Those UPS devices you buy for your computer usually have a gel-cell battery that lasts for a few years. Less if your power goes out a lot. When you replace them, you pay a bundle, even if it's a standard cell. This short Instructable will demonstrate how to rework an older UPS for more capacity with cheaper battery power.

The picture shows some sample UPSs and an example of the gel cell from one of them. The UPSs come in various capacities and, although you can boost the capacity, the output power is fixed. When you start out, make sure that the UPS you're going to modify will provide the volt-amps and power that you need. Also note that the volt-amp rating is higher than the power rating. The difference is because AC powered devices have a power factor. Check online for more info about this. Another, similar Instructable, also warns against trying to max out the capacity of your UPS because some use transformers that will run continuously at the rated output. It really depends upon the quality of the UPS, but plan to run at not more than about 75% of rated output capacity.

Another thing to consider is whether or not your scrap UPS has AVR or Automatic Voltage Regulation. You'll want this if you can find it.

Step 1: The Guts

First, for safety's sake, unplug the UPS. This pretty much goes without saying. Also realize that the battery inside the UPS may be charged, so do not short circuit any metal parts inside the box.

When you open the UPS box, you'll usually find either one or two gel cell lead-acid batteries. You're going to replace it / them.

What you'll need:
1 scrap UPS - but it needs to be a WORKING UPS!
4 feet of #10 copper wire (2 feet of red and 2 feet of black if you can)
You may need to adjust this length, but keep it as short as you can tolerate.
4 spade lugs (two mating pair
2 ring lugs for single battery or 4 if you have two in the UPS
1 or 2 marine, deep-discharge batteries (85 - 120 AH capacity)

A drill with bit set
Crimper for the lugs
Wire stripper
Sandpaper or a small file to smooth out holes in plastic

Some notes on the parts: look at the pricing of the batteries and get the capacity that gives you lowest cost per amp-hour. Sometimes the 110-140 AH batteries are only a little more than the 70-90 AH ones. Check warehouse clubs for good pricing. Sometimes you can reclaim the core charge with an old motorcycle or car battery you have lying around. Make sure that what you get is a deep-discharge type battery. Some batteries are labeled as marine, but not deep-discharge.

Make sure that your battery has adapter studs that clamp to the lead posts. Then, get ring lugs from your hardware store, electronics store, or online store that will fit over the threaded studs and also accept #10 wire.

You can either get two pair of mating spade lug connectors, or get one set that are the mating connectors to the ones that come from the UPS. In the picture, these are the black and red wires that connect to the batteries.

