Thermal emergency shutdown in SMC1000I / SMT1000I - is it supported and how does it work?

[progmars_apc]

I just saw this video which raises some safety questions:

https://youtu.be/dQYT3pCEg5Q?t=127

Indeed - how didn't his SMT turn off when the temperature of the batteries rose so high that they bulged that huge?

I see the following text in descriptions of SMC1000 and SMT1000:

"Temperature-compensated battery charging. Prolongs battery life by regulating the charge voltage according to battery temperature."

But in this case it's not about charging nor about quality of the batteries (he was using the original ones, just 2 years old). It's about thermal shutdown.

How to prevent this from happening? Do I have to somehow activate and tune the thermal shutdown function? Is it at all supported on these two UPS models and will it work also when the UPS doesn't have any computer running PowerChute?

I'm just afraid to imagine what might happen when I'm away from apartment for a few hours. I guess, I'll have to fully disconnect the UPS from the mains power when I'm not at home or even at nights. I've heard that it might be not healthy for batteries when the UPS is turned off for prolonged periods of time, but better safe then sorry.

[BillP]

Hi Martin,

There are a few unknowns in the video (in what conditions have the batteries been stored or how they were used), but APC UPS units have a number of thermal protection features that do decrease the likelihood of these types of events occurring. For example, on the battery side, a thermal switch closes, and the charger is shut off, once the internal high temperature threshold is reached. Or, the UPS output is turned off, once the internal heatsink temperature sensor exceeds its high temperature threshold. 

These are built in safety features that do not require management options like Powerchute. Powerchute would enable additional options like graceful shutdown based on ambient temperature (used in conjunction with network management card and temperature sensor). 

Smart-UPS battery chargers are smart too, and they work at regulated capacity, as required by the battery. If the UPS is off, or in standby, and the batteries are fully charged, the charger will turn off too.

[progmars_apc]

Thanks for the explanation.

Well, it seems in this case (and I've heard many similar stories about bulged batteries) thermal protection did not work and I do not understand why. It doesn't matter if the batteries are good or bad or dying - if they start bulging and smoking, it means the temperature was going up rapidly and the sensor should have shut down the charger (or better - the UPS) immediately.

So, do I understand correctly that it's impossible to use internal thermal sensor alone to configure thermal shutdown in Powerchute and I would need an external sensor? That's sad and it wouldn't work for SMC because it has no slot for management cards.

I guess, I'll have to buy some other thermal solution with alarm. I could even create it myself out of simple Arduino board, speaker and thermosensor.

Still, it makes me sad that I have to append some artificial solutions to an expensive Smart UPS (400 - 500 EUR which is half of my equipment cost) just to make it safe to use. Thermal shutdown shouldn't be an advanced external accessory; it should be a basic safety feature. If the device heats up enormously above expected range, turn the UPS off completely and don't charge it anymore until user investigates the situation and decides if it's ok to restart the UPS. Simple and straight forward, especially for a device that has "smart" in its name.

[progmars_apc · Accepted solution]

I just talked to some guys who seem to have experience with batteries and they explained that unfortunately bulging may occur also very close to room temperature. So, unfortunately thermal shutdown wouldn't help. Maybe only some kind of a smoke detector would work.