Strange Power Distribution Problem

Working on a 48V DC power drive driven Rover to spray weed and fertilizer in my backyard.

I am experiencing a very strange issue all of sudden and looking for someone who has experience in DC power design and ground loop issues.

Please review this diagram. (Label corrected)

  1. The Rover use a Lead Acid 48V battery rated at 24Ah.

  2. I am using an e-Bike controller to control the drive motor and have no issues making the motor to work using receiver PDM signal and converting it to analog.

  3. The weed sprayer is a 12V North Star spray pump rated at 8A max power draw.

  4. To turn the Rover, I am using a simple 480Kg high torque servo which runs at 24V.

  5. At this point simply using an RC receiver and PDM Relay to turn the sprayer on.


  1. Yesterday I accidentally shorted the 24V and 12V outputs of the buck converter which fried the 12V converter. Bought a new one and installed. Please note prior to this incident I had no problem turning ON and OFF the sprayer.

  2. I can measure all the voltages upon power up that is battery is at full capacity at 48V, the 24V converter is giving out 24V, the 12 volt converter is giving out 12V and so does the 5v step down converter.

The rover moves forwards and backwards no issues, no steering problems.

The problem I am facing is that when I try to turn the sprayer ON the relay just clicks ON and OFF and the sprayer will not get proper power to stay ON. Interestingly, when I turn the relay ON for the sprayer I loose RC receiver connection with my Radio. This is driving me nuts, what causing this problem?

If I apply 12V power directly to the sprayer it works fine so no issue with the sprayer. Maybe the sprayer needs a high amp (20A) buck converter? This is the only thing I can think off. The new buck converter is rated at 10A so I have just ordered a 20A version just to see if that is the issue.

I will upload a video on you tube shortly and here is the link.

Do I have a ground loop problem or did I fried some functionality of my e-Bike controller when shorted 12V and 24V buck converter outputs?

Or even 24V converter got fried too even though it is still making Steering servo (which requires 24V) to work correctly…

I have another relay thats put the rover in reverse and forward mode and that is working fine as shown in video.

I changed the sprayer relay board but the problem persists.

Any suggestions?

Thanks for your help.

In that diagram the sprayer is connected to ground from the battery and ground from the relay board - which may just be a drawing mistake. Is the relay board meant to pass through the regulated 12v when it operates?

Will the 12v converter run directly from the 48v supply?
Can you fit extra electrolytic caps on the output of the 12v converter (and maybe even the 48v converter) ?

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Yeah, thats a drawing label mistake. I will correct the labeling. The relay is used to connect and disconnect +12V. GND is going to common ground.

I think I have a current draw problem. The replacement 12V buck converter is rated at 10A and I think I previously I used a 20A.

There is one more problem that I can’t get this another relay board to switch using PDM signal. Two relays, one gets turned at high PDM signal and then the other at Low and when the switch is in the middle none are activated.

They work fine if I use a servo tester and switch but when connected to RC receiver will not switch and just blink when you toggle a switch on TX between high and low.

Maybe I need to take a break for a day…

The buck converters I am using are off very high quality, designed for Golf carts, no need for external caps.

I think its a power draw issue or the e-Bike controller is damaged.

Not sure, waiting on 12v @20A buck converter to arrive… oh well…

I have to also dig up my old electronics books to figure out if we have a ground loop problem.

p.s. this is a good article


It was power draw problem. Once I installed a 20amH step down converter all problems went away.

The sprayer is drawing a lot of power I may need a separate battery for it.

All relays are now working as well. RSSI signal lost went away as well.