power supply

[e67]

This DC power supply is the cheap kind that switches between voltage and current by turning the dials in a certain way...
I don't use it for current but am curious about something....You get the voltage screen at first by turning the current knob a little bit... and then you set the voltage for charging...but if you want to maximize the current do you continue to increase the current knob until the screen turns back to current and max it to the right for max current at your already selected voltage??
These units are popular so someone here probably knows here....look at the pic..its the Longwei 10 amp 30 volt charger..they are about 30$..

 

[sunshine_eggo]

This DC power supply is the cheap kind that switches between voltage and current by turning the dials in a certain way...
I don't use it for current but am curious about something....You get the voltage screen at first by turning the current knob a little bit... and then you set the voltage for charging...but if you want to maximize the current do you continue to increase the current knob until the screen turns back to current and max it to the right for max current at your already selected voltage??
These units are popular so someone here probably knows here....look at the pic..its the Longwei 10 amp 30 volt charger..they are about 30$..

I have that or a very similar unit.

To measure voltage, current must be non-0 as even a voltage measurement requires >0A. It appears this unit must be SET for >0A to simply adjust the voltage.

You can max out current as you describe, or you can short the leads together and set the current to the desired amount.

 

[e67]

and when I max out the current on the current knob the voltage will stay to what I put it at??
that's important..

 

[LakeHouse]

and when I max out the current on the current knob the voltage will stay to what I put it at??
that's important..

If you set the voltage with an open circuit (leads attached to nothing) and then don't move the voltage dial, the unit won't exceed that voltage regardless of what you do with current dial.
Think of those two dials as setting Voltage to not exceed, and current to not exceed.

 

[sunshine_eggo]

If you set the voltage with an open circuit (leads attached to nothing) and then don't move the voltage dial, the unit won't exceed that voltage regardless of what you do with current dial.
Think of those two dials as setting Voltage to not exceed, and current to not exceed.

agreed. This is the intended outcome, but with cheap equipment, don't be surprised if the values drift a little.

 

[Bop]

I have two of those identical units (sold under a different brand name ie QH, they are all the same I have found though) and they are NOT a charger, but a power supply (although they can be used as a 'dumb' charger) I use as my 'extra' bench PSUs (they are actually quite a good little unit- although their power rating is a little 'optimistic' imho)
You set the voltage first to whatever you require, then set the maximum current next- this will allow the current to go to the maximum you set (up to the limits of the power supplies internal power rating)- in practice I found that going above 25A, they will tend to shut down after 10-15 minutes of continuous use)

 

[reiters]

It might be easier to change your thinking about what the power supply is doing. It's a limiter. It limits to what you set it at. Current is a function of the load and voltage. The knobs set the upper limit of what can be output. That's why you set the voltage (limit) with leads connected to nothing and typically current at zero (your device may need current slightly above zero). Then you short the leads and set the current (limit).

If your load has very high resistance then even if your device says 12v 10a you will not be getting 10a. You are limited to a maximum of 10a but your load resistance doesn't allow that much current.

If your load is very low resistance then the power supply will limit the output voltage so that the desired amp limit is achieved. Meaning that if you hit your 10a set point at 6v then the power supply will clip the voltage at 6v instead of going up to 12v as set because 12v would result in more amps.

I assume in your case the load is a battery which has an "internal resistance". Battery charging is a little harder to wrap your mind around as a load and they require some delicate treatment to prevent charging too fast.

Someone else correct me if I am wrong. I'm used to dealing with buck-boost cheapies without a fancy shell and leads.