Can you get a shock from these UPS battery tentacles, considering the fact that these connect to a 12v battery? I made a temporary 12v battery (no BMS , I am noob ) using 4 small Li-ion batteries. I connected that battery to the UPS and it worked. The UPS detected low battery, so I connected the UPS to the main line. I was holding the battery (negative terminal of the battery was touching my hands) when I was connecting the UPS to the main 220v line. Exactly when the UPS plug touched the main 220v, I got a deadly shock from the negative terminal of the battery. Like someone had hit my hand with a hammer. As far as I know, these 2 tentacles draws current from battery and also charge the battery.. so charging voltage range can be between 12-15 volt. Then How can i get such deadly shock from these 2? Or there is something wrong with my UPS ? Or I am just stupid

 

There are many ways of making a UPS, so not an easy question to answer.
Some have 325V batteries.
Some have lower voltage batteries which are isolated
Some have low voltage batteries which are directly connected to the mains.

If you received a deadly shock, are you writing from beyond the grave?

 

Can you get a shock from these UPS battery tentacles....?

Yes you can. Anything that plugs into the mains carries that risk, especially in this age of cheap poorly-designed equipment.

A simple rule is: if you don't FULLY understand the device you are poking inside of, make sure it is unplugged.

A better rule is: if you don't FULLY understand the device you are poking inside of, don't poke around inside it. But that is no fun.

 

You can still get a shock from a UPS even if it is unplugged - otherwise it wouldn't be a UPS!
It should be labelled "This equipment is supplied from two power sources: isolating it from the mains does not make it safe" or words to that effect.
If it were an emergency lighting unit compliant with EN50171 then the battery must by law be isolated, but UPSs for other purposes do no have to comply with such stringent regulations.

 

I got a deadly shock

I'd say "Welcome to AAC" but since you're dead, "We'll miss you."

I made a temporary 12v battery (no BMS , I am noob ) using 4 small Li-ion batteries. I connected that battery to the UPS and it worked.

OK, yes, you got a good shock. Exactly like you described. But a far greater danger to you is using Li-Ion batteries in place of what is likely an SLA battery (Sealed Lead Acid). The different chemistries require an entirely different sort of BMS or Charge Profile. Far worse than the shock you got, which, yes, could be life threatening; you could experience a fire or explosion. Both of which could render you homeless. Nothing worse than surviving death only to live homeless.

 

Consider that the internal batteries of a UPS system may not be isolated from the mains since there is no normal mode that will leave them accessible while the mains power is connected. So it could have been a mains power shock or a mains power plus DC voltage shock. Non-accessible portions of equipment are not required to be isolated from the mains.
So you could have received a lethal shock instead of a terribly hurting one. The TS is indeed very fortunate to not be rather dead.

 

Yes, it's possible. Some UPS are designed in such a way, that the battery is not isolated from the mains. I got a shock once when replacing batteries in the "ECM" UPS. Two bateries 12V each were used. Later I dissasembled the UPS and found the battery pole is tied to the mains thru a small ferrite choke

 

OKAY! Consider that no portion of the transformer is part of a user-accessable portion of a UPS package, it is not reasonable to think that it would be isolated from the mains.
That fact tells me that the suggestions for using UPS batteries, while installed, for an external 12 volt supply, may be a poor choice.

 

A side note: do not just swap a lead acid battery for a lithium battery, there's a good potential for fire. The charging profiles are different, and lithium does not tolerate over or under voltage very well. Lead acid is much more forgiving.

 

in a UPS the batteries would be permanently on float charge.
Permanent float charge will cause a lithium battery to explode.

 

Just to answer your question directly, no, you should not get a shock if you touch ONLY the battery terminals. If, however, you touch one of the terminals and accidentally touch either a live part of the circuit or ground it might be possible to receive the kind of hammer to the elbow shock you felt. If the battery is 12 volts then you should only feel (if possible) 12 volts.

ON ANOTHER HAND: If the battery isn't a battery but rather a capacitor, even at 12 volts a capacitor can deliver a nasty snap. Depending on its size larger capacity is worse than a smaller capacity. Now, and I certainly don't know this for any kind of factual information, maybe there's a cap across the two battery terminals that may stand ready to deliver high current to kick start the generating of the 110 (or 220) VAC the UPS operates at. But again, I don't KNOW this to be so. Others will probably pick this statement apart. That's OK. It offers me a chance to learn something more.

 

After thought
I think I've had a UPS that takes line current and charges a battery. The battery and line current are then used to generate line voltage for the items plugged into the UPS. In other words, it's always running off the battery and charge circuit. If power fails, the UPS is already running the items plugged into it from the battery. Thus, it's truly uninterruptible.

 

Just to clarify post #12

So, you should not receive a deadly shocking from just the battery terminals alone.

 

ON ANOTHER HAND: If the battery isn't a battery but rather a capacitor, even at 12 volts a capacitor can deliver a nasty snap.

12 Volts from a battery feels exactly the same as 12V from a capacitor.

 

12 Volts from a battery feels exactly the same as 12V from a capacitor.

I suppose so. You know I've been wrong before. Thank you for policing me.

 

Just to clarify post #12
View attachment 331313
So, you should not receive a deadly shocking from just the battery terminals alone.

I seriously suggest that you investigate the interior of a typical home-office sized UPS device. Very often they are available for free because the inflated price of the failed battery package approaches the price of a new UPS system. Opening up and exploring the interior will show that MOST of the internal circuits are tied to the mains in some degree. So almost any part inside the enclosure is likely to have some level of shock hazard present.
Of course, only do the suggested exploring with the UPS disconnected from the mains.

 

Been many years since I opened one. It was as described in post #13. Even not connected to line voltage there was a hazardous voltage present. Using test meter probes I accidentally shorted two components and blew out a main MOSFET driver. End result was that it got tossed into the scrap bin and used for parts.

 

Question

Can you get a shock from these UPS battery tentacles, considering the fact that these connect to a 12v battery?

Answer

So, you should not receive a deadly shocking from just the battery terminals alone.