UPS Batteries Questions - Page 1
Forum section: electronics / beginners

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 15, 2014, 08:04:43 pm
content: Hello,I have an APC UPS SUA1500i (220v) which uses two sealed lead acid batteries rated at 12V 18AH.I've seen some people on the internet that hacks the ups and uses large capacity batteries instead of the rated batteries.Like:AndAndAnd this video:My question is:What are the dangers/precautions of such hack?Thank you.

author: fubar.gr
author_rank: Unknown
timestamp: July 15, 2014, 09:03:54 pm
content: I had a similar setup for years. No problems at all.Just keep in mind that these batteries can vent or leak. They have to be placed in a well ventilated place and on some suitable tray or such that can contain the acid in the event a battery leaks.

author: fubar.gr
author_rank: Unknown
timestamp: July 15, 2014, 09:07:08 pm
content: Also make sure the cable gauge is big enough for the current. The battery terminals should be covered too. These batteries can produce tons of current. You dont want some metallic object shorting the terminals.

author: edy
author_rank: Super Contributor
timestamp: July 15, 2014, 10:22:08 pm
content: Just a thought... Any concern about using Automobile batteries versus Deep-cycle Marine batteries? The OP didn't get into detail about what kind of large batteries to use, but I figure it is better to use deep-cycle especially if there is a power-failure and the batteries start to deplete quite a bit... You don't want them ruined after one deep drain cycle. Marine or deep-cycle batteries will tend to withstand more drain before plates start to warp/etc. Also the ones in the photos don't appear to be "SLA" type so will there be a need to maintain them and top-up with water periodically? How will it be known when and how, and will the UPS be able to properly monitor the health?

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 15, 2014, 11:16:34 pm
content: I would go with deep cycle batteries of course, Automobile batteries won't be able to withstand a lot of charging and discharging cycles as far as I understand.Those photos are only for demonstrating the idea.I don't think the UPS will be able to probably monitor the health of the batteries. If you the UPS uses the voltage to show how much power the batteries have left then it might work but then it might not.I more concerned with safety issues, like leaking acid, releasing hydrogen and oxygen and making an explosion, extended periods of charging that the charging circuitry and transformer may not be designed for.

author: eliocor
author_rank: Unknown
timestamp: July 16, 2014, 12:18:44 am
content: beingthisUPS a line-interactive model, it was not designed for continuous usage:its components (especially the transformer) were designed to be used for only the strict time required for the original battery to discharge (6-7 minutes at full load / 25 minutes at half load).If used for more time than what allowed by design, there are several risks of overtemperature/faults (transformer windings / mosfets / ...).Only if you are using an online UPS you will be able to use bigger batteries without any trouble: this particular topology is designed to work flawlessly at full load 24/7/365.The other problem is the battery charger: it was surely designed for its specific battery capacity (I think 24V/18Ah): it will take a much more (proportional) time to completely re-charge the much bigger batteries. This can also put some strain on the charger, especially if it not well protected from overloading.BTW, i found the "Typical battery recharge time" of only 3 hours a bit "cheesy", but maybe they are talking about a battery which is not completely depleted!!!P.S.: In my previous work I was an UPS developer (for about 11 years)P.P.S.:to me, if the UPS was not developed supporting external battery packs, doing what you are suggesting, is a really dangerous choice

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 16, 2014, 12:54:02 am
content: Thank you eliocor for input, very helpful.A lower capacity unit (SUA1000) used to have external battery units that could be attached to it, like this photo:Mine does not have that external Power Connector though, but is it safe to assume that the transformer and the charging circuit can withstand more capacity since a lower model can use external battery packs?Also is not safe to assume as an APC product that the charger will have the proper protection for overloading?Here are other people doing the same thing with the same model:http://www.hearth.com/talk/threads/pellet-stove-battery-backup-on-a-budget.61296/http://nissandiesel.dyndns.org/viewtopic.php?p=20961&sid=230ea897e4e53995f8829ff0f098f05b#p20961Thank you.

