, although the ones already on the board are only 16V 22 uF. General rule is you can pretty much always safely go up in voltage rating, but never go down. So anything you find that's 16V or higher will work, as long as the capacitance is 22 uF.

You can start out looking on places like Digi-Key or Mouser Electronics; those two are pretty much guaranteed to have exactly what you need, but you may find it easier to find them on eBay or Amazon.

For C41 you can use pretty much any physical size of electrolytic capacitor; with through-hole caps you just bend the wires to go through the holes in the circuit board, solder it in and you're done. If you want to get as close as possible to the original, measure the height and diameter and search for ones of that size.

For the other two you'll need to fit the existing footprint on the circuit board. I'm pretty sure you'll find that they're a standard size; again, measure the height and diameter and search for SMT versions of the value you're looking for. Ideally you could measure the footprint for the unused C4 capacitor right near the top of C41; the data sheet will tell you the exact dimensions of the part you're looking at; just match it up with the two solder pads that are there for C4.

So yeah, that pretty much describes how vasvir fixed the same problem you're looking at, so I'd say it's worth a try.

Good luck, and keep up on the updates!

P.S., If you do replace the capacitors make sure you get the polarity correct. With electrolytic caps, unlike others like tantalium, it matters which way they're connected in the circuit. Note where the white stripe on the side of C41 is and make sure your replacement goes in the same way. For C40 and C3, the black spot on the top has to go in the same orientation it was originally in. Fortunately you've got pictures to refer to, so no worries about forgetting which way they go.