Strange Battery Charger Behavior... Any Ideas?

• Strange Battery Charger Behavior... Any Ideas?
  Posted by bigjoncoop on 20 Apr, 2024 15:56
• Hey just want to say thank you guys ahead of time for all of your help over the years!!!
  
  This time I got a strange scenario going on using two digital smart Chargers in parallel charging 1 battery.
  (PHOTO ATTACHED)
  
  So I have two of these Chargers and I'm powering both of them through one repurposed server power supply, and they're both connected to the same battery.
  
  I set each one to 14.6v, but when I start one of them the other one also shows about the same charging current on the output... WTF???    So to clarify, when I start charger "A", the display on Charger "B" is also showing roughly the same charging current on the output but is still off(it's powered up but but not started)....
  
  Oh in case it's relevant, I'm not using the Chargers in their "charging mode" but using the adjustable CC/CV power supply feature that's built in.
  
  *** I haven't tried to start charger "B". As soon as I started charger "A", I realized what was happening and didn't want to risk burning them up ***
  Is this a common occurrence or is something strange going on?
  I've used (carefully & monitored) different types of battery chargers in parallel before (not these), and have never had this happen though.
  
  Would installing a diode in forward bias on each one, stop this from happening or does it even matter? Is it safe to just start both Chargers?
  
  
  

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• #1 Reply
  Posted by IanB on 20 Apr, 2024 16:18
• If it does not say in the instructions that you can use one battery charger in parallel with another charger on the same battery, then you are not supposed to do this.
• #2 Reply
  Posted by floobydust on 20 Apr, 2024 17:52
• Many battery chargers switch the output on/off using a low-side N-ch mosfet.
  Because you are using the two chargers in parallel (same power source) the one with output ON is providing a (-) return for the other that has output OFF.
  I think you're just bypassing that OFF charger's (low-side) output switch, so it starts providing current.
  Does that make sense? If you reversed roles, other charger ON and this one OFF, same drama.
• #3 Reply
  Posted by PlainName on 22 Apr, 2024 16:37
• Quote

  Any Ideas?

  
  Sure. Learn to use the forum's image tools, and then something other than just one quarter of some huge photo will fill my browser window and I'll be able to see what you're asking.