Found a free UPS with dead battery

[nobb]

Hi.
I found a Tripp-Lite Internet Office UPS for free. Inside, it came with a 2.2 aH lead acid, which was dead. I replaced the battery with a spare 4 aH lead acid that I had laying around. I then tested the UPS by plugging it into the wall and plugging something into the UPS. When power was removed, the UPS did its job and kept power going to my test load. So then I left the UPS plugged in and after a few days, I noticed that my battery was drained to 11.4 volts and the UPS would not be able to perform its job. So I was wondering if anyone knew what is happening? Do UPSs "sense" the type of battery plugged into it? I thought all lead acids should operate similarily with similar charging and operating voltages. So shouldnt any lead acid work with any UPS designed for lead acid? Also, if no one has any idea one why this may be, does anyone know of a way to turn a UPS into an inverter? The UPS only activates once it has been supplied with 120 VAC and that voltage is removed. I was just wondering if there was a way to just turn the UPS on and off with a simple switch connected somewhere.

 

[MWink]

I've seen almost the exact same problem with another UPS. It turned out to be a blown micro fuse. I replaced it and it's worked perfectly ever since. The fuse probably blew when it was trying to charge the dead battery. Like yours it would work when connected to a charged battery, but would slowly drain the battery even when connected to AC. Depending on how much you know about working on electronics, you might be able to fix it yourself.

BTW are you sure it had only a 2.2Ah battery? That's really small. The smallest I've seen is a 3Ah battery in APC's Back-UPS ES 350 and IMO that is not really enough to power any realistic computer. What is the VA rating of the UPS?

 

[Rubycon]

2.2 Ah is TINY! That's what's in those chloride exit signs (sometimes eagle picher) but anyway...

Don't even try to make an inverter out of those things. They have short run times for a reason! The inverter heatsinks are MINIMAL. Running them at full load for more than a few minutes will heat the transistor junctions past SOA and they will blow out. Small inverters can be had for cheap unless you need true sine wave which a cheap PC UPS most certainly is not.

 

[nobb]

Thanks for your replies. Yes it was a 2.2 Ah since I took it out myself. The UPS is rated at 300VA. I am comfortable with soldering and replacing parts on circuit boards and I was curious as to what a microfuse looks like. I've already confirmed that the "normal" looking fuses are not blown. So if I replaced the microfuse, would it blow again from trying to charge my 4Ah battery? Perhaps the microfuse was blown before? Or perhaps I should just to buy a replacement 2.2 Ah battery like the inverter was designed for, rather than trying to overload the charging circuit with a 4Ah.

In regards to the turning it into a inverter idea, I already know what the heatsink looks like and I am comfortable with modding it to dissipate more heat. I just dont know how to get by the fact that the inverter requires a 120VAC voltage to be present before going into inverter mode.

 

[MWink]

My guess is that it came with a blown fuse. It probably blew when it was trying to recharge its dead battery. I don't think it should blow just trying to charge a slightly bigger battery as long as that battery is in good condition.

The micro fuses I've seen look a lot like a normal resistor but without the stripes (obviously). You can also tell they are a fuse because the PCB may have the value printed near it, for example 125V 5A. If you want I can show you a picture of one.

 

[nobb]

Thanks for your offer for pictures, but I dont think they would be necessary. On the circuit board, the different components are labelled with R, or D, or F etc.. R for resistor, D for diode, and F for fuse. I checked all the F's (fuses) and they are not blown, so I dont think its a problem with the fuse. Thanks for you suggestion anyways.

 

[thescreensavers]

no wonder I am missing a UPS !!!

 

[MWink]

If you have another good battery or can recharge the battery you used before, you could check to make sure that current is flowing in the correct direction with a multi-meter. That was how I originally determined that the one I had the same problem with, was not charging the battery but running it down even when on AC. BTW if you have or want to take some pics of the UPS (PCB, etc.) I could take a quick look and see if I notice anything.

 

[JimPhelpsMI]

Hi, Have you checked to see if the UPS's charger is working? There should be about 13.5 to 4.5 volts across the battery when the charger is on. That is if the batt is good. MAYBE!

Jim

 

[nobb]

Wow! Thanks for everyone trying to help so far. In regards to the suggestion to check whether the charger is working, I forgot to mention that I had already tried to disconnect the battery and test the wires with a multimeter. I found it strange that the voltage was only ~1 volt instead of the ~13.8 volts required to charge lead acids. Although I cannot see anything obviously wrong with anything on the circuit board, here are pictures anyways, incase anyone is interested.


