Hello all. New to the forum and have a question. I have an HPDPS – 1200 FB-1a power supply. My question is a little opposite of the ones previous. I am trying to reduce the voltage of this particular supply down to somewhere between 11-11.25 vdc. I have two different supplies wired in series along with this one and with the pots on all three supplies turned down as low as the voltage will go. I’m getting 35.75 V. unfortunately, my charger will max out at a 35 V input. I bought this particular supply because it says the minimum output voltage is 11 to 13.5 VDC. Although I’ve done the mod that everybody is aware of, the lowest voltage I can turn it down to is 12.05.
Would very much appreciate any help if anyone knows how to reduce this power supply voltage. I also have 2HPDPS – 1200 FB-A very similar, but slightly different interior designs. If it’s possible to reduce their output voltage that would accomplish the same task. Thanks again for any help. Greatly appreciated.

 

A couple of diodes in series with the output will drop the voltage below 35 volts.

 

A couple of diodes in series with the output will drop the voltage below 35 volts.

So it’s possible. Where would I install?them in relation to the board, or outputs? Also, what size diet would you recommend? Sorry, I wish I had a little more knowledge. My soldering skills are decent and I’m sure I can handle it. It’s the lack of knowing where to install them and what size diode to acquire? Thank you again for your response. Greatly appreciated.

 

So it’s possible. Where would I install?them in relation to the board, or outputs?

How much current does the charger draw at 35 volts?

 

How much current does the charger draw at 35 volts?

This is the spec sheet for the charger. However, it’s unlikely I will ever be pulling more than 30 A combined between both channels.

 

The input voltage to the charger specifies 10 to 34 volts.
Why the need for three supplies in series when one 12 volt supply should suffice?

 

The input voltage to the charger specifies 10 to 34 volts.
Why the need for three supplies in series when one 12 volt supply should suffice?

It’s a dual channel charger, with 1000 W/30amp per channel. I sometimes parallel charge four batteries, and on my current 12 V set up. It takes too long. people at my club use the same charger with a 24 V set up and it’s much improved. My goal was to try to hit 35 V. I know the charger specs does not state it, but it will operate at 35 V. Again, I don’t plan to push it that hard however, I tend to like to maximize everything I do. I failed dimension, this is for a RC set up and I’m charging Lipo batteries.

 

Recommend this Diode, mounted on a heatsink, one will be enough to drop the voltage to 35 volts max.

 

Recommend this Diode, mounted on a heatsink, one will be enough to drop the voltage to 35 volts max.
View attachment 343114

 

Thank you so much for your assistance. I truly appreciate it, I’ll send you some pics when it’s complete and working.

 

Don't skimp on the heatsink as that diode may need to dissipate up to 50 watts.
A heatsink can be made from aluminum or copper stock.

 

Don't skimp on the heatsink as that diode may need to dissipate up to 50 watts.
A heatsink can be made from aluminum or copper stock.

I have a piece of aluminum Heat sink 50 mm x 40 mm. 4mm thick. Would that be sufficient?

 

Worth trying.
I'm no expert on heatsinks but I was thinking something larger like 100mm x 100mm.

 

Specs are 10 to 34 V input This is one way using a grounded heatsink. 68W needs a high speed fan and the surface area of an old CPU heatsink.

 

OK, I see that you are hoping to push to the maximum limit. Are those power supplies at all adjustable?? If they are each adjusted down to 12 volts could you use two of them in series adjusted UP to 14 or even 17 volts??
With those three supplies put in a stack like that there will not be very much cooling air pass thru them. So heating of the supplies may become a serious problem. And running at the rated maximum is seldom a best choice. What sort of batteries are you charging?? They look rather small in the one photo.

 

My current charger I would like to max out at 35 V and 1500 W bridged. This should allow me to charge for Lipo batteries in parallel with my charging board. Those batteries I intend to charge are 3S 2200 MAH Lipo. This has been done numerous times with higher voltage, chargers, however, the one I purchased Max is out at 35 V. Spec show 34, but it operates fine at 35. The three power supplies are adjustable, but when I turned them all the way down, they equal 35.75 V. Which the charger will not operate at. So if I can get the power supplies down to 35 V series, I will barely be pushing them at 1/3 of their capacity, charging the four batteries. My problem is voltage, not amperage simply to allow the charger to operate. sorry, I am not an electrical engineer by no means. But I’ve been dealing with hobby electronics for years so occasionally I dip in the areas I may not be qualified for, lol.

 

I got no answer to what the maximum voltage out is on those 3 supplies. What is the max from two of them in series??

 

I got no answer to what the maximum voltage out is on those 3 supplies. What is the max from two of them in series??

I’m using three supplies, two of them are the same, one is different. The first two models DPS1200FBA, lowest voltage I can reduce potentiometer to is 11.8 V. The other one which is a DPS1200FB – A1, Lowest voltage after reducing potentiometer is 12.05 V. The first two I mentioned can be increased to 12.6 5V, the last one which is the.– A1 can reach 13.2 V. I am trying to acquire 35V across all three in series. I need to reduce voltage by .75v

 

How much faster will the battery charging be with the 35volts supplied instead of 24 volts???

 

How much faster will the battery charging be with the 35volts supplied instead of 24 volts???