Higher Rated Replacement UPS Battery

Hi All,

I've circulated this question before but am still not 100% sure of the answer.

I have 2 generic UPSs both rated at 1400VA

One has 2x7.2Ah Batteries, the other has 2x12Ah Batteries.

I would like to replace all with 20Ah batteries.

So there would be a large increase in Ah for both the UPSs.

I know that this is possible but there are a few problems.

1) I contacted the manufacturers of similar UPSs and they said no, you must use the same battery or it will burn out. I just think they want me to buy a bigger UPS, which I will not.

2) Apparently if you you use a higher Ah battery, it will recharge slower so to fully recharge it will take more time.
The problem with this is that if it slows down too much there will be hardening of (forgot what) on the battery inside and it will reduce the life of the battery.

Now the thing is that the 20Ah battery will give me more life, which is what I need, but I don't want to go out and waste money on batteries which will just blow my UPS or which will die within a few discharges.

I really need some definite answers from people in the know here.

Thanks
Peter
Pete2003Asked:
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tmj883Commented:
Can the charging circuit withstand the prolonged charging cycle and associated heat? Most likely. If the batteries fit in the case physically,,,go for it...T
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nobusCommented:
there is a catch to using bigger batteries:
a battery is charged with a current, let's say 10% of the max current, and so is the circuitry that delivers it designed.
Now you can probably hook up a bigger battery, and let it work; however, if the battery gets discharged much, the needed current to recharge it may exceed the capacity of the charging circuit.
If there are limiting circuitry in this, there should be no big problem. If there is no limiting circuit, you can burn out the charging circuit.
If you want to try it, i suggest trying with a resistor or bulb charge to unload the battery.
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Steve McCarthy, MCSE, MCSA, MCP x8, Network+, i-Net+, A+, CIWA, CCNA, FDLE FCIC, HIPAA Security OfficerIT Consultant, Network Engineer, Windows Network Administrator, VMware AdministratorCommented:
I would look a the design of the circuitry inside and if the circuitry can handle the additional load.  The charging system might not be able to handle it.  You must also look at warranties too.  Many of the UPS's, APC for one gives a warranty to cover the connected equipment should something attached to their UPS get damaged or destroyed.  I can guarantee that using non standard or recommended batteries in their UPS's will void that warranty.
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mysticaldanCommented:
Larger batteries is definately equal to more backup time but the main thing as all the experts above have mentioned is the charging part. If we go by what you say then even a small 250 VA UPS shud be able to charge large batteries much larger than the capacity.

Thats where things change. To charge a battery a reverse current is circulated thru the circuit leading to a reversal of the chemical process and shifting equilibrium in a manner that the batteries can get charged. Now this current is a certain value, excess will lead to breakage of ions in the battery rendering it useless which is why battery chargers taper of the current as the batteries keep getting charged.

Less current will mean that the current flowing in the forward direction is more than the currrent being applied in the reverse direction to charge the batteries. So either it will charge very slowly or might not charge at all. If the circuit is in such a way that the charging current can vary then the charger might try to apply more current to charge the battery and burn itself out. Usually for a 1400 VA UPS u shud be able to charge batteries for upto a 1600-1800 VA UPS without too much trbl but any more is asking for trbl. The battery size u mention is almost for a 2400 VA UPS so i doubt if thats gonna work for u .

Dan
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Pete2003Author Commented:
The UPSs were dumped by my company cos the batteries were dead .. they have no warranty and are old 1400VAs ...

The only thing that worries me that on the standard 7.2Ah  and 12Ah batteries even one PC will nos survive more then an hour .. with bigger batteries I can run it longer and our power outs are between 1-3 hours ...

The batteries don't fit but i don't mind .. I just don't want to spend money on batteries I'll have to use as door stops on the day I get them
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nobusCommented:
Well, in that case, try it as i suggested, let them unload for 40-60% on a resistor load, and try charging them with the load attached. if it works, you're fine, if it doesn't, what's your loss?
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Pete2003Author Commented:
can you please explain 'bulb charge' and resistir load ??? I'm not sure what you want me to do there
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Pete2003Author Commented:
and the loss is about U$1000 for all the batteries ... they expensive over here ...
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mysticaldanCommented:
well no easy way out of that. What u can try is to get ur charging circuit fortified and use External Batteries instead. In that case ur UPS act like voltage regulators and make sure that the batteries keep getting charged regualrly. I have  similar setuup with  1200 VA UPS with huge batteries but for that I had to get my charging circuit redone and they attach externally now. They work fine although they dont charge that fast but they get the work done for me.

