Trying to identify a blown thermistor

Thread Starter

SailCS33

Joined Mar 18, 2021
32
Now, why don't you make one?
Actually i would love to. Been looking over some circuits but truth is I lack expertise. I would be comfortable assembling a circuit if i knew and had components. So far i only dealt with bunch of Arduinos and RPi. But all breakout boards have already been assembled.
Now that I have a junk throw away power supply, i might try repairing it replacing what blew up. Would be great to upgrade anywhere i can.
At the end of the day, I still need 14v 40amp power supply.
 

Ian0

Joined Aug 7, 2020
1,922
There's not just one way to approach it . . .
What do you use it for? How accurate does the 14V have to be? How much ripple is tolerable? How long do you run it for? How much heat dissipation is tolerable?
If I wanted a power supply of about that voltage, needed 40A for short periods of time, I'd buy a lead-acid battery and a charger, and keep it on float charge.
 

Thread Starter

SailCS33

Joined Mar 18, 2021
32
There's not just one way to approach it . . .
What do you use it for? How accurate does the 14V have to be? How much ripple is tolerable? How long do you run it for? How much heat dissipation is tolerable?
If I wanted a power supply of about that voltage, needed 40A for short periods of time, I'd buy a lead-acid battery and a charger, and keep it on float charge.
I need the power supply to charge lifepo4 battery bank. In fact, right now I'm using car charger but it has few drawbacks. It's too "smart" and tends to get tricked by the battery BMS. Also it can only do 13A. It takes forever.

The 40A would need to crank out for couple of hours. Problem with lithium batteries is they will sock up almost any amperage you throw at it. I could only impose a limit in BMS settings but that would just shut off the charge until it senses a drop.

As far as voltage, tolerance is very wide. From 13.6 i think all the way to about 19??
 

Ian0

Joined Aug 7, 2020
1,922
If you need a Lithium battery charger, then build or buy a lithium battery charger!
I had a friend who charged lithium batteries from a power supply - it burned down his conservatory.
 

Thread Starter

SailCS33

Joined Mar 18, 2021
32
Forgive my ignorance but aside from managing charging profile, what is the difference between a lithium battery charger and a power supply that claims to supply 40A with no reference to the duty cycle?
 

Ian0

Joined Aug 7, 2020
1,922
A charger has a CCCV characteristic - it delivers a constant current until it reaches the target voltage then it delivers a constant voltage. Some power supplies (bench power supplies in particular) can do that, but most don't. They deliver a constant voltage, or, if they are for LED lighting, a constant current. The type you have is constant voltage. It has overcurrent protection, (which may be a simple over-current trip, or a fuse, but not current regulation. It is probably not designed to run permanently in overcurrent protection mode which is what it would be doing if it were charging a battery with a terminal voltage of less than 15V.
You are quite lucky that the nice people at AliExpress gave you your money back, if they knew you were using it to charge batteries without any current regulation they wouldn't have been so generous (and rightly so).
 

Thread Starter

SailCS33

Joined Mar 18, 2021
32
Thanks Ian for taking the time to explain this. Interesting that not Ali nor the seller ever asked what was the PSU used for. Perhaps this difference is not a common knowledge apparently. None of the listings or specifications talk about limited use to LED only (or similar). Had it listed at least limited duty cycle I would have thought twice about using it.
 
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