SUA 1500

[Anonymous user]

The model number is actually SUA1500

I saved a SMT 1500 from the trash yesterday. I got it home and plugged it in, and when I powered it on, the online light blinked a few times, then the alarm went off and the replace battery light was flashing. This thing looked as though it had never been used, so I popped it open to see if there were any smoking guns inside. Inside was imaculate, and I took a voltage reading and got 26VDC. I put it back together, simply plugged it in and I had 1 charge light lit. Let it sit for a half hour and a second lit. I thought great, the battery was completely discharged and just needed to get charged up. Left it plugged in a few hours and went up to 5 bars. I was happy and left it plugged in over night. This morning I hit the power/test button and I got the dang alarmn and replace battery light again. I opened the disconnect on the back and took some voltage readings there, and I was getting 17.5VDC. I got confused and opened it up again and took a reading at the terminals and got 27VDC. So this thing did a proper charge, but there is something else wrong internally it looks like. I am trying to figure out how to repair this thing, but I'm not sure how to move ahead without schematics or drawings. I am pretty sure the battery itself is good, as 27vdc sounds about right for a 24v lead acid battery. But 17.5vdc at the disconnect doesnt sound right at all. And Im guessing the circutry is sensing this bad voltage and that is why I am getting the replace voltage warning.

Any ideas out there?

Message was edited by: blitzgp

[Anonymous user]

The model number is actually SUA1500

I saved a SMT 1500 from the trash yesterday. I got it home and plugged it in, and when I powered it on, the online light blinked a few times, then the alarm went off and the replace battery light was flashing. This thing looked as though it had never been used, so I popped it open to see if there were any smoking guns inside. Inside was imaculate, and I took a voltage reading and got 26VDC. I put it back together, simply plugged it in and I had 1 charge light lit. Let it sit for a half hour and a second lit. I thought great, the battery was completely discharged and just needed to get charged up. Left it plugged in a few hours and went up to 5 bars. I was happy and left it plugged in over night. This morning I hit the power/test button and I got the dang alarmn and replace battery light again. I opened the disconnect on the back and took some voltage readings there, and I was getting 17.5VDC. I got confused and opened it up again and took a reading at the terminals and got 27VDC. So this thing did a proper charge, but there is something else wrong internally it looks like. I am trying to figure out how to repair this thing, but I'm not sure how to move ahead without schematics or drawings. I am pretty sure the battery itself is good, as 27vdc sounds about right for a 24v lead acid battery. But 17.5vdc at the disconnect doesnt sound right at all. And Im guessing the circutry is sensing this bad voltage and that is why I am getting the replace voltage warning.

Any ideas out there?

Message was edited by: blitzgp

[Anonymous user]

I am having a similar experience with two SUA1000's. I installed new batteries in both and get similar results. Proper voltages, minimal heat, full charge as indicated by both status lights and powerchute. But when I reset the units the charge goes back to nothing, the batteries still show 27.4 volts but the unit starts another charge cycle. I thought I might have picked up bad batteries until I tried a battery from a fully functioning SUA1500 in both units and got the same results. I expect it's something wrong with the charging circuit, possibly the mosfet's but I haven't had time to check them.

[Anonymous user]

whem i pulled the battery i pulled off the plastic cover on the vents/terminals and tested there. after it went throught he charge cycle, i tested at the disconnect and got the 17.5, which made no sense, so i pulled the battery again and tested and got 27. i might not have been using the correct terminals, but i did test the battery directly and saw a 1v increase from pre charge and post charge. however, when i retested the unit and got the alarms, i was doing some of the other tests, like just using battery power and i was having all sorts of light shows and beeps. i was testing using a tiny fan as the load, and it would sporadically power up and down as i was testing. After my tests, i plugged the unit back in and it started the charging sequence over again. Started off with online light lit, and the bottom charge light blinking, then after a while went solid, and at this point, the 4th light is lit. Is this charge circuitry voltage based or time based? I am waiting for it to finish this charge cycle, but it is not generating any heat, so I dont think it is doing anything at all.

[Anonymous user]

when i plug it in, there is either 1 solid light or 1 blinking light in the battery bar which should be 0-24% battery capacity per the instruction manual. its probably just based off voltage, which in reality should be 20VDC (I dont know the exact curve for the specific battery, but with a 24VDC nominal voltage and a 27-28vdc max capacity voltage, 20vdc sounds about right for a fully discharged battery). Over a period of a 1-2 hours, the lights will slowly light up until all 5 are lit. This will stay like this indefinately, the online light lit and 5 battery capacity lights lit. When I unplug the unit, the battery capacity light drops to 1 or 2 bars, does the normal alarm that you are on battery power, then after a few min, the continuous alarm goes off indicating 2 min left, but this only lasts for 15-20 seconds. However, the battery still has 27vdc taken at the internal disconnect. I am trying to decide if there is a problem with the battery or the circuitry.

edit the test load I was using is a tiny little fan that draws hardly any current. I also added a 100w light, but it would only power on for a very short amount of time.

I got it for the price of "not putting it in the garbage", and I assume it is out of warranty so there is no point to pay for it to be serviced or looked at, on top of shipping a 50lb unit around. However, if it is just a burned out battery, the cost of a replacment is actually justifiable for a commercial grade ups.

I am kind of leaning towards a circuitry issue, because no heat is generated in the cell. If there was any internal short, this sucker would heat up pretty bad. It should also heat up on charge or discharge, which it is not. So basically I am getting conflicting indications. On the charge cycle (which is why I was asking if the charge cycle was time based because larger battery charges are in fact time based) I get the lights indicating a full charge (along with on contact voltage readings), but during discharge mode, it indicates 24% or less, and rapidly decays to 0 in under a minute.

Basically my next step is to turn this into a science experiment and gut the unit and attempt to weld with the battery to test its actual capacity, but I dont want it to come down to that, lol.

Message was edited by: blitzgp

[Anonymous user]

does the powerchute software allow you to perform equilizing charges? or any other special charges and or capacity testing? i havent been able to install it yet because i cant find any of the old scholl stadard usb cables

[Javik_apc · Accepted solution]

You need to replace the batteries and it will probably be fine.

Old lead acid batteries that are almost totally shot can sometimes be recharged a very small amount, totalling something like 0.1% of the original capacity.

Most battery chargers are stupid and only measure cell voltage to determine charge status, but cannot tell what actual capacity is available. So yeah as you charge the ruined battery, cell voltage does slowly climb, so yeah the charge indicator also climbs.

But full charge in this case means practically nothing since what you have is maybe 0.1 amp-hours available in a "fully-charged" battery pack that was supposed to hold 100 amp-hours. Put any actual load on it like the UPS self-test, and battery voltage instantly bottoms out because it cannot supply the amperage to maintain the voltage.

The charge indicator on the UPS is mostly a liar, which is why run-time calibrations are needed to make the UPS more honest about what amount of runtime really is still available in an old battery pack.