Note the blue wire. The batteries are in series in this UPS, so it requires 24 volts (black terminal connected to red terminal). Do not try to power it with one battery if it comes with two! Get two more ring lugs if you need two batteries.
<p>Adding a larger capacity may prove dangerous as the charging circuit will need to run longer to recharge also the increased runtime may overheat the ups as its initial design maybe for only a few minutes not hours. </p><p><a href="http://www.apcrbc.com.au/general-ups-information/2-replacing-ups-batteries/11-can-i-put-larger-batteries-in-my-ups" rel="nofollow">http://www.apcrbc.com.au/general-ups-information/2-replacing-ups-batteries/11-can-i-put-larger-batteries-in-my-ups</a></p>
<p>You are right. I'm doing this with APC ES550 at home. I took out the 12v 7Ah battery and used 3 12v 12Ah batteries in parallel. I think the UPC charging block is probably tickle charging the 7Ah battery because you need 16 hours to do the initial charging. But I left the one at home as is. If a 10A charger is used with a 12v 75Ah car battery then I would need a 12v 2A charger outside the box to replace/bypass the charging circuit. For the heat issue I would cut some vents and get a 12v dc fan and control circuit.</p>
<p>correction: 12v 6A charger instead of 2A. Probably the UL test for run time is at least 5x at max output which it passes so it could possibly be more.</p>
<p>I modified an APC350 using a car battery with a 600CCA rating, just over 3 years ago. This unit runs on one of our shop computers, 5 days/wk - 24/7. Our area is prone to blackouts from 5-10 times per year on average and this &quot;baby&quot; never overheats and the battery still passes it's load test. I've never tested the true amount of time this UPS can keep our shop system running, until it dies but the longest power outage I've witnessed at 40 minutes and it was running just fine!</p>
<p>My current ups uses 2 gel batteries in a parallel connection, so thats 24volts. i want to know if i can rewire the ups so that i could use one 12v, 100amp battery instead.</p><p>any ideas if its possible would be appreciated.</p>
<p>Are you sure it's a parallel connection? If there is more than one battery in a UPS, they are typically connected in series, so you get double the voltage with the same current. You would have to analyze the circuit (they are all different) to determine if there is a simple way to convert it from 24VDC to 12VDC. It seems unlikely. By using a higher input voltage, the components on the primary side only need to handle half the current load and would likely be undersized for a lower input voltage. Also, my guess is that a higher input voltage provides for more efficient conversion.</p>
<p>Yes, tThe two batteries in the photo are in series. </p><p>In the case of the UPS in the photo, you would need two 12V batteries and these external/additional batteries MUST be in series as a set and and the set must connected to the existing batteries in parallel at the red and the black wires.</p><p>Alternately, you <em>can </em>connect each individual extra battery to each of the internal batteries in parallel, but that would mean extra connections.</p>
<p>Erm... in general if you place batteries in series, the voltage is additive. If you place them in parallel, the available amperage is additive.</p><p>So two 12V batteries in parallel would not be 24V</p>
<p>You could use 2 DC-DC converters, one step down from 24-12 and one step-up from 12-24. Then connect 2 diodes (one for each converter in opposite directions) to prevent getting a circular looping circuit. However this is not something I would do. If your UPS is designed to run on 24v, that also means it's charging algorithm is designed for 24v. A DC-DC converter and a diode would change the voltage across the circuit enough to cause significant problems. Better to connect two batteries.</p>
<p>I am trying to get a backup for my garage door openers. A stock APC350 will not run the garage door, I am guessing not enough amps coming through? If I put a larger battery will it have a higher amperage output, or will it just last longer. I guess the question is does the circuitry limit the output? </p>
<p>If you haven't solved this problem yet, an inverter/charger like this http://goo.gl/y5c1A6 is probably a better solution for you.</p>
UPSs are typically rated by volt-amps (VA) which is not the same as watts because of phasing between voltage and current in AC power. Electric motors such as the one in your opener have a large stall torque in startup, which pulls much more power than when they are moving at a constant rate. Check the power rating on your opener and find a UPS with at least that rating (particularly the amperage rating).
<p>It will just last longer. You will need a UPS capable of delivering more amps than the APC350</p>
<p>It will just last longer. You will need a UPS capable of delivering more amps than the APC350</p>
<p>So I am trying to maintain a raspberry pi, a Dlink wifi router and an LED 8 watt light bulb using a 350 watt UPS with a 3.5aH battery. I have wired in a 100 aH deep cycle battery and a Genius charger to take the load off the UPS charger. Our power can go out for days at a time and we are away, so need the link up in the house to monitor temperature in winter. When we are away, the light bulb is off. </p><p>Minimal load, so there should be no issue with overheating. Any comments on this set up?</p>
