Can I Parallel a Bigger Battery With a Computer UPS?

Yes, so do I. We'll have to compare notes. I have two, at this point APC, one powered by a group 31 the other a 27. The original gel batteries failed and have been removed.

I once had a couple of off brand UPS, one had the surprising ability to apply line voltage to the battery terminals. Imagine my surprise when I checked the fluid levels!!. My current APC don't offer this feature.

UPS, by there nature, are inefficient, I also have a suitably sized inverter if the power is going to be out for awhile. As others have mentioned, the UPS charging circuit is small, it takes a long time to recharge, you might want to invest in a larger charger

I installed a digital voltmeter on the battery box, the type with an amphour meter are of limited value as you must reset it after each use, they don't run "backwards" when recharging.

The UPS will not run either my Hughes or cable modems. The inverter does power the Hughesnet. If this is an issue, you will need a "full sine wave" inverter for the modems. I had two name brand units, both failed. One because of the above line voltage issue, the other wore out after 150 or so hours.

Hope this helps. I will send you my thoughts on generators later. After Irma/Maria went through, I needed them for 9 mos.

Interesting, especially the UPS that applied line voltage to the battery. Seems like fire hazard, not just a guarantee of short battery life!

If I'm not being indiscrete, where do you live? From the geo. coordinates, I'm guessing central America.

Puerto Rico. And yes we lose it frequently. Sometimes for maintenance.

Generators. The first is to determine the size, what do you want to run. Second, what is the length of the outages. The third is the type of fuel. Diesel was unavailable here for close to 10 weeks, hospitals got first dibbs, then stores. When those started to fail due to lack of maintenance, diesel became available for a short period, then dried up again. Gasoline was available within a couple of days, but of course it was cash only, and limited to $20 daily, no internet to verify CC transactions. Dual fuel or propane would have been a great option.

Refrigerators need to run for 8 hrs continuously to cycle through the defrost cycle, some new refrigerators and A/C units use are "inverter" types. That is they convert AC to DC, the compressor runs continuously, but at higher or lower power levels depending on how much "cooling" is needed. Washing machines and electric stoves are other considerations. (I now have a gas stove).

I don't see much in the way of the 220 VAC"inverter" type generators. If they are available, they work well and sip fuel. The drawback is severe voltage droop when providing a large load like a microwave. This can be minimized to an extent, by turning off the low power mode. I still unplug the fridg (and keep it off for at least 5 minutes) when using the microwave. Compressor stalls are expensive.

My main generator was Briggs and Stratton 3500 run 4200 surge. It consumes 7 gallons over 12 hr period. (There went my $20 daily gas allowance.) So I would cut it back, that is how I discovered the refrigerator defrost issue. That generator failed in December. My neighbor has a 25KW that he started to use at night once diesel became available. I ran 180 ft of #10 and was able to get by with that (only $30/week). By mid December, we had limited internet, and generators started to appear in the stores and I bought an 1800/2300 watt inverter type. I use it for most of the outages, unless it is too hot when I need to run the AC.

If you have nearby neighbors you might consider sharing a generator.

As for the UPS, the battery was in a box, I only discovered the voltage when I touched the terminals. As you run 220 single phase, you may not have that issue. The batteries are not in parallel, the original battery failed. I have a low voltage shut off set for 11 volts, so I don't ruin the battery. It takes just about 15 hours for the UPS charger to bring it back. That is why I use an aux charger to speed the process. Unfortunately there are no longer old school, iron core, selenium rectifier chargers.

The Briggs and Stratton is now repaired. The original plastic gas tank cracked along the mounting screws, a friend made a new one of aluminum. The muffler bolts backed out of the head, the resulting vibration caused the carburetor throttle linkage to break. The carb was $65 and new head was $120. I repaired the old head and now have a spare, next project is to replace the muffler with an automotive muffler to reduce the noise. Yes, it will burn the exhaust valve, don't care, I can replace the head in an hour and valves in 2.

I've lived in a number of East Coast states. All have issues, P.R. certainly does, but the weather is great, I'm off to the beach for the daily swim. Water is getting cool, mid 70's.

Would you like to hear my Imelda Marcos story?

Aie. Puerto Rico. What a mess that seems to have been. From the newspaper articles, it made the Philippines seem like paradise.

I've pretty well managed the sizing of the gen. Despite my preference for diesels, I am leaning toward gasoline because my only car is gas-fueled (I sold the diesel van) and there is the option of converting the gen. to LPG, though conversion kits for generators are not currently available here. My main load, as in most homes, is the refrigerator. Thanks for the tip about the defrost. My 'fridge is over ten years old and on its third compressor - don't know if the defrost problem had anything to do with that. I learned about fitting an auto muffler to a generator from Home Power magazine (I think) but I didn't know about the effect on the exhaust valve. Have to add a periodic top end overhaul to the budget, or try my own scheme of using an ejector, both to move air through the acoustic compartment that I will build and to partially silence the exhaust (the enclosure taking care of the rest)

I'm not sure what you mean by an "inverter" type generator. All generators vary their output according to load, so that can't be it.

Back to the temporary outages: I will grab a UPS that needs a new battery (the one for the TV) and try the solutions recommended by various people on this forum: direct connection of an oversize battery, with or without prior, separate charging, etc. With any luck, that should solve the most common problem

Yes, I would love to hear your Imelda Marcos story. If it is not too off-color, I will retell it to my wife, who collects them.

