Application:
our device working is like it wake up 5 times a day wake up period is nearly 30 sec and during this time take measurement from sensor and send data on zigbee and go to sleep.active mode current is nearly 80ma and sleep mode is 1.6ma.we are using two new Li-socl2 non rechargeable battery in parallel configuration(reason is that continuous current of one cell is 50ma so we use 2 cell in parallel to counter this situation).cell name is LS 14500 shaft battery.what we observed is,
1-in some device for particular time(for ex on some day during we voltage of this parallel battery pack is down to 3.0v compare two normal working day which is 3.6v,and during this time some time micro controller board restarted(teensy 3.6).after some time voltage again switched to normal condition 3.6v and continue to work normally.
2- we are also measure voltage for our reference of this cell pack using bq35100 ic.in here we used practice to meassure voltage between wake up and powering on all other module(so only teensy micro controller board is on) to avoid fluctuation in voltage.but here same thing observed for some hours or day voltage is drooped down from 3.6v to 3.2v or 3.3v and after some time again switch to normal 3.55v.
so i am not able to understand why for some days voltage is stable and for some day its drop down and after that again go bake to normal.
NOTE:i recently received one such battery pack from site and for checking purpose i open its plastic coting and check both parallel battery separately one is showing open circuit voltage 3.6v and running voltage is drooped to 3.0v.Other battery showing 2.4v in open circuit and same on running(here i think board is not powered on properly in this condition).so we can say that in-spite of parallel condition one cell is discharged more than other(both are new cell when first taken in use).
can some one help to understand this situation??
Best Answer
Ohhh boy.... Please immediately stop using these primary lithium metal batteries in parallel without additional protection. You must use a diode on every cell to prevent the current from flowing into that cell - because these are non-rechargeable chemistries that have a chance of catching fire when mishandled this way. You do not want to deal with a lithium metal fire in any capacity.
When you receive the batteries, you should de-passivate them - put a 20 ohm load across the battery for upto a minute (monitor voltage). In storage these batteries become passivated and need a wake-up before being put in service.