Design UPS for long outage

[woodchucker]

OK, time to fess up

I just let the smoke out of my back-UPS APC 1500 power supply with extra deep cycles batteries

Like to know if its a design problem.

When I built gen 1, I learned the deep cycles must be separate from the internal dry battery because of voltage difference when not in use. The dry batteries go to 16V and the UPS will pop an error if lower. The deep cycles are at 13.8 to 14.4 when not in use. So I installed a power relay with 110 coil normally open. If power fails this relay closes and brings in the spare batteries. See pic of relays on UPS box.

We had an eight hour brown out, not power failure and the system went down. Never thought of this issue before.

The deep cycles are old, time to replace. AND letting the smoke out of the UPS is a BAD thing, time to replace that too.


View attachment 414216

Looks like you hooked it up in series, not parallel.
I can't see all the wires, but that's what it looks like to me. So you put 24 volts in, not 12.

 

[Karl_T]

Well, I proved the dime store version of UPS just dies if extended power outage.

Now the unit in my post #7 claims long term power at 1200 watt. I need just about 100 watt, tiny fraction of this unit's capacity. I'll plan on connecting it to two each deep cycle RV batteries. Or i could connect it to a 12 volt forklift battery. I am NOT interested in going all the way to a portable genny.

So, am I just wasting my money??

EDIT. I should add the dime store system worked through multiple short term failures over the last eight years. Most power failures are minutes to maybe an hour. Plus don't want a potential theif to just pull the meter to disable the system.

 

[woodchucker]

I have thought about this very problem quit a bit, and concluded that until you get into some major industrial hardware it is marginal at best. If I ever decide to install a UPS I'm going to do it a bit differently.

I'll buy an inverter that will handle about 2X my planned load, then buy enough batteries to run in parallel to feed the system for the amount of time required. Then I'll buy or build a battery charger that will handle at least 2X the base load.

The system will run continuous off of the inverter, no relays involved. If the power fails or sags, the battery charger just stops charging until the power comes back. Absolutely seamless switchover, the affected equipment doesn't even know there was a power fail. You could add solar panels to the system to supplement the battery charger to reduce that load. This setup is common in the RV industry where you have charging coming from shore power, solar, and vehicle charging with seamless switchover.

That's how I ran my computers for 14 days after Sandy hit us.
I still had to work, and figured my power inverter would run the computers and I would keep a constant charge on my deep cycle batteries. It worked well enough for 14 days. When my generator would run out of gas, I would not lose any connections and could keep working.
Very important for the systems I was working on, as you needed a new password for every login.. So that was a pain in the arse.

 

[RJSakowski]

The IPS's that I have had experience with have all used 12 volt lead acid gel cells of around 6 - 10 amp-hr capacity so an external lead acid deep cycle battery would be compatible. Whether the internal charging circuitry could handle charging is another manner. Lead acid batteries have a nominal open circuit voltage of 12.6 volts and are quite comfortable with charging continuously at 14 volts. Automotive batteries spend most of their life in standby mode with the alternator supplying 14 volts.

When my deep cycle batteries are close to discharge, they will initially draw more than 40 amps of charging current. I designed my chargers with a small series resistance of around .075 ohms to to drop the voltage and limit the surge. I used 40 amp constant voltage switching power supplies as a starting point for building my chargers. For one, I used three five volt switcher, obtained at a hamfest for $5 each and adjusted to 4.67 volts. For another, I used two 7.5 volt switchers adjusted to 7.00 volts each. These are built into metal tool boxes with digital volt/ammeters, external cooling fans and current limiting resistance. All the switchers were surplus units picked up for a few dollars each which is why I used them. Were I buying switchers off the shelf, I would go with a single 15 volt unit. A Meanwell 600 watt switcher can be purchased from Mouser for $75.

 

[tq60]

Simple...

Buy the correct ups and be done with it.

Many BETTER ups have a connector for add on battery.

Been that way for many years.

Apc and Toshiba both have this.

The battery add on looks just like the ups and it usually has a piggy-back connector so you can add additional units.

The Toshiba 1kva unit does 7 minutes full load, it uses 3 12 volt batteries stacked for 36 volts.

We have another unit that has 5 stacked.

Many use 2 stackedfor 24 volts.

If you used a single battery on a ups with more than one battery then likely wrong voltage and smoke was released.

So go to the manufacturer pages and locate it there first, then Amazon to buy it maybe.

You are NOT looking for a consumer unit but a commercial or office unit.

Sent from my SM-G781V using Tapatalk

 

[pontiac428]

I've got one of these 3kVA commercial-grade monsters. It weighs like 200 lbs and gets ignored most of the time, but keeps all my gear alive when the power gets twitchy. Only downside is the batteries are good for 4 years, tops. It costs a couple hundred to replace all those. I feel like I just replaced them, and it's been overdue. The UPS is offline until I can stomach the new price of sealed AGM lead-acid batteries.

 

[tq60]

Battery prices are nuts now.

The Toshiba units use the smaller common alarm size batteries but what was 19 bucks a copy is now 30.

A 1 kva unit with battery expansion should do the job.

Also of note.

Manage your power!

You only need backup power for the working parts.

Cameras, storage and communication.

Monitors not so much.

The better ups include power management where different outlets can have different support.

As time goes on it drops lesser important loads.

This is what we support, many in service

Google Toshiba ups 1000va for a sample.

Comes in standard and rack mount.

External battery connector.

6 outlets with load shed

Computer interface for management

Optional alarm relay.


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[Shotgun]

I didn't want to spend money on a UPS that is just a boat anchor with slowly dying batteries for most of it's life, but I needed more power reliability when I started working from home. Being out in the country a bit, thunderstorms often bring down the power.

I got 1500 watts of used solar panels. Six panels at about $50 each. These were put up to shade the southern exposure of the house, helping to keep that side cool. I'll eventually get around to surrounding it with windows to give my wife the greenhouse she wants.

The panel feeds into an "all-in-one" solar charge controller/inverter. It'll handle 3kw of load and cost around $600. It drives a sub panel that I put several of the house's circuits on. The circuits drive my computers, communication equipment, and a small freezer. It also accepts power from the grid, but doesn't feed back into it. It is backed by a couple 12V 100Ah batteries. Lithium. Another $650.

Because the system isn't just passive, I'm actually saving on my power bill. It was going to be 2yr payoff time, but I started with lead acid batteries, and they've bit the dust after a year. . . hence the move to lithium (which cost only about $100 more than the L-A). Now, I'm looking at 3yr payoff.