You can, but you may need to charge the batteries separately before connecting them in parallel... Some UPS are made for paralleling and have additional battery pack available that just plugs in...I have a couple of these...

https://www.amazon.com/dp/B07YCS2PHL/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B07YCS2PHL&pd_rd_w=g3ZWL&pf_rd_p=45a72588-80f7-4414-9851-786f6c16d42b&pd_rd_wg=ed7Rf&pf_rd_r=WK4G5R9VFCY2A1H136WV&pd_rd_r=509f1e41-201c-46ba-862e-23685d435dc6&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySDJZUDZNNEU4Mkg2JmVuY3J5cHRlZElkPUEwNjUxODIyMzBaRjdTT05WWVk2NCZlbmNyeXB0ZWRBZElkPUEwNDAxODYyMTkxMkI2VjJSOFNROCZ3aWRnZXROYW1lPXNwX2RldGFpbCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

https://www.amazon.com/APC-External-Battery-BR1500G-BR24BPG/dp/B0047E5B90/ref=pd_cp_23_3/144-8699111-5708226?_encoding=UTF8&pd_rd_i=B0047E5B90&pd_rd_r=8ff79649-ad57-4db5-ade6-b6f58d130d8f&pd_rd_w=Zvsfv&pd_rd_wg=LFeJo&pf_rd_p=0e5324e1-c848-4872-bbd5-5be6baedf80e&pf_rd_r=RMBT494Y9MK57G7WJGP3&psc=1&refRID=RMBT494Y9MK57G7WJGP3

" A desktop computer uses between 60 and 250 watts, depending on whether it is idle. A 22-inch LCD monitor uses an average of 25 watts..."

Let's take 225 watts as an average load...

1500VA/ 865W ups would last ~ 30 min

This system should give ~ 1 hour backup...

These units are expensive, and suitable for servers or data centers! They do have the built-in parallel capacity, though.

Well you could take a couple of car batteries and hook them to about a 750 watt inverter, and use that to feed the computer, but I don't know how clean the power would be....still going to be a few bucks...You could just switch to a laptop, batteries built in....

That's pretty much what I'm doing now during extended outages, when I'm under pressure to deliver a translation job. It works, but I'm looking forward to having a genset for extended dead grid operation.

Consider having a small backup generator that you can plug the UPS into during a power outage. Assuming the computer is only on when you are there, you could manually move the UPS plug from line to generator and start the generator. Amazon has some small gas powered or solar powered generators that would work for under $300.

If you need automatic starting and switchover you will be looking at higher cost - over $1000.

I will have a generator soon, but starting it, then shutting it down after fifteen minutes is basically a complete loss of time during the interval. It's also not very good for the generator. I'm looking for something that allows me to keep working during brief interruptions.

The backup generators usually will start themselves and run for about 15 min once a week. This is probably to keep the crankcase oil circulating, keep the fuel circulating, charge the battery and to alert the operator to problems.

From my experience most UPS systems use Sealed Lead Acid batteries which have a very short life span when continually on float charge. Why not ditch the internal battery and use a maintenance free vehicle battery which will have a higher Ampere Hour rating are made to handle sudden loads and last many years.

The charging circuit will be current limited and have a float voltage limit which may need to be increased for the bigger battery at least any I have worked on contain both these features. When the UPS is idling then the battery will be getting charged and will soon make up any loss of charge. For a lead acid on continuous float a voltage of 14.1 to 14.2 will keep it in great condition but it can be lowered to 13.8V

Some UPS systems charge the battery and the battery is always connected to the UPS to supply the output while others bypass the UPS and run off mains until the supply drops below set values and then the UPS is connected to the load.

Yes, I once did this. Replaced the internal 12V 6Ah battery with a small external car battery of 30Ah (IIRC). No probs but it did take 24 hours to get back up to 13.8 V from 50% discharged.

There are laptops available these days with a suggested 10h battery life.

Last resort for me. I have a lot of trouble doing translation work on my laptop. It's not just the awkward keyboard - there's the odd problem of the MS Word cursor spontaneously relocating itself; never figured out the cause of that.

So do I. We should compare notes. Yes, I currently have two. APC seems to work the best. I had a Costco/Sams special for awhile. It had one drawback. 120 VAC appeared on the battery terminals to ground. I'm using a group 31 on one and a 27 on the other. UPS's are by nature inefficient. If the power is going to be off for awhile I also use an inverter. The charging circuit on the UPS takes awhile to recover. You might want to use a larger charger to bring it up. I installed a digital voltmeter in the battery box. I've found the ones with a built in amp hour meter to be somewhat useful. My Hughes net will operate from the inverter but not the UPS, my cable box works from neither.

Hope this helps

Some UPS units do not produce true sinusoidal output but a chopped square wave roughly approximating the sine wave. A true sine wave inverter is a large thing indeed with chokes and ac capacitors all used to turn the output into a sine wave. I worked on 1KVA and 1.5 KVA units that ran on 48V dc and 72V dc and they were the size of a small bar fridge with a battery bank to match.

A lot of electronic equipment objects to the harmonics in the chopper inverter and just refuse to run.

Good point. I don't have an oscilloscope, so I don't know what kind of inverter there is in the UPS or what kind my separate inverter is.

If it doesn't say true sine wave on it, then it's not...because they are more expensive and a big selling point...pure sine wave is recommended for electronics and motors...

https://www.altestore.com/blog/2015/10/pure-sine-wave-vs-modified-sine-wave-whats-the-difference/#.XfcQdehKiUk