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 16, 2014, 01:03:09 am
content: This expansion external battery pack does not seem to include anything more than 2 more battery packs in it. (4 batteries with 12v 18ah ratting)http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SUA24XLBP

author: SeanB
author_rank: Super Contributor
timestamp: July 16, 2014, 04:48:36 am
content: Just remember that a lot of the cheaper UPS units do not isolate the battery from the mains, so it will be internally connected by some path to the incoming mains, and will float at some high voltage with respect to ground. Thus make sure the covers for the batteries and the cabling are rated for mains voltage, and place the batteries in an insulated housing. The lack of isolation is done to make the internal mains monitoring easier and cheaper, and is fine with the original batteries inside the housing as they are isolated by the case. Any control from the computer side is done using a simple board with 2 opto isolators on it to drive the serial port, or to drive the USB-serial adaptor on the newer boards.

author: pickle9000
author_rank: Super Contributor
timestamp: July 16, 2014, 05:40:19 am
content: Most RV parts stores sell plastic head to toe weather proof covers for batteries.

author: Skimask
author_rank: Super Contributor
timestamp: July 16, 2014, 05:45:14 am
content: The photo in the first post was my main mode of PC ops for a number of years... A cheap 12VDC->120VAC 750watt inverter (with an extra couple of fans on it), fed by a good 12V marine battery, charged by a decent charger that would just barely keep up with the PC under max load, battery sitting in a plastic enclosure with vents/etc. Power was fairly spotty where I used to live and the system would easily run for an hour or more under battery power alone. If the power was going to be out for a few hours or more, I could easily charge up the battery off the car every hour or so. Good times. IIRC, the whole thing cost me < $200 to set up with the battery being the most expensive. That was 12+ years ago and I'm still using everything on my NAS. Works good enough...

author: Psi
author_rank: Super Contributor
timestamp: July 16, 2014, 06:01:21 am
content: My UPS smelt a bit hot/burny when i tried to run it for much longer using bigger external batteries.Adding fans sorted that problem out just fine.

author: johansen
author_rank: Super Contributor
timestamp: July 16, 2014, 08:05:25 am
content: i recently blew up my 1500va rack mount APC UPS while experimenting with it and making a number of detailed observations.First off, these line interactive true sine wave machines can indeed be used indefinitely at about 75% load. provided, you beef up the 10 awg wires that run between the 50 amp APC or APP (anderson power pole) (APC has custom connectors i don't like. they are keyed differently but they are for the most part APP clones) so replace those 10 awg wires with 8 awg wires. 30 amps at 24 volts is only 680 watts.and you should glue a heatsink or three on the transformer.furthermore, the voltage drop accross those connectors is also significant and that fools the inverter into thinking the battery is discharged more than it is, so consider bypassing them entirely.installing bigger mosfets is easy enough, but the impedance of mine worked out to 8 milliohms, so i didn't bother trying that.the resistance of the lowside transformer coil worked out to 5 milliohms if i recall correctly.what i do recommend is installing an inductor in series with the low voltage side of the transformer.i used 7 turns of wire wrapped around a ferrite core of 1 inch (25mm) diameter, gapped at about 1mm physical air gap.such an inductor should cut the idle wattage in half and will also improve full load efficiency by reducing the high frequency pwm copper losses at full load as well.have fun deciphering my posts here if you likehttp://www.fieldlines.com/index.php/topic,148266.0.html

author: johansen
author_rank: Super Contributor
timestamp: July 16, 2014, 08:12:15 am
content: Quote from: dark_hawk on July 16, 2014, 12:54:02 amthose cascaded battery packs really grind my gearsyou know the solder joint on the circuit board between the 10 awg wires and the battery connector will probably melt before the batteries drain completely.