Dan
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Pete2003Author Commented:
ok then the $1000000 dollar question .. how do I get my circuit fortified and can I do it myself ??
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nobusCommented:
bulb charge = light bulbs, like from car lights
resistor load = you can use any resistor with the necessary wattage to uncharge the battery; current calculation is done with Ohm's law :
r = V/A; so with a 12V battery, a 1 ohm resistor will draw 12A, while a 2 ohm one will draw only 6A
the light bulbs are a cheap resistor replacement, AND indicate also when the voltage drops.
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mysticaldanCommented:
Nope.. it wud be better to have someone have a look at it since all charging circuits are differently made. I am not sure if the UPS guys wud listen to you so that u buy a newwer one from them.

Dan
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Pete2003Author Commented:
hmm .. ok cos I don't know who could look at it .. I searched on the net and didn't find any cluse on how to do it ... so I'm still,  after all that,  not sure if I can buy the bigger batteries ..
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nobusCommented:
Can't you find the specs of the UPS? if there is something like max load current; or load current limit - you may have something.
just curious : how many batteries would you have for 1000$? Man, that's alot of money...
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CallandorCommented:
You should be able to use bigger batteries, as long as the voltage is the same.  Trickle chargers are used for keeping car batteries fully charged, and they output a miniscule amount of current.  APC also lets you hook up battery packs to extend run times, so this is a tried and true practice.  For more reading, see here: http://www.pcguide.com/ref/power/ext/ups/funcCapacity-c.html
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Pete2003Author Commented:
8 batteries .. 20 AH each
 
And there is nothing ... the manufacturer doesn't know the specs as they no name brands ..

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nobusCommented:
is there no indication, or number?
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Pete2003Author Commented:
It's a blazer 1400 ... but a lot of diffrent companies use the blazer name / range
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nobusCommented:
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Pete2003Author Commented:
I've seen that one and their support pple said I can't connect ... so don't know if it's a sales pitch or what

The batteries are for the one 7.2Ah x 2 and the other 12Ah x 2 both for the 1400 VA ...

Now looking at the specs .. not sure if they allow me to add a bigger battery
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nobusCommented:
here :

http://catalog.bestsol.com/catalog/pdf/Blazer_1000_1400_UPS.pdf

they say : discharge, overcharge and overload protection; look at the email down under for asking a question too

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Pete2003Author Commented:
ok so that means that the UPS should be fine ... does that also mean that the battery wan't get used up to quick ?
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Pete2003Author Commented:
Increased points cos I'm nagging so much :)
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nobusCommented:
>>  does that also mean that the battery wan't get used up to quick ?  << you mean the battery life? that depends on the battery characteristics, you can look them up when you're ordering them

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ridCommented:
If you are using any kind of normal UPS these batteries are lead-acid. A larger battery takes a little more charging current, but the difference between a 7.5, 12 or 20 Ah battery is small when it comes to charge current. A drained 7.5 Ah battery will take a hell of a charge current until the cells have built up EMF, because the internal resistance in these cells is so low.

I think you can safely switch batteries to 20 Ah type. The possible danger is of course a badly designed charge circuit, BUT if the UPS is really uninterruptible, the same circuits that charge the batteries will also feed the AC inverter that in turn feeds your equipment. Thus, if your batteries are drained, you will be safe (in my opinion) if you can avoid using full power output during the first part of the charge cycle.

Also, lead-acid batteries are normally charged with constant voltage chargers. This means that the larger batteries will be fully charged after a bit longer time than the origina ones, but they *will* be full eventually. Charge current will be high in the beginning, but then it tapers off as the battery voltage increases.
/RID
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DabRainCommented:
I have a tech friend that hooked up a car battery to a 300va ups that originally had a 7.2ah battery in it, and he ran it for several years like that with no problems.

The bigger the battery the longer it will take to discharge under load and also to charge as you may find your ups' have a fixed max charge rate.

Charge into a battery is regulated by the voltage supplied by the charging circuit and the battery actually regulates the current to it if it is not in a current regulated charger like a ups. Ideally the voltage should not go above 13.9v for a 12v battery.

I would put an ammeter in line with the original batteries to see what the charge current is then put the new batteries in and check their charge current, if it is similar then don't worry. but if it is a lot higher get an electronics tech to see if he can work out the charging circuit or add a current regulator into the circuit.
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Pete2003Author Commented:
All these UPSs have Fuses .. I think I'll just bit e the bullet and see what happens .. thanks all
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