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Ben333

Folding for Team 32!
Joined
Feb 18, 2007
So what if I just used a cheap car battery with thick wires in place of the UPS battery? Are you saying that the battery would die pretty fast or faster than a lead or calcium battery would? I'd like to just get the cheapest battery I can that will take the 220w load of my server (said by UPS utility) for say an hour, the longer the better but if a good quality battery will make a noticeable difference or last longer then I might look into one.

EDIT: Also, what do you think of these? http://www.bgmicro.com/index.asp?PageAction=VIEWCATS&Category=298 (thinking the last or second to last) Would a couple of those in parallel do better than my stock battery?
 
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OP
Freezer7Pro

Freezer7Pro

Member
Joined
Apr 20, 2008
Location
FINLAND. EVERYTHING IS EXPENSIVE HERE.
So what if I just used a cheap car battery with thick wires in place of the UPS battery? Are you saying that the battery would die pretty fast or faster than a lead or calcium battery would? I'd like to just get the cheapest battery I can that will take the 220w load of my server (said by UPS utility) for say an hour, the longer the better but if a good quality battery will make a noticeable difference or last longer then I might look into one.

EDIT: Also, what do you think of these? http://www.bgmicro.com/index.asp?PageAction=VIEWCATS&Category=298 (thinking the last or second to last) Would a couple of those in parallel do better than my stock battery?

Massive TL;DR coming up again.

Well, the batteries in the link are probably smaller than the stock ones in your UPS, I'm afraid. Most UPSes in that class use two 7 or 12Ah batteries in series, so that wouldn't offer much improvement. You could hook them up in parallel, but then the problem is the same as last time; They would get discharged at different rates.

You should first of all open up and check what batteries there are in the UPS, so you're sure you get the right voltage when you buy new ones. If there are two batteries, you have to get two batteries.

To offer any kind of improvement in runtime, you should look into 17-18Ah batteries if the ones in your UPS are 7Ah, and a bit over 20Ah (22-28) if there are 12Ahs in it.

If the load from your server is 220W, and you want an hour of runtime, it's quite easy to figure out what you need. If we take it that the UPS is 85% effective (pretty typical for home ones) at that load, we get a power draw of 253W from the batteries. That means you will need at least 253Wh of power in your batteries, or 21Ah in a 12V configuration. However, this is where the tricky part comes in. You see, lead-acid batteries of all kinds are less effective when discharged rapidly. In a one-hour discharge cycle, you'll only get about 50-60% of the actual capacity of the battery, and to make it even more confusing, you never, ever use 100% of the capacity. UPSes usually go down to about 75% before shutting down. A 20Ah battery becomes something in the lines of 9-10Ah usable power, and your current (likely) 7Ah ones are something laughable.

So, even if you theoretically only need around 20Ah, what you will have to buy is closer to 50Ah. But don't panic, this isn't as horrible as it sounds, as your UPS with quite high certainty is running on 24V, you don't need to get some 50Ah beasts, as Watts (Or capacity)=Current*Voltage, you can split it up into two batteries. On top of that, the lower current draw is much lighter on the batteries, so you can get more efficiency out of your batteries, perhaps around 70%, in which case, two 17Ahs could suffice pretty well.

As for different kinds of batteries, about every battery you use in a UPS is lead-acid, but there are many different kinds. There are normal starter batteries, like those found in cars, non-spillable gel batteries, like those in UPSes, calcium, silver... The list could go on forever. There are basically four kinds that you are interested in:

Standard batteries: The ones with caps that you find in cars. They're pretty cheap, can work pretty good in a UPS, and if kept charged can last over a decade. These are, however, designed to give massive currents for a short amount of time, rather than the fairly little one delivered for an extended period of time in a UPS, and thus get quite a low efficiency (Around 55% for one hour of discharge). These are also not very good at handling deep-cycles. 10-20 cycles (I.e, running the UPS on battery until it shuts off from low battery voltage) could ruin them and steal more than half of their capacity. They're cheap, simple, not very safe (Quite easy to spill acid if you tilt it) These can be found in any well-sorted car accessory shop.

