Trying to replace li-ion 7.2 volts with power supply... failed.

Thread Starter

Guytas

Joined Apr 29, 2021
7
Hi,
I have 12 ikea powered blinds installed. The batteries last anywhere from 2 weeks to 3 months. Since I have to use a 8 foot step ladder to reach them, I got fed up charging the batteries and decided to run a cable between 6 of them and connected to a 7.2 volts power supply. I removed the batteries and made sure the power supply had enough power to feed them all at the same time.
So... I started by connecting the first one... fine. Connected the second one... fine.. but then, one of the DIED. I’ve checked the voltage of the power supply and it was about 7.4 volts. The battery itself shows a voltage just over 8 volts so I assumed I was ok. I guess not.

Not sure what went wrong. But I’m scare trying other things. I can’t afford to blow out another one. I’m wondering if the power supply was wrong, or if one’s noise can affect the others...
Any idea what I can do?
 

wayneh

Joined Sep 9, 2010
17,153
Any idea what I can do?
Can you provide any info on your supply?
The lower voltage of your supply is a question mark. I wouldn't normally expect a problem but it's something to consider.
It's possible that the one motor went belly-up just coincidentally with your project. Any chance it's just a poor connection?
And finally, I'm assuming you've connected all the motors in parallel to your supply, not serial?
 

Yaakov

Joined Jan 27, 2019
3,464
The blinds appear to use a 2 x 16384 pack but there isn't any technical information available on the battery or the blinds that I can find.
 

Thread Starter

Guytas

Joined Apr 29, 2021
7
Thanks for responding.

the power supply was this one:

https://www.amazon.ca/SoulBay-Universal-Switching-Selectable-Electronics/dp/B01N7RS0NG

It’s a 30 watts and each blind use only 0.4A @ 7.4v (from the label on the motor itself). So I assumed it needs only 7.4 x 0.4 = 2.96 watts. 6 blinds should use less than 18 watts.

The battery is this one. Yes it could be just coincidence but I’m looking for professional advice before trying this again ;)
 

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BobTPH

Joined Jun 5, 2013
3,652
From what you said, it should not have killed your blind. Did you possibly connect the second one with the wrong polarity?

Bob
 

Thread Starter

Guytas

Joined Apr 29, 2021
7
I’m sure not. It did work for at least.... 30 minutes or so.

by the way, yes i connected them in parralel
 

wayneh

Joined Sep 9, 2010
17,153
What? That is enough to blow out the blind?
What would be the way to make them electric only?
Not sure what you're asking. But as @anniel747 asked, can you scope the power supply while it's under load? The hypothesis is that it may have behaved badly under load.

It occurs to me that your motors are an inductive load, and the power supply may not be designed for that kind of load. If it really caused a motor to burn out (which I'm still skeptical about), it could be because of bad behavior related to an inductive load.
 

Thread Starter

Guytas

Joined Apr 29, 2021
7
Ha ok. Good point. I'll test that under load. And no I did not check if it is the motor or the circuitry that failed. But I guess it would be the circuitry.

What kind of power supply is required for inductive load? It would be better to try with a better power supply I guess but not sure what I need.
 
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