APC Battery Backup - Extending Run Time with BIG Battery Bank

vsheetz

Rather than kluge a APC, consider equipment designed to do the job:

Switches automatically from AC/DC power supply to battery power, charges pretty much whatever battery bank you want to connect:
http://www.westmountainradio.com/SuperPWRgate.htm

Run the output to a DC to AC inverter, such as from Tripplite.

Commonly used for ham radio emergency power.

homerb

Thanks for showing this! It's not that expensive, either.

I have an 800W cont 1600W peak AC inverter and a 1.5 amp "battery tender" trickle charger. I don't think I'll leave it running continuously with things plugged into it, like with an APC. But, it's still good for emergencies.

homerb

Sorry to revive an old thread. Coincidentally, it's been almost exactly a year since I started this thread!

Just had an outage during a storm and this system I made ran perfectly. It ran everything in my living room including my LCD TV, DVR, Cable Modem, Router, Computer, and Table lights (CFL's), An approximate 600W load for 4 hours straight until the power came back on. It probably had another 2-3 hours left in it before the batteries died.

I didn't even have to fire up my generator. My Generac 7500 EXL is really loud and I'm afraid it would bug the neighbors. I'll only use that for extended outages when the battery backup goes dead and when I need to keep the fridge and hot water heater going.

This is the first real "test" of my system. Now that I know I can have at least 7 hours of runtime (probably more with a lower load), I can use the battery backup at night to avoid attracting attention, and then use the generator during the day.

Has anyone else done anything similar?

Homer

RandomEE

That's awesome, thanks for the post.

I have a similar backup unit plugged into my Linux server. I can only get about 20 minutes of run time on it, which seems kind of short for having only one computer on it.

In my garage I have a couple of massive APC 3750 Watt, 5000 VA backup units, but they both require 220V inputs. Unfortunately for me that means about $450 to run a new circuit to a new breaker, as I'm out of spots in my panel.

Your post makes me want to wire up 2 or 4 of the batteries that are just laying there collecting dust. I would be curious to know more about what you ended up doing for your setup.

Attached Thumbnails

 

Red Squirrel

Great to hear that it worked out. I've been thinking of doing this for a while now. They do make inverter chargers which are made for it, problem is the switch-over time is too long, most equipment would still go down. Making a dual conversion UPS would be nice too, but good luck finding a 300 amp battery charger to keep up with the load.

Marty1Mc

Have you considered how you're going to re-charge these batteries? I am sure the APC unit doesn't have the capacity to re-charge two car batteries in series/parallel to the unit.

homerb

The smaller APC units that only have a 12V system have a pretty weak charging circuit.

However, the larger units that have the capability to be expanded with a separate battery pack have a more robust charging circuit. As far as the APC is concerned, it just thinks it has the "add on" battery pack. Nevertheless, it's still a small trickle charger. They don't need to be charged up fast anyways.

Red Squirrel

I would imagine it would take a while, but I'm sure it would eventually still charge up fully. You could possibly add another charger to the circuit so you can charge em faster after an extended outage, though I'm not sure what effect that would have on the UPS's charger. They'd probably do funny things with each other. Could keep the system offline and charge separately I guess. Would only need to do this when it's been completely depleted.

Would probably take a couple days to charge with just the UPS, but unless you get tons of outages, this is probably acceptable.

Though, I wonder if an inverter charger like this would be better than an APC:

http://www.ebay.ca/itm/8000W-Pure-Si...item5d302e2abc

It has a transfer time of <8ms which I imagine is acceptable for computer equipment. It's 220v though, but there are more, and cheaper ones too. Idealy a 240/120 unit would be perfect as you could just hook up a small sub panel to it and wire circuits in directly and have both 120 and 240 voltages.

homerb

Sorry to resurrect an old thread, but has anyone thought of this lately?

dazium

I too have been trying to do the same. i am runninf 6 12/12 sl;a batteries for 72 ah and 12v. when i attached the paralelles bank to the ups, the shunt vaporised, in thoery this should have not happened because the voltage has remained the same. i have email apc about this and am still awaiting a reply from them. i did replace the trace shunt with copper wire. upd works again on single battery but still not the bank. Yes i am getting 12.6 v tested from the bank. no its not overvolted. yes i did fix the shunt, works now. when plugged into wall, and with single battery but not the bank??? any ideas?

homerb

If it's a 12 V system, make sure that all of your batteries are wired up in parallel like you mentioned. That means that all of the positive wires are hooked up to the positive leads in the battery and all the negative wires hooked up to the negative leads on the battery, as opposed to running them in series where you go from positive to negative to positive to negative and so on. And make sure you test the output voltage of the entire bank before you hook it up to the APC unit. Output voltage of the entire bank should be nearly identical to the output voltage of a single battery.

If that is the case, the APC shouldn't even be able to tell the difference between one battery two batteries or three batteries and so on. Because you have increased the capacity and the amperage rather than the voltage by wiring them in parallel.

dazium

They are all paraleled. I have made banks before. i also have a custom ebike runing 88-96 v with lithium packs. 24s. I custom buikt the wiring harness for both. do you think that maybe the precharge from the batteries to the unit. charging the caps with lots of current, could have fried the fuses. i will be adding an online fuse to the pack to keep the current below 30amp. other than that, idk what is wrong with the ups. this is a small battery bank for me.

homerb

You said that you were able to get it to work with just one battery. Hook it up with that first battery and let it charge and run. Then, add more batteries to the bank when the first one is still hooked up. That way you would gradually be increasing the capacity of the bank without introducing a sudden jolt or charge that might be exaggerated by a bank of more than one battery.

Yoyizit

Post a schematic of your intended network. The number of spurious current paths can be large and resistances can be extremely low.

Red Squirrel

Seems odd it would have vaporized as even though there is more current available, the system is only going to draw what it needs. Could it be that there is a very momentary short circuit that happens during the switch over? Maybe the relay is make before break and during the transition period it is shorting the batteries. So with a small battery not a big deal, but with a huge bank, then it is. Just a guess though.