Calcium-enhanced batteries and/or marine/golf cart/deep-cycle batteries: These are the kind of batteries I prefer. They're still fairly cheap, come in all sorts of capacity, and are generous with the deep-cycles; They can often take closer to 50 cycles before dropping in capacity, many even several hundred, and in most cases have several enhancements to improve deep-cycle- and short-term discharge performance, often hitting 70% in a one-hour discharge cycle. These usually don't have any caps on top, but instead a small chamber with a catalyst to re-combine any hydrogen gas emitted with the electrolyte, making them 100% maintenance-free, and very hard to spill. Can be found in boat shops, off-road shops and well-sorted car shops.

SLA (Sealed Lead-Acid) batteries: These are the kind currently in your UPS, and in the link you posted. These are about the most expensive lead-acid batteries you can find, but they have very strong advantages and disadvantages. The largest ones tend to be 17-30Ah, and they can reach up to 80% efficiency in quick discharge cycles, and virtually take no harm from deep-cycles at all, most being able to take 200+ without damage. They're virtually indestructible (trust me ;)), and more or less 100% safe to use. You can't spill them, you can drop them, you can hit them with a hammer, and they just work. They should make tanks out of them. Really. The disadvantages are short and clear: 1. They cost. The $:Ah you pay is ridiculous. 2. They're short-lived. Five years is the average life span, compared to 12-15 for the ones above. 3. They don't come big. If you want something that lasts during long outages, you can't get one big, you gotta get 50 small.

Motorcycle batteries: These are usually of type 1 or 3 mentioned above, and come in sizes between 4 and 20Ah. They could be something you're looking for, as two 17Ah ones in series would give you pretty much backup time, as long as you think a little about the power draw.
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
Thanks for all the info! My BackUPS has one 12V battery pack, looks just like the battery from my old UPS unit. So maybe one or two marine batteries would do the trick? I was reading an article last night about this sort of thing and the author said that to keep the battery's max capacity up you want to charge the batteries at something like 14V every now and then and top off the acid (if using car batteries).
 
OP
Freezer7Pro

Freezer7Pro

Member
Joined
Apr 20, 2008
Location
FINLAND. EVERYTHING IS EXPENSIVE HERE.
Thanks for all the info! My BackUPS has one 12V battery pack, looks just like the battery from my old UPS unit. So maybe one or two marine batteries would do the trick? I was reading an article last night about this sort of thing and the author said that to keep the battery's max capacity up you want to charge the batteries at something like 14V every now and then and top off the acid (if using car batteries).
Could you perhaps post a picture of it (battery pack), or the UPS model? You can never be sure enough when it comes to batteries.

And that charge thing is correct. You should bring your batteries up to 14.4V (15V for SLAs) at least once a year, it'll make them live much longer. You should run the battery pretty empty before doing so, though. Best is to give a topping charge after every power failure.
 
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OP
Freezer7Pro

Freezer7Pro

Member
Joined
Apr 20, 2008
Location
FINLAND. EVERYTHING IS EXPENSIVE HERE.
I've got a Back-UPS ES 750. I also had another idea, getting a good battery and a cheap charger or two and an inverter to make a UPS like this http://www.dansdata.com/diyups.htm What do you think of that method?

EDIT: Also here http://www.dansdata.com/upsupgrade.htm
Well, since you already got a good-ish inverter and charger combo in your current UPS, the point of building a new one from scratch isn't really there. Your current UPS will do a good job at charging the batteries (Given that you perform an initial full charge), and provide a cleaner output than most cheap DC/AC converters. Besides, your UPS is nothing but that first DIY UPS, only that it's in one package.

The second link is basically just about what I have done and you are about to do. He puts up quite a lot of guidelines, just like RC ratings. RC ratings are good guidelines, but they're often pulled straight out of the manufacturer's rear, I'm afraid. But hey, what isn't nowdays? ;)

To mod your UPS, all you need is to purchase a battery. A single 12V of desired capacity, as well as whatever cabling you might need. You might want to add some extra cooling on the transistors if you're planning on running on more than perhaps 40% load. That UPS isn't designed for extended runs, and it WILL overheat if put under heavy load and run it on larger-than-stock batteries. Hell, 100% load and stock batteries almost make them overheat. I suggest you take some old RAM heatsinks and stick them on the transistor heatsinks. Or perhaps remove the casing and put a fan on it.

