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Electric Vehicle issues


Unclejake
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Howdy all, I'm helping a retired couple diagnose a problem with a Hisun side by side ATV. 

The vehicle is almost exactly 12 months old. It's a plug in 48 volt 4x4 that has suddenly refused to go up hills and is throwing a few error codes (dunno exactly what codes just now).

It has 8 x 6 volt batteries. I isolated three of the batteries (one at a time) and measured them at 11.8, 13.4 and 13.4 volts respectively... which seemed impossible so I stopped there and went back to work. The batteries seem to be lead/gell cell - but I'm not sure (they're covered in mud and very hard to read due to all the brackets holding them in place)

I have a call into the Hisun techs but they're Auckland based so will be in lockdown.

Question: Is it even possible to charge a 6v battery up to > 13 volts, or could my digital multimeter be crook?

@Ned or @Llama

 

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Sounds unlikely that a 6V would get up to >13V.  If it was 12V (or you were somehow measuring two) then 11.8V unloaded sounds pretty bad, which could explain your issues.

Just spitballing, but if it can drive but not produce much torque then:

  • it's in limp mode because its detected a dud cell and doesn't want to blow it up
  • a dud cell has high internal resistance which is reducing current (since it sounds like all the batteries are in series)
  • anything else that will put it in limp mode (At least on a Tesla, there are 50 million reasons, but most common reasons are being in a minor crash, losing coolant from the battery pack, any of the stability/traction systems freaking out, losing coms to one motor)
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The batteries are definitely 6 volt (I could read that on their labels) and I was testing each battery with both the positive and negative terminals disconnected, so the were very much stand alone. I question my multimeter though. It's a bit too automatic for my liking, but my second multimeter shit itself yesterday (I have a third which I'll drag out of a box tomorrow)

One more bit of info which I should have mentioned: The eight batteries are wired in series. The dear old girl who's machine this is (she's almost 80) had a 12 volt sprayer connected to one (I think it was one  battery. I didn't pay as much attention as I should have) of the eight 6v batteries using alligator clips when I arrived. I disconnected it immediately and asked her how long the sprayer had been connected but I haven't got an answer. It was the 6v battery that she had the sprayer connected to that read 11.8v

I'm a bit stumped as to if that spray unit was getting 6 or 48 volts. Thoughts? I'm confused on this detail

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Correct no need to disconnect

running something of one battery will pull that battery’s voltage down and probably affect the whole thing

 

always Been taught/told to prove test prove your meter

Check it against your trucks (fairly) known voltage to ensure its accuracy 

 

also check what the charger is outputting as that could be stuffing it all up 

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  • 2 weeks later...

I should update the post to explain:

  1. The roof in one of my trucks leaks.
  2. My delightful staff members put my mulitmeter in a bucket and chucked it right under the leak, so I got a new multimeter sent over 
  3. It was that new MM which was telling me 6v batteries had ~ 12v charge
  4. EVIDENTLY one needs to turn the knob to DC rather that AC (not that it says either DC or AC on the MM face) or else one will see roughly double the battery's voltage on the display
  5. I went back, retested the EV and have tentatively diagnosed one dud 6V battery (the one a 12V sprayer was hooked up to)
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