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UPS Question..


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Guest Kasamiko

Today I got an APC Back-UPS 600 with a dead battery inside, I replaced the battery with a bigger truck battery about 60AH capacity, I know that the ups has a build-in charging circuitry for its battery but I don't know if it will function the same if attached to other kind of battery? The same voltage, different capacity..


Rhonn

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Guest Kasamiko

The original battery is two 6 Volts Lead-Acid type connected in series..

@
"I hope that the charge circuitry doesn't have a charger timer."

I'll be looking for its schematic to verify that.. ;)

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Rhonn,

It's a very low current charger, which will spare the battery (which is good) but. Question is: will the current be high enough to fully charge a battery with much lower internal resistance? You have to monitor the charging over time to se if it reaches 13.2 to 13.5 Volts.

Ante ::)

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Guest Kasamiko

I wonder if what is the correct OPEN CIRCUIT voltage of a fully charge Lead-Acid battery?? Right I'm finishing the battery charger circuit that we've on the other post and I'll let you know the result.. ;)


Rhonn

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Congratulations Kasamiko!

This is about finding schematic diagram on this ups!

Well, I'm dealing with servicing all the APC upses.

60Ah is about 6 times bigger than the capacity of the original UPS batteries. So, as long it is a lead-acid battery, there will be no problems to use this external battery.

But, there is some things You have to know:

1. The charging time will be about 6 times longer than charging time of the ups with original batteries which means about 80 hours!

2. The cooling (thermal) system of the UPS is not calculated to make possible working on battery at full power more than (7-8) minutes!

3. If the internal discharging current of the new battery is essential, the battery will not be able to charge to 100% of its cappacity.

You cal easily test the charging process of measuring the battery voltage while the ups is charging the battery. Remember to wait enough, because the charging current is low for such kind of battery. The battery is fully charged when the voltage of the terminals while the ups is charging it is between 13.6 - 13.8 V

If You like to charge the battery faster, You can make external charging unit and You can switch off the internal charger of the UPS by simply break the charging diode which is in series with the charging circuit.

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Actually, Deep Cycle batteries have their own inherent problems. I would stick with the common less expensive automotive battery if you must use a lead acid battery. LDanielRosa is correct that the automotive battery does not take well to discharge. You should make sure that the battery is kept charged. Another thing that most design engineers leave out of a design is some sort of loading. Batteries also do not like to be left dormant. If you will use a battery in a system where it will not be in use for long periods of time, you should add some type of loading circuit that comes on at a specific time interval to keep the battery in some type of light function instead of just sitting there dormant. Another concern is battery temperature. If the battery will not be indoors, then the temperature should be monitored. Most people know that batteries do not like to get real warm which is a reaction usually due to charging, but batteries do not like the cold temperatures either. In places where the battery will be stored in cold temperatures and not used a lot, I usually allow a heater circuit as the loading circuit that I just mentioned. This will keep the battery active and will keep the temperature at a level which will allow the battery to last longer.
All of the little tricks for batteries help to keep them functioning longer so that you do not need to replace them quite as often.

MP

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Guest Kasamiko

The charging voltage of the ups goes beyond 13.5 VDC.. which I think is high enough to maintain the battery at full charge. Since mostly what I experience is not a total power failure (Blackout) but a sudden "DROP" in our AC supply or a brownout that last only for about 10 seconds.. The battery with this capacity will never be discharge fully..
The battery is always keep fully charge since the ups is always turned ON.
Now based on the charging circuit schematic that I attached, is there anyway that my battery will be overcharge?? This is my most concern..

@ grigspace
Since your servicing APC UPSes, will you be kind enough to send me some USERS MANUAL for this particular model (Back-UPS 600)
I saw a DIP switch at the back of the unit and don't know what the're used for..

Best Regards to all.


Rhonn ;)

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Can you tell what the charging voltage is? (The regulator cut-off?)You might be ok. If not, you can build a regulator. I would be surprised if this unit did not already have one in it. In this case, you could adjust it if it is not where you want it.

MP

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I'm attaching the sheet You need.