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 16, 2014, 06:09:50 pm
content: Thank you for the reply johansen.Unfortunately most of the things you said are way above the understanding for a newbie like me.I can maybe change the wire from the board to the battery and get some beefier APP connectors, but adding heat sinks to transformer or dealing with voltage drops across terminals or adding an inductor to the circuit are really beyond my understanding.The point is that I won't use the UPS at more than 10-30% load at any given time, will that put me on the safe side regarding heat from the transformer?You didn't mention what exactly blew up in your UPS.

author: johansen
author_rank: Super Contributor
timestamp: July 16, 2014, 08:03:17 pm
content: I shorted something out. still haven't found what.if you have those split clip on EMI chokes, you can put a piece of tape over the core halves to insert a paper thin gap, and then clip the choke over the wires going into the transformer on the low voltage side. not both, just one of them. use as many as you can, each one will add just a little bit of inductance. they may buzz a bit but don't worry about it.and at only 30% load you'll run into no problem with transformer overheating. your ups has a fan correct?

author: Strada916
author_rank: Frequent Contributor
timestamp: July 16, 2014, 09:20:07 pm
content: I am running two small car batteries with my APC1500. Have done for over 3 years now and only topped the baatery fluid up and they still run like a charm. Have better run times too. I really do not like SLA as they die really quickly if not cycled. ie kept on float charge will kill them.

author: xygor
author_rank: Regular Contributor
timestamp: July 16, 2014, 11:30:06 pm
content: Another thing that to keep in mind: flooded cells typical of a 12V car battery generally like to be float charged at 13.6V. AGM, the type of SLA typically used in a UPS, generally like the float charge at 13.8V. Some UPS allow setting the float voltage in a service/setup menu.

author: johansen
author_rank: Super Contributor
timestamp: July 17, 2014, 02:29:11 am
content: lol, no, the manufacturers like you to float them that high. take a guess why.

author: dark_hawk
author_rank: Regular Contributor
timestamp: August 07, 2014, 08:31:50 pm
content: I want to fuse the battery cables running to the UPS.The UPS is rated at 980 Watt. Using 24V battery pack this means I need a 40 amp fuse on the positive battery cable.What type of fuse do you recommend?Will something like this one suffice:http://www.powerwerx.com/fuses-circuit-protection/maxi-fuse-holder-ring-terminals.htmlThe original RBC7 ups battery pack have a 100Amp 32V fuse between the positive and the negative terminal or the two batteries, do I need to add another fuse between the positive and negative terminal of the batteries too?

author: zerorisers
author_rank: Regular Contributor
timestamp: August 07, 2014, 08:51:02 pm
content: I did a hack like this myself to get the most storage as possible. Some batteries have shorts in them that I need to fix so I have set them up in such a way that the two that I know work are providing current while the others I believe may have shorts are in parallel. That way I can get as much storage as possible, test the batteries, And still have an operational UPS system. I am using a Back-UPS XS 1500. So you should be able to use any 12 volt batteries. 2 "lines" that are in series.(Poorly drawn example)- |- |- |- |- |- |- |________neg term of UPS+|+|+|+|+|+|+|__\- |- |- |- |- |- |- |__/+|+|+|+|+|+|+|________ pos term of UPSEach row is a bunch of batteries in parralell. Same voltage but much more storage. Both rows are in series equaling the necessary 24 volts to power the UPS. At least mine is 24 volts. I hope this helps!

author: dark_hawk
author_rank: Regular Contributor
timestamp: August 07, 2014, 08:57:02 pm
content: Thank you for the reply zerorisers.I won't add any more batteries in parallel to the 2 batteries I will be using.I figured that the original batteries are 18AH, using a 100AH is quite enough for my needs.Those are the batteries I will be using:http://www.newmaxbattery.co.kr/eng/product4.php

author: dark_hawk
author_rank: Regular Contributor
timestamp: August 08, 2014, 11:03:33 am
content: Quote from: dark_hawk on August 07, 2014, 08:31:50 pm

author: axero
author_rank: Regular Contributor
timestamp: August 08, 2014, 01:42:20 pm
content: Look at the supplied image, wouldn't this be a safe way to expand battery capacity if the charger circuit of the UPS cannot handle the extra battery?During normal operation a triple high amperage relay circuit keeps the extra bank of batteries disconnected from the UPS unit while they are kept to full charge with a separate smart charging device. Once there is a power surge, the relays close and connect the extra battery bank to the UPS unit. A ballast coil protects the circuitry from sudden rushes of current, and a diode between the banks prevents current from going the "wrong" way.