0:00 This is an APC Smart UPS 750 that I picked up from a e-wast bin. Someone was throwing it away and I've been using it at home to back up the router, cable modem, backup hard drive, that sort of thing. And so the way it works is it takes two of the standard 12vt, typically 7 to 9 a hour rechargeable lead acid batteries. They go in here. They actually run in series and they run at 24 volts and then the input to the unit is through this Anderson style connector, power pole connector uh in there and that powers the unit during a power outage. 750 VA or volt amps, so roughly equivalent to watts. It's a decent unit for running kind of low load stuff that I've got. But I have it apart
0:45 because I'm trying to recondition the batteries that go in here. So, they're on a charger in the other room, and I'm going to try to desulfate them a bit. The reason I have it taken all the way apart, though, is I wanted to see if there was an easy way to add in some extra battery capacity. And I think I found a way that I can do that. So, when I took everything apart and started investigating where the different connections are, I figured out that the connector that the battery plugs into connects to this red wire and the negative wire is this one that is soldered directly onto this logic board. So, what I'm intending to do is to tap into these and add a connector on the
1:30 back here somewhere that will be in parallel with these wires and thus in parallel with the original battery connectors up front here. And so, it'll basically be 2S 2P, which is actually two batteries in parallel. Each of which is actually two batteries in series. So, it'll be four batteries total, but in the end, everything will be 24 volts, and it'll all be charged as if it was one big battery. I'll be able to unplug that from the rear and still be able to use the internal batteries, or I'll be able to use the original disconnect here, which will break the connection to the internal batteries. So, I've taken the logic board off and at least disconnected enough to be able to pull it away from
2:16 the rest of the chassis. So, my plan is to reroute the positive cable backward and then to desolder this negative wire and run it backward. And it will solder into some leads that will go to a connector back here. And then that connector will also have new leads that go forward to those original connections. To the UPS, it won't know the difference. It'll just see that there's a 24volt lead acid battery there for it to use and to charge. and it already didn't know that that was made up of two 12volt batteries in series. And now it'll be just as oblivious that there's two 12volt batteries in series here that are in parallel with two more 12volt batteries in series here. And
3:01 externally I could expand that to my heart's content. I have moved it over to my soldering bench. I've got a soldering iron set up here along with uh some regular leaded solder that I can use. Hopefully that will make the solder melt at a little bit lower temperature. This is the wire that I want to remove. And you can see it's on this section of the board that has a whole bunch of extra soldered traces. And that's for that's for extra current handling. And the result of that is that it's also going to sink more heat. So, I'm going to give it a go. What I usually find is that using some of this regular old home users leaded solder by adding that to the joint and alloying that in with the lead free solder that is certainly on here from the factory. When those mix
3:47 together, the solder temperature, melting temperature drops. And so perhaps unintuitively, by adding solder to the mix, it's actually making it easier for me to desolder this wire. And that turns out to be true. This is not going to be too big of a problem at all. So, as long as I keep it nice and hot, I should be able to pull this [Music] through. That's kind of a extra tough problem because I'm heating all this thermally resistant space on the board for handling current and I'm also heating this heavy wire, but I was able to get it out. And you can see that's a 12 gauge wire with looks like a some sort of little reinforcement on the end.
4:34 That's interesting. In any case, I was able to get it out. So, next I'll use some solder braid to clean up this hole. I can't really turn the board upside down. Not practically. So, I'm trying to get as much of the solder off from this side as I can. It seems like I always try to take the minimum number of components apart and then by the end of any project, I've got it completely taken apart anyways. And that's definitely what's happened here. I ended up just taking this upper board off. This is the one that flips over and sits here on top. I was working around it by pulling it off to the side and I started to realize that I was going to accidentally knock off or bend one of these capacitors or one of these little components and and never be able to track down what I had damaged. So, rather than doing that, I started looking at the connectors, and they're actually really easy to take off.
5:19 They've just got this little um tab on here. If you push this back, that pulls back the tiny little pin that locks it into the spade connector. With a pair of tweezers, I was able to get all those off. And so, this board is out of the way. Now, with the rest of the unit, it's really straightforward now that I have the the top off. For the connector on the back, I'm going to use the same that's already on the front. I think that just makes sense to use the same kind of connector. So, that's an Anderson Power Pole connector there. And I've got the same connector style here. If I wanted to get really fancy, there's probably a a bulkhead version of this or a a surface mount version that I could mount on here, but I'm not going to do that. I'm just going to drill a hole through here, put a grommet of some sort in there, and have the lead hanging out, and then an extra battery could be plugged into this pair of connectors.
