Switching power supply 12v to 13.8v

[dbtoutfit]

Hi,

Whats the best way to bump the 12v rail to 13.8?
I do need to keep the amps (20, 30 and 40)

Thanks for your time.
Eric

 

[rjvh]

what is the power source at this moment???

 

[dbtoutfit]

The 12v source is a ac to dc converter switching power supply.

 

[Nigel Goodwin]

The 12v source is a ac to dc converter switching power supply.

Then just adjust it to give 13.8V instead of 12V - why do you want 13.8V anyway?.

 

[dknguyen]

You realize you are going to lose a bit of amps right? Power in always greater than power out, and you are turning some of it into higher voltage so that means a little less current.

Is there a reason you need it at 13.8V and not 12V though? I would imagine most things would run fine like that. I think 12V would be the nominal voltage for a 12V SLA battery and 13.8V is the peak voltage for the same battery pack.

 

[dbtoutfit]

hi,

As the amps are pulled (about 6 amps) the voltage tends to drop to around 11.4v

I am using it to power my chargers. They will error out at times complaining of loss of voltage due to this drop in to 11.4.

Is there a "POT" I can turn? Or do I need to add something?
How much amp drop would I be looking a you think?

 

[dknguyen]

If I understand you right, your power source can't provide enough power. YOu need another power source. YOu can't make extra voltage and current from nothing. A 12V supply that could actually supply 20A doesn't need to be bumped up to 13.8V.

Your local hobby store probably sells some power supplies.
https://www.fcsurplus.ca/shopping/shopdisplayproducts.asp?id=86&cat=Regulated+Power+Supplies

I use the PS26KX.

 

[dbtoutfit]

is it typical for a 12v power supply to drop to 11.4 volts at 6 amp pull?

Or is this a regulator problem?



I understand you cant get it form nothing but I have seen talk about putting a load on different voltage rails to increase the 12v rail or atleast make it stronger.

Like adding a sand bar to the 5v+ to increase the 12v.

 

[Funny NYPD]

you probably need make your own power booster for the big current you listed.

 

[dknguyen]

is it typical for a 12v power supply to drop to 11.4 volts at 6 amp pull?

Or is this a regulator problem?



I understand you cant get it form nothing but I have seen talk about putting a load on different voltage rails to increase the 12v rail or atleast make it stronger.

Like adding a sand bar to the 5v+ to increase the 12v.

It's not typical for a 12V, 20A power supply. It probably is typical for a 12V, 7A power supply. Power supplies have a current rating and if you go beyond that, the power supply either overheats or the voltage droops down to zero as you pull more current.

Are you talking about placing a capacitor between the rails to supply the peak current demand? That might work if the peak currents are small enough for a short enough time and the converter is able to handle the average current over time, but not the peak currents.

 

[mvs sarma]

is it typical for a 12v power supply to drop to 11.4 volts at 6 amp pull?

Or is this a regulator problem?



I understand you cant get it form nothing but I have seen talk about putting a load on different voltage rails to increase the 12v rail or atleast make it stronger.

Like adding a sand bar to the 5v+ to increase the 12v.

Where this measurement was taken/if it is at the load point, obviously the lead drop would be there. the regulation components generally have to monitor the last point where from the load is to be connected. More expensive units have a 4 wire arrangement and the voltage feed back is taken right from the load itself. this type caters for correcting the voltage drop across leads to some extent.
then, if the output is taken after an isolating diode in series to the +ve lead, the voltage will drop on load , while on open measurememt with a DMM it might show 12V.

 

[dbtoutfit]

while underload I used my MM to check.

 

[Torben]

while underload I used my MM to check.

What is the amp rating on the power supply?


Torben

 

[mvs sarma]

while under load I used my MM to check.

The difference 12-11.4, indicates a possible diode in series to load. If so, it is better to set it to the required voltage+diode drop.

 

[dbtoutfit]

What is the amp rating on the power supply?

20A max on the 12v rail

 

[dbtoutfit]

The difference 12-11.4, indicates a possible diode in series to load. If so, it is better to set it to the required voltage+diode drop.

Sorry I dont understand

 

[mvs sarma]

a 12V smps dropping just by 0.6V while on load can be attributed to a diode in series to the +ve output lead.Generally battery charging circuits provide a diode in series to avoid discharge of battery thro the charger circuiytry, when power is OFF.

