LITHIUM BATTERIES - My Charger is not Fully Charging My Batteries

The DIY lithium conversion can save you quite a bit of money, but the documentation and troubleshooting available online is often complicated & underwhelming. Through troubleshooting with our customers, we have found a relatively common issue that has a fairly simple solution.


Commonly Occurs After

  1. New lithium battery conversions
  2. Using multiple 12V Lithium batteries vs. using single 48V battery



The Problem

You have multiple lithium batteries wired together that are out of sync and have different voltages or levels of fullness.


Lithium can be purchased either as one big 36v or 48v battery or as individual 12V lithium batteries. Either 3 batteries are wired together to make 36V, or 4 are wired together to make 48V. 

When you have multiple batteries, each one has a BMS (Battery Management System) that controls the charging. These batteries will regularly get out of sync about every 6 months. When charging them all at the same time with the FORM Charger, if 1 battery gets full, its BMS will tell the FORM charger to shut off for all the batteries even though the other may not be finished charging. This causes the overall pack of batteries not to be full to their maximum potential.

 

 

How to Confirm

  1. Set Multimeter: Set your multimeter to DC Voltage at 200VDC.
  2. Red Probe: Place the red multimeter probe on the positive terminal of battery 1 of your golf cart.
  3. Black Probe: Place the black multimeter probe on the negative terminal of battery 1 of your golf cart.
  4. Record Reading: Write down the number that the multimeter is showing.
  5. Test Each Battery: Repeat steps 1-4 for each of the batteries.
    • If the number written down for any battery is more than 0.1V different from the rest, then we have confirmed the  problem.



How To Fix

  1. Use a 12V lithium trickle charger to charge each battery individually to full.
  2. Repeat every 6 months or if you notice that the batteries have reduced capacity and are out of sync.

    

Equipment Used / Where To Buy

 

Alternative Solutions

Lithium customers, if the above solution doesn’t work, we recommend reaching out to your battery manufacturer to troubleshoot a faulty BMS.

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