Lithium batteries

Plucka
Plucka Registered Users Posts: 130 ✭✭
I have two 12 volt lithium batteries in parallel that started out 3years ago the same. Now one  battery reads 12.97 volts and the other one 13.2 volts. This difference never varies .So when one battery is fully charged the other is not .These different readings remain the same although the batteries are joined in parallel  .I'm using two solar controllers and tested with a meter and both give the same result. Is it possible one battery is damaged.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,606 admin
    If the batteries are truly in parallel... The two terminal voltages (under resting conditions) has to be "identical"...

    If you are charging (or discharging) the batteries, depending on how they are wired in parallel, that could account for the voltage differences:

    http://www.smartgauge.co.uk/batt_con.html

    If they differ under load (or charging) now and were "identical" before--You may need to check the battery connections for dirt/corrosion/loose connections/failed crimps.

    If one battery was "going bad", it (in theory) could be discharging the "good" battery (i.e., high self discharge in the "bad" battery).

    If you had a DC Current Clamp Meter--you could confirm there is no current flow between the two batteries when resting...

    https://www.amazon.com/gp/product/B019CY4FB4 (mid-priced AC+DC Current Clamp DMM--Digital Multimeter)

    You can also do things such as--Put your meter on 200 mV (or most sensitive scale) and measure the difference between - post on one battery and - post on the other (same with + posts too)--There should be near zero volt difference if paralleled. Again, a difference means there is current flow or bad connection(s) somewhere.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    edited June 2021 #3
    Thanks Bill i'll check everything you've suggested when it stops raining [4 days]
  • BB.
    BB. Super Moderators, Administrators Posts: 33,606 admin
    edited June 2021 #4
    What's this thing you call "Rain"? (aka the typical "end of California" drought, again, this year.)

    -Bill  :)
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset