Change float voltage through powerchute

[BillP]

My float voltage on my SUA1500 is way too high, sitting at 27.9. I believe this is the root cause of my batteries always dying after a year or so. 

Is there anyway to change that voltage (to let's say 27.0volt) through the powerchute software? what's my options here?

thanks,

[Brad_C]

No, not through any official software. Plenty of links on the web on using a terminal emulator to do it however.

The SUA was the first series with the ability in hardware to tweak the float voltage (used to provide thermal compensation), so you *can* lower that with software.

Whack "smartup sua float voltage" into google and the first hit will tell you what you need to know. All units older than the SUA need a hardware tweak.

Bear in mind you won't change the voltage the UPS reads, just what it actually does (both my units here have been set to float about 0.8-0.9V lower than what they report).

[BillP]

That's what I thought. I have the APC AP9630 management card in there but I don't think I still have the APC proprietary serial cable. Is the serial cable the only way to configure it or I can get away otherwise? 

I'm also curious if the newer models (ie: SMT1500) have the same float voltage issue and if there is any way to modify the default configuration?

[BillP]

The newer UPSes, which I have, do not allow for modification of the battery charger parameters via any provided user interface.  Although the newer UPS lines have improved battery charger circuitry, all electronics are subject to drift and, over time, are susceptible to going out of tolerance.

[Brad_C]

You will need the serial cable, and you'll need to pop the management card out of the UPS.

I found a link recently that indicated that the SMT is at a basic level just an SUA with an add-on processor that manages the display and implements the microlink protocol. I can't actually find the well written and documented link I originally read, but a quick search turns this up : http://forums.overclockers.com.au/showthread.php?t=1205748

So yes, it would appear you can recalibrate the battery voltage on those if you are willing to get a bit dirty.

[BillP]

Hello Jonathan, 

I just wanted to say that in no way can we recommend changing the float voltage of the batteries in any of our UPS systems. 

There are many different reasons that the battery life can be shortened, such as temperature, times discharged, etc. 

We do have  kbase document on expected battery life and what affects it. 
http://www.apc.com/us/en/faqs/index?page=content&id=FA158934

Thanks,

Shanon

[BillP]

thanks for all the input guys,

@Shanon You mention you don't recommend changing the float voltage but this is likely the root cause of the high temperature I'm having. When I removed the battery from the UPS, it was pretty warm (30 to 35 degrees), although the UPS was sitting at a room temperature.

I did some tests and the float voltage is at 27.9 volt. I then took out the batteries and use a regulated power supply. I did run it at 27.0 and 27.9 and I noticed a 4watts difference in terms of charging at the source and roughly a 3-5degrees difference between the two voltage (temp at the battery). Again, this was done outside of the UPS.

That being said, that 4 watts difference was clearly being dissipated into the system as a source of heat.

In order to keep the batteries cool at that voltage (27.9), I would need to remove the batteries and have other cooling system in place, which won't happens.

Reading about difference float voltage references and most importantly, the batteries manufacturer, 27.9 volts (2.32 volts / cell) seems to be way too high.

Customers are tired of changing batteries soo often, because of the float voltage being too high, this kills our batteries.

[BillP]

Hi Jonathon,

What I think you have is a failed charging circuit in your UPS and it's something I've dealt with in the past with APC.  If the UPS is in warranty, I am fairly sure that APC would work with you to replace it.  If it is out of warranty, there's not much that APC will do other than offer you the ability to use their "Trade-UPS" program to get a replacement at a nominal, very nominal discount price.  They don't repair them and there are very few companies in the US, at least, that offer a "repair service" and that is really nothing more than selling you an equivalent used model and taking yours in as a "core" charge.

Several tinkerers here, me included, have repaired or otherwise modified hardware to restore operation of older, out of warranty, UPS systems.  Yes, it would be nice if there was a way to tweak the charge float voltage as that would appeal to me as well.  I do, however, understand the rationale for not providing that capability to end users.  For every ten of us who would choose to lower the voltage to extend battery life, there would probably be one or two souls out there that is thinking, "If I raise the voltage a bit, I could get extended runtime!"  So either by design or by accident, they turn up the juice, fry the batteries or the UPS itself and then expect APC to replace it because "the adjustment" was there and available to me.  To me, it's just not a safe or prudent thing to do.  Not wanting to cast any aspersions on anyone or APC itself, but their recommendation is the only thing they can do to protect themselves.

I share your frustration because we know what needs to be done but, because APC considers these items expendable and not repairable, they don't offer schematics or any other repair level documentation that would help us out.

I wish you much luck and success in keeping your unit running!

[Terry_Kennedy_apc]

I can understand APC not providing service information for competitive reasons, and there are enough differences between different revisions of the same model as they've been Muntzed along the way that there would need to be a separate set of schematics for each.

I do find it odd that the float voltage always seems to go out of calibration at the high end, never the low end. However, I've also had battery packs suffer thermal runaway when the float voltage is correct - sometimes this "just happens" on old batteries.

APC seems to be offering Charge-UPS again for some models (Charge-UPS is a RBC combined with a 1-year warranty extension). However, my experience is that the original batteries last 3 years, the first replacement 2 years, and the second replacement less than 1 year due to the float voltage going out-of-spec. So you'll probably run through the Charge-UPS warranty extension before the battery fails for the second time.

[Brad_C · Accepted solution]

On 6/12/2016 8:00 AM, Terry said:

do find it odd that the float voltage always seems to go out of calibration at the high end, never the low end.

The resistive divider in these units is (approximately) a 100K to the battery and either a 10K (48V) or 22.1K (24V) to ground (delivering 5.0v to the charger ASIC at the desired float voltage). If a resistor drifts due to age, it tends to drift high and drift is generally proportional to value (almost like a drift in tolerance). This results in the voltage drifting up rather than down.

Oddly enough, I refurbed a 2000 vintage SU2200I recently that had a divider from the factory of 113K/11.5K giving a projected charge voltage of 54.1V, so maybe on some units they tweaked that in the factory. They were both 0.1% tolerance resistors and close enough to spot on.

I understand why APC would never recommend tweaking the float voltage, but the fact remains their design voltage targets are always right on the top borderline of the battery manufacturers recommendations (even when temperature compensated). Yes, that buys you a smidge more runtime, but it does shorten the battery life. It also guarantees that as the unit ages if the divider resistors *do* drift they will slaughter batteries. At least on the SUA units you can tweak the voltage in software (they have a PWM output that allows them to marginally adjust the reference voltage to the charger ASIC to allow for dropping the float voltage for temperature compensation). The older 3 & 3.5G units have fixed references and dividers that need adjusting in hardware.