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[Rubycon]

LOL @ the solid block "heatsink".

TO220's aren't very high power devices AND look at all of the ones with bare tabs. :shocked:

Then again what do you expect for $30? That cannot even buy a Hubbell or Crouse Hinds 30A 3? 208 twist-lock. :laugh:

 

[JimPhelpsMI]

Hi again Nobb, No good to test the batt leads when they are disconnected. What really matters is what you get with the batt connected. Probably you would get voltage on the leads without the batt, but the charger may be an "Intellegent" type and thinks the batt voltage is way up with the batt disconnected. Test with the UPS disconnected from the AC. Should be above 12 V a little. They plug it in. Should then see the 13.5 to about 14.4v. If that unit sat around more than about 6 mos then the battery is sulphated and probably will never again take a charge. Batt goes down with no use in about 6 mos and sulphation starts. Completely coated plates don't work anymore. Partially coated reduces the capacity of the batt.

More luck, Jim

 

[nobb]

Hi again JimPhelpsMI. Well with the battery connected, the voltage is above 12 volts because I am using a 4Ah lead acid that is working perfectly well and is fully charged. I already recycled the old 2.2Ah that came with it. The thing is, I can plug in the 4Ah battery and the UPS works normally. By normal, I mean that the UPS can provide backup power to my computer if I were to suddenly pull the AC plug. But the problem is that after a few days, the battery will drain past 12 volts (way too low for comfort). I dont actually know how low the battery will drain, and I dont intend to find out because I dont want to destroy a perfectly good 4Ah lead acid.

Btw, did I mention I got the 4Ah lead acid for free too? =)

 

[JimPhelpsMI]

Hi Nobb, Don't really understand. The computer etc. does not run off the battery when the UPS is plugged in and the AC Power is good. Sounds like it's always running on the battery and the charger can not keep up. UPSs usually use a relay, usuallysolid state, to switch from AC to Batt operation. Maybe it's shot. Lead acid batts are usually charged with constant voltage so the voltage across the batt would be constant when the AC is present. Same as your car although car regulator has temperature compensation to give a high rate just after a start and in cold weather. Maybe modern UPSs have different ideas. My first experience was Home Office Service Dept with a Point of Sale computer nearly 30 yrs ago that had the UPS built in. The engineers that designed that quit and went into the UPS business. Any other clues?

Luck, Jim

 

[MWink]

Can you tell what that cylindrical thing is in picture 6 that is up and to the left of the big capacitor? Also to see if the charger is working you should connect the multi-meter to one of the terminals of the battery in SERIES (not parallel like when you test voltage) and see which way current is flowing when on AC and when on battery. The number should be negative or positive when in one state and switch when the UPS switches to AC or battery. If it does not change between negative and positive when the UPS switches states then logically the UPS must always be pulling from the battery (as current can't be flowing into the battery when the UPS is not connected to AC). This likely means the charging circuit is bad. I hope this makes some sense.

 

[JimPhelpsMI]

Hi, If the charger Voltage measured across the battery is same polarity as the battery and about 13.5 to 14.5 volts then the charger is working. If your multimeter can handle up to about 10 amps then it might be worth it to check the charge current. I think he has already established that the batt is good and he is charging it from an external charger. MAYBE!

Jim

 

[Rubycon]

Originally posted by: MWink
Can you tell what that cylindrical thing is in picture 6 that is up and to the left of the big capacitor? ...

Looks like a microtemp:



Text

 

[MWink]

Originally posted by: MS Dawn

Originally posted by: MWink
Can you tell what that cylindrical thing is in picture 6 that is up and to the left of the big capacitor? ...

Looks like a microtemp:



Text

Yeah I saw the thermal fuse but I was talking about the thing directly up and to the left of the big electrolytic capacitor, above the green thing, right of the diodes, and below the white wire.

 

[Rubycon]

That looks like a choke.

 

[JimPhelpsMI]

Hi, I think Dawn is correct about the "Black thing". It reminds me aslo of a "CUP CORE" a torodial wannabe. Cheaper and easier to wind than a toroid. Switching Power Supplies make use of Torodial transformers for efficiency.

Jim