Modding a normal UPS with a bigger battery

[TheMafioso]

Hi Guys,

I have an APC Back UPS 500VA with me.
It gives me only around 5 min backup on my computer, during power faliure, which i find very less
I checked out its battery, its got a 12V, 7.2Ah Rechargable sealed Lead-Acid battery.

So my question is can i put a bigger 12V battery with Higher capacity, like say a car battery, to increase the power backup on the UPS ?

Regards

 

[BrownTown]

seems like it should work fine, but the nagain amybe a bigger battery can source more current and blow a fuse or something, but I wouldn't expect that unless there was too much laod on it. There is probably some reason why it won't work, but I am an EE student and can't find it. At least in an ideal situation it should work, real life my be differnet though.

 

[TheMafioso]

So u'r trying to say is i should keep the load on the UPS low, to avoid blowing up the fuse....?
Well the load on UPS would be the same as previous, i.e. around 200W

 

[Navid]

In fact, there are some APC units that have an optional extra battery to get and hook up to (Link).

One thing you need to consider is charging. You need to make sure that the current that the UPS provides to the battery (when on AC) is not too much or too little. I don't know if the battery technology used in a UPS is identical to what is used in cars.
Too little charge current can make the recharge time, after a power loss, very long. Too high a charge current can damage the battery.

Another possible problem is that you may not be able to fit the new (larger) battery inside the UPS unit. If you install the battery outside, the wiring may get messy (and possibly unsafe). You don't want the wires to short, which may happen if they are exposed, over time.
Make sure you do not place the battery on its side just to possibly fit it in! You don't want the acid to leak!

One more thing: Increasing the battery capacity is not going to make it or the UPS overload or blow a fuse (as long as the battery has the same voltage).
But, shorting the ports of a battery can be very dangerous. The larger the battery, the more dangerous it can be!

 

[Jeff7]

The UPSes I've worked with (consumer grade things) use sealed lead acid batteries, generally gel-cells.

 

[TheMafioso]

Originally posted by: Navid
In fact, there are some APC units that have an optional extra battery to get and hook up to (Link).

One thing you need to consider is charging. You need to make sure that the current that the UPS provides to the battery (when on AC) is not too much or too little. I don't know if the battery technology used in a UPS is identical to what is used in cars.
Too little charge current can make the recharge time, after a power loss, very long. Too high a charge current can damage the battery.

Another possible problem is that you may not be able to fit the new (larger) battery inside the UPS unit. If you install the battery outside, the wiring may get messy (and possibly unsafe). You don't want the wires to short, which may happen if they are exposed, over time.
Make sure you do not place the battery on its side just to possibly fit it in! You don't want the acid to leak!

One more thing: Increasing the battery capacity is not going to make it or the UPS overload or blow a fuse (as long as the battery has the same voltage).
But, shorting the ports of a battery can be very dangerous. The larger the battery, the more dangerous it can be!

Yeah i know, some APC UPS come which comes with external battery option, but for some reason, thier price is more than 2 times the price of normal UPS here and besides i don't wanna buy a new UPS, i already have one.
And yeah, i don't plan to fit the car battery inside...lol, i was thinking of extending the battery wires from the UPS and putting the battery outside.

Any ideas, how can i measure charge current provided by the UPS ?

 

[Navid]

Originally posted by: TheMafioso
Any ideas, how can i measure charge current provided by the UPS ?

You can disconnect the positive (red) wire connecting the battery to the UPS and reconnect it through a DC multimeter (UPS to the positive port of the meter, battery to the negative port). Connect the UPS to the AC wall outlet. You will then see the current measured by the meter.

The charge current should be at maximum when the battery is fully discharged. As the battery charges, and the battery voltage increases, the charge current should decrease.

Please be extremely cautious not to short the battery terminals!

Edit:
Corrected the polarity of the meter. If the meter is connected with the opposite polarity, you will see a negative number if it is a digital meter. If it is an analog meter, you will not be able to read a value.

 

[TheMafioso]

^^Okay, thanx for the help buddy, will try it out as soon as i get my hands on ammeter

 

[Navid]

I just realized that I gave an incorrect direction for connecting the meter!

When charging, the current flows from the UPS to the battery. So, to see a positive reading, you should connect the UPS to the positive port of the ammeter and connect the negative port of the meter to the positive port of the battery (red wire). I am sorry about that.

 

[Jeff7]

Originally posted by: Navid

Originally posted by: TheMafioso
Any ideas, how can i measure charge current provided by the UPS ?

You can disconnect the positive (red) wire connecting the battery to the UPS and reconnect it through a DC multimeter (battery to the positive port of the meter, UPS to the negative port). Connect the UPS to the AC wall outlet. You will then see the current measured by the meter.

