SMT3000 indicating incorrect battery voltage

[Anonymous user]

Hi all, really hope someone can help me out. I am getting a bit desperate ....

My SMT 3000 appears to show an incorrect battery voltage. It continously indicates the battery voltage to be 5,4 V higher than it actually is when measured with my fluke .....I have tried a couple of things like "brain dead"and "cold start" and even faking a battery replacement, but nothing will help. When disconnected, it will "give" 49,5 Volts on the battery connector, which is also strange.... 

When I connect the batteries that I have charged in another unit, and hold the fluke connected to the batteries, the batteries will show 49,2 Volts and simultanously the display will show 55,7 Volts. This is a contradiction. Consequently, the unit thinks that the batteries are full and does not charge.

I suspect there is a problem with the charging section. Somehow it's measuring fails and measures an incorrect voltage, does this make any sense ?

Anyone any clue as where to look at ?

Many thanks ahead, Michael

[BillP]

Hi Michael,

The charging or float voltage of a battery is typically higher than its nominal voltage. This is the voltage at which a battery is maintained after being fully charged, to maintain that capacity by compensating for self-discharge of the battery. 

The SMT3000 uses a 48VDC battery cartridge (comprised of two 24VDC modules) so a 49.2 or 49.5VDC battery would mean it is charged. The display would still show the higher charging voltage, as the UPS charger connectors (where the battery modules plug into) would measure around 27VDC each, so a higher than nominal voltage measurement shown on the UPS display is expected behavior.

New / good batteries would be expected to hold their float voltage for a while even after being disconnected (i.e. each battery module to measure around 27VDC), unless the measurement is applying enough load to discharge them to nominal voltage.

[BillP]

My SMT2200 went out this way, I couldn't find any faulty parts and ended up replacing it.

[Anonymous user]

Hi Szabi,

Many thanks for your reply. However the strange thing is that none of my other units have this issue. All units indicate the exact float voltage, beimg the correct voltage of 27,7 or respectively 55,4 both on the display, in powerchute and on the Fluke.

There really is an issue with this unit, but APC refuses to help out, which really is a shame. It cost me a brand new set of original batteries that have been ruined by the unit, as the unit also discharges too deep because of the voltage offset....

Cheers, Mike

[BillP]

I bought a set for my 2200 before I found out the issue was the UPS, I am starting to think my replacement may be heading that way 3 years on as the battery drops to 60% within seconds. I need to get the meter on it as I have the extended warranty.

[Anonymous user]

Hi all,

There is definitely an issue with the UPS. At least in my case.... The unit is clearly mistaking and probably due to a simple hardware failure on component level (which is not abnormal, this may happen), or to an offset in the firmware.

I am disappointed about the help I get here from APC. On the phone they keep asking me over and over whether I really used original batteries and after having me performed the same functional test over and over again they simply tell me that they can not do anything for me. APC will not take the unit in for repair.

I can understand that they can not issue me a complete service manual, but I refuse to believe that this is an isolated issue and I find that someone could be so helpful to point me in the right direction or help me out in any other way. Is that too much to ask?

For me it has become quite principal in the mean time, and I will advise my customers to contemplate alternatives

One pays decent money for these units and one consequently has a right to expect a decent life-time in my view

I keep hoping for help for a while ....

[BillP · Accepted solution]

Hi,

We are sorry for you inconvenience. 

On 10/17/2018 4:51 AM, Michael said:

I am disappointed about the help I get here from APC. On the phone they keep asking me over and over whether I really used original batteries and after having me performed the same functional test over and over again they simply tell me that they can not do anything for me. APC will not take the unit in for repair.

We do not offer repair services for SMT Smart-UPS however for your region we do offer a trade-UPS program. You can trade in the original UPS for a new unit at a discount. Our research has shown that trading in is more cost effective than repairing. By trading in the unit, you get a new unit with the 3 year warranty and the ability to purchase extended warranty. We send you the new unit and provide shipping labels to take the original unit back for recycling. 

On 10/17/2018 4:51 AM, Michael said:

I can understand that they can not issue me a complete service manual, but I refuse to believe that this is an isolated issue and I find that someone could be so helpful to point me in the right direction or help me out in any other way. Is that too much to ask?

We take users safety seriously and therefore do not recommend opening the UPS. I understand you will find posts on this forum where members discuss component level repairs however our policy is safety first.