<p>Would be nice to see how your set up runs, I have a similar setup. I actually got rid of all my AC-DC adapters for my modem, routers, switchers and access points, and run them on pure DC straight from the battery (through a solar charge controller so that I can benefit from the low voltage disconnect). From a 100AH 12v battery (1.2KWh) I get 3 days no problems. Under normal conditions your battery voltage would range between 11.8v and 13.6v (stable open circuit voltage). Most DC circuits would be able to handle the extra voltage as it would jsut be dissipated as heat. My current network switchers are all 9v but I run then on a 12v line. They run a bit hotter than normal, but they run just fine. To this same battery I have connected a UPS (diode connected to prevent UPS from charging battery) to power critical lights in a power outage, and I run a 120W solar panel to keep the battery topped up (during extended bad weather my panel doesn't provide charge, but the battery still lasts about 3 days for my small load)</p>
<p>I haven't explored how the internal chargers in UPSs behave when another charger is connected in parallel. The unit may sense that the Genius charger has brought the battery to the right voltage, but without some knowledge about how the circuit behaves, there's no telling for sure.</p><p>What is the total draw of all the devices? Every device that plugs into AC has a tag with input voltage and current rating. If you're connecting the Pi directly to DC, it may be harder to find out how much it draws. If you're using an AC adapter, it should have the current requirements. Add up the current (number of amps) from each adapter, multiply the total by 10, and then multiply by 1.5 (to account for conversion efficiency) to get the current draw from the battery. Divide 100 (the AH rating of your battery) by this number to get an estimate of how long it will last with the power off.</p><p>For example, if the adapters and bulb draw 1, 1.5, and 0.1 amps, then the estimated draw would be 39 and the duration would be 2.5 hours. In practice, this is an underestimate because the current ratings on the AC adapters is the maximum amount: they likely draw about 1/10th that amount because they are only operating intermittently and not anywhere near full load. I calculated the 0.1 A for the LED light by dividing 8 watts by 120 VAC and rounding up. If your adapters are only runnning at 10% of capacity, then you get a MUCH longer run time of about 25 hours. Still, it's not several days.</p><p>Here's a possibly better hack: check the opertiong output voltage of the adapters. If they are 12 VDC outputs, you could try connecting them directly to the battery. Get a 12V LED bar intended for cars to replace the 8W bulb, and you can dispense with the UPS entirely (you'll still need the battery charger, obviously). Just be careful because the actual output of the battery is about 14.1 VDC. Check to make sure that the Rasp Pi and the router will safely operate up to that votage. Some regulators on Arduinos will blow, for example, if you run at the higher voltage and draw a lot of power.</p>
<p>Nice instructable; I have a similar setup to run some critical lights. Keep in mind that many UPS's are not designed to run as an inverter for long durations (not more than a few minutes) and will get hot. Depending on the quality your UPS you may need to install a small fan to keep things cool. Also for all battery systems, there is a general rule of thumb that the charge and discharge rate in amps should be between 5-13% (ideally 10%) of the capacity of the battery bank to prevent the batteries from over heating. A typical UPS may only be able to charge the batteries at 1-2 amps, so if you have 200AH battery bank you would want to charge at a rate of at least 10amps preferably 20amps. Never the less, very good post, this is a good way for people to economically get started with extended power backup times.</p>
<p>Just a suggestion, You might consider using Deep Cycle batteries. They have much higher AH ratings. Which means longer run times. Plus they are made to be drained to almost nothing without damaging the battery, just as long as they are quickly charged back up and don't sit empty for long. Regular car batteries on the other hand won't have a very long life if you let them drain all the way. Keep in mind that car batteries are designed for brief high AMP loads ( like starting an engine), which is not something you need in a UPS setup. </p>
<p>Yup. The list of what you'll need says: </p><p>1 or 2 marine, deep-discharge batteries (85 - 120 AH capacity)</p>
<p>Yup. The list of what you'll need says: </p><p>1 or 2 marine, deep-discharge batteries (85 - 120 AH capacity)</p>
<p>Please tie knots in the wire going through the holes (inside the case) instead of relying on the crimp connector to keep the wire from pulling through the hole. A knotted wire is way less likely to fail if yanked. Crimp connectors are notorious for failing, even without the stress of being pulled on.</p>