The charge current should be at maximum when the battery is fully discharged. As the battery charges, and the battery voltage increases, the charge current should decrease.

Please be extremely cautious not to short the battery terminals!

That might not work. Chargers may be able to sense when a battery is attached, and most will provide charging voltage and current depending on the battery's current state of charge. If it's a voltmeter attached, you might not get an accurate reading of what the charger actually delivers to a battery.

 

[Navid]

Originally posted by: Jeff7

That might not work. Chargers may be able to sense when a battery is attached, and most will provide charging voltage and current depending on the battery's current state of charge. If it's a voltmeter attached, you might not get an accurate reading of what the charger actually delivers to a battery.

There is no Volt meter involved!
It is an Amp meter (current meter or an Ammeter). A current meter has a very low (negligible) resistance. The charger will not know that it is there.

 

[GalvanizedYankee]

OP, a real consideration re.run time, is heat Why do you think the high-end UPSes have cooling fans for battery run operation?? MMmm. I doubt your unit has the transformer, sinks or other componets for the extended run time a deep cycle external battery would offer. You might pick up a minuet or two but your UPS will overheat and shut down. I think even adding a fan won't help much.


...Galvanized

 

[Navid]

OP,

If you want to use a larger battery in hope of getting more power (and more VA), you are going to fail because increasing the battery capacity is not going to increase the power capability of your UPS.

But, if you want to use a larger battery to increase the run time (with the same power load), you will have no problem as far as heat goes.

The larger UPS units offer higher VA. They are supposed to provide much more current (which generate much more heat) when fully loaded.

The 500VA unit you have linked is capable of delivering 500VA (apparent) power. As long as you do not draw more than 500VA, which with your line voltage of 230V means 2.1 Amps RMS, you will have no problem with heat that you did not have before.

 

[GalvanizedYankee]

OP, I stand by my original post. Register over at badcaps.net and ask the repair techs.
They know where the rubber meets the road. Then link the reply thread here.
You will find a UPS thread over there on this topic.

...Galvanized

 

[Calin]

Originally posted by: Navid
In fact, there are some APC units that have an optional extra battery to get and hook up to (Link).

One thing you need to consider is charging. You need to make sure that the current that the UPS provides to the battery (when on AC) is not too much or too little. I don't know if the battery technology used in a UPS is identical to what is used in cars.
Too little charge current can make the recharge time, after a power loss, very long. Too high a charge current can damage the battery.

Another possible problem is that you may not be able to fit the new (larger) battery inside the UPS unit. If you install the battery outside, the wiring may get messy (and possibly unsafe). You don't want the wires to short, which may happen if they are exposed, over time.
Make sure you do not place the battery on its side just to possibly fit it in! You don't want the acid to leak!

One more thing: Increasing the battery capacity is not going to make it or the UPS overload or blow a fuse (as long as the battery has the same voltage).
But, shorting the ports of a battery can be very dangerous. The larger the battery, the more dangerous it can be!

If the UPS assumes it loads a battery with a certain internal resistance (like a deep cycle small battery, optimized for slow charge/discharge), the UPS could deliver too much current to a bigger battery - with lower internal resistence. If the current the UPS wants to give to the battery is too much, it will blow the UPS's power IN fuse

 

[Navid]

Originally posted by: Calin
If the UPS assumes it loads a battery with a certain internal resistance (like a deep cycle small battery, optimized for slow charge/discharge), the UPS could deliver too much current to a bigger battery - with lower internal resistence. If the current the UPS wants to give to the battery is too much, it will blow the UPS's power IN fuse

The voltage of a battery changes significantly as it charges. So does the charge current (the lower the battery voltage, the higher the charge current up to a limit defined by the charger current limiting circuitry). The UPS should be able to handle that change in current. The difference in the charge current due to the internal resistance difference between two different batteries should be negligible compared to that.

A fully depleted battery would draw the maximum charge current when initially placed in a UPS and plugged to the wall. Would you expect a UPS to blow out a fuse if you put a fully depleted battery in it?

You have a point. Changing the battery of a UPS with a different model should be only attempted after taking every aspect into consideration.

 

[wwswimming]

once i worked for a company that made test bays for aircraft carriers, including UPS'.

we had one product that had the equivalent of 18 car batteries for battery backup.

one day it shorted. it made a plasma ball about the size of a soccer ball. i didn't hear about it for about 20 minutes. by the time i got there most of the smoke had gone and there was this "sculpture" where the UPS used to be.

basically it was like that scene in Terminator 2 where the 2 Terminators materialize in a "plasma ball" and everything in the way gets kind of vaporized.

though, with the UPS, it wasn't kind of vaporized. it was GONE. aluminum, stainless, circuit board, everything.

lucky nobody got hurt.

