Off the shelf "charger" as power supply (no battery)

Thread Starter

Dolphran

Joined Jul 18, 2022
1
Hi all,
I am not charging a battery. I have a circuit that I would like to power with a 12.6VDC power supply (wall wart), not 12.0V. (why I want that is not germane to this question). My current draw will be in the 100 - 250 mA range. Although many 12VDC wall warts are readily available, the 12.6V variety that I can find are all listed as "chargers" (for example: https://www.amazon.com/MTYTOT-Universal-Adapter-100-240-Transformer/dp/B09X477NVB/ref=sr_1_3 ). They support Li-ion charging phases with an LED indicating:
No-load status LED is green; Charging, the first phase of constant current charging, LED indicator is red. Charge to the rated voltage into the second phase of constant voltage charging, the current slowly decreases. When the battery power reaches 90-95%, LED lights turn green. At this point the charger will continue to charge with a small current until it is full.
I don't know what circuitry is typically in these to provide that functionality. My question is: Can this be used simply as a constant voltage power supply (no battery) if my load condition stays in the 10% to 25% of the rated capacity of the "charger"? Are there drawbacks to this relative to a standard power adapter? Might I have start up issues? Are things like ripple worse (or better?) with the charging variety? TIA!
 

Boggart

Joined Jan 31, 2022
55
Does it need to be a wall wart? Enclosed power supplies like the Meanwell RS-15-12 for example usually have adjustable outputs. That particular model is adjustable up to 13.2V. Just fit one inside a suitable enclosure with a mains lead and you're done.

There are also desktop-style power supplies with variable outputs, not quite a wall wart, but a fully enclosed and insulated supply none-the-less. eBay item number 385016612848 is an example of these.
 

Jerry-Hat-Trick

Joined Aug 31, 2022
175
Although many 12VDC wall warts are readily available, the 12.6V variety that I can find are all listed as "chargers"
My experience with such power supplies is that the stated voltage varies sginificantly with load so if your current demand is low the voltage may be higher. I'd recommend a similar inexpensive supply with a higher nominal voltage, say 15VDC and use an LM317 linear voltage regulator which, with two resistors will give you a clean 12.6V output reasonably immune to current demand.
 

Reloadron

Joined Jan 15, 2015
6,991
I have a Mean Well sitting hear. Adjustable from 11.5 to 13.7 VDC. Current is 1.67 Amps and their cost is between $15 USD and $20 USD. They can be had on Amazon or any of dozens vendors.

Ron
 

BobTPH

Joined Jun 5, 2013
5,810
The described charger cannot be used as a constant voltage supply. The first thing it will do is check the voltage of the battery it is expecting and likely shut down if it does not see one.
 
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