<p>That's a great point. You don't want a bare wire end flopping around inside one of these thins!</p>
<p>Why not connect the extra batteries with the original ups batteries in parallel if the voltage is the same?</p>
<p>Batteries don't charge as well in parallel. This is even more pronounced when the batteries are of different types (regular lead-acid vs. marine deep-discharge vs. gell). More importantly, if the original battery(ies) are worn out and have internal leakage, they would tend to discharge the new battery.</p>
<p>As my budget is less, cannot afford bigger batteries and my doubt is also about charging the batteries when on mains.</p><p>will the charger circuit that is inside UPS will be able to charge these little high Ah batteries? and will the circuit in ups handle the high current coming from the batteries? these are my concerns going ahead with this new Idea of increasing to bigger batteries? Do i have to install a fan for my circuit as a cooling solution. I am also attaching a photo, I am unable to read the details of transformer. Can you guide me. </p>
<p>It's difficult to tell without more documentation, and even then mfrs generally don't tell you. I've had good luck with a CyberPower 900AVR and a Power99/500VA using 85 AH and 115 AH marine batteries. Both of these came with the standard 7 AH gel cells originally.</p><p>Tell all of us more about where you live and the power conditions there. In my case, the power rarely goes out since they reworked the local substation a few years ago. Although I've tested the upgraded UPSs for hours just to see how long they last, I have not actually had to use them more than a couple of times, and I minimized the load on them so they would last even longer. So in my case, even a regular starting battery might work, because they are good for a couple of deep discharges before they start to die.</p><p>If your power does not go out very often, perhaps a couple of cheap used batteries might be sufficient. Just make sure to clean them, maybe with some baking soda, to get all the acid off the outside. Also put some kind of pan under them or put them in a battery case.</p>
<p>I have a 1000va UPS and my computer is 550W constant power SMPS powered.</p><p>I am getting 10 mins of back up or even less. Yesterday i have opened my ups and checked that it has 2 batteries connected in series. 2 Batteries are of 12v7Ah capacity. Can in i connect 2 12 V 12Ah batteries to increase to atleast 20 mins? </p>
<p>Just scale the capacities like so:</p><p>12 AH / 7 AH * 10 = 17 minutes with 12 AH batteries. That's approximate, of course. If you used two 85 AH marine batteries in series, you could get as much as 2 hours of runtime.</p>
What about charging high-capacity battery with ups rated for use with 7-9 ah batteries? Will it charge new battery correctly?
<p>Some of them will charge properly. It varies by brand. My CyberPower AVR UPS worked great with the larger batteries and recognized the longer run time they provided. (Sorry for taking so long to reply. I've been working on a bunch of other projects!)</p>
<p>I made a similar system with APC smartups 1500. My problem seems to be that the UPS</p><p>has no idea of the battery capacity. When i check the UPS status with Network Ups Tools. It gives an alarm &quot;ups.alarm No battery installed!&quot; yet it gives the battery percentage as 68 or something. This is 1-2 minutes after detaching the cord, ie starting to run on batteries, My batteries are 2 80Ah Bosch batteries in series. </p><p>Should i run some sort of self-test with the system to get it to recognize the battery?</p><p>I'm worried the UPS might not charge the batteries to full capacity, and/or shutdown the system when it still has a lot of runtime left.</p><p>Thx beforehand.</p><p>Ps. sorry for typos, not a native. </p>
<p>I have not had that issue with either a CyberPower or APC, but I've only used the single battery APC. What kind of cells are your Bosch? They must be deep-cycle marine or gel cell. These types of batteries have different charge rates and voltages than plain starting batteries that are not designed to be deep-cycled.</p>
<p>I have two near new 1000VA/600Watt UPS, each containing one 12 volt battery. Each will run a computer for about 15 minutes on battery. I have completed the conversion to 12 volt marine 100 amp hour battery on each. They both work as planned when plugged into main electric supply. However when unplugged from mains they will carry only a small load such as small light or fan, but the minute i add a computer the fuse blows. Conclusion, the computer is too much load for the unit when combined with the 100 amp/hr battery. Can someone offer a solution.</p>
<p>Two things I can think of to check. The first is to try unplugging the UPS from the wall outlet while the computer is running on the outlets supplied with battery power. That best simulates what happens when the power goes out. Some UPSs get wonky if you change the load after the power goes out. The second is to check the fuse rating. For reference, the input current rating on the CyberPower 900AVR in the photo is 12A. A 600W UPS should have at least a 5A fuse, and that would very likely blow every time you turn something on, just because of the surge current. You should either have a fuse that is equal to or slightly higher than the input current rating, or a slow-blow fuse that can tolerate surge currents.</p><p>Is this fuse that's blowing on the outputs from the UPS or on the input from the A/C line? The input fuse has to be able to handle both the full output of the UPS as well as the charging current required to simultaneously charge the battery and run whatever is plugged into the unit.</p><p>One more thing: Recheck your wiring to make sure that something didn't actually get shorted. No wires touching bare metal anywhere, no screws that dropped inside the device, etc.</p>
