12v power supply outputting 15v? - RC Groups
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Jun 08, 2004, 08:15 PM
Registered User

12v power supply outputting 15v?

I have tried two different 12v 1.5A wall plug AC to DC power supplies and both output 15+ (15.05-15.10) volts. I like these wall plug power supplies because I can get them cheap and thay are not big like a bench or PC power supply.

The problem is that I'm trying to use this as an input to my Apache 2500 Lipo charger which is designed for a 10.5 - 15.0 volt input.

It seemd that the 15+ volts causes the charger to flag the error light when I plug in my battery. If I try a dozen of times over a hours or so the error light will eventually stay off and the battery will charge normally.

Is there a way I can reduce the voltage to below 15 volts without changing the amprage?

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Jun 08, 2004, 08:54 PM
Registered Taranis User
Miami Mike's Avatar
You can add one or more rectifier diodes in series to reduce the voltage by about 0.6 to 0.7 volts each. Use diodes with an amp rating of 2 amps or more.

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Jun 08, 2004, 09:39 PM
Repair Specialist
Ken-Ohki's Avatar
I dont know allot about lipoly, but I have read if they are drawn down to low you will get a error message on your charger,, repeated attempts to cycle teh charge puts a little voltage in each time before teh error kicks in,, eventualy, the battery will reach the level it needs to be at to accept charge...

the reason I mention this is you said after repeated attempts you got it to take a charge.. If suffering from imput voltage was the cause, I do not believe you would have gotten it to charge , However, I do not believe that is the cause.. your 1.5 amp wall brick will only allow the charger to put out about 1 amp after its converted to DC. SO that would limit your charging rate a bit but should still allow it to function.

what was the voltage reading on your pack before your attempt to charge? and what are its spec's??

"I make things do what I want them to, The hell with what they are designed to do."
Jun 08, 2004, 10:18 PM
Registered User
Thanks Ken-Ohki, I think you were right. The pack was at 6v which I thought was OK for Lipos, but it seems that the Apache 2500 is really sensitive and did not like the low battery voltage. I used another charger to get the battery volts up a tad and then the Apache 2500 worked fine. Then again, it might of just have been that that try was the one that worked again. I'll have to note the battery voltage in the future to see what the Apache wants the battery to be.

Jun 08, 2004, 10:24 PM
Registered User
The diodes will reduce the voltage a bit but the worry would be voltage ripple. Adding a capacitor paralleled to the supply leads will help fill the dips. The voltage spikes can be limited with an inductor.

Use a 3000+ microfarad electrolytic capacitor and abide the polarity. Its marked.
Jun 09, 2004, 02:52 PM
Registered User
My Pyramid power supply (PS-14KX) is doing something funky when used with my Triton charger. When the Triton drops the current to check the standing voltage on the battery pack, the power supply outputs > 15 V temporarily and the Triton indicates a voltage input error.

The power supply used to be fine but now appears to not regulate as well as it used to. I belive it's the sudden load change that is the problem. Can a capacitor be placed across the terminals to smooth the voltage out? I'm usually charging between 2-4 A.