In fact, Back-UPS 600 is a very old model and is no longer manufactured.
But these series of UPSes on APC is a very hard made with very detailed manulas. You can do all with this UPS - there are variable resistors inside with wich You can adjust all tha parameters on the mashine. Unfortunately this is different at next generations of Back-UPSes....

If You need different manuals than this, I'm attaching, You can visit this link:
http://www.apc.com/tools/mytools/index.cfm?action=umfamily

If I were You, I would make external charging system with automatic discharg cycle every week at about 50% of the capacity.

Back-UPS_BK250_BK400_BK450_BK600_BK900_BK1250_Sheet_2008-6.pdf

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Guest Kasamiko

@MP
I monitor the voltage at the battery terminal while the UPS is ON, and I measured 13.5VDC +/- 2 volts.
Look at the attached schematic and please make a comments.

@ grigspace
Thank you so much for the file..that was very detailed. ;D
and I agree with you..it is very rugged and hard-working machine..
Unfortunately this was designed for 120VAC source and I'm on 220VAC, can I convert it to suit my needs??
Can you also supply me some data for some "TWEAKS" you mention..
BTW: I check your link and got this error:

"Element PCATNAME is undefined in FORM.


The error occurred in D:\iis\server\docs\tools\myTools\umsearch_family.cfm: line 185
Called from D:\iis\server\docs\tools\myTools\index.cfm: line 330
Called from D:\iis\server\docs\tools\myTools\index.cfm: line 328

183 : <tr>
184 :    <td height="38" colspan="2" valign="baseline" class="bodyText"><p> <span class="bluesmall">
185 :             <a href="javascript:history.go(-1)"><span class="bluesmall"><cfoutput>#FORM.pcatname#</cfoutput></span></a>
186 :       
187 :             <cfif FORM.selectpscat IS "Unspecified">

"

Thanks again.


Rhonn ;)

post-0-14279141636371_thumb.gif

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Guest Kasamiko

It never goes above 13.8 VDC.. ;D ;D and I'll keep an eye for the water level..
I'm drawing the schematic of a battery charger I found on Encyclopedia of Electronics Circuit III and planning to post it as soon as I finish and let see if it is suitable for my needs..

Here's the schematic of a battery charger I used before. Take a look..

Rhonn ;)

post-0-14279141636568_thumb.jpg

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Guest Kasamiko

The circuit confused me too MP.
The actual circuit does not provide the value for the transformer. I just used the value of some common charger I found.
The text says " a seperate connection is provided for external charger when GREATER THAN 3 AMPS. is needed to charge a partially discharge battery" this makes me conclude that the transformer can't supply greater than 3 AMPS.!
Now if the transformer can't supply more than 3 Amps., what is the purposed of 2 overkill power transistors??
With big filter capacitor at the input and 2 power transistor, it looks like a regulated power supply to me used in HAM equitpments..
What can you say?? ???


Rhonn ;) ;)

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Guest Kasamiko

Hi ANTE,
The original circuit has no value for the transformer, I just copy the value of the transformer used in this project.

http://users.otenet.gr/~athsam/car_12v_battery_charger.htm

which uses a 17 Volts 4 Amp. transformer. You might ask me what makes me conclude? The article says
" you can connect another external charger when GREATER THAN 3 AMPS. is needed to charge a partially discharge battery"
So I assumed the transformer can provide more that 3 Amps. Am I right? ???
But what is the function of 2 series pass transistor? aren't they function as some sort of regulator??
Confusing or deceiving?? ??? ???

Rhonn ;) ;)

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Rhonn,

The voltage at the bases can be adjusted between 6.5 to 11.5 volts if my calculations are right. The voltage at the collectors is about 25V, does this make any sense to you? The output will not charge a 12V battery, or am I missing something?

Ante ::)

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Guest Kasamiko

Honestly ANTE the actual transformer I'm using right now is 36 Volts Center-tapped (18-0-18) @ 20 Amperes. Since it looks to me as regulated power supply, I adjusted the trimmer for 13.8 VDC and got a RPS for my HAM equiptment.. ;D

Rhonn ;) ;)

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