Thnx Surfer for your help. I added a 15A fuse inbetween the posivite side of the new 100A battery to the UPS as a safety precaution. That is the fuse that keeps blowing. It is not a slow fuse. Soon i will add a 30A here, and if that blows, a 40A. couldnt find a 50A without going to a very large and expensive fuse holder. I will also add a surge arester. And because you are interested i will report back. Maybe it will help some other poor slob. And if all that fails i give up.
thnx so much for quick response.<br>o.k. here is how I have this wired - pos to pos, neg to neg, just take out the old small battery and insert the large new battery. just like this and several similar web sites - all say much the same. no shorting, plastic housing, no wires touching, and good 10 gauge wire with crimp connecters from unit to battery. I noted the unit also charges nicely, as when i got the new battery it read 12V, but after charging for 24hr, now ready 13.2V and charger light changed from blinking to solid on meaning fully charged. the only thing I am doing different is I inserted an in line automotive type fuse of 20 amps. this is the fuse that keeps blowing. there is also a 5 amp fuse in the unit, but that doesn't blow. So again I tested, with the unit plugged into mains it will carry anything. then I have a small light and small fan running, unplugged from mains, beeps as normal, fan and light stay on, and fuse remains intact. then I unplug light, fan, and plug in computer (no monitor even) unit runs find plugged into mains, but the minute I unplug from main, the 20 amp fuse blows. maybe it is all the 20 amp fuse I inserted. I guess I can take the in line fuse out. comments please??? thnx again Ron
<p>12v * 20a = 240 watts. Doesn't seem surprising your fuse is blowing running a computer. I assume the 5a fuse mentioned before is for the 120v AC power to the unit rather than the 12v from the stock battery. 120v * 5a = 600 watts. You need a 50 amp fuse on your 12v wiring to support your 600 watt rating. 10 gauge wire looks good for that.</p>
<p>I have an old Avaya industrial charger I picked up a while back. It's rated at 10000VA, 8.3 amps 50/60 Hz output. What sort of baterry can I use this? Can I use the old battery from my truck?</p>
<p>That comment should actually go here:</p><p>No idea. Is it's a charger, then it likely converts AC to DC, which is not what a UPS / AVR does. The UPS combines a filter, charger, and inverter in one small box. If there's no inverter in your device, sticking a battery in it is not going to do you much good. Do you have a link to a web page for it?</p>
IT's an UPS, dont know why I called it a charger, must be I was thinking of terms of the battery I want to connect to it. As far as a link for the device's web page, I haven't found one yet. It seems the UPS is too outdated to still be included on the manufacturer's website.
If the batteries are hooked up as shown, they will be in series and will be 24 volts. That would be fine if your UPS had two 12 volt batteries. However, if the ups you are using had only a single 12 volt battery, but you wanted to extend the capacity by using two AGM deep cycles, wouldn't you hook the repalcements up in parrallel?
<p>The number of batteries is addressed in Step 1, but it's good to reiterate the need to match the original battery configuration in terms of voltage. In this Instructable, the goal is to simply increase the AH capacity by using larger batteries. You could use multiple batteries in parallel at the required voltage, but then you run into battery balancing and overcharging issues.</p>
Got a question,I have a apc 550va, Will this work? Tapping the stock 12 volt battery terminals and connecting to my vehicles 12 volt system? I would disconnect while starting the vehicle, just want to know if the alternator would have any bad effect on the ups?
I recently built a ups from scratch. I built the switchover circuit and inverter. It converts the ac to 12v dc, which is used to charge the battery and power an inverter. When power goes out, the batter is switched in place of the dc power supply to power the inverter.
Do you have a website on building your own UPS, or how you did it? Might want to post an 'ible yourself...
I don't have a website for it, I didn't document it very well. Maybe someday, right now I'm just trying to learn and spending less time on projects.
Just by adding more battery.
If the batteries sink below that charge level, wouldn't it be better to pull them out (if set up that way) and charge them with a standard battery charger, instead of trying to use the float charger in the UPS?

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