A good plan could be to go to the local junk yard and look through the cars for batteries that aren't sulfated and have around 12.6V in them. Could snatch some little piece of gold there.
 

Hipcrostino

Member
Joined
Mar 5, 2006
Location
Canberra, Australia
well looks like i might try this too. i need a UPS for a server we run, however they have always been to expensive due to the battery replacement issue. Just found an APC 700VA 450W UPS for sale on ebay nice an cheap. Assuming i win it, i would like to hook it up to some deep cycle marine batterys (only the amount i need, one for 12v input, 2 for 24v.)

Ive read your above posts, about using thicker cables, battery types etc. Anything else i should know before embarking on this adventure, or can i just hook it all up and see. Im ok with electrics, as in i can solder and know enought to get me around a car or computer. I don't forsee any problems. Just wondering if you have any more advise.
 
OP
Freezer7Pro

Freezer7Pro

Member
Joined
Apr 20, 2008
Location
FINLAND. EVERYTHING IS EXPENSIVE HERE.
well looks like i might try this too. i need a UPS for a server we run, however they have always been to expensive due to the battery replacement issue. Just found an APC 700VA 450W UPS for sale on ebay nice an cheap. Assuming i win it, i would like to hook it up to some deep cycle marine batterys (only the amount i need, one for 12v input, 2 for 24v.)

Ive read your above posts, about using thicker cables, battery types etc. Anything else i should know before embarking on this adventure, or can i just hook it all up and see. Im ok with electrics, as in i can solder and know enought to get me around a car or computer. I don't forsee any problems. Just wondering if you have any more advise.

Well, there's not much more to say. Keep in mind that most UPSes don't drain the batteries all that much, and that lead-acid batteries have some remarkable recovery. During an extended outage, you can probably get just as much runtime again, after the UPS has shut down due to low battery, after about 12h of rest. A good idea is to get Calcium batteries, due to their higher terminal voltage (about 1V), as these will be drained much further before reaching the UPS termination voltage. You can get 30-50% more runtime out of them due to that. Non-Calcium marines tend to be designed to have a quite flat discharge curve, though, so you can probably drain one of those further than a normal starter battery, too.
 
OP
Freezer7Pro

Freezer7Pro

Member
Joined
Apr 20, 2008
Location
FINLAND. EVERYTHING IS EXPENSIVE HERE.
Today, I made a find. A very good find, too.

IMG_0001-6.jpg

At the bus stop, I noticed a couple of awesome batteries inside the doors of an office building. I took a peek at them, and they looked in need of some care a'la Freezer. Being the opportunist that I am, I went inside to ask if they were trash. I got the reply no, but I could buy them if I wanted to. He explained that they had only used them for testing the emergency lighting. We took a look at them, and I made an offer of 65€ for both, which he gladly accepted, and thanked me for getting rid of them.

Sucker.

The warranty stickers were filed in December 07, so they're just about a year old, and after measuring them, I found out that they had been stored well, and are in prime condition. I checked with the local reseller for that brand, and they cost 80€ new. A piece. Bargain.

They're about the same capacity as my main UPS batteries; 60Ah.

Now to come up with some actual use for them ;)
 

hitokiri_808

Member
Joined
Jan 23, 2005
Location
Hawaii

=ACID RAIN=

Member
Joined
May 19, 2003
Location
Kingwood, TX
I've been doing this for months now, with an old APC CS 350 and a tractor battery. So far it has run my network equipment (~35w draw) for 2 hours in a power outage :)

I had some pics but I can't find them right now. Maybe I'll take some later.
 

=ACID RAIN=

Member
Joined
May 19, 2003
Location
Kingwood, TX
Never said it died. The power came back on first ;)

It is small though, and just cost 22 bucks. I just wanted a cheap backup, nothing huge for that equipment.

I have a spare smart-ups 700 that needs replacement batteries. I might double-up on two batteries for this one, to run the DVR and HTPC.
 

=ACID RAIN=

Member
Joined
May 19, 2003
Location
Kingwood, TX
D: <-- that face always cracks me up.

I wouldn't think it would get deleted...? Topics last for years on here without getting deleted.