6:05 So, like I say, next step is just to add those wires that incorporate um the new leads and the old leads soldered into the terminals for this new connector. Okay, I mostly finished making my adapter leads. Now, that's this part here. And the original positive wire from the internal battery comes from here, leads up to its original connector, which then feeds into the opposite side spade connector, which I put on here. It goes to the positive Anderson power pole connector, which is also soldered together with this lead, which then has the corresponding connector to plug into the board on this spade connector here. Then on the negative side, the negative wire comes from here, which is actually connected
6:50 to the original factory power disconnect for the built-in battery. That's this black one. It's soldered together in the Anderson power pole connector to this lead, which currently, you see, it's just cut off. And actually, what I did is I clamped it in my helping hands vise and melted some flux down in there and melted some solder down in there. So, I haven't stripped it yet, but the idea is I want to have a little bit of a a stiff saw pre-soldered section of wire that I can then feed up through this hole. I guess it'll be the opposite direction cuz this is upside down. But by doing that, I can uh save myself the frustration of, you know, stranded wire coming apart as I try to feed it through the hole. So, I'm actually going to try to go ahead and strip it right here and see how successful I was. Probably don't
7:36 need to strip off all that much. Okay, there we go. And yep, sure enough. So, this is stranded wire, but it's actually been soldered while inside the insulation. And you can do that because this is silicone insulated wire. This is 12 gauge and it says 200° C. I know for a fact it'll get up into the 5 or 6 700° Fahrenheit range because that's what I typically have my soldering iron running at. And I've never melted any of this sort of insulation. So, nice little trick there. Should save me a little bit of time. The next thing I've got to do is come up with the passage through the back here. So, it's probably just going to be uh I'll drill a hole and add a grommet. I may need to take the terminations out of the actual plastic
8:22 housings here, feed them through, and then put them back on. But in any case, this will be hanging out the back with um some sort of protection wrapped around the wires to keep them from chafing on this metal housing or shorting, that sort of thing. So, in any case, that's the next step. pass that through. Then reinstall this board. Then make these connections back in the original places on that board. Here's the UPS all buttoned back up with the expansion connector coming out of the back. Don't mind these pins I was trying to connect to the serial interface on the network management card. But in any case, here are the batteries that I'm going to use as the expansion. Now, these actually came out of a Black & Decker 36V lawnmower battery. So, there were three of these in series and I picked the best two and I actually measured their capacity. In this case,
9:09 looks like 9.94 and 9.31 amp hours at a 3 amp draw rate. Now, the trouble with measuring the actual capacity of a lead acid battery. It's twofold. One, the total capacity goes down drastically as you increase the amp draw on it. And the other thing is that you don't actually want to use the full capacity of these batteries cuz that will degrade them very quickly. In other words, you don't want to drain these all the way to zero. If you look at the ratings that are printed on the battery, you know, 12 amp hours, that is drawing all the way down to 0% state of charge and at a very, very, very low current level. So, it's not realistic, but that is the nominal rating that you find on these batteries. So, these are 12vt 12 a batteries. There's a pair of 7 amp hour batteries
9:55 inside of here, which is pretty standard for this size of UPS. So, all combined, I should have plenty of run time. I can't quantify it exactly, but these are the batteries I'll be using on the outside in addition to the ones on the inside. And I made up this extension cable. It's a 12 gauge stranded wire inside a nice thick, heavy insulated cable. And it's as easy as just plugging it in. Well, it should be easy. There we go. So, at this point, the UPS won't know that there's four batteries in the mix. These batteries, of course, like I've said, are in parallel with the batteries that are inside. So, the UPS will just be charging to a set voltage limit and discharging to a set voltage limit. That's all that it knows. So,
10:40 that's how I've got it all configured. Let's set it up in the real world. Well, there is one more step I'm going to take before putting these batteries in the UPS, and that is to charge them all to the same level. If you look through the maze of colors, I've got all the positives and negatives connected to each other. So, they're all in parallel and then connected to this variable power supply where I'm charging them up to 14.4 volts, which is the absorption voltage typically for a lead acid 12volt battery. And while it's important to get them fully charged up, it's actually more important that they all be at the same state of charge. And that is, as a beat a dead horse saying, this UPS doesn't know that there are four batteries. It doesn't even know that there's two batteries in series. It just has a charge limit, which is probably 28.8 volts in this situation. and that
11:26 is going to break down to 14.4 volts per battery if they are equally charged. However, if one starts at a higher state of charge and the other lower, well then that 28.8 volts is going to be distributed amongst them and one is going to be overcharged and one is going to be undercharged and underutilized while the one that was overcharged is going to wear out faster. So, you want them to be all balanced at the exact same level for optimal function in the UPS. So, as they approach 14.4, we should see the amperage dropping down. And once that gets close to, well, close to zero, I'll know that these are fully charged, but more importantly, all equally charged. So, here's the finished setup up and running in my little makeshift wiring closet. So, the APC
12:11 connected through that rear connector I added to an extension cable down to the additional 12 a batteries in the lower compartment here. That extension cable means that I can remotely store those batteries somewhere else. But in any case, the APC is powering a cable modem, wireless router, a Lutron lighting controller. We've got a switch here with Ethernet to other parts of the house, and a time machine backup. And it powers these really easily. The load, last time I checked, was only about 25, I believe, 25 watts. Yeah, load power 20 25 watts. Only 5% of what it's saying its current capacity is. So, plenty of run time in the event of a power outage with this small load on it, and the opportunity to
12:56 add even more batteries, more run time if I needed to simply by building a larger 24V pack. Well, this is a fun and pretty straightforward project. And like many projects I enjoy, it also let me rescue some stuff that would have gone into e-waste and probably onto the landfill. So, that's pretty cool, too. I can't quantify it exactly, but it looks like I've at least doubled my estimated run time, and I should have at least 4 hours with modem and router and basic internet things when there's a power outage. I imagine this applies to lots of other people as well. You can find these UPS's for free or cheap all day long because people don't bother to change the batteries. You can put in new batteries and now you can expand them, too, if you just follow the steps in this video. If it was helpful, hit that like button. If you've got any questions
13:42 or anything I didn't clarify, do go ahead and put them in the comments. I'm happy to answer them there. And thanks very much for watching.