 

[dbtoutfit]

My power supply has 3 banana jacks on it.

All coming from the same 12v rail.

When on and no pull, I get a about 12.06v

When I test the 12v voltage I plug in two of my chargers and turn the power supply on. (if not it will trip into protect mode)

I then stick my MM into the last set of banana jacks that have nothing plugged in. I make sure the MM probes have a solid connection.

Then I plug a battery to each charger and begin charging them at 3 amps a piece.

Monitoring my MM I notice as the chargers bump up closer to the 3.0 amps the Voltage drops lower and lower. ( My chargers start the charge low at first and then bump up to the max charger rate)


I do not know everything about electronics but do understand less complex terms.

I guess the bottom line is that you can not get a 12v power supply to supply 13.8 volts without a major overhaul.

Also if the power supply drops voltage before it even reaches half it's max amp output then it's highly over rated. In My case the PS is 20a at the 12v rail Max.


Is there a way to test the max amount of amps my PS can supply? At least a real world way?

 

[mvs sarma]

if the charger output is measured without connecting any load, perhaps it has to show 13.8V
if the design is protected such that the supply would NOT switch ON without connecting battery, it is fine and you may have to connect a fully charged battery --then it will have to show 13.8V, at least after few minutes.. if you connect a normal battery that is partially charged, after some time the charging will be complete, where upon it will have to show 13.8.

Don't expect the charger to show 13.8 by connecting a discharged / partially charged battery.

yes there is a way to test for full load current. you may connect a battery and start the charger. then add artificial load like high wattage head lamps , or a artificial load resistor -please take precautions for dissipating the heat. (total wattage will be 12*20=240Watts.) then you may remove the battery once charger switches ON. (this method will help switching on for those chargers having protection to startt only with battery in circuit).

 

[dbtoutfit]

if the charger output is measured without connecting any load, perhaps it has to show 13.8V

At this point with nothing connected it reads 12v.
Bumping to 13.8v would give me the extra 1.8 volts to keep the charger from complaining of low voltage. I notice many power supplies designed for chargers supply 13.8 volts.

if the design is protected such that the supply would NOT switch ON without connecting battery, it is fine and you may have to connect a fully charged battery --then it will have to show 13.8V, at least after few minutes.. if you connect a normal battery that is partially charged, after some time the charging will be complete, where upon it will have to show 13.8.

It's more simplistic than that. I simply have to have the chargers plugged in first. Not to pull a load to turn the PS on (I use a 10watt 10ohm sand bar on the 5+v to ground for that) When you plug in charger after the PS is on it spikes the PS and causes it to go into protect mode. at any rate I don't have to be charging a battery. I can simply plug the chargers up and then flip the PS on, in turn the chargers come on and wait for my input as to what battery type to charge, what rate etc. It's a computerized charger.

Don't expect the charger to show 13.8 by connecting a discharged / partially charged battery.

So it is normal for a power supply to drop voltage while amps are being pulled?
If so what are the rules of this? Should it not lose volts till the amps are pulling close to the max or close to the "max continuous" amp draw?
The point of bumping up to 13.8 is to give more of a Voltage ceiling to pull from. So instead of reading 11.6 on a 6amp draw it would read at or more than 12v.

yes there is a way to test for full load current. you may connect a battery and start the charger. then add artificial load like high wattage head lamps , or a artificial load resistor -please take precautions for dissipating the heat. (total wattage will be 12*20=240Watts.) then you may remove the battery once charger switches ON. (this method will help switching on for those chargers having protection to startt only with battery in circuit).

Could a buy some high wattage 12v lights and make an array to run many at once each with it's own switch to turn off or on so I can bump the amp pull per light? Also is their a easier way?

I would like to get it with in 10% of what my max continuous amp pull is.
Going from 6amp pull to 15 is to much to get it down to 10% of the max continuous pull it.


Also I have a couple of these power supplies and 2 of them have no blown fuse and the fans kick and the fan lights flash (these ps have fans with fancy led in them) and then it goes off. Instantly as if it has a dead short on the DC side. I have looked everything over and there is nothing visible. dry sockets, cracks, garbage shorting anything out etc. I assume it's a capacitor or something of that type. I do know one if not both have had more than the rated amps pulled form them and I guess the Protection did not kick in and shorted one of the components.

Thanks for the help