 

[Navid]

Originally posted by: wwswimming

once i worked for a company that made test bays for aircraft carriers, including UPS'.

we had one product that had the equivalent of 18 car batteries for battery backup.

one day it shorted. it made a plasma ball about the size of a soccer ball. i didn't hear about it for about 20 minutes. by the time i got there most of the smoke had gone and there was this "sculpture" where the UPS used to be.

basically it was like that scene in Terminator 2 where the 2 Terminators materialize in a "plasma ball" and everything in the way gets kind of vaporized.

though, with the UPS, it wasn't kind of vaporized. it was GONE. aluminum, stainless, circuit board, everything.

lucky nobody got hurt.

This is a serious matter. But, I cannot stop laughing. I am sorry!
Any pictures you can share in the public domain by any chance?

 

[wwswimming]

that was in 1990.

it was a rack mount box, maybe 15 inches high. had some large transformers & circuit boards inside. the circuit boards were about the size of an ATX MB, maybe 2 large circuit boards in the box. transformers towards the rear.

till it went "poof". gnarly fumes. wouldn't have wanted to breathe that.

the company had been bought in a leveraged buyout for $17 million in about 1985, and then re-sold for $40 million to a British company towards the end of 1989. there were 5 managers involved in that get-rich-quick scheme. they did all sorts of things to boost the appearance of the company. like bidding 9 month jobs at 3 months, to get the order on the books. then, after the sale, they tried to cancel the contract, because it was a money loser. the customer threatened to sue, big-time. so they sat down with the engineers and said, "you have 3 months to do 9 months worth of work. Go !"

after i'd been there about 3 months, i told them "this is not how to do engineering." they had hired me as a mid-level manager. i left.

about 3 months after that, one of the techs - who had been laid off, with a family to support - came back, packing heat. he shot and killed one of the 5 vice presidents that was also one of the primary slave-drivers (VP manufacturing).

among us engineers, there was not a lot of respect for the "LBO 5".

to what extent the exploding UPS was related to shortcuts taken because of bad management, i can't say (i don't know).

 

[Navid]

I am seeing references to car batteries generating hydrogen gas! I did not know that.
Hydrogen is highly explosive!

Based on that, and also the possibility of acid leakage, I highly advise against using a car battery indoors.

 

[RayH]

Originally posted by: Navid
I am seeing references to car batteries generating hydrogen gas! I did not know that.
Hydrogen is highly explosive!

Based on that, and also the possibility of acid leakage, I highly advise against using a car battery indoors.

Excellent point. Most car batteries are meant for starting and not deep cycling which is what you would want for a UPS.

The only car batteries I would consider are sealed ones that are made for deep cycling like the Optima yellow tops.

 

[SparkyJJO]

Originally posted by: RayH
The only car batteries I would consider are sealed ones that are made for deep cycling like the Optima yellow tops.

I was going to say the same thing.

One of my friends had an old APC UPS that the battery died in, so he hooked up a couple car batteries (not sure if they were sealed or not) and it worked fine. It was ungainly and messy looking but it gave him a long run time. Took forever to charge those batteries though

 

[Calin]

Originally posted by: Navid

The voltage of a battery changes significantly as it charges. So does the charge current (the lower the battery voltage, the higher the charge current up to a limit defined by the charger current limiting circuitry). The UPS should be able to handle that change in current. The difference in the charge current due to the internal resistance difference between two different batteries should be negligible compared to that.

A fully depleted battery would draw the maximum charge current when initially placed in a UPS and plugged to the wall. Would you expect a UPS to blow out a fuse if you put a fully depleted battery in it?

You have a point. Changing the battery of a UPS with a different model should be only attempted after taking every aspect into consideration.

Would you expect a UPS to blow a fuse if you short circuit its battery terminals? If so, then batteries (car batteries especially) have very low internal resistance

 

[Navid]

Originally posted by: Calin
Would you expect a UPS to blow a fuse if you short circuit its battery terminals?

I expect the UPS to have a limiter at its output (to the battery) to limit the maximum current that it can send out. So, if you short the output (to the battery) of the UPS, it should only provide a (limited) constant current through the short.

 

[TheMafioso]

Originally posted by: RayH

Originally posted by: Navid
I am seeing references to car batteries generating hydrogen gas! I did not know that.
Hydrogen is highly explosive!

Based on that, and also the possibility of acid leakage, I highly advise against using a car battery indoors.

Excellent point. Most car batteries are meant for starting and not deep cycling which is what you would want for a UPS.

The only car batteries I would consider are sealed ones that are made for deep cycling like the Optima yellow tops.

I can safely say, its not the case, as i have seen people using car(or rather truck) batteries with UPS that come with external battery support.

As far as the MOD goes, these day's i'm really busy 'coz of exams, so couldn't try it out, but sometime next month i will give it a go...

Thanx for all your replies